Bent Life History of the Field Sparrow
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 Field Sparrow - the common name and sub-species reflect the nomenclature in use at the time the description was written.
SPIZELLA PUSILLA PUSILLA (Wilson)
Contributed by LAWRENCE H. WALKINSHAW
Though it is a fairly common bird in old fields and brushy fence rows in much of temperate North America, the field sparrow is not so well known as some of its relatives. It rarely nests near houses as do the chipping and song sparrows, it is not brightly colored, and its voice is neither loud nor striking. Yet its plaintive spring song does attract some attention, and interested persons eventually become aware of the singer. Many people know it as a likeable, friendly little bird living in and along the edges of their open, unplowed fields, and its gentleness is often commented on.
T. D. Burleigh (1958) writes of the species in Georgia: "As its name implies, it is a bird of fields and pastures overgrown with briar thickets and deciduous underbrush. Open pine woods are avoided unless changed into open slashings by logging operations, but when this happens, the Field Sparrow soon takes advantage of the new, favorable environment. It is noticeably more retiring than the Chipping Sparrow, and rarely if ever will be seen far from the brushy fields that it prefers. Here it can be found in small flocks during the winter, and here it nests during the, summer."
I had the pleasure of studying this bird for 11 years on an old uncultivated farm near our home in Battle Creek, Mich. Much of the following account is drawn from my published reports (1939b, c, 1945) of those studies. I have also drawn extensively from the unpublished master's thesis of Malcolm P. Crooks, who studied the species on its breeding grounds near Ames, Iowa.
Lumbering in northern Michigan in the nineteenth century, followed by fires, produced thousands of favorable acres for this species which, together with the towhee, clay-colored sparrow, and indigo bunting, followed the lumbering operations north to the Straits of Mackinac. Much of this land has now grown back to forest, but many brushy spots still remain where field sparrows summer. When the young planted pines were small, the field sparrows nested in them; as they became taller the chipping sparrows replaced the field sparrows in them.
My study area, near the northern edge of the species' range in Michigan, consisted of about 100 acres of which (1939b) "about sixteen were woodland and marsh and thirty acres covered merely with grass, so that fifty-four acres, uncultivated and grown up to shrubs proved the most suitable to the species. * * * Through the tall grasses of these regions were to be found patches of blackberry (Rubus), staghorn sumac (Rhus typhina), dwarf sumac (Rhus copallina), New Jersey tea (Ceanothus) and bush clover (Lespedeza). Small trees, oak (Quercus), hickory (Carya) and hawthorn (safaegus) were scattered along the side hills and valleys. On this favorable 89 acres, 23 pairs of birds were known to nest [in 1938], a ratio of one pair to each three acres."
Crooks (MS.) writes that his "principal area studied is 31 acres of abandoned pasture land at Ames, Iowa. It is virgin prairie soil and has been used as pasture for many years, including the summer previous to the study. The terrain is very rolling and includes three separate hills. An oak woods borders half of the southern part of the area with a heavily grazed pasture on the remaining part. * * *
The grassy cover of the area itself is mainly Kentucky bluegrass, Poa pratensis, in the valleys and on the hillsides, and needlegrass, ,Stipa Rpartea, on the hilltops. Some wild barley, Hordeum jubalum, was found in the valleys while the following plants grew mainly on the hillsides: prairie larkspur, Delphinium carolinianum, daisy fleabane, Erigeron ramosus, many-flowered aster, Aster multiflora, honey vervain, Verbena striata, harsh-leaved goldenrod, ,Solidago patula, wild indigo, Baptisia leucant ha, evening primrose, Onagra biennis, bindweed, Polygonum convolvulus, and bull thistle, Cirsium Lanceoiat urn.
The south central to southeastern part of the area is level and is thickly grown with crabapple, Pyrus ioensis, and wild hawthorn, Crataegus moths. Most of the trees in this area are from 2 to 20 feet tall, much larger than the same species of trees in other sections of the area. Each of the eight small valleys has numerous hawthorns with a few crabapples interspersed. Often these trees grow in clumps, giving very thick cover, but they are also scattered over the hillsides so there are no large areas of open land. The trees generally grow taller in the valleys than on the hillsides.
Another area is a pasture of about 25 acres used by 14 cows. The lower part is in woodland, and only the upper 15 acres were used by field sparrows. The type of cover these birds used was sparse with only occasionally hawthorn shrubs that survived the grazing and trampling of the cows. * * * The predominant cover is Kentucky bluegrass. Hawthorn shrubs are scattered thinly over the area, while the overstory is mainly English walnut, Jugians repustris, cottonwood, Populus deltoides, and green ash, Fraxinus ianceolo.ta.
Spring: From their wintering grounds in the southern United States the field sparrows closely follow the warming spring northward.
They migrate mostly at night, traveling in small flocks, often with other sparrows. They do not first appear on their northern breeding grounds in flocks, however, but arrive a few individuals at a time. Suddenly one nice warm morning, an area where hitherto no birds were in evidence is found to have three or four singing males scattered widely over several hundred acres of brush-grown fields. If the weather turns cold, no new birds appear until the next warm spell brings additional males. They continue to trickle in until soon territories are established in most of the available habitat. When in a few weeks the females begin to arrive, they come m more rapidly, but still individually and not in flocks.
The average date of arrival of the first males at Battle Creek was March 31 over a 43-year period; the earliest date was Mar. 14, 1957, and the latest was Apr. 15, 1924. The females generally arrive 3 weeks later, in late April.
Territory: Though not so belligerent about it as many other species, the field sparrow is strongly territorial. Immediately on arrival each male selects a territory which he proclaims and defends against encroachment by other males. He flies from one tree or bush to another on the area he wishes to claim and sings from four or five favored spots, usually the tops of prominent shrubs or saplings. From each of these he pours forth his plaintive little song, most actively during the early morning hours.
If a new male arrives and tries to settle adjacent to his territory, the two birds begin to establish a definite boundary between their domains. This may take several days of intermittent conflict. The established male chases the new bird back and forth along the boundary whenever he encroaches on it until one or the other tires and both stop to rest. The new male sings a low song again and again; the established male sings less frequently. The chase renews, and sometimes the new male chases the established one. Seldom do the two come into bodily contact, the pursued bird managing to keep just out of reach, 2 to 5 feet ahead of the other. Occasionally, however, they do clash in mid-ak, and fall to the ground in a flurry of beating wings and scratching feet. For several days they chase each other for hours along the boundary until it is apparently established. Then both stop chasing and fighting and return to singing, unless one wanders over the line.
Should another male move in on another side, the established bird has the same procedure to go through again. Sometimes when several new males try to establish themselves in the vicinity the chasing conflicts are almost continuous and revolve from one bird to another. It may take the first bird many mornings to maintain his territory, which may also have become much smaller than the many acres he claimed on his first arrival, though still adequate for the needs of a family.
The sizes of the individual territories I found varied somewhat during the 11-year study. Which they seemed to average about 3 acres, some years most were less than 2 acres in extent, and in other years, after a severe fire had swept the area, territories were of 5 or 6 acres.
Stewart and Robbins (1958) report breeding population densities in Maryland varying from a low of 7 territorial males per 100 acres of "damp deciduous scrub with standing dead trees" to highs of 79 males per 100 acres of "abandoned field with open growth of young scrub pine" and 80 per 100 acres of "unsprayed apple orchard with unmowed ground cover."
Observations on color-banded birds showed that usually the older males were the first to return in spring, and each invariably came back to the identical spots he had defended the previous year. Younger males coming to breed for the first time had to find leftover spots or try to squeeze into suitable places between already established territories. Banded birds that did not return I felt certain had perished, and the varying percentages of birds returning each year suggested the death toll was higher some winters than others. Of 50 banded birds that returned in subsequent years, all but one of which was banded as an adult, 27 returned the 2nd year, 12 the 3rd, 5 the 4th, 4 the 5th, and 2 the 6th year.
One of these 6-year birds, as I have detailed elsewhere (1945), reared two broods successfully with his mate that year. The other 6th-year male tried repeatedly to maintain his territory, but was unable to do so against the much stronger new unbanded males. He tried to chase them, but soon they were chasing him the most. After the encounters he flew to the ground and rested, panting as though he was very tired. He remained only a few days, then disappeared, and I never saw him again.
Often between territories were stretches of ground that neither male defended and on which both fed, sometimes only a few feet apart.
Later these feeding grounds were sometimes used by three or four pairs, none of which acted aggressively toward the others on it. Each pair worked along the ground only a few inches apart while another pair fed similarly a foot away.
Courtship: After the male has sung steadily each morning for about 3 weeks during which he has established arid defended his domain in innumerable territorial squabbles, one morning a new bird appears on it, the female for whom he has been waiting and singing. Atfirsthe flies at her as if trying to drive her away, but she merely dives into a bush and hides near the ground. When she reappears he may pounce at here again, but still she does not leave, and Iris attitude quickly changes to one of tolerance and then of acceptance. In a few hours the two become inseparable, and as a rule they rem am so for the entire summer.
The return percentage for females is much smaller than for males. 'rhis is perhaps to be expected, for the male usually accepts the first female that arrives on his territory. If his previous year's mate does not arrive in time to mate with him a second year, she often settles on a nearby territory with a new male, who may or may not have been there the previous year.
As soon as pairing is accomplished, the male sings much less often and less vociferously. The change is so marked that I have usually been able to tell which males are and which are not mated by their singing behavior. For the next several days the two birds stay close together. They fly around the territory only a few feet apart, spend much daylight time feeding together, and they roost very close to one another, usually in the same bush. The male continues to maintain his territorial integrity closely, and chases every other field sparrow that ventures over his boundaries. Sometimes he is extremely busy indeed, tending his mate and fighting territorial battles with one or possibly two neighboring males simultaneously.
Pairs start copulating usually during the nest-building period, from 2 to 5 days prior to egg laying. The act is generally performed early in the morning. Typical were the actions of a female I watched working on her nest at 7:00 one early May morning. Sitting on a low branch, she crouched into the receptive stance, body held rather low across the branch and head extended. The male trilled, fluttered carefully down, mounted her for a few seconds, then flew away with rapid wingbeats and trilling softly. She sat still a moment, their also flew away chipping softly.
Early one morning I watched another male copulate with his mate on the ground and then fly to a far corner of his territory. After he left his mate continued chipping softly and maintained her receptive pose. A neighboring male flew across, copulated with her, and immediately returned to his own territory. She still maintained her position, and a second neighboring male came and copulated with her. Her rightful mate then came flying swiftly back, and drove the second intruder away. He then returned to his mate, and both fed together as usual on the ground, softly chipping to each other.
lvi. P. Crooks (MS.) states: "Copulation usually occurred while the female was perched on a low limb or a small shrub, though occasionally on the ground. All but three of the many copulations witnessed took place during the nest-building period and between 6:45 and 9:30 a.m. I saw one pair copulate April 27, 11 days before the female began nest building and 15 days before she laid her first egg. Two other acts took place July 31, after the females had completed laying all the eggs for the season.
"One pair was seen copulating at 7:15 a.m. on the 3rd and last day of nest building. They had been feeding together for the previous 10 minutes. After the act the female sat quitely for about a minute, then resumed feeding. The male flew a short distance away and preened, chipping very softly meanwhile. At 7:47 they copulated again, and once more at 8:03 a.m. After this both continued to feed and preen, and the female did not go back to nest building the rest of the morning."
Nesting: During normal seasons the field sparrows start nesting in northern United States and Ontario before the trees and shrubs start to leaf out. Consequently the first nest is almost invariably built in a thick clump of weeds or under a grass tuft on or very near the ground. On my Michigan study areas most of the first nests were built beneath the drooping leaves of fall witch-grass, Leptoloma cognata that grew on the sides and tops of the hills. As the season advanced later nests were built off the ground in small thick shrubs.
From 1938 through 1948 I measured and recorded the heights of 661 nests. Of 173 May nests, 135 were on the ground, the highest was 31 centimeters above it, the average height was 7.46 centimeters. Of 239 June nests, 36 were on the ground, the highest was 84 centimeters, the average was 21.35 centimeters. None of the 240 July nests was on the ground; they ranged from 8 to 97 centimeters high and averaged 30.64 centmeters. The nine nests built in August ranged from 15 to 58 centimeters high and average 30.8 centimeters.
The nests were built in the following vegetation: 124 in New Jersey tea bushes, 122 in or under fall witch grass, 80 in blackberry bushes, 61 in small hawthorns, 45 in cinquefoil, 42 in small oaks, 30 in goldenrod clumps, 19 in small hickories, 13 in hazelnut bushes, 11 in sweet clover clumps, 10 in black raspberries, 10 in grape vines, 10 in grass clumps other than Leptoloma, ~ in dwarf sumac, and less than 4 each in Canada thistle, elderberry, catnip, wild rose, wild lettuce, wild spirea, box elder, lespedeza, lilac, and dewberry.
The early nests were made largely of coarse dead grass stems and leaves interwoven with finer grasses and lined with rootlets and hair. Some were lined entirely with black horsehair, some wit.h very fine grass, others with rootlets or a combination of these materials. Later nests usually contained some live grasses. Measurements of 90 nests were: outside diameter 85 to 210 millimeters, average 124.3 millimeters; outside depth 47 to 110 millimeters, average 63.8 millimeters; inside diameter 43 to 55 millimeters, average 50.2 millimeters; and inside depth 25 to 62 millimeters, average 39.3 millimeters.
After examining a number of locations, the female chooses a site and starts building the nest. She does all the work on it, but the male is almost always close by, especially at first nests. Before she starts building, I have seen the male occasionally pick up bits of nesting material and offer them to her, but he always dropped them in a few seconds. He usually flies back and forth with her on her trips for material. At later nests he is often busy tending the young of a prior brood, and the female builds anew without his company. He stays in the vicinity, however, and warns her of approaching danger: mammals, hawks, cowbirds: by chipping in alarm. Both birds seem acutely aware of cowbirds, and when one appears nest building ceases and the birds start innocently feeding.
Most of the work is done between 6:00 and 11:00 am., and periods of construction are interrupted by periods of rest. The female will suddenly start working, build for several minutes, then stop just as suddenly and begin feeding. She may gather some material within a few feet of the nest, but usually gets it from 20 to 65 yards away. She may spend considerable time selecting and gathering it, but then flies directly to the nest, often landing momentarily a few meters away before flying into it. The coarser material for the exterior she usually brings a piece or two at a time, drops it at the site, and goes back for more. As the nest takes shape she brings finer and finer materials, until by the time she is working on the lining, she often brings it in large beakfuls. When interrupted by a cowbird or other intruder, she drops the entire mass, and begins anew later on.
First nests may take 3 to 7 days, usually 4 or 5 days to build. Later nests are generally built in 2 or 3 days, with some lining material occasionally added the 4th morning. Almost invariably after a nest loss, the female lays the first egg in the new nest on the 5th morning.
Eggs: The field sparrow usually lays from three to five and rarely s~x eggs. They are ovate and slightly glossy. The ground is creamy, very pale greenish or bluish white, and speclded, spotted, or occasionally blotched with "army brown," "Verona brown," "sayal brown," "russet," or "hazel." Undermarkings are "light mouse gray," but these are often absent. 'Phe eggs are somewhat delicately marked, and the spots may be either sharply defined or clouded. rrhe markings tend to be concentrated toward the large end, where they may form a loose wreath, but they are often scattered over the entire surface. The measurements of 58 eggs average 17.6 by 13.1 millimeters; the eggs showing the four extremes measure 19.8 by 14.0, 17.8 by 14.8, 1,5.8 by 12.5, and 17.3 by 11.9 millimeters.
A total of 446 clutches in my Michigan study area varied from two to five eggs with an average of 3.37 eggs per set; early nests contained more eggs, later ones fewer, as the following table shows:
Two-eggThree-egg Four-eggFive-egg Total Average Alovtth sets sets sets setssets per set May 0 23 78 7 108 3.85 Juno 6 55 79 2 142 3.54 July 19 148 17 0 184 2. 99 August 3 9 0 0 12 2.75
The measurements of 1,308 eggs averaged 17.9 (16.1: 2t.0) by 13.5 (12.3: 14.7) millimeters. Their average weight was 1.73 (1.35: 2.1) grams. As described above, the eggs vary considerably in color, and those laid by each female were often so distinctive I was confident which female laid them in many nests I found, even before I had positively identified her. Eggs in the same set were often similar in size, and I found no discernible trend in measurements and u-eights of eggs as laid in the set; some first eggs were smaller, some larger than those laid later.
Almost invariably one egg is laid per day until the set is completed. Eggs were laid early in the morning, some before 5:00 am., but the majority between 5:00 and 6:30 a.m. Occasionally the last egg of a clutch was laid slightly later, even after 8:00 am.
Incubation is entirely by the female, but on rare occasions a male may be found on the nest. One male I watched spent the entire night over young that had just hatched when the female was afraid of the trap I had placed over the nest. But if a female was killed, rarely did the male continue the nesting activities until he acquired a new mate. One male fed the small young but did not brood them, and they soon died.
Though the female may be found on the nest almost any time after the first egg is laid, she usually does not start incubating steadily until the night before she lays the last egg. Crooks (MS.) found that females incubated 70 percent of the daylight hours and were off the nest only 30 percent. While the female incubates the male sings near by, stopping occasionally to feed. At times he brings food to the female on the nest, usually large larvae. When the female leaves the nest to feed, the male joins her and they go to the feeding grounds together. While she feeds he remains very alert, and gives a low warning "Zeee-zeee-zeee" if an enemy appears, especially a hawk.
In 74 sets of marked eggs I found the incubation period ranged from 10.5 to 17 days and averaged 11.6 days. In 44 of the 74 clutches the last egg hatched 11 days after it was laid.
Young: On Aug. 7,1938 an egg hatched while I held it in my hand. Pushing with its head, neck, feet, and wings, the young bird finally split the egg near the larger end where the shell had been incised by the egg tooth. It took several minutes to emerge because it rested for a few moments between each attempt. The empty shell weighed 0.3 gram. I placed the fledgling in the nest with a sibling that had hatched an hour earlier, and it curled up in the bottom. When I touched the nest it responded immediately by raising its head and opening its mouth. From my notes I (1939c) described it as follows:
The color of the skin and legs is pinkish, the bill pinkish, grayed near the tomia. The lining of the mouth is yellowish, pinker near the side. The small egg tooth, near the tip of the maxilla, is white and soon disappears. The eyes show in large gray areas beneath the skin and are closed. No suggestions of feather tracts are visible.
The weight of the young bird which hatched in my hand was 1.5 grams. His wing measured from the bend to the tip, 6 mm. The tarsus measured 5 mm. and the culmen 3 mm. * * *
By the second day the primaries showed in dark lines through the skin. The dorsal feather tracts were discernible. The ventral regions showed merely as lines but were easily seen on the third day. The occipital regions were dotted black at two and one-half days.
Newborn nestlings varied in weight from 0.9 to 1.5 grams and averaged 1.62 grams on the day of hatching. On the 2nd day they weighed 3.67 grams, on the 3d day 5.43 grams, on the 4th 5.43, on the 5th 7.31, 6th 8.61, 7th 9.64, 8th 10.2, and 9th 10.1 grams. They attained the full adult weight of 13 grams on the 13th day.
The female stays on the nest and broods the young at night until they are 6 days old; females were found on the nest over 6-day young at night only about 50 percent of the time, and over 7-day young only 25 percent. She also broods the young a great deal during the daytime during early nestling life, and especially during periods of inclement weather. This decreases steadily as the young feather out, and ceases entirely by the 6th day.
Both parents feed the young and tend to nest sanitation. As the fledglings mature they are fed more and more frequently. At a nest with three young under 3 days old, the parents brought food 23 times (the female 18 times, the male 5) and removed excreta 3 times during 312 minutes of observation. When the young were 5 and 6 days old they were fed 11 times in 100 minutes, an average of once every 9.1 minutes. At 7 and 8 days of age they were fed 25 times in 253 minutes; the shortest interval between feedings was 1 minute, the longest 23 minutes, and the average 10.1 minutes. Young were also fed more often late in the day than at mid-day. Three young about 6 days old in a nest I watched in early August between 7:50 and 8:20 p.m. were fed 7 times or once every 4.2 minutes.
Lynds Jones (1913) watched a pair of field sparrows feeding four 6- to 8-day-old nestlings for 19 hours and 12 minutes. "During that time 237 pieces of food were delivered and 31 excreta removed. The shortest time between feedings was one minute and the longest 21 minutes, the average being 10 minutes between feedings. If each of the four young were [sic] fed in regular rotation each received food once in 40 minutes. There were 154 Geometrid larvae (104 green, 37 brown, 13 white), 45 grasshoppers, 24 moths, 3 scattering, and 11 unknown."
Undisturbed young usually left the nest when between 7 and 8 days of age, and when disturbed, often at 6 days. The departing fledglings hopped first to the nest rim, then to the ground. When disturbed they often erupted from the nest in a group, tumbling out awkwardly, each heading in a different direction. They usually hopped unsteadily on the ground a short distance and then stopped. Sometimes the female would lead them farther away from the nest and then leave them. They kept xdthin their own territories as a rule, and seldom wandered into neighboring ones.
After leaving the nest the young remain near it on the ground or in a low bush, where the parents feed them about once every S to 10 minutes. If they are not fed often enough they begin to "chip," which they never do in the nest, and the parents seem to try to keep them quiet by continuous feeding. When they have been out of the nest 5 days they can fly short distances, but the parents still keep them together in their territory. The male now assumes more and more of the care of the nestlings, and all of it when the female starts to renest.
By the time the young are 25 days old, their tails have reached approximately adult length, and shortly thereafter they are on their own. Malcolm Crooks (MS.) gives the age of independence in Iowa as attained between 26 and 34 days. I have watched adults feeding young from 25 to 30 days of age at different nests gradually acquiring their independence. At this point in my study area the young gathered in small flocks of 10 to 12 individuals in the dense thickets of hawthornes in the general nesting area. The male field sparrows to whom the territories belonged did not bother them, and the young birds, now fully grown, fed and played together, often flying up and down at each other, and then returning to perch in the hawthornes.
Late in the summer some of the young males occasionally sang brief snatches of sweet song, much shorter than the adult version.
If undisturbed by predators and other mishaps, field sparrows in Michigan probably raise three broods of young each summer. I have known two pairs to accomplish this during my 11-year study. I found the nest of one banded pair May 28, 1939 with four young that left the nest June 4. Their second nest I found June 28, and its four young left July 2 and 3. On July 21 I found their third nest, whose three eggs hatched July 28, and all three young left the nest successfully August 4th.
The usual field sparrow pair is seldom this fortunate. Too many enemies are searching for food, too many cowbirds are looking for foster parents for their eggs. Consequently the female field sparrow often builds many extra nests during the summer. The most I recorded for one female was seven in one season. I found her first nest May 24, 1945; its three eggs hatched May 28, and the nestlings were gone May 30. On June 1 she was building a new nest, in which she laid two eggs June 4 and 5; these were gone on June 6. I found her third nest newly completed on June 11; she laid one egg in it June 13 which was gone June 14, and she deserted. Her next nest I found June 26 with one egg; the next morning, though she had laid her second egg, a cowbird had also laid one and her first egg was gone, and again she deserted. She finished her next nest July 1 and laid three eggs in it July 2, 3, and 4; when two of these disappeared July 5 she left it and started the next day on a new nest, which she finished July 8. In this she laid three eggs July 9, 10, and 11, but the morning of July 18 it had been destroyed. She built her seventh nest July 20: 21 and laid three more eggs in it July 22, 23, and 24, which hatched August 3 and 4. On August 9 the nest was torn to pieces and the young gone. Thus from May 14, when I estimate she laid her first egg, through August 9 when her last nest was destroyed, a period of 87 days, she laid a total of 17 eggs in her seven nests; 6 of her eggs hatched, but she fledged no young. I have records of females laying 18 eggs in a single summer.
My (1945) published totals on 462 nests observed showed 159 or 34.41 percent of them successful, and from 1,235 eggs laid, 447 young fledged, or 36.19 percent. In Malcolm P. Crooks' (MS.) Iowa study six nests of 17 fledged young, yielded an almost identical 35 percent nest success. Of the 45 eggs laid in these 17 nests, 27 or 60 percent hatched, but only 12 young, or 26.66 percent survived to migration time.
Plumages: Dwight (1900) gives the color of the natal down as "mouse gray." D. K. and N. S. Wetherbee (1961) describe the hatchling as "light orange with down that varied from light to dark gray.
The upper mandible was gray on the anterior half; the mouth was bright red and the rictal flanges yellow." The natal down is replaced by the heavily streaked juvenal plumage, which G. M. Sutton (1935) describes as follows:
* * * In general appearance the eight to ten day old birds are more streaked than are older birds, especially on the crown and chest. By the time the juvenal plumage is fully unsheathed there is practically no streaking on the crown and hind neck, and the streaks of the underparts have much the appearance of spots or flecks. The postjuvenal molt begins when the individual is about sixteen days old, toward the end of June or early in July in young of the first brood. This molt involves only the body plumage (including the wing coverts) as a rule, though Dwight tells us that "the middle pair of rectrices is occasionally renewed."
* * * Four specimens at hand, all with fully developed juvenal flight feathers (July 14 to 30), are in various stages of the postjuvenal molt, the back in every case having two distinct types of feathers: the comparatively dull, huffy-edged, loose, plumulaceous type characteristic of the juvenal plumage in all Fringillidac; and the sleek, firm, red-brown type that is characteristic either of this species' first winter plumage or of some intermediate, postjuvenel plumage. The specimen taken July 30 (U.M.M.Z. No. 75012), is naturally the brightest of these, about a dozen new red-brown feathers showing plainly in the back.
In a series of 15 juvenal field sparrows Sutton found a considerable variation in the amount of streaking below. Not one of his Michigan specimens showed any streaking on the throat as Dwight (1900) mentions.
Of the first fall and winter plumage T. S. Roberts (1932) notes. "The stripes on underparts are lost at the postjuvenal molt and the young closely resembles the adult, which, in the fall and winter dress, are more rusty and huffy than in the spring and summer plumage." The breeding adult plumage which, as Dwight noted, is acquired largely by wear, Roberts goes on to describe thusly:
Grown and nape rusty-brown with a more or less evident median gray stripe; sides of head gray with a rusty-brown stripe back of eye and a small spot in front of eye; an indistinct buffy eye-ring; back and scapulars rusty-brown, streaked with black, rufous, and buff; rump and upper tail-coverts light grayish-brown, lightly if at all streaked; below grayish-buff on breast and sides, paler on throat, and shading behind into white or grayish-white on abdomen, belly, and under tail-coverts; wings dusky, primaries narrowly edged with light, secondaries and tertiaries more broadly with rufous; coverts dark centrally, edged with rufous, and the middle and greater tipped with white or huffy-white, forming two more or less conspicuous wing-bars; tail grayish-brown, outer feathers narrowly edged with white. Bill pinkish; legs and feet pale flesh color, darker on feet; iris brown.
Food: In his classic work, Judd (1901) notes that the field sparrow eats about 41 percent animal and 59 percent vegetable matter. The animal food consists of weevils, beetles (May, click, leaf, ground, and tiger), grasshoppers, caterpillars, leafhoppers, ants, flies, wasps, and spiders. The vegetable matter is made up of grass seeds (crab, pigeon, broomsedge), chickweed, purslane, lamb's quarters, gromwell, knot-weed, wood-sorrel, with some oats after harvesting time.
Martin, Zim, and Nelson (1951) state of the field sparrow's animal food: "Insects eaten consist chiefly of beetles, grasshoppers, and caterpillars. Various other invertebrates, including ants and other Hymenoptera, leafhoppers, true bugs, and spiders are also consumed." Plant food from 137 specimens from the northeast consisted mainly of bristlegrass, crabgrass, broomsedge, panicgrass, some oats, and lesser amounts of dropseed grass, sheep sorrel, pigweed, ragweed, wood sorrel, timothy, and goosefoot. From 38 stomachs from the prairie states, the main plants eaten were bristlegrass, panicgrass, dropseedgrass, and crabgrass, with lesser amounts of vervain, goosefoot, wheat, redtop, and gromwell.
Crooks (MS.) noted that the field sparrows began feeding before it was completely light in the morning; they fed a great deal up to about 9 a.m., intermittently for brief periods during the day, and then heavily again from 6 to 6:30 in the evening. He also noted that the female fed for longer periods, up to 14 minutes at a time, while the male's feeding periods averaged around 4 minutes.
My observations confirm those of Malcolm Crooks. Pairs often fed for many hours during the early morning before they nested, and seemed to be picking up grass and other seeds. During nesting they continued to feed on seeds, but began eating many more insects, including grasshoppers and large larvae, and the incubating female devoured any ants that ventured into the nest. The nestlings, as stated above, are fed entirely on insect food. Later in the summer as the flocks began to form they again fed largely on grass seeds.
Voice: Much has been written of the song of the field sparrow, which Cornelius Weygandt (1930) epitomized most aptly as "a little song, a trembling and lonely melody, minor, but never uncheerful." To me the song sounds like "seeea-seeea-seeea-seeea-wee-wee-weewee." The male usually begins to sing just as day begins to break, usually from a prominent perch on his territory, and, if he is not mated, he continues on and off during the entire day, though noteably less in the afternoon. After he is paired he sings little after daybreak until nestings starts, when he sings more often, and always most during the early morning, usually at the rate of about three or four times per minute.
F. H. Allen, in notes to Mr. Bent, describes the commonest song of the field sparrow as "several long, slow notes with falling inflection followed by a rapid trill on a higher pitch." A bird he heard at West Roxbury, Mass., July 17, 1916 "held himself erect, threw back his head, and kept his bill open while singing, the mandibles moving only slightly at the beginning, and gradually closing with the final trill."
Aretas A. Saunders (1922b) writes: "The Field Sparrow song is of short duration. The average length of the song, based on the one hundred and forty-nine records I now have, is 2.7 seconds. The longest song of all is 4.6 seconds, and the shortest 1.6 seconds. * * * One specific time character, that holds in practically all songs, is acceleration. The introductory notes are the longest and the terminal notes the shortest of the song, the latter often so rapidly repeated that they cannot be counted and must be recorded as a trill." He notes that the pitch of a single song never varies greatly. The range is exactly one octave, from D"" to D"'; most songs range between C"" and F"'. The song varies little in intensity, and its quality of a clear, sweet whistle makes it very attractive.
A. R. Brand (1938) reports the approximate mean vibration of a field sparrow song at 4,100 per second, with the highest note 5,100 and the lowest 3,650.
In addition to the song, the field sparrows have a number of other notes. When they are 4 or 5 days old, nestlings utter a low "Zweep" or "Zeeep" when the parent approaches with food. As the female feeds the young she gives a low "Zeee, Zeee." While searching for food for the young the male and female call to each other with a low "zee-zee-zee-zee" or a "chup-zup-zup-zup-zup." After the young, leave the nest they give a sharp "chip" when they are hungry. The adults use a similar sharp "chip" for an alarm note, often repeated in a rapid chipping. When a hawk appears over the breeding area, all the field sparrows give a penetrating "zeeeeeeee" and disappear into the cover. A male trying to entice a neighboring female was heard to give two calls, a "chip-chip-zip-zip-zip-zip," or just a plain "zip-zip-zip-zip-zip."
Behavior: J. S. Y. Hoyt (1948) reports a pair of field sparrows nesting within 18 inches of the nest of a pair of red-eyed towhees in a small white pine. Both species fed the young in both nests at time; if the young in one nest did not offer to take food from the parent, the old bird went over and fed the young in the other nest.
An outstanding characteristic of the field sparrow is its gentleness. It is seldom aggressive toward other species or its own kind. It feeds amicably through the fall and winter in mixed flocks of its own and other species. Its cheerful yet plaintive song, usually given 5 to 25 feet up in a tree on its territory, adds much to its personality.
Field marks: The field sparrow is most apt to he confused with its congeners, the chipping and clay-colored sparrows, with which it is often found in fall and winter. Its most striking field mark is its pink bill. Its chestnut cap is not so bright as that of the chipping sparrow, and lacks the center stripe of the clay-color's cap. Peterson (1947) also stresses: "Except for the pink bill, it resembles the Tree Sparrow and the Chippy. It has less noticeable facial striping; this and the eye-ring gives the bird a blank expression, Young birds in summer are finely streaked below like young Chippies, but lack the well-marked head-stripings."
Enemies: Field sparrows are subject to predation by the usual animals capable of catching small birds. Cats, dogs, foxes, raccoons, skunks, and weasels must all take the contents of ground nests occasionally. Evidence points to cats killing a number of females on their nests at night in my study area. Dogs destroyed at least one nest, and probably more. Once a weasel working through the neighborhood of several nests came to my squeaking. Smaller mammals such as spermophiles, chipmunks, and field mice were also present, and I was sure some of them took eggs or young at times, usually when the nest contents disappeared one at a time.
Among bird predators, Cooper's and sharp-shinned hawks were present during most of the nesting season, and whenever they appeared the field sparrows took to cover. They also showed alarm when blue jays came near. Jays foraged commonly in family groups over the sparrow territories from mid-summer on, and definitely destroyed at least one nest. Crows also appeared now and then, but seldom fed in the sparrow nesting area. M. P. Crooks (MS.) watched a house wren destroy a set of field sparrow eggs in Iowa. E. A. Mason (1938a) reports a loggerhead shrike capturing a field sparrow he had just banded and released in Summerville, S.C.
Snakes also take a considerable toll of birds nesting on or near the ground. I (1943) reported incidents of nests of the chipping sparrow, prothonotary warbler, and goldfinch despoiled, respectively, by a garter snake, a pilot snake, and a blue racer in Michigan. On July 11, 1943, I found a milk snake swallowing the eggs from a field sparrow nest in my study area; I killed the snake, extricated the eggs, and put them back in the nest. E. D. Nauman (1929) reports a rattlesnake eating an adult and a nestful of nearly grown young field sparrows in Iowa.
Unquestionably the chief enemy of the field sparrow in northern United States is the brown-headed cowbird. Cowbirds are almost always present in or near the fields where the sparrows, whose nests are not too hard to find, are among the commonest breeding small birds. Though I have seen them outwit the cowbirds many times, nevertheless 182, or 27.4 percent of 664 nests in my study area were parasitized. G. 0. Hendrickson (1953) reports 80 percent of 16 nests parasitized at Ames, Iowa, and R. T. Norris (1947) only 15.8 percent of 57 nests at Butler, Pa. In my 182 nests the cowbirds laid 234 Eggs: 135 had one, 42 had two, and 5 had three eggs. The field sparrows immediately deserted 100 of the 182 nests (with 134 cowbird eggs) and from the 234 eggs fledged only 27 cowbirds, a nesting success of 11.6 percent. While the average production of only 2.45 young cowbirds per year for the 100-acre tract over the 11-year period does not seem overly serious, nevertheless cowbird interference retarded the field sparrow nesting cycle and production of young considerably. As the cowbirds usually laid no eggs after mid-July, the sparrows did not have this trouble to contend with during their last nesting.
H. S. Peters (1936) lists 13 different ectoparasites found on the field sparrow, including four species of biting lice (Mallophaga), two of flies, four of mites, arid three of t.icks. R. 0. Malcomson (1960) adds another Mallophaga to this list, and C. Herman (1944) reports finding the blood protozoan, Plasmodium in the species twice.
Unseasonable spells of inclement weather such as extreme cold with snoxv or sleet, extreme heat, and heavy wind and rain all take their toll of this species. M. P. Crooks (MS.) reports all the eggs and young he was studying were lost during a late spring snowstorm. In early nests before the vegetation has leafed out enough to provide shade, the hot sun may cause the young to leave the nest prematurely. I have found a number of such young dead within a short distance of the nest, killed either by the heat or by small red ants which had already partly devoured them. These ants were found to kill healthy small young, left unprotected in the nest by adults, in an hour. Heavy downpours with high xvinds often wrecked nests in bushes or dumped eggs or young out onto the ground.
I have found many field sparrows killed by cars on the roads. The most recent modern perils for these and other night migrants are the ceiometer beams at airports and tall television towers. A. H. Laskey (1957, 1960) reports at least 23 field sparrows killed by flying into the tower at Nashville, Tenn. H. L. Stoddard (1962) reports 24 field sparrows among the some 15,200 individual birds of 150 species killed at a television tower 20 miles north of Tallahassee, Fla., between 1955 and 1961.
Fall and winter: After nesting activities in Michigan cease in late summer adults and young start forming flocks that remain on their favorite brushy fields throughout most of September. Hundreds may be found together in especially good feeding areas. They roost at night in small trees or bushes still heavily covered with leaves. Banding operations show the birds start moving southward in mid-September, and the population changes continually as the migrants keep coming through until the 2nd week of October. Though individuals occasionally linger into November, most have left by mid-October.
In Nashville, Tenn., where the species both breeds and winters, Mrs. Laskey (1934b) found, through banding, that the population changed regularly. Though she captured immature birds she considered to be migrants as early as July 19, most of the migrants came through in October and returned again in March.
In Alabama Imliof (1962) says: "In winter it is abundant and widespread throughout the state. Usually it occurs in brushy fields, old overgrown pastures, wood borders, and the like, and it is the most common sparrow of broomsedge fields." Burleigh (1958) says about the same of it for Georgia: "During the winter, the Field Sparrow is an abundant bird over the entire state, its numbers being increased by numerous flocks of transients from farther north." In Florida Howell (1932) says "The birds are rather shy and retiring, and are found usually at some distance from farm buildings. * * * In winter they often associate with Chipping Sparrows and other ground-feeding species.
Range: Minnesota, Michigan, southern Quebec and southern Maine south to southern Texas, the Gulf Coast, and southern Florida.
Breeding Range: The eastern field sparrow breeds from central Minnesota (Nisswa), north central Wisconsin (Holcombe; Oconto County), north central Michigan (Crawford County), southern Ontario (Wasaga Beach, Arnprior), southwestern Quebec (Montreal), and southern Maine (Bangor) south to eastern Texas, northwestern and southeastern Louisiana (De Soto Parish, Hohen Solms), southern Mississippi (casually at Bioxi), central and southeastern Alabama (Greensboro, Abbeville), and Southern Georgia (Savannah); casually in northern Florida (Waukeenah).
Winter Range: Winters from eastern Kansas, central eastern Iowa (Davenport), southern Wisconsin (Beloit, Lake Geneva, Racine, Milwaukee), central Michigan (Traverse City, Midland), southern Ontario (London, Hamilton, Richmond Hill, Toronto, Pickering), central New York (Rochester, Syracuse, Dutchess County), Massachusetts (Belmont, Newburyport), and coastal New Hampshire south to southern Texas (Brownsville), the Gulf coast, and central Florida (Tarpon Springs, Winter Park); casually south to Nuevo Le6n (Linares) and southern Florida (Cape Sable).
Migration: The data deal with the species as a whole. Early dates of spring arrival are: District of Columbia: March 5. Maryland: Laurel, March 8. Pennsylvania: Somerset County, March 6; Beaver, March 12; State College, March 15. New Jersey: Cape May, March 22. New York: Tioga County, March 4; Westchester County, March 7. Connecticut: New Haven, March 14. Massachusetts: Concord, March 26; Martha's Vineyard, March 28 (median of 7 years, April 5). New Hampshire: New Hampton, March 27 (median of 21 years, April 14). Malne: Lewiston, April 14. Quebec: Montreal area, April 20 (median of 7 years, May 2). Illinois: Urbana, February 20 (median of 20 years, March 22); Chicago, March 10 (average of 16 years, March 27). Indiana: Wayne County, March 16 (median of 8 years, March 26). Ohio: central Ohio, March 9 (median of 40 years, March 12). Michigan: DetroitWindsor area, March 3; Battle Creek, March 14 (average of 43 years, March 31). Iowa: Sioux City, March 27 (median of 38 years, April 10). Minnesota: Minneapolis: St. Paul, March 23 (median of 15 years, April 19). Kansas: northeastern Kansas, March 4 (median of 13 years, April 10). Nebraska: Douglas, March 26. South Dakota: Sioux Falls, April 14 (average of 7 years, April 28).
Late dates of spring departure are: Florida: northern peninsula, April 21; Gainesville, April 17. Alabama: Gull Shores, May 1. Georgia: Fitzgerald, April 30. Maryland: Laurel, April 29. 1111nois: Chicago, May 31 (average of 16 years, May 23). Ohiocentral Ohio, median of 40 years, May 3. Texas: Sinton, April 12 (median of 5 years, April 9). Nebraska: Webster, May 2.
Early dates of fall arrival are: Nebraska: Logan, September 15. Ohio-central Ohio, median of 40 years, September 15. Illinois: Chicago, average of 16 years, September 22. Mississippi: Gulfport, October 28. New York: Tiana Beach, September 27. Maryland: Baltimore County, September 13; Laurel, October 2. Georgia: Fitzgerald, October 6. Alabama: Foley, August 28. Florida: Tallahassee, September 22; Pensacola, November 2.
Late dates of fall departure are: South Dakota: Millette, October 7. Nebraska: Red Cloud, November 22; Lincoln, November 9. Kansas: northeastern Kansas, November 12 (median of 11 years, October 26). Minnesota: Minneapolis: St. Paul, October 17 (median of 6 years, September 17). Wisconsin: Milton, December 1, Waukesha County, November 11. Iowa: Sioux City, October 29 (median of 38 years, October 17). Michigan: Battle Creek, November 7 (average of 36 years, October 18). Ohio-Buckeye Lake, November 12 (median, October 30). Indiana: Wayne County, November 15 (median of 5 years, November 11). Illinois: Chicago, December 9 (average of 16 years, October 28). Tennessee: Nashville, November 16. New Brunswick: Kent Island, October 14. Quebec : Montreal area, October 23 (median of 7 years, October 8). New Hampshire: New Hampton, November 6 (median of 21 years, October 17). Massachusetts: Concord, November 25; Martha's Vineyard, November 12. Connecticut: New Haven, November 30. New York: Rockland County, November 19; New York City, November 13. New Jersey: Cape May, November 21. Pennsylvama: McConnellsburg, November 29.
Egg dates: Connecticut: 20 records, May 18 to June 13.
Georgia: 35 records, April 7 to August 12.
Illinois: 79 records, April 20 to August 11; 40 records, May 17 to June 10.
Iowa: 17 records, May 12 to July 30.
Kentucky: 10 records, May 7 to June 5.
Manitoba: 1 record, June 30.
Maryland: 265 records, April 21 to August 25; 105 records, May 10 to June 8.
Massachusetts: 35 records, May 15 to July 25; 18 records, May 21 to June 10.
Michigan: 708 records, April 28 to September 18; 55 records, May 15 to June 30.
Missouri: 7 records, May 4 to May 17.
New Jersey: 35 records, May 5 to July 13; 19 records, May 15 to May 31.
New York: 23 records, May 3 to August 10; 11 records, June 10 to July 22.
Ontario: 21 records, May.. 9 to July 19; 11 records, June 10 to July 22.
Texas: 3 records, April 22 to May 4.
West Virginia: 65 records, April 30 to July 16; 36 records, May 15 to May 31.
WESTERN FIELD SPARROW
SPIZELLA PUSILLA ARENACEA Chadbourne
Contributed by LAWRENCE H. WALKINSHAW
Arthur P. Chadbourne described this western race of the field sparrow in 1886 from wintering specimens taken in Laredo, Texas. He diagnosed the subspecies as "Similar to S. pu.siila but with the rufous replaced by brownish-ash, and of slightly larger size, with decidedly longer tail and somewhat heavier Fill." The following year C. Hart Merriam gave specific rank to breeding specimens from South Dakota and Nebraska. Later evidence showed the form to be only subspecifically distinct, and it has been so recognized by the A.O.U. Check-List ever since.
Little has been published about the ecology or the breeding habits of this form, which presumably do not differ materially from those of the eastern race.
Range: Montana and North Dakota to Goahuila, Nuevo Le6n, Tamaulipas, and Louisiana.
Breeding Range: The western field sparrow breeds from northwestern (rarely) and southeastern Montana (Billings, Paris) and northern North Dakota (Charlson, Minnewauken) south to northeastern Colorado (Boulder, Fort Morgan), western and central southern Oklahoma (Arnett, Arbuckle Mountains, Lake Texoma), and Kansas (intergrades in east with S. p. pusilla).
Winter Range: Winters from Kansas, central Oldahoma (Oklahoma City; Creek County), northern Arkansas (Winslow), and northwestern Mississippi (Rosedale) south to northern Coahuila (Sabinas), central Nuevo Le6n (Monterrey), northeastern Tamaulipas (Matamoros), and southeastern Louisiana (Mandeville).
Casual records: Casual in migration west to New Mexico (Lea County, Los Alamos) and east to eastern Iowa (Giard) and western Tennessee (Tiptonville, Hickory Withe).
SPIZELLA WORTHENI WORTHENI Ridgway
Contributed by J. DAN WEBSTER
It sounded like a chipping sparrow; however, there was a peculiar initial phrase: a slur that was most unchippy-like: and so I investigated. The sparrow sang from a waist-high thorny bush, and scrutiny with binoculars convinced me that the bird was one I had been anxious to meet: the little known Worthen's sparrow. This spot where I first encountered the species is still the only one where I have ever seen it, and other recorded localities are few. The only record from the area of the A.O.U. Check-List is the type specimen, which was collected by C. W. Worthen at Silver City, N. Mex., June 16, 1882; otherwise the species has been found only in Mexico.
There is some doubt as to whether the Worthen's sparrow is distinct from the field sparrow. Burleigh and Lowery (1942) hold that the two are conspecific; whereas Webster and Orr (1954a) argue that they are not. Present information is inadequate for any real conclusion. However, the present investigation turned up one more argument in favor of specific status for wortheni, viz.: there is definite sexual dimorphism in plumage coloration in wortheni: more, in fact, than in any other species of the genus Spizella excepting, possibly, atrogularis. Ridgway's (1901) statement, "Sexes alike," is erroneous.
Ecology: Brown (in Thayer, 1925) found the species near Miquihuana, Tamaulipas, breeding in weedy, overgrown cornfields and in prickly shrubs in uncultivated foothills. Ray (in Burleigh and Lowery, 1942) collected a specimen in shrubby desert near Saltillo, Coahuila, in April, which was probably a migrant. My own observations (Webster and Orr, 1954a; Webster, 1954, 1958, and MS.) concern a colony, estimated at eight breeding pairs in 1954, 9 miles northwest of Sombrerete, Zacatecas, at 7,800 feet elevation on the northeast shoulder of Cerro Gordo. Here the birds occupied a tract of heavily grazed open rangeland or grassland which was dotted with small trees and bushes. Shrubby junipers (Juniperus deppeana) were the chief woody plants, averaging from 15 to 35 yards apart; most of them were 6 to 8 feet tall, the highest 12 feet. Other shrubs, sparsely distributed, were Cowania mexicana, Acacia sp., Opuntia sp., and Pinus edulis. Ground cover consisted of numerous tufts of the shrub Brickellia spinulosa 6 to 12 inches high, and a sparse sod of grama grass (Bouteloua sp.) and herbaceous weeds. The commonest associated birds in June and July were the brown towhee, bush-tit, lark sparrow, eastern meadowlark, house finch, and chipping sparrow.
Habits: On sunny mornings in June and early July the male Worthen's sparrows sang almost continually from daylight until 10:00 or 11:00 a.m. One territory was 100 by 25 yards, and others seemed about the same size; several shrubs or trees served as song perches. Feeding was ordinarily on the ground, but once a~ bird jumped into the air to capture two flying insects and once one was seen foraging in a low bush. Singing was invariably from a perch, and danger always caused the birds to take refuge in a bush. Feeding was on the territory, except that once a rival male was tolerated for a few minutes while both fed on the one's territory. There was usually no water on the nesting area in June and July, and occasionally one or another bird flew off toward the creek ~ to 1 )~ miles away, presumably for a drink. Usually rival males were driven off vigorously with an aerial chase and fight, followed by strong singing by the victorious defender.
Brown (in Thayer, 1925) writes, "I found the Worthen Sparrow breeding in overgrown cornfields where it nested: invariably in low weeds of the mint family.
"In habits the Worthen Sparrow is almost exclusively terrestrial, though during the nesting season it sings from the tops of high weeds. Its song is a faint trill. In one instance I saw a Worthen Sparrow, perched on a high weed, dart into the air several times after insects, like a flycatcher.
"Outside of the cornfields, in the foothills, where the land is uncultivated and conditions are natural, this bird nests in prickly shrubs, the highest being about four feet from the ground."
Voice: The song of the male Worthen's sparrow is sometimes a trill indistinguishable to my ear from that of the chipping sparrow. More of ten, however, there is an initial slurred-down note followed by the trill: ~ or pee chrrm-r. The entire peee is usually pitched lower than the trill, but one bird sang the initial phrase several tones higher than the trill which followed. Most birds sang the initial phrase softer, with less carrying power than the trill. As compared with the field sparrow, the middle notes are lacking and there is no gradual aecelerando.
Nest: The nest of the species is unknown save for the several Brown collected at Miquihuana, Tamaulipas, in 1924. Brown (in Thayer, 1925) describes the nest as "well made, compact, and well concealed. It is constructed of rootlets and grasses and lined with fine fibers and sometimes with horsehair and is placed without exception within six inches of the ground. Sometimes it even rests upon the ground like a Song Sparrow's nest, but supported by the weed in which it is built."
Charles H. Blake, who kindly examined for me the 27 nests complete with eggs in t.he Thayer Collection at Harvard writes: "In dimensions and wall construction I doubt that the nests could be told from those of field sparrows. The lining is a little more like that used by the chipping sparrow, mostly composed of very fine rootlets. Some nests include a few long, black hairs. The external diameter runs from 75 to 95, mostly about 80 to 85 millimeters. The internal diameter is 45 to 50, and the depth 25 to 35, mostly 30 to 35 millimeters. The smallest nests are about 65 millimeters in external diameter, but without reduction of the internal diameter."
Eggs: Worthen's sparrow usually lays three or four eggs. They are ovate with some tending toward elongate ovate, and are slightly glossy. The "bluish glaucous~~ or "Etain blue" ground is speckled, spotted, and occasionally blotched with "natal brown,' "snuff brown," "Mars' brown," or "Brussels brown." The majority of eggs do not seem to have undermarkings, but when present these are "light neutral gray." The spottings, either sharply defined or somewhat cloudy, are generally concentrated toward the large end. The measurements of 50 eggs average 18.1 by 13.4 millimeters; the eggs showing the four extremes measure 19.7 by 13.9, 17.9 by 14.5, 16.2 by 13.1, and 18.3 by 12.1 millimeters.
Field marks: A slender, clear-breasted sparrow with a pink bill and a white eye ring. Persons from the eastern United States will note the resemblance to the field sparrow; the differences are the grayer, more ashy shade of the back, the lack of the brown postocular stripe, and the presence of the eye ring in the Worthen's sparrow. Adult males are marked, in addition, by a prominent gray nape, or collar, and a gray forehead, rather sharply setting off the chestnut pileum.
Plumages: The immature plumages have never been described. A female taken July 5,1924, at Miquihuana and now in the Museum of Comparative Zoology, is similar to a juvenal-plumaged field sparrow, but differs in possessing a prominent, pale huffy eye ring and a more prominent and more buffy postocular stripe. The flight feathers are full length, but only a few postjuvenal feathers can be distinguished: on the crown, amongst the scapulars, and possibly the tertials. The general effect of the dorsum is nearest huffy brown. The ground color of the crown, back, and wings is close to bulfy brown, streaked prominently on the back and moderately on the crown and nape with a blackish brownish olive. The nape and forehead are not very distinctly set off; they are between dark gray and brownish olive in color. The underparts are generally a pale smoke gray, darker anteriorly and tinged slightly with buffy and streaked prominently on breast and flanks with blackish olive. *
An adult female in rather fresh plumage (December 10) is nearest huffy brown on the back, with the ground color a little more cinnamoneous and blacker than that shade and streaked prominently with blackish olive. The scapular, secondaries, and coverts are edged with buffy brown, which forms very indistinct wing bars. The crown is buffy brown, obscurely streaked with a blackish shade of the same. The nape is a little grayer than the crown and back, but is not well differentiated. The forehead is dark gray with a buffy brown tinge. The side of the head is medium gray, except for a narrow white eye ring; the auriculars are tinged with buffy brown. The underparts are clear, pale gray on the belly and under tail coverts darkening to smoke gray on the breast and throat and between smoke gray and buffy brown on the flanks. The flight feathers are dark blackish olive, the rectrices and primaries narrowly edged laterally with smoke gray.
No male specimen in completely fresh plumage has been seen. Specimens taken from March to July differ from females in the coloration of the head; the pileum in males is more chestnut, less streaked, and more distinctly demarcated from the more purely gray nape (collar) and forehead. Specifically, the pileum of adult males in nuptial plumage is between chestnut and tawny or blackish between chestnut and tawny, more or less obscurely streaked with a darker shade of the same tint. The nape is medium gray or dark gray, sometimes obscurely streaked with blackish. The side of the head, save for the white eye ring, is pure gray, from dark gray to medium gray. However, one specimen (Louisiana State University Museum)
*MI colors in this section were compared directly with the Palmer arid Reilly (1956) color standards. taken in April, has the auriculars, especially dorsally, tinged with huffy brown.
Examination of most of the extant specimens (42) of Worthen's sparrows provides the following information on molts: as in the field sparrow (Sutton, 1935) the juvenal body plumage is at least partially lost and replaced from July to September by an adult-looking first winter plumage. I took two females in postjuvenal molt in Zacatecas, Aug. 16, 1961. A scanty prenuptial molt in May, sometimes extending into June and even July, includes primary 1 and secondaries 1: 3 and sometimes also primary 2 and secondaries 4: 7 and 1 or 2 or all 12 rectrices. The postnuptial molt begins on the head in June or July and extends posteriorly, probably not being completed until November. Two specimens (June 7 and July 12) showed what was apparently an overlap of the prenuptial molt (1 rectrix and 1 tertial, 1 rectrix and 2 tertials) with the beginning of the postnuptial molt (forehead).
Apparently Worthen's sparrow is endemic on the high, temperate grasslands of northern and central Mexico, and formerly, the United States border. The only definite breeding localities are Miquihuana, Tamaulipas, and near Sombrerete, Zacatecas. However, the June specimen from Silver City, N. Mex., probably represents an extirpated breeding population in the United States, and the August specimens from Salinas, San Luis Potosi, probably indicate a breeding colony there. March specimens from Chalehicomula, Puebla, and Ojuelos, Jalisco, and a December skin from Tepetate, San Luis Potosi, represent our only knowledge of the winter range.
A specimen taken Apr. 16, 1941, on the desert near Saltillo, Coahuila, was either a migrant or a wintering bird. Dates on Brown's, and Nelson's and Goldman's specimens from Miquihuana range from May 27, 1924 to July 12, 1924. Near Sombrerete, my records range from June 19, 1952 and 1954 to Sept. 6,1955.
Two subspecies of the Worthen's sparrow are recognized: the palercolored nominate S. w. wortheni in New Mexico, Tamaulipas and (in winter) Puebla; and a darker race (S. w. browni) in Zacatecas. Specimens from San Luis Potos~ are apparently intermediate and one from Coahuila is unassignable to race.
Range: The species breeds in southwestern Tamaulipas (Miquihuana); possibly formerly to New Mexico (one record, the type specimen taken at Silver City, June 16, 1884); Zacatecas (Cerro Gordo).
Recorded in Coahuila (Saltillo), San Luis Potosf (Tepetate, Salinas), Puebla (Chalchicomula), Jalisco (Oj nelos), and Veracruz (Lim6n).
Egg dates: Miquihuana, Tamaulipas, Mexico: 27 records, June 4 to July 15; 15 records, June 15 to June 30.