The Yellow-billed Magpie is endemic to California, meaning that it is found only there and nowhere else in the world. Its relative the Black-billed Magpie is much more widely distributed. Yellow-billed Magpies establish nesting territories, though only the immediate area around the nest is defended very aggressively, and nests are often spaced in a semi-colonial pattern.
Late in the summer, after fledging, family groups of magpies come together to form social flocks for the fall and winter. Most breeding pairs are at least three years old, and in exceptional cases magpies can live to be over ten years old.
Photograph © Greg Lavaty
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Description of the Yellow-billed Magpie
Photograph © Greg Lavaty
This distinctively pied relative of crows and jays has a black head, back, and breast, glossy greenish-blue wings, a very long greenish-blue tail, and a white belly and large white patch above each folded wing. The bill and the bare skin around the eyes are yellow, and white primaries are visible in flight.
The sexes are similar.
Seasonal change in appearance
Juveniles are similar to adults, with slightly greener wings.
Yellow-billed Magpies inhabit streamside trees, farms, and rangeland with scattered trees.
Yellow-billed Magpies consume a varied, omnivorous diet of insects, carrion, eggs and young of other birds, and some plant products such as seeds and berries.
Yellow-billed Magpies forage on the ground, and occasionally take ticks from the backs of large mammals. They are often seen in small groups.
Yellow-billed Magpies are resident in parts of northern and central California. The population appears to be stable.
The Yellow-billed Magpie is endemic to California.
Yellow-billed Magpies sometimes nest in loose colonies of more than 20 pairs.
A series of harsh “shek” notes or other loud, nasal calls are given.
- The Black-billed Magpie, found throughout much of the western U.S., is similar except for having a black bill and black facial skin near the eyes.
The Yellow-billed Magpie’s nest is a very large, rounded structure of sticks, 2-3 feet in diameter, with a side entrance. It is lined with mud and plant materials and is placed high in a tree.
Number: Usually lay 6-7 eggs.
Color: Pale greenish-blue or tan and heavily marked with brown or gray.
Incubation and fledging:
The young hatch at about 16-18 days and fledge at about 30 days, with an additional dependency period of about 1-2 months.
Bent Life History of the Yellow-billed Magpie
Published by the Smithsonian Institution between the 1920s and the 1950s, the Bent life history series of monographs provide an often colorful description of the birds of North America. Arthur Cleveland Bent was the lead author for the series. The Bent series is a great resource and often includes quotes from early American Ornithologists, including Audubon, Townsend, Wilson, Sutton and many others.
Bent Life History for the Yellow-billed Magpie – the common name and sub-species reflect the nomenclature in use at the time the description was written.
PICA NUTTALLII (Audubon)
California contains within its borders the whole range of the yellowbilled magpie. Localities occupied are known with exhaustive detail. They are restricted to that part of the State west of the Sierra Nevada from Shasta County, at the north end of the Sacramento Valley, southward to Ventura and Kern Counties, and are chiefly in the Sacramento and San Joaquin Valleys and the coastal valleys south of San Francisco. The area occupied is less than 150 miles wide and extends for about 500 miles from north to south.
The yellow-billed magpie is obviously a close relative of the blackbilled magpie. Some persons like to think of this relationship as subspecific; others consider the two kinds as distinct species. Probably it makes little difference which way we think of them so long as we recognize the nature of the characters and ranges of the birds, insofar as they represent the true relationship, for it is scarcely possible to prove the correctness of either opinion. The most nearly obvious distinctions have to do with the possession of the yellow pigment, which shows in the bill, claws, and some places in the skin of the yellow-billed form, and its generally smaller size. Some differences in habits also may be seen on close study of the two birds. The ranges do not overlap; in fact, the gap separating them is about 50 miles wide at its narrowest place.
The situation is not much different on the opposite side of the range of the black-billed bird, where it approaches the nearest representative of the group in Asia. The relationship indicated there seems even more remote than that with the yellow-billed bird, but it is commonly recognized as a subspecific one. It is true that the birds in western Europe appear structurally to he much like the Amer~-an black-billed ones, although these two kinds are separated by several forms that differ considerably from them. Somewhat similar problems arise in determining the phylogenetic status of the magpies in southwestern Europe and northern Africa. The anatomical, behavioral, and geographical situations there are much like the ones encountered in California. The whole question of relationships and trends of variation in the magpies is an attractive one for the person who may be able to collect the pertinent evidence.
A feature common to situations inhabited by the yellow-billed magpie is the presence of tall trees, usually in linear arrangement bordering streams or in parklike groves, either on valley floors or on hills. Another is open ground either bare, as in well-kept orchards, or comprising cultivated fields or grassy pastures and slopes. This particular kind of magpie appears not to extend its range into lands where there is frequent high wind, long, snowy, and cold winters, or especially dry and hot summers. The nature of the restriction in each case is more or less obscure: sometimes, as with the strong wind, it is evidently some direct influence of the environment upon the birds. Again, the limitation may act indirectly by so reducing the available supply of food that magpies could not exist for the whole year or for a time sufficient to rear their young. Restrictions of water supply may be important in preventing spread of these birds into desert regions. Water seems to be necessary for the birds to drink and also as an aid to nest-building.
Courtship: Observations pertaining to courtship in the magpie are hard to separate clearly from those concerned with competition and with intolerance exhibited toward other individuals. Until the suitable distinctions between these types of behavior can be made, it may be better to consider all the observations made in the early part of the breeding season, which appear to indicate special attention of one member of a mated pair toward the other member. Also it may be permissible to extend the scope of this topic to include examples of attention directed toward other birds, even of other species, exhibited at this season.
Observations made on the Frances Simes Hastings Natural History Reservation, in Monterey County, Calif., where most of the material contained in this account was obtained by numerous watchers, show that activities connected with nesting begin early in fall. In one instance a magpie in a morning early in October (3d) flew from a sycamore into a locust, carrying a piece of sycamore bark 3 by 2 inches in dimensions. It hopped about, eyeing four otber magpies already in the tree. After visiting three twig clusters such as provide nest sites, the bird dropped the bark and paid no further attention to it as it fell to the ground. The other birds ignored it also. One on October 31 was carrvin~ a 6-inch-long stick or root in its bill. This behavior was considered to be a sign of early nest-building.
Another and more easily interpreted example was noted on the morning of November 12, 1937, when one of two magpies in a regularly used blue-oak nesting tree was carrying a dead twig about 10 inches long as it moved from branch to branch. At about the same hour the next morning the two magpies were seen again in this tree and one of them was carrying a 10-inch stick. A few seconds later there was excited calling and then a pursuit flight round and round in the top of the tree. Several magpies flew to the tree and joined in the chase.
Fifteen minutes later two magpies flew into this blue oak and wiped their bills on branches, apparently returning from a foraging expedition. After a few seconds they flew, together, downslope to where two others were foraging, but when these flew up toward them and called, the first two circled back and returned to the tree. Later they left together in another direction. This behavior surely indicates segregation by pairs.
After another return to the tree these two magpies flew down and joined the two they had approached earlier. All four strutted about with tails held high for a few minutes, and then the first two flew back to the oak.
Further evidence of segregation into pairs in fall was recorded on November 18. Two birds were foraging in a stubble field and occasionally flying up to fence posts. One took some food, probably a large insect, to a post where the morsel was picked to pieces. When a person approached the birds, one flew off to willows along the adjacent creek, while the other, engrossed in its foraging, stayed a moment longer and then flew off to an oak in the opposite direction. The two then called to each other with several rattling calls, which were answered. Other calls heard up and down the canyon indicated that magpies were scattered over an area extending for several hundred yards. Several times birds in flight were in pairs.
In the afternoon two pairs were perched in a locust tree, the birds of each pair sitting within a few inches of each other. Low, musical notes, a primitive song, were heard. Both pairs flew off at about the same time. Other magpies, also active and noisy in the vicinity, were flying from one tree top to another, usually in pairs. Even when they started for the roosting place in the evening, magpies on this day seemed still to be segregated by pairs. Two birds started off across the canyon, followed immediately by ten others from various points. These converged until all were strung out in a single file along the same line of flight.
It is desirable to keep in mind, in considering these happenings, that they took place before the start of winter, long before the start of nest building and several months before time for egglaying. Through much of this interval most of the magpie activities, too, are centered about the flock, in the daytime as well as at night.
Fighting among magpies takes place generally through the spring months, beginning, in the yellow-billed form, usually in January. On one of these mornings, January 20, when rain was threatening, magpies seemed to be more quarrelsome than usual on the Hastings Reservation. Three were flying at one another. One would make a short dash at another, which would fly out of reach and then, perhaps, return the attack. Then the third one would attack one of the others. Later, one of five magpies in a tree seemed to be the object of occasional attacks by two of the others. Three or four times when this one hopped to a lower branch, the two jumped at it, causing it to hop out of the way. Occasionally it picked a leaf and let it fall. Once it tugged at a twig but was rather apathetic about it and was driven off by the others.
Apparently members of a mated pair do not always join together in the pursuits. Often a third bird follows the quarreling two but takes no part in the conflict. Once one of three birds was seen to fly to and enter a nest, not taking any nesting material, but it was routed out almost immediately by one of the other two, and all three flew away together. This casualness seems to be a normal feature of the fighting. Often in the nest-building season a magpie can be seen making a short dash toward another, evidently without serious intent, for no response can be detected, and there is no further indication of enmity. Sometimes excited vocal sounds among a small group are the only indication of quarreling, and there is no apparent reason for conflict.
After a brief fight between two magpies on the ground heneath a nesting-tree, one bird called loudly about five times. Several magpies within 30 feet of this spot then quickly flew there, whereupon one of the first two fle~v away about 20 feet. This ended the disturbance, and the magpies scattered and resumed their foraging.
Fighting in the nesting season does not always take place at the nest. One morning six magpies were foraging in a small pasture beside a creek. Two birds started fighting, and soon two more out of the group were fighting. When the fighting, which lasted only a short time, stopped, one of each pair of fighters went off with one of the other pair. Apparently the two males were fighting, and at the same time the two females were in combat.
Encounters between pairs from adjacent nests in the incubation period were watched on a morning early in April. Twice, one pair went to a nest tree other than their own. The first time, the pair quarreled on the roof of a chicken pen, with the male from this nest, and immediately the female flew down to join the group, but there was no more fighting. Next time, when the same three birds were on the ground directly under the nest, the brooding female flew toward them with many excited calls.
On another occasion the four birds from two nests in trees at opposite ends of a barn were together for about 5 minutes at one corner of the barn. Their loud calls indicated excitement. One, with raised tail, quivered its wings slightly, possibly indicating an early stage in the begging which the females develop. Then there was fighting in which all four birds took part, but which led to no decisive conclusion. Finally one took a stick to one nest, and its mate tried to carry one that was too heavy, so it went to the nest with no load. Both birds of the other pair then went to their nest. The purpose of the fight was obscure; possibly there was no immediate purpose, but only an indistinct urge to fight.
Study of numerous examples such as have been recounted brings the conclusion that the accounts reported so often as examples of courtship and pairing in the European magpie may have been encounters between groups of birds already paired. The pursuits could have been merely attempts to drive away intruders. And the congregation of small assemblies of excited birds could have been exhibitions of the common magpie trait of hurrying to investigate any disturbance. Also the reported examples have occurred too late in the nesting season to expect them to represent the very earliest stage of nesting. Recent observations indicate that pairs are well established in fall and that spring is the season for noisy squabbles incident to competition for nest sites or indicators of jealousy toward intruders. Until marked individuals can be traced through the whole cycle, it is not justifiable to consider this interpretation as conclusively established, but it now seems more reasonable than the traditional one.
There are other segments in the series of actions that amount almost to preparation for the behavior to come in the incubation period, and these are to be observed before, through, and after the period of nest building. Even though the birds are seen oftenest in small groups or flocks, it is probable that the units in the organization are pairs that remain together throughout the year. During and after the long period of nest building, or reconstruction, a large share of the time is spent at or near the nest. The two birds of each pair spend several hours of each fair day perched side by side on some limb close to the site. At such times one of them often utters a song that T have been able to hear as far away as 100 yards. There are other indications that during this preincubation time a magpie’s attention is largely centered about its nest and its mate.
One of these attentions is the preening of one member of the pair by the other, presumably the male. I had opportunity to watch this at close range at the San Diego Zoo. In a cage of mixed kinds of corvids there were two yellow-billed magpies, considered by their keeper to be a mated pair. During most of the time I watched, one bird, apparently the male, was perched close to the other, and was working its opened bill through the feathers about, mostly on top of, the head of its mate. This is just what I have seen mated pairs do many times in the wild. The feathers were preened and worked over just as if the bird were searching for parasites, but the real significance of the behavior must be connected with mating. Most of the wild birds observed behaving in this manner have been perched directly on the nest or on a limb very close to it.
The most conspicuous habit in the series connected with courtship in the magpies is mate-feeding by the male. This begins to be developed at about the time the nest is completed and becomes well established by the time incubation begins. One demonstration of an early stage in the development of this habit was watched on a day early in March. One magpie was walking in a circle about 5 feet in diameter. It was fluttering its wings and walking around another magpie, which it seemed to keep in the circle. The second bird walked just a few inches ahead of the fluttering one, which kept its tail turned toward the center of the circle. When a third magpie lit nearby, the antics of the two birds stopped and they began to feed.
Another pair demonstrated the early stages in the establishment of the mate-feeding behavior. These two birds were foraging in a grainfield where the ground was nearly bare. The male walked about, paying little attention to its mate. The female at first ran after and put herself in front of the male, facing him with bill open, head lowered, and wings quivering. This bird seemed to hold its wings less widely opened and to move them more rapidly than did other individuals noted. The response of the male was merely to turn and walk in another direction. Once the female picked at some object on the ground, and immediately the wing-quivering reaction was aroused, and the bird hurried over to its mate, but again the response was negative. After about ten fruitless beggings the female began to pick up objects, presumably food, and for the next three or four minutes she was picking almost continuously, with only an occasional tendency to flutter the wings slightly. Next, the male flew to the top of a fence post. The female flew to the next post, and immediately upon alighting her wings were opened slightly. When the birds were on the ground, the female picked at objects much oftener than did the male. The supposition was that these actions were preliminary to actual incubation which was to begin shortly.
By late March, usually, food begging by females is conspicuous in yellow-billed magpie behavior. This is near the time of the start of incubation. In one such example the female of a pair was first noted perched just outside the nest, uttering the loud food-begging call. Later when the birds were back at the nest after an absence, they lit side by side, the female begging with widely spread wings, but no feeding was seen. Next it appeared that the male led the way to the nest, and when the female came near to it the male quickly left and the female entered and became quiet. It may be that the male thus coaxes the female back onto the nest to incubate when the urge is not strong, possibly in the early stages.
By the time all females are incubating, the late afternoon seems to be a normal hour for the female to come off and beg for food from the male. Males appear still reluctant to feed their mates, especially away from the nest, and they usually avoid the begging female, which crowds near with waving wings. At the nest they appear more tolerant, and it seems certain that feeding takes place at the nest as an inducement for the female to resume brooding. Often the feeding takes place wholly within the nest.
Late in the incubation period the brooding female appears restless and leaves the nest more often than in early stages. Then the feeding usually takes place in a tree but away from the nest itself. Usually the female flies out to meet the male on some nearby perch. It is possible also that the impulse to feed the female latterly becomes weaker in the male. They do not then, however, try to avoid the begging bird but will feed whenever she comes near. Sometimes, though, the female continues the pursuit and begging after it has received the food.
The forage range of individual male magpies during the incubation period varies from the near neighborhood of the nest to a place more than half a mile distant. Sometimes the bird hunts for food on the limbs and among the foliage of a tree, but oftener the foraging is done on the surface of the ground. A male from one nest tends to fly off in the same direction on all trips each day, but this direction may vary through the whole period. All the birds of a colony may forage over the same ground, or they may go in different directions, but, so far as I have been able to determine, they then ordinarily pay little attention to any magpie other than the brooding mate.
The mate-feeding is quickly terminated upon hatching of the young, and with the cessation of the persistent, loud calls, which are a part of the food-begging, the nesting colony becomes suddenly silent and the behavior is inconspicuous.
Presence of other birds about the nest is discouraged sometimes by magpies by vigorous pursuits. Two magpies watched in February were greatly concerned over a golden eagle that perched near their nest, and they tried repeatedly to drive it away. Special animosity is directed toward sparrow hawks in the vicinity of the nest, as if the magpies recognized the intent of these intruders. In one instance great effort was put forth to drive away two hawks from a nest, but when a western bluebird lit on a limb close to the nest, the magpie paid no attention to it. Once when a red-shafted flicker lit close to a magpie nest, the owner came immediately and drove it away. Similar effort has been watched with respect to California woodpeckers near occupied nests.
Other members of the Corvidae are treated with special enmity whenever one approaches a magpie nest. Magpies are able to drive away California jays ordinarily, but sometimes these smaller birds display an extra degree of persistence in refusing to leave the nest tree. Crows near a magpie nest arouse special activity, and they are driven away if it is possible. Sometimes they refuse to be driven and even turn on their pursuers and drive them from the site of their own nest. Once a nesting magpie attacked an intruding meadowlark with such fierceness that the two fell for 20 feet, or halfway to the ground, before the smaller bird escaped and fled with notes of alarm.
Defense of a nest site more than ordinarily effective against intrusion by a crow was noted on a morning early in February. A pair of magpies was discovered in a large valley oak, about a hundred feet from their nest site, where they had driven a crow to seek shelter in a thick clump of branches. One magpie would make a dash at the crow and retreat, and then the other would move toward it, but each took care to keep out of range of the crow’s bill. Several times the crow dashed out after one or the other of the magpies, but always it retreated back to the protection of the limbs. This was kept up for 3 or 4 minutes, until four more magpies came, when the crow gave up, moved to the outer part of the tree, and then flew away. The magpies then dispersed.
Another incident in another year but in the same group of trees concerned a crow carrying a twig for its nest, which it had pulled from a blue oak about 80 feet from a new magpie nest. The pair of magpies kept such close watch of the crow and dashed toward it so frequently that it was unable to leave the tree with its stick. Finally, it placed the twig on a limb and tried to drive the magpies away, but this was not successful and it was forced to leave the tree without its twig.
Nearly all the examples of defense of nest site included in this section occurred in early stages of nest-building, before the start of incubation. When this stage is reached, the magpies seem too much occupied with their own program to pay much attention to other birds except on special occasion. Ordinarily this stage of nesting is reached nearly at the same time by almost all the pairs of magpies in a colony.
Nesting: Habits connected with nesting in the yellow-billed magpie are, in general, like those of the black-billed species, but they contrast in several ways. Possibly the difference in nesting behavior between the two kinds seems more marked than in other types of behavior because the results of it, being definite objects, are more easily perceived by the human observer.
First, the nesting colonies are more compact and the nests are closer together in the yellow-billed form. This may have some connection with a more favorable foraging habitat that permits the yellow-billed form to live in a more gregarious society. Or it may reflect the result of some different need for group response to disturbance by intruders.
The actual position of the nest provides one major difference between the two kinds. In the yellow-billed one the nest is nearly always in some tall tree and far out on the limbs, or if in a medium-sized tree, it is likely to be in the periphery. Thus it is regularly at a different level and in a different site from the low, bushy one occupied by the American black-billed birds in their nesting.
Trees prominent among the ones nested in by yellow-billed magpies are sycamore, valley oak, live oak, blue oak, poplar, cottonwood, locust, and willow. One colony observed near Oroville by W. B. Davis tried repeatedly to nest in a clump of digger pines but with poor success, for these trees provided poor anchorage for the nests. They were easily dislodged by the wind, and sometimes the weight of the nest itself was enough to change the slope of the limb so that the structure would slide off to the ground. (See Linsdale, 1937.)
A curious item of yellow-billed magpie nesting, commented upon at length by Dawson (1923), is the resemblance of a nest to a clump of mistletoe. It happens that in California the area occupied by this bird and that occupied by two kinds of mistletoe are closely similar in their boundaries. Not only are the areas nearly the same, but the species of trees concerned are the same. Cottonwoods, sycamores, and valley oaks are the kinds of trees mainly involved in this peculiar relationship. The bird not only nests in trees having many clumps of this plant, but also it often builds actually within a mistletoe clump. Whether or not intentional selecdon is made by the bird for this purpose, it is obvious that the close resemblance of the two objects helps to screen the presence of nesting birds. Even a person experienced in detecting the nests is unable to distinguish one from a mistletoe cluster at a distance, so nearly alike are they in size, shape. and position. It seems possible that such a lot of decoys, even if the relation is the result of accident purely, might save some nests from discovery and destruction by persons not closely observant.
The inaccessibility of the nest because of its position on small limbs far above ground is sufficient to save it from the ordinary prospects for destruction by people climbing to it. Although the nests can he reached, the handicap is too great for most climbers. Forty to sixty feet is the normal height above ground for these nests. Thus the hirds can live close to human habitation and nest with greater freedom from the kind of molestation ordinarily encountered by nesting colonies of blackbilled magpies. This may account partly for the greater apparent lack of fear generally shown by the yellow-billed birds.
The mild winter climate in the range of the yellow-billed magpies seems to encourage, or rather to permit, an exceptionally early start at nest-building. In Monterey County, even in the mountains at the highest levels inhabited by the species, magpies regularly begin to build around the middle of December, before the shortest days come. Often a nest will reach a late stage of construction during a series of warm days at this season, hut the coming of storms interrupts the progress, and the pairs rejoin the flock. With the return of warm, clear spells in February or March the building is quickly resumed. Normally the nests are completed soon enough for the laying to be completed before the end of March. Thus the egg-laying comes four to six weeks before the corresponding stage in the cycle of the black-billed birds living near the same latitude, but subjected to the more rigorous climate of the interior.
Warm, cloudless days late in January seem to arouse an extra amount of nesting activity, even when they follow as much as a month of nearly complete inactivity. Once, nest-bt’ilding at lining stage on January 29 was carried on through a light rain. In three hours of morning watching, the pair carried 12 loads of material, sticks or mud, to the nest. Through a cloudy period the following morning the magpies were busy foraging, but when the sun broke through the clouds they went immediately to the nest. On the same (late of the previous year, soon after a rain stopped and while it was still cloudy, several magpies were perched quietly in the vicinity of nest sites. One working pair left when the rain started again.
In this locality twigs for nests are regularly pulled from valley oaks, sycamores, and black locusts. Sometimes many in succession are tugged at before one can be loosened. The birds have some trouble in picking a route through the trees where the twigs they carry will not catch on the hranche~. During active nest-building. periods from 10 to 30 minutes elapse when no bird appears at the nest and when the pair is off foraging. In the active periods the whole effort of both the birds is directed to getting sticks to the nest and working them into place.
The urge for nest-building seems to grow stronger with the advance of the season. Also the member-pairs of a colony seem to approach such a synchronized program that they reach the stage of incubation at about the same time even though they do not start building together. Ho~vever, some examples indicate that nests are sometimes begun long after the normal time. At the Hastings Reservation one season a pair of magpies was watched one morning, on May 11, busily carrying sticks to a nest in its early stages. Several sticks picked up from the ground were carried to it. A magpie was seen to enter this nest on July 24, but no actual use of it was made until the following year. Then a brood was brought off in the normal season.
Another late start at building a nest was noted in June. On the 19th a magpie carried a stick to a site in a fork about 50 feet up in a sycamore, and where 35 or more sticks already had been placed, many of them within the preceding 24 hours. No bird was seen about this nest again until the early morning of June 24, when each member of the pair brought a stick. Each bird then called and perched near the nest for about a minute and then they, separately, flew off to the ground. Again, a considerable quantity of material had been added since the preceding day. No more material was added. Two birds perched close to the site on June 27, but 5 days later all the magpies on the Reservation left for a period of days, thus apparently ending the story. But early in the morning of July 15 a noisy flock of magpies settled in this vicinity. One of the birds went three times to the partly built, late nest and crouching on it with wings aquiver uttered low, throaty, harsh calls, which sounded like currow, and turned around several times. Half an hour later the same performance was seen at the nest, but there was no further indication of its use at any later time.
Like the other kinds of magpie, the California one builds a nest that is sought by other birds as a home, but this use seems rather restricted to the sparrow hawk. Nearly every colony of yellow-hilled magpies has at least one pair of nesting sparrow hawks. Although it may not be evident all through the season, there is considerable strife between these species when nest sites are being selected. After a given nest has been successfully defended and all the pairs are settled, the two species appear to take little notice of each other.
Pursuits of magpies by sparrow hawks are noted often in fall, beginning in September. Sometimes a magpie turns in a chase and pursues the hawk. These pursuits, however, may have little significance in the nesting activities. A different situation is prcsent early in spring. An example was noted on an early day in March, when, just after 5:30 P.M., a sparrow hawk flew to a magpie nest in a sycamore. The two magpie owners came immediately and drove away the hawk. The possibility of the hawks taking permanent possession of a nest at this time of day, just before dark, may provide an explanation for the repeatedly observed circumstance that pairs of magpies keep an especially close guard in the tops of the trees over their nests for about half an hour each evening just before dark.
During the early part of the nesting season whenever sparrow hawks singly or in pairs approached and attempted to enter an occupied magpie nest, one or both of the rightful owners would come immediately and drive them from the vicinity. When smaller birds, for one example a flock of juncos, came near a magpie nest, the magpies paid no attention. They seemed to recognize the nature of the threat offered by sparrow hawks.
Eggs: Seventy sets of eggs contained in the Museum of Vertebrate Zoology or collected by W. B. Davis made up a total of 455 eggs, or 6.5 eggs per set. Number in a set ranged from five to eight, and the modal number was seven. This indicates a slight tendency toward smaller sets than are laid by the black-billed kind.
Laying time for this bird is usually the latter part of March. Late nests are rare, and as already indicated they are almost certainly never completed or used in the season they are started. Extreme dates for nests with eggs are March 30 and June 2. All but six of the 70 sets mentioned above were collected in April. This no doubt indicates a shorter, and earlier, season suitable for nesting than that of the black-billed magpie.
Dawson (1923) described coloration of the eggs as yellowish glaucous or pale olive-buff, finely and rather uniformly speckled and spotted with huffy brown, or citrine drab, or grayish olive, or deep grayish olive. A considerable degree of variation in color was observed by Kaeding (1897) in the 30 or more sets of eggs he collected. Some were heavily blotched ~vith lilac and huffy or purplish brown. Bendire (1895) observed that eggs with a greenish tinge in the ground color appeared more frequently in this than in the black-billed magpie.
Measurements of 195 eggs of this magpie were given by Dawson (1923) as follows: Average 30.8 by 22.4 millimeters (1.22 by 0.88 inches); index 72.1. Largest egg, 37 by 23.4 (1.46 by 0.92); smallest 26.7 by 20.3 (1.05 by 0.80). Measurements of 62 eggs in the United States National Museum were as follows (Bendire, 1895) : Average 31.5.4 by 22.54 millimeters; largest 34.29 by 22.86; smallest 28.45 by 21.34. Kaeding (1897) has commented on the diversity in shape shown in his collection of over 30 sets; some eggs were short and rounded, while others were long and elliptical.
A set of eight fresh eggs ranged in weight from 7.6 to 8.8 grams, average 8.3, thus being considerably lighter than eggs of black-billed magpies.
Young: Length of incubation period for the yellow-billed magpie is not definitely known but is assumed to be close to that of the black-billed one, or around 18 days.
Hatching of the young apparently changes the magpies to silent birds. One pair carried food to a nest at least 10 times in the 40 minutes it was watched on the morning of April 12, the visits thus averaging four minutes apart. Usually it was not possible to distinguish any objects in the bill, but once or twice supposed large insects could be seen projecting from the bill. The birds flew directly toward the site, but they perched on some limb 3 to 10 feet away and toward the main crown of the tree for a few seconds before going into the nest. The birds always entered the nest from the same side and left through the opposite one. Nearly always when one of the parents left the nest it flew directly to the ground and immediately began to search for food. On this date whenever a parent visited the nest, the young birds made calls that could be heard by a person 60 to 75 yards distant. These calls began when the parent entered the nest and they ceased as soon as it left. Once, both adults arrived at, and entered, the nest at about the same time. They flew away together a few seconds later, and one of them dropped a fecal sac from its bill when it had gone 50 yards.
These adults nearly always flew to a nearby orchard to forage, and four-fifths of their trips were to some freshly disked ground. On several trips one of the parents perched in the top of an orchard tree before going to the ground. They usually were silent, but once or twice a short series of notes was heard at the nest. The time spent at the nest on each visit averaged between 10 and 20 seconds.
Apparently typical behavior of a family of six young out of a nest and being fed by parents was watched for an hour near the time of nestleaving. At first three of the young birds perched in a tree 30 yards from the nest. Later this tree held four young and two were in the nest.
The usual procedure in feeding on this day was for the young to keep a sharp lookout and, whenever an adult magpie came within sight, to start up a series of loud calls, higher in pitch than those ordinarily given by adults. If the approaching adult were not the parent of this brood, it continued on its way, and as soon as it had passed the cries would cease. If the approaching bird happened to be one of the parents, it would go to the group of young birds and the cries would be continued until a young one had been fed and the old one had left.
The cries of the young birds were accompanied by energetic flapping of the wings. The white on the wings helped to make the birds con-. spicuous while thus flapping, so that chances for the attention of the approaching bird being directed to them were increased. This may be an important function of this set of white markings. Whether developed because of its adaptive value or not, it certainly operates to disclose the locations of the young birds to the human observer and presumably likewise to the parent birds when they are approaching with food.
The brood of young magpies, being separated and in different trees, gave a good opportunity to see additional features of the response of parents to begging young. The destination of the approaching parent seemed to be controlled entirely by the amount of commotion made by the young. The group that began calling first and kept it up with greatest vigor was the one finally approached. Sometimes a parent abruptly changed its course when headed toward one group and went to another, apparently because of a greater persistence in begging there. Once, when an adult started to leave, it was attracted by calls from another group and turned back and went there. It was not determined whether any food was delivered to the second group.
The young magpies showed little ability to distinguish their own parents. Any magpie flying toward them aroused the cries and wing flapping. These ceased, however, as soon as the flying bird passed and took a course away from the young birds. Once the young birds begged when a California woodpecker flew over them. The amount of begging seemed to be a direct expression of the degree of hunger. Apparently the two young that stayed at the nest were not yet able to fly. The others could fly; hence they probably were larger and possibly they required more food than the ones at the nest. At least more trips were made to them by the parents. But the ones at the nest were not neglected. For a few trips after food was taken to the nest, the young ones there would remain almost quiet, giving only one or two notes during each visit.
When a parent landed in some tree other than the one holding the young birds, they would fly to that place, flap their wings, make loud calls, and attempt to get in front of the adult. The latter did not remain long after food was placed in the widely opened mouth of some one of the youngsters. Each parent, in turn, left and went to the nearby orchard to obtain another supply of food. The trips were about five minutes apart. The adults generally were quiet, but occasionally they uttered series of alarm notes, usually when away from the young ones.
Between feedings the young magpies moved about on the limbs of the tree by walking, hopping, and making short flights. Their legs appeared to be long, and their claws were the chief means of keeping a hold on the bark. When alighting they had difficulty in regaining a balance. Their tails were only 3 or 4 inches long. Not once was one seen on the ground. Their time was spent picking at the limbs, preening their feathers, or just drowsing. At frequent intervals a young magpie would raise both wings and stretch them over its back, partly folded, but would not extend theni.
These young birds were quiet except when a flying bird approached them or they were being fed. During each feeding all the young kept their mouths opened widely while calling. Once one kept its bill widely opened as it flew from one tree to another. On another occasion a young bird flew out 15 or 20 feet to meet an approaching parent, which, however, paid no attention to it but continued on to the tree and fed another one. When a person tested their responses to disturbance by walking over to the tree, at first all the young uttered warning notes. After a few minutes they became quiet, and the ones at the nest withdrew into it. One of the other young ones flew to another part of the grove. Parents came, uttered alarm notes, and left. They returned in half an hour and there were more alarm notes.
In Monterey County a brood of bobtailed young at nest-leaving age was studied early in June. The parents came down to lower limbs within 6 or 8 feet of the intruding person to protest at his ‘presence. Other adults came too. Notes of the adults and young differed considerably, the latter being weaker, softer, and higher. After being disturbed the young magpies moved into higher parts of the tree.
Another young bird, watched in early morning, was begging from an adult perched on a wire nearly 10 feet above ground. It crouched with wings quivering, held its bill near the adult’s bill, and uttered low notes, but the old bird did not feed it. The youngster then flew down to the ground and foraged for itself.
An example of communication between adult and young was observed when a young magpie with tail two-thirds grown was handled in a room. Its cries attracted an adult (parent?), which perched on a limb outside the window and squawked long and loudly. Soon after the adult began to call, the young one stopped. The adult flew away. Again the young one called, the adult returned and squawked, and the young one became silent. When the young bird was released outside, the adult perched in a tree overhead, screaming loudly, but made no move. When a person caught the young bird again, however, the adult swooped down at him.
Plumages: Plumages and changes of them in the yellow-billed magpie seem to be so nearly like those of the black-billed magpie, already described, as not to require separate treatment. Possibly the calendar of molt differs, but this has not been worked ‘out.
On at least several of the magpies I noted on October 9, 1929, in the Sacramento Valley, bright yellow of the exposed skin could be seen extending back from the bill, below and nearly around the eye. On sonic, if not all, of the magpies observed on November 11, 1930, the yellow, bare area around the eye could be seen distinctly.
Four freshly killed birds from Santa Clara County were examined by me on October 19, 1929. All were in molt. In one, a female, the molt was nearly completed; the sheaths still showed on the contour feathers on the breast and around the head. The skin was yellowish, especially around the head, the base of the tail, and on the body at the bases of the feathers. The yellow bare space behind the eye was 10 by 10 millimeters in size. A male in the same stage of molt showed more yellow on the skin, especially on the under sides of the wings. Another female was farther along in its molt; it showed scarcely any yellow on the skin except around the head. All but the feathers of the throat and chin were free from sheaths. The fourth bird showed sheaths on the feathers about the head, those on the chin and throat being least developed.
Abnormal plumages in the magpie attract more than ordinary interest because of the possibility, which seems almost probability, that some of the existing geographic forms arose by the preservation of this kind of character. This preservation might have been accomplished by means of the kind of geographic isolation that now characterizes the yellowbilled kind. It is interesting, if not significant, that the yellow bill, which is the conspicuous mark of the Californian kind of magpie, has been discovered as an abnormality in other parts of the range of the genus.
Food: Kalmbach’s (1927) study of the food of this species made him conclude that it is somewhat more insectivorous than the blackbilled species. At the same time, he pointed out, it is capable of committing practically all the offenses of which the latter is so frequently accused. He considered that its scarcity precluded the possibility of the yellow-billed magpie’s doing serious damage. The stomachs examined indicated that 70 percent of the bird’s food is obtained from animal matter and 30 percent from vegetable. Insects made up more than half the food. Conspicuous among these are grasshoppers, which appear to he most of the food after midsummer, until the cold weather of fall. Bees, ants, wasps, ground beetles, flies, carrion beetles, and true bugs ranked high. Carrion is consumed in winter and early in spring.
Observations on the manner of feeding have been recorded at length on the Hastings Reservation. Capture of flying insects on the wing is a habit regularly noted. During a period of warm sunshine on a January afternoon, magpies were making flights out and up from a dead oak on a knoll, presumably after insects. The flights ranged in length from 15 to 50 feet. At the end of each one the bird generally swooped and zigzagged up and down as if in pursuit of an insect. Return was to the same dead oak. Similar behavior was noted in the fall.
Another habit, characteristic of foraging magpies, is to search under objects such as chips of wood or cow dung. These sites are hiding places for a great variety of insects and other invertebrate animals. They are generally inaccessible to most foraging birds, which are too weak to uncover them, hut magpies can get them with slight inconvenience. In addition, from the heaps of dung they often get grain.
Magpies keep a close watch for new food sources. They quickly find scraps of waste about houses, such as garbage or bits of food that may be thrown out on the ground. They watch other feeding animals, birds or mammals, and rush to retrieve any bit of food that may be lost or discarded. Other foraging magpies even are watched closely, and many pursuits occur when one attempts to carry some item of food. Any object too large to be swallowed immediately or to be carried away is likely to be the center of a contest so long as any of it remains. These encounters rarely reach the stage of actual combat.
To force others away from food, the magpies use a posture as a sort of bluff. Both parties in such a dispute stand very high, point their bills upward at nearly a 7Q0 angle, throw out the breast and throat, and work the muscles as if producing calls. If any are made, they are inaudible to a person 50 feet away. The successful bluffer then walks toward the other bird as if to bump his chest against the other. This sometimes occurs, but oftener the gesture is sufficient to retire the opponent. This pose seems to leave its maker in extremely vulnerable position with sensitive throat exposed to attack, but no blows have been seen struck there. The retiring bird crouches down and shrinks aside, still holding its bill up.
Sometimes a bird resorts to blows instead of bluff when another becomes too persistent. Then a swift hop and peck at the head of the intruder drives it off. So long as the other birds do not try to feed, they are permitted to stand so close to the feeding bird as to bump it occasionally. When pursuits occur, they may he only for about twelve inches, but in the interval an onlooker usually takes possession, and frequently it then refuses to be driven away.
Some individuals merely wait their turn to feed. Occasionally one watches for a long time and then suddenly forces away the possessor. It may be that this period of watching serves to build up courage. Some individuals, which appear to the observer to be weaker ones, rush in to snatch morsels while the feeder tears loose another or pursues another bird. While feeding, these magpies often produce throaty songs, like pleasant squeals. Others squawk as they watch but do not sing.
Magpies exhibit the same sort of nervousness shown by smaller birds when they forage over open ground, and they commonly rush off at intervals to perch in trees or bushes. One morning 23 of them were foraging in a recently planted grainfield. When something disturbed them all flew nearly simultaneously into willows near a creek. If not badly frightened, some lit on fence posts instead. Usually they began to return to the field within 45 seconds. An occasional bird, however, dropped to forage in a pasture on the opposite side of the creek. Generally when two or more birds flew up, the whole flock rose, but one bird’s leaving did not cause them to follow. Fewer and fewer returned to the field after each flight until the whole flock was foraging in the pasture.
Storage of food by magpies is noted regularly. Jt occurs oftenest in winter but has been observed also at other times of the year. Storage takes place usually in shallow pits dug by the magpie in the top layer of soil, but crevices among limbs of trees may be used too. The objects most often stored, at least in one locality, are acorns, but carcasses of small animals and left-over pieces of food may be stored also. Nearly always the cache is covered over with stems of grass or leaves and is so carefully hidden as to be nearly invisible. It may be found by a person only after marking the spot well. On occasion some object may be carried for a long time, as long as half an hour, and then buried, or it may be placed in the open on top of the ground and left. An item being carried may be laid on the ground while the bird examines or eats some other object. Acorns may be buried entire without the shell being opened or they may be partly eaten first. Whether magpies return to a cache once it has been hidden has not been observed, but they have been seen raiding the stores of other birds, always shortly after they were covered.
In some years acorns provide a large share of the yellow-billed mag pie’s food for several months beginning in mid-September. Live oaks and valley oaks provide most of the ones eaten on the Hastings Reser vation. Sometimes the acorns are picked up from the ground, but oftener they are taken directly from the tree. The acorn is then carried to the top of some fence post or to a limb in another tree, where it is held underfoot and pounded until the shell is broken and the desired portion of the kernel is removed. Normally the acorn is carried with the small end pointing ahead and only one is taken, but sometimes it is turned, and the bird carries an extra one. Limbs of blue oak, black locust, and valley oak are used as an anvil for pounding the acorn, but the valley oak seems to be the favorite. Apparently the rougher bark and larger branches make this tree more satisfactory.
In hammering an acorn the bird does not strike with vertical blows; instead the bill comes down toward the feet at an angle of 800 from the horizontal. The bill is not lifted immediately on striking the acorn but is pushed into it. Sometimes hundreds of blows, in series of about 20, are required to open the shell. A magpie exhibits jealousy over an acorn in its possession and normally takes it to some secluded spot away from the other birds. Also it appears reluctant to leave one when disturbed by a person. Effort is likely to be made to retrieve an acorn that is dropped by accident. However, on their own accord, they commonly discard any acorn that proves difficult to open, and many partly eaten ones are left for another occasion or where some other bird can get them. These traits are exhibited with respect to other kinds of food, but they are more easily watched when large objects like acorns are concerned.
Additional mannerisms are shown by the following account of an incident watched on the Hastings Reservation. Four foraging magpies, on November 18, assembled under a live oak and looked up at the periphery of the tree where another one was clinging to an acorn-laden limb, which bent to a 600 slope under the weight of the bird. An acorn was wrenched free and carried to the ground. Another bird flew up and, after searching in three places, found a suitable acorn. This was seized at its base, transverse to the axis of the bird’s bill, and wrenched free. The acorn fell to the ground, and the bird followed it swiftly, but too late, for one of two magpies on the ground had reached it and then the retriever refused to give it up. The dispossessed bird returned to the tree and obtained another acorn, which also fell. But this one it followed so swiftly that the other two birds could not reach it, and it retrieved and carried away the acorn with a squawk. The bird that had stolen the first acorn deserted it to try for the next one to fall and then returned to the first acorn and began to hammer it. As many as eight magpies were seen carrying acorns under this tree. Nearly all the acorns were obtained by loosening them and following them to the ground. If no other magpie was close, the bird got its acorn; otherwise a bird already on the ground got it. Each acorn finally retrieved was carried away, placed underfoot, and hammered open.
Other kinds of food obtained regularly from plants in this vicinity were figs and fruits of poisonoak, coffeeberry, and grapes. The fruits of coffeeberry ordinarily are carried to some perch where the pulp is extracted and swallowed and the skin is discarded. The seeds seem to be swallowed sometimes and discarded at other times.
When magpies are feeding broods of young they sometimes discover the nests of other birds and take the contents, but this happens on rare occasions. Once at the end of May, in the Sacramento Valley, I observed a commotion caused by a magpie in a large colony of nesting cliff swallows. At my close approach the magpie flew out from under the bridge that held the nests. It went back again and then out and away. All this time the magpie was being pursued by the large flock of adult swallows. Circumstances indicated clearly that the magpie was there to get young swallows, which at that time filled most of the nests. But no actual raid was seen. Many of the nests had long entrance tunnels, and they appeared too long to permit a magpie to reach into the main cavity of the nest.
Nearly 10 years elapsed before I again found a yellow-billed magpie molesting nests of small birds. In one tree where a pair of magpies and three pairs of Bullock orioles each had nests, several encounters were noticed between the species. One morning a magpie went to one of the oriole nests and poked its head into the cavity, but just what happened was not learned. It left and was pursued by the orioles. On other occasions the orioles were particularly bold in attacking young magpies just out of the nest.
In the same season and close to this spot o~e magpie acquired the habit of searching out and destroying linnet nests placed in crevices about the farm buildings. Apparently these raids were made to get the young linnets, but actual captures were not seen.
Behavior: The yellow-billed magpie exhibits the general manner of the black-billed kind, but it appears less timid throughout its range and seems to live closer to human habitations. Possibly the black-billed magpie would respond just as quickly to the near presence of people if permitted to do so, but it regularly encounters a more aggressive disfavor. Whatever the cause, it appears obvious that the birds live closer about houses in California and they encounter less molestation. This means that it is easier to study them, for they willingly permit approach in many places to within 10 or 15 feet. At the same time they retain the capability of cautiously watching for danger, and they quickly slip away if disturbed by shooting. Much of the area occupied by the species is relatively free from this danger.
On the ground a magpie walks, hops, runs, dodges, or makes short leaps with the aid of its wings. The flight is usually short, and in the wind it is wavering, for the long tail then proves to be a hindrance, although ordinarily it gives the bird a graceful appearance. Types of perching places oftenest used when the birds are not on the ground are the larger-sized limbs of big trees. On telephone wires they appear to have no difficulty in balancing. When coming to a stop the bird may jerk its tail upward four or five times and then maintain its balance with the tail held close to 450 below the horizontal. Foraging birds may jerk their tails upward independently of need for balance. A slight jerk of the tail often accompanies a vocal note.
When starting to fly away after being disturbed the birds do not flap evenly. Several spurts may be distinguished. In one example the rhythm was three easy beats followed by two vigorous ones. The contrast was audible as well as visible in a bird flying 25 feet overhead. On another occasion this irregular flight consisted of five to eight rather weak wing beats and then four or five rapid, strong beats. The flight of the several individuals, however, was not synchronized. Another habit of flight observed often is that of gliding downward for long distances, extending the wings, and braking the speed at regular intervals.
Flocks of yellow-billed magpies may be seen all through the nesting period, but these are mainly temporary formations, probably accidental assemblages. When the young birds leave their homes, however, the flocking tendency soon becomes conspicuous again, and the birds form definite aggregations that have the quality of permanency. The unit of organization for this species then changes from the pair to the flock. For the next half year the behavior of the flock is our chief concern with this species.
A striking example of responses of members of a flock to a certain note of one of their species was observed in late November. At 4:30 P.M., after the birds had congregated and just before they started off to roost, they were perching quietly in some oaks. A dead snag broke under one of the magpies in the vicinity, causing it to fly away squawking in alarm. The flock, calling noisily, flew in a compact body to the scene of the disturbance. The birds perched on the remaining limbs of the snag and on nearby trees and then became silent. From there they finally flew off, 15 and 20 minutes later, to roost.
Roasting time is the occasion for congregation of the largest and most compact flocks. The birds assemble in tree tops and then seem to await the move of one to act as leader. Sometimes the group flies out to join one or more individuals flying overhead; sometimes they follow one of their number as it makes a start from the perching tree. If one bird turns back the whole group is apt to follow, whether the bird is ahead of or behind the others. On such occasions they are likely to come swooping back down to trees or thickets, swerving erratically. and wings whistling. In these assemblages there is apparent a great reluctance to make the first move, but once it is made the remaining birds rush to follow.
Daily routine of activity in the yellow-billed magpie is, perhaps, more easily traced than in most other birds, mainly because this bird is so conspicuous. Aiso at many places the magpies are so continuously and so easily accessible for observation in the vicinity of human living quarters that it is possible to trace the daily and seasonal changes year after year. Thus it becomes obvious that while the daily program is fairly rigid it is also highly variable.
The recorded program of the magpies on a normal day begins with the arrival of the flock, as a unit or in sections, from the roost. After a reassembly in trees, the birds scatter somewhat and begin to forage. Late in the morning they retire to trees for a midday rest, which is broken for another period of feeding before they form another group to fly off to roost. Through the main part of the nesting period this behavior is modified considerably by the necessity of keeping close to the nests.
Magpies regularly congregate to roost in a group through most of the year outside the nesting season. The site oftenest used on the Hastings Reservation is in a small ravine about a hundred feet wide, facing the west, and grown over with live oaks. The magpies roost in these dense trees. Each night, nearly an hour before finally settling at the roost, the birds assemble in sycamores or oaks in the canyon or the low hills a quarter to a half mile to the north of the roost. Half an hour after congregating, they fly to the roost. The assembling flock seems to become more and more unified, the longer the birds stay. Often there are squabbles with other birds, as crows or hawks, in which the whole group participates, at least vocally.
For 10 or 15 minutes preceding the flight across the canyon the magpies are rather silent. They perch mostly in tree tops, several in a tree, and there is little foraging. This period is followed by a series of outbursts of calls or a single one. Large groups make greater outbursts. The flight then begins. After a few outcries the birds become quiet as they fly more slowly and gain altitude steadily. The destination of this flight is a group of trees, usually leafless black oaks, used as gathering places both morning and night. Ten or fifteen minutes are required for all the birds to make the flight. Cold, strong wind, cloudiness, and rain tend to advance the time of flight across the canyon. Encounter with some other species tends to delay it. Change of roosting place from a common gathering place outside the normal daytime range of the colony to the nest site occurs usually in January.
Response to disturbance on the long flight to the roost is indicated sometimes by the birds when they suddenly change the course of their flight and dive back downward to the tops of thickets of trees. Their wings make a great roar, then all is silent. Within a short time, two minutes in one example, the flock rises and proceeds normally on its way.
Departure of the magpies from the roost on a fall morning is somewhat as follows: The birds fly up from the roost in live oaks in a ravine and enter large, leafless black oaks on a ridge. Calls are to be heard often before any birds appear and as early as 20 minutes before they finally leave the hill. The flight to the exposed trees is made singly or in pairs, and the birds perch silently, with heads drawn down close to their shoulders. They finally become vociferous, but the calls are short and quiet compared with ones made later in the day. Calls increase slightly or cease altogether before the birds leave. Gradually the single birds begin to move about and combine to make small groups. Sometimes all these groups unite into one big one, especially in disturbed weather, as rain, fog, strong wind, or low temperature. Finally the magpies leave the hill and fly, swiftly and low, to a wooded knoll on the canyon floor, where the long columns of birds converge in the tops of one or two trees. Calls become louder and more frequent than they have been on the hill or in the flight. If the groups are small, 10 or 15 minutes are required for all the magpies to leave the hill; if large, the time may be as little as 5 minutes. Next, the birds scatter from the trees to the ground.
Change in time of sunrise is followed closely by c.hange in tinie of roost-leaving by the magpies, but there is considerable variation in the time of the actual flight from the hill. On many mornings, especially in December, the magpies, instead of all going to the lower part of the canyon, split up into groups, and some of them fly directly across the canyon to the top of another sunlit, warm hill. From there they move back later in the morning to the floor of the canyon.
Behavior of magpie flocks at the start of their day on the Hastings Reservation was observed on several occasions in the second half of July in 1938. Once, at 5 :55 A.M., an observer suddenly became aware of raucous magpie calls. A flock in compact formation arrived near the center of the normal nesting area and split into three groups of six or seven birds each. Twenty were counted in all. Two groups lit in blue oaks, the third in a sycamore. All were calling loudly, harshly, and continuously. There was a constant interchange of individuals between the groups. The birds moved into many trees but stayed in the top branc~hes. When they first arrived the din was terrible, as all 20 birds squawked loudly at the same time. Twenty-five minutes later the birds had spread out and the calls were more widely spaced.
Usually only two to four birds were calling at once. Two came down to drink at a water trough, but none had gone to the ground. The calling slowed down so that intervals of 10 to iS seconds elapsed without a sound. By 6:30 the interchange from tree to tree had ceased.
In another 15 minutes small groups of two or three birds began to move off toward the north and the number of calls was still further reduced, so that as many as 45 seconds sometimes passed with no sound. Soon all the magpies had left the area where they had first settled.
Water troughs on the Hastings Reservation, originally set up for cattle, provided water for birds, but their shape proved to be a slight handicap in use. Magpies regularly bathe at these troughs by standing on the rim, tipping forward, and flapping their wings. They then fly to nearby trees to dry their plumage. A different procedure was noted on a cloudy, windy afternoon in January when a magpie drank twice from one of these troughs. The bird then jumped about 6 inches into the air and, with beating wings, gradually lowered itself until belly and feet touched the water. With the tail held up so as not to touch the water, it kept this position for about 15 seconds and then flew to the top of a nearby post to rest. After repeating this three times at oneminute intervals, the magpie flew to a locust tree where it ruffled and shook its plumage, picked at one or two breast feathers, and flew back to the trough. It perched beside another drinking magpie for two minutes and then took two more dips. The other magpie then drove this one off to a fence post where it dried its plumage and the two flew off to forage.
In many parts of California, for example in the Sacramento Valley, the planting of trees and the extension of cultivation have apparently favored the local spread of magpies. Study of present-day conditions in that region indicates that extension of human occupation of this land has, also, over a long period of years, resulted in increased numbers of this bird there. At an earlier time, from 1850 to 1890, there was a period of persistent destruction of magpies in California, which resulted in greater wariness of the birds and led to a disappearance of the species from some localities on the edge of its range. Besides the direct killing by shooting, magpies in this area, according to the testimony of numerous observers, have been killed by placing poisoned bait to prevent their taking of cultivated crops, by poisoned baits placed for coyotes, and by poison used in rodent-control campaigns. Despite the rather widespread notion, however, that the yellow-billed magpie is rare and that it is on the verge of extinction, there seems to be at present no reason for immediate concern over its welfare as a species. Extermination might conceivably be possible, but it would be so expensive and difficult that it would not occur under ordinary circumstances.
The yellow-billed magpie exhibits the tendency shown by magpies elsewhere to be attracted to herds of large mammals. The birds are seen regularly about sheep, cattle, and horses, but they seldom gause any actual injury to these animals. Mostly they are after insects and grain, which they find in greater abundance close to domestic stock. Horses seem, ordinarily, unconcerned at the attentions of magpies. Once I watched a cow that appeared much disturbed by magpies; several times it moved quickly toward one on a fenc,e post and by shaking of its head caused the bird to move on to the next post.
Magpies in the vicinity of one house developed an active feud with a sheep dog, which continued for several months. The birds learned that a certain whistle by a person meant that food was to be given to the dog. They always caine too and sometimes arrived even before the animal. The resulting quarrels over bits of food seemed to trouble the dog so much that it would become aroused over the mere presence of magpies or other birds of similar size and would rush after them with many barks whenever they came close to the ground. Late on a summer afternoon a magpie, perched on a clothesline, was watcYilng the dog eat a bone. Three times the dog started to leave and each time the magpie flew down to the spot only to be driven off by the return of the dog. On the fourth departure the dog did not return when the magpie flew down to the ground, picked up the bone in its bill, and carried it away for at least 60 feet.
Yellow-billed magpies may be called resident wherever they occur even though there may be periods of several days each year when not a single individual can be found. Usually the longest period of absence from the Hastings Reservation each year lasts for about 10 days for the species and possibly longer for many individuals, and it comes in the early part of July. Apparently the helpless young hold the parents at the nesting site even after living conditions may becpme unsuitable in the long, dry days of midsummer. When the young are able to fly and care for themselves, small groups of magpies may be seen for a few days, and then some morning it is realized that not a single magpie is in sight. How far and just where and why they go are questions that have not been answered. Before the birds come back to stay regularly, single individuals may show up for a few hours or a flock may come to roost for a night or so, but obviously these birds are not following the regular schedule which is the routine for the species for most of the year.
This well-marked break in the regularity of seasonal occurrence may result from some local peculiarity in the environment that makes it intolerable for a few weeks. The annual extreme in dryness usually reached at this time when there is a minimum of green vegetation, of animal activity, and of moisture on the ground may drive away these birds, as soon as they are free of nesting duties, along with other species that disappear at about the same time. The exodus may last only until the shortening of the days reduces the evaporation and brings better conditions. Movement toward the coast of only a few miles would bring the birds to cooler and moister places.
The annual departure of the magpies, however, may reflect merely physiological change in the birds independent of the conditions in their habitat at this season. After the young are released from parental care, there may be no attraction in one spot of ground to hold any of the birds: nothing to keep them from wandering freely. But after a rest of a few weeks, faint beginnings of a new reproductive cycle may require a definite home area, and thus the birds come back to begin anew the cycle they have so recently completed.
No doubt a nucleus of the returning birds consists of individuals that left the same place, but the recorded observations indicate that a different number and presumably a slightly different set of individuals return. Some of the recently hatched birds may stay in new spots; they may join with other wandering groups and go to their home sites; they may come back with the parent colony. Thus the returning number may be smaller or larger than the colony at the end of the nesting, but it is rarely of the same size. The stabilization of numbers may require several months, and always it extends over a much longer period than the actual absence of the species from the area.
Thus may be seen, in a species ordinarily considered as strictly resident, behavior that appears exactly like that of migratory kinds which leave for long periods and which travel long distances. Once more it appears that migration is a characteristic of all birds and may be exhibited only in lesser or greater degree. It is not necessarily a basis for sharply limited classifications of species.
Voke: Special attention to study of the voice of the yellow-billed magpie led Richard Hunt to conclude that in fall the birds had only one type of utterance, which, however, was varied. (See Linsdale, 1937.) The three variations or phases listed here he considered distinct enough to be described separately. His statements have been verified in field observations by me. The three phases are as follows:
1. Qua-qua, qua-qua-qua, etc., given in series from two to six qua’s. The utterance is usually quite rapid when the qua’s are more numerous. The note is loud and the expression is rather good natured or well disposed. The timber is raucous. It has more than a slight resemblance to that of the California woodpecker’s “cracker” notes. When birds of the two species are heard calling at the same time, the timber of the two calls is almost indistinguishable. An element in this utterance suggests the rich, harsh, scolding chaack note of Bullock’s oriole.
2. Quack? A single note, rather mild in expression, yet querulous. This note has the same general timber as No. 1.
3. Queck or kek. Sometimes uttered alone and sometimes heightened from phase No. 2. The utterance has an almost absurdly weak tone. It reminds the observer of the call of the black-necked stilt. It is more piping than the other types of notes and is a little nuthatchlike. When first heard it was written down as p~ip. The sounds in this note are less distinct and of the three types it is least spellable and least utterable by a human being.
Comparison of the voices of the two kinds of magpie in America is diffic.ult when the birds must be studied separately. Some observers have been unable to distinguish them on this basis. Wheelock (1904), however, considered the call note of the yellow-billed form as less harsh and loud than that of the black-billed, and this is an observation that might be anticipated after studying other habits and the surroundings of the birds.
The primitive song similar to that of other corvids is produced often by yellow-billed magpies in December, January, and February, and apparently it is a normal part of the early segments of the nesting season. Indications are that it has siguificance in the nesting habits and possibly in other phases of magpie life.
Field marks: The yellow bill provides an easy and certain means of distinguishing this species from the black-billed kind at ordinary distances. Its slightly smaller size is of little help bec.ause the two kinds do not occur together naturally. It may be separated from other birds by the general characters of the black-billed magpie.
Predators: The horned owl may sometimes eat magpies, but so far the evidence is only circumstantial. At the Hasting Reservation, once in June, 20 minutes after three magpies had gone to the roosting place, a great horned owl flew up to a ridge near them where it hooted three times. One of the magpies moved over to investigate and became very excited, calling loudly for about four minutes before becoming quiet again. Other disturbances heard at magpie roosts were thought to be caused by the near presence of a horned owl. Most of these occurred before the birds settled for the night or after they left their roosting trees.
A long series of observations of accipiters and yellow-billed magpies brings the conclusion that magpies must sometimes be captured by sharpshinned or Cooper’s hawks. In summer and fall flocks of magpies carry on almost continuous squabbles with these hawks. Usually the hawks appear to take the initiative in the pursuits, but actual captures have not been seen, and many times the chases seem to be only a form of exercise. Many times when capture appeared certain, the hawk turned away just before reaching the magpie. Once two accipiters flew after the same magpie. Possibly these flights serve to make the magpies less cautious so that capture is easier when the hawk is really hungry.
One flock, in August, was flushed by a Cooper’s hawk that flew into the tree. The hawk pursued the birds as they scattered and then reformed a group, each one flying erratically and yelling in a sort of “confusion chorus.” Termination of the chase was not seen, but it was thought that no capture was made.
Teamwork on the part of two magpies to drive away a sharp-shinned hawk was seen early in November. They took turns maneuvering into position to dive at the hawk as it pursued or fled from the other. The hawk soared upward, which it could do as fast as the magpies could fly. Thus it got above them and out of range of easy flight for them, but it was forced finally to leave the vicinity.
When a sharp-shinned hawk struck and carried off a Zonotrichia, one magpie fled before it, but four others immediately pursued it to a rose thicket, dived at it three times, and forced it to double back and seek refuge in a more dense thicket. The magpies then stationed themselves around the hawk, one above on a fence post, one in the bushes, and two on the ground, and they remained there watching silently for nearly five minutes.
In another example magpies in and close to a blue oak were excited over pursuits by a sharp-shinned hawk and a sparrow hawk, both with quarters in the same tree. The former was much more persistent in its drives, pursuing the magpies more swiftly and going closer to them. Each pursuit, however, was abandoned after about 50 feet, and the birds would return to the tree, the hawk in the lead. Behavior when the magpies were driven from the ground was much the same. On such occasions a harsh, growling note is uttered by each magpie just before the hawk reaches it, and this may have something to do with the latter’s turning aside just before reaching the magpie. No magpie was touched, so far as could be seen.
Once three magpies, all making the growling note, joined in pursuit of a sharpshin, flying about 10 feet behind the hawk, and following it into a sycamore. Another time this hawk pursued a single magpie, which zigzagged to evade three attempts at capture and growled continuously. The mere presence of the hawk as well as its pursuits seemed to bother the magpies. After these disturbances the magpies moved to denser parts of the foliage of a tree and especially to places where there was a protective barrier of branches close overhead. Flocks pursued by hawks in the evening seemed to be harried more persistently than in chases at other times of the day.
Range: Confined to California; nonmigratory.
The range of the yellow-billed magpie extends north in the Sacramento Valley to Redding and Anderson. To the east it is found to Smartsville, Placerville, Hornitos, casually Dunlap, and Three Rivers. The southern limits of its range are in the vicinity of Santa Paub, Santa Barbara, and the Santa Ynez River. West to San Luis Obispo, Paso Robles, and Monterey.
Egg dates: California: 112 records, March 9 to June 2; 56 records, April 9 to 22, indicating the height of the season.