With a highly specific and limited breeding habitat, the endangered Kirtland’s Warbler requires careful management of both forests and the nest parasite the Brown-headed Cowbird. Kirtland’s Warblers winter in the Bahamas, and based on the rarity of North American sightings outside of its breeding grounds, they probably migrate there in one nonstop flight.
Kirtland’s Warblers are hurt by cowbird parasitism in several ways. They are more likely to desert parasitized nests, cowbirds often remove a warbler egg when laying their own, larger cowbird eggs get most of the heat from incubation, and larger cowbird young get most of the food brought by adults.
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Description of the Kirtland’s Warbler
The Kirtland’s Warbler has bluish-gray upperparts streaked with black, yellow underparts with black streaking on the flanks, and a broken eye ring. Length: 6 in. Wingspan: 9 in.
Sexes similar, though females are duller.
Seasonal change in appearance
Juveniles resemble adult females but are browner.
Young jack pine forests.
Insects and berries.
Forages in low vegetation or on the ground.
Breeds primarily in a small area of Michigan and winters in the Bahamas. Currently increasing thanks to intensive management.
Bent Life History
Visit the Bent Life History for extensive additional information on the Kirtland’s Warbler.
Kirtland’s Warblers defend larger territories than most other warblers.
Some Kirtland’s Warblers are extremely tame and will allow a close approach to a nest.
The song is a series of sharp notes and whistles.
The Yellow-throated Warbler has a darker, patterened face, white belly.
Magnolia Warblers have greener backs and more white in the wings. Underparts are a brighter yellow.
The nest is a cup of plant materials, hair, and fibers placed on the ground.
Color: Buff with darker markings.
Incubation and fledging:
– Young hatch at 13-15 days.
– Young fledge (leave the nest) in 9 days after hatching but remain with the adults for some time.
Bent Life History of the Kirtland’s Warbler
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 Kirtland’s Warbler – the common name and sub-species reflect the nomenclature in use at the time the description was written.
DENDROICA KIRTLANDII (Baird)
CONTRIBUTED BY JOSSELYN VAN TYNEHABITS
Kirtland’s warbler was not described until 1852; yet the earliest scientific specimen was collected by Dr. Samuel Cabot, Jr., aboard ship near Abaca Island of the Bahamas in the second week of October 1841. Cabot, however, was on his way with John L. Stephens to Yucatan, and he became so preoccupied with his studies of the spectacular tropical birds of a country then entirely untouched by ornithologists that the little Bahaman warbler skin, brought back to Boston and deposited in his collection, remained unnoticed for more than 20 years (Baird, 1865).
On May 13, 1851, Charles Pease at Cleveland collected a male of the still unnamed warbler and gave the specimen to his father-in-law, Jared P. Kirtland, the well-known naturalist. A few days later, Spencer F. Baird, returning to Washington from a scientific meeting in Cincinnati, stopped a day in Cleveland with his friend Kirtland and was given the specimen to take back to the Smithsonian Institution (see DalI, 1915, p. 264). The next year (1852) Baird published his description of the new warbler, naming it Sylvicola kirtlandii in honor of Dr. Kirtland, “a gentleman to whom, more than [to] any one living, we are indebted for a knowledge of the Natural History of the Mississippi Valley.”
In the following 27 years, five more specimens, four in Ohio and one in southern Michigan, were taken, all during spring migration. Then on January 9, 1879, Charles B. Cory, collecting a specimen on Andros Island of the Bahamas, discovered the winter home of the species. The location of the breeding ground, although many guesses were made about it, remained unknown until 1903, when E. H. Frothingham, of the University of Michigan Museum, and T. G. Gale went trout fishing in Crawford and Oscoda Counties in north-central Michigan. There, on the jack-pine plains, they found numbers of an unfamiliar warbler in full song. They preserved one collected by Gale, and when they returned to Ann Arbor, Norman A. Wood identified it as the still little-known Kirtland’s warbler. Wood immediately went north to investigate; on July 8 he found a nest with two young and one egg and on July 9 a nest with five well-grown young (Wood, 1904).
Kirtland’s warbler proved to be restricted to the fairly dense stands of young jack-pines (Finus banlcsiana) that spring up after forest fires. The exact environmental requirements have not been definitely determined; they include a stand of small trees, predominantly jackpines (though a considerable number of small oaks and other deciduous trees may be scattered among them) and a fairly thick ground cover: usually made up of blueberry (Vaccinium myrtilloides), aromatic wintergreen (Gaultheria procumbene), bearberry (Aretostaphylos uvaursi), sheep laurel (Kalmia angustifolia), sweet fern (Comptonia peregrina), or various combinations of these. The warblers first appear in this cover 9 to 13 years after a fire, when the new pines may be barely 5 feet high. The nesting warblers usually occur in very loose colonies varying from a few pairs to hundreds, but isolated pairs have sometimes been found. As the pines grow, they increasingly shade out the ground cover; after 6 to 12 (rarely 15) years, when the pines have become 12 to 18 feet high, the habitat is no longer used by the warblers. A thick, even stand of pines becomes unattractive to Kirtlands sooner than a thin or uneven stand.
Courtship: Up to the present, apparently, nothing about the courtship of Kirtland’s warbler has been published. Verne Dockham, who has watched and recorded the arrival of Kirtlands in Oscoda County for 11 years, believes that the warblers are paired when they arrive on the breeding ground. At least, he reports, he always finds a female with each “first-arrival” male.
On June 8, 1945 (a very late season), northeast of Red Oak, Oscoda County, I watched a pair on their territory all day. The female spent much of her time on or near the ground, apparently searching for a nest site. (Actual construction of the nest began early in the morning, June 10.) The pair kept close together most of the time, with the female: who searched all parts of the chosen area, even the very edge: usually in the lead. The male made a few long flights from one side to the other of the territory, which was roughly circular, measuring 195 yards from north to south and 212 yards from east to west. A number of times (always in the immediate vicinity of the female) the male performed what seemed to be a courtship or display flight. This began at a height of 6 or 8 feet and was made with rapidly beating wings. It was a slow, slightly descending flight, usually carrying the bird directly over the female.
The male sang steadily except on the infrequent occasions when he participated, briefly, in the search along the ground for a nest site. Several times he drove from his territory the males of three adjoining areas. Once this led to’ a meke of three birds: the intruding male and both birds of the pair I was following: but the action was so fast that I could not tell whether the female took any active part.
Nesting: The nests are usually very well concealed in the ground cover, often completely arched over by vegetation, with entrance from one side only. They are almost always placed within a few feet (commonly within a few inches) of a jack-pine; occasionally, though still among pines, they are in quite open situations. They are always built directly on the ground and are usually made of dead grass and other such fibrous vegetable materials. Sometimes they are lined simply with finer grasses, but commonly with red sporophyte stalks from moss or with white deer hair. They measure 40 to 45 millimeters inside depth and 48 to 55 millimeters inside diameter.
The nest is constructed entirely by the female, but the male is always nearby and seems to follow the work closely. As Axtell (1938) observed, the approach of a female with nest material is “invariably heralded by a resumption of song on the part of the male.” Between June 10 and 13, 1945, near Red Oak, Harold Mayfield and I watched the entire building of a nest. The female (who had searched the whole territory most of the day on June 8) began investigating the site a half hour after sunrise. An hour later she brought what was quite surely the first piece of nest material. Except for short periods devoted to feeding, she worked hard through the remainder of the day, obtaining most of the material at certain favored spots 50 to 70 feet from the site. She made 131 trips that day and 59 on the following, thus completing the main structure of the nest. On the third day she made 7 trips, and on the fourth day 6 trips, for the lining (a total of 203 trips with nest material). The first warbler egg was laid on the fifth day (June 14) about an hour after sunrise.
Unless normal routine is disturbed by a cowbird, the eggs are laid in the early part of the morning and on successive days. Incubation, performed by the female alone, begins with the laying of the third egg. The male brings food for the female at intervals, and she commonly leaves the nest at his approach, meeting him in a nearby pine and fluttering her wings like a young bird. As incubation progresses, the male sometimes comes to the nest to feed his mate. When flushed from the nest, the female usually flutters along the ground in an “injury feigning” display. Incubation routine seems to consist of 10- to 15-minute periods of absence from the nest, alternating with periods of an hour or more on the nest (extremes: absent, 4 to 23 minutes; on the nest, 48 to 112 minutes).
Eggs: There are usually four or five eggs in a set. Most nests reported with 3-egg sets probably contain incomplete clutches or have been raided by cowbirds; many such nests contain one to three cowbird eggs. The eggs of Kirtland’s warbler are ovate to short ovate and are rather variable in color and pattern. They are creamy white or slightly pinkish white, speckled and blotched with “fawn color” and “wood brown.” Occasionally the markings are rather uniformly distributed over the whole surface, but usually there is a concentration of markings in a wreath or cap about the larger end. In spite of this great range in markings, cowbird eggs can be distinguished from them by their larger size, more bluish ground color, and the fact that the two ends are marked alike. The eggs of Kirtland’s warbler usually measure about 18.5 by 14 millimeters; extremes recorded are: 19.25 by 14.75; 18.0 by 14.75; 18.5 by 15.0; 18.5 by 14.0 millimeters
Young: The incubation period is reported by Verne Dockham as 14 days and by L. H. Walkinshaw as 14 to 15 days. My extreme dates for young on the nest are June 9 (1944) and July 17 (1930), but most dates of hatching come between June 11 and June 20. Hatching ordinarily occurs in the early part of the day. The female carries away the eggshells. During the first day or two, the female may stay on the nest much of the time and give to the young the food that the male brings; later both parents feed the young directly. Frequently a male is observed that makes more trips to the nest than the female does. When disturbed at a nest with young, both parents give quite elaborate “injury feigning” displays. The young normally remain in the nest 12 to 13 days. Only one brood is raised, but a second nest is built if the eggs or small young in a first nest are destroyed.
Plumages: The natal down is “hair brown.” The juvenal plumage was described by N. A. Wood (1904) as follows:
Above dark slate color, lighter on the head, eacb feather tipped with light sepia hrown; those of the mantle broadly edged with whitish spots; those of the back, with huffy white; wings and tail dark, slightly edged with light brown; * * * lesser and middle coverts * * like the back; * * * greater corerts broadly edged with huffy brown, making distinct bars; lores, sepia brown; sides of head otherwise similar in color to the upper parts, hut rather paler, fading gradually Into pale huffy brown on the chin and throat, this gradually changing to light brown on chest, sides and flank; each feather of the chest and sides with a dark center, widening at the tip, giving a distinct striped effect; abdomen, pale huffy, tinged with yellow.
Early in July the young begin to molt into the first winter plumage, which is apparently similar in the two sexes and is much like the winter plumage of the adult female, except that the young’s breast is heavily speckled. This molt does not affect the flight feathers, but the body plumage is completely changed. Wayne (1904) reports collecting an immature male in South Carolina with molt not yet entirely completed on October 29. The prenuptial molt takes place “late in February, and the new plumage is assumed by March 10” Maynard (1896). However, Bonhote (1903) described a male taken March 25 on Little Abaco, Bahamas, as “undergoing a thorough moult of the head and throat.” The prenuptial molt involves most of the body plumage but is less complete in first-year birds than in adults. First-year males in May and June show a mottled appearance above, with fresh bluish feathers on the crown and sides of the head and old grayish feathers on the nape and back. Males in their first breeding season are usually distinguishable, even in the field, by the paler yellow of the under parts and the presence of a speckled band (sometimes very faint) across the breast. The type specimen is a first-year male, and Baird (1852), with remarkable acumen, noted that it was “not quite matured.” Maynard (1896) described this distinctive first breeding plumage of Kirtland’s warbler, but his description has been completely ignored, and the statement is generally made that Dendroica chrysoparia (golden-cheeked warbler) is the only Dendroica requiring two years to reach the adult plumage. Adults have a complete postnuptial molt (which may begin as early as July 4).
Food: Kirt]and’s warblers feed mainly in the small jack-pines among which they nest, but they also hunt insects in the little oak trees among the pines, usually remaining 3 to 8 feet up, and often flying out from a tree to catch an insect on the wing. Sometimes they feed on the ground (especially in the dense pine thickets where the ground is nearly bare) and sometimes in the tops of tall jack-pines, fully 50 feet from the ground. However, one seen near the tops of tall pines is usually a singing male and is perhaps not there primarily in search of food.
N. A. Wood (1904) reported that the food of the Kirtland on its nesting grounds “seemed to be span-worms, living upon jack pines, and a small light-colored span-worm moth.” He “saw the warbiers capture these moths during flight,” and he shot a male Kirtland that had a deer fly in its mouth. Leopold (1924) wrote: “The food consists largely of centipedes, worms, and caterpillars. However, the birds also eat deer [flies] and horse flies, grasshoppers, crickets, white and dusky millers, with relish. . . . The birds also eat or drink the white pitchlike fluid which exudes from the branches of the pine.~~ My own observations indicate that the Kirtland’s food consists of several kinds of Lepidoptera (adults and larvae), tabanid flies, winged ant-lions, small Orthoptera, and other insects. The young are first fed principally on little green and little reddish caterpillars, but after a few days, moths, adult ant-lions, and other winged insects are brought to them. Feces are usually eaten (by both parents) in the first days, later carried away.
Food is apparently very easy to get in the Michigan jack-pine country. In fact, we can probably say that, within the breeding area of this warbler, food supply is never a critical factor. Parents feeding young will often do much of their hunting within 30 or 40 feet of the nest. It is even common to see a warbler leave the nest after feeding, pick .up some insects within a yard or two of the nest, and turn back immediately to feed the young again.
Kirtland’s warblers have apparently never been seen drinking water, and they refuse water offered to them experimentally near the nest. However, as Leopold noted, they sometimes take drops of liquid pitch from the surface of jack-pines, and I have seen one eagerly pick up and eat drops of black automobile lubricant it found on a twig near its nest.
Behavior: C. J. Maynard (1896) reported that Kirtland’s warbler is a shy bird while in its winter range in the Bahamas, but all observers comment on its tameness in the Michigan nesting area. However, there is great individual variation. Some nesting pairs are much tamer than others, and it is common to find one member of a pair definitely tamer than its mate. Leopold (1924) found the males of two pairs much tamer than the females, and one male actually ate from his hand. L. II. Walkinshaw found a very tame female at a nest, with eggs, near Red Oak on June 21, 1932. As he lay on the ground near the nest, the bird hopped around on him and even allowed herself to be caught in his hand and banded. Her mate would not come near. Southeast of Mio in June 1944, I had similar experience with a female warbler. The bird frequently alighted on me as I inspected the nest, and if I found her on the nest when I wanted to examine the young, I usually had to push her off with my finger. She not only hopped about on the nesting-area map, which I once laid on the ground near by, but she even hopped into my open box of bird bands, picked up a string of bright yellow celluloid bands and flew up into a tree with them.
A very noticeable characteristic of Kirtland’s warbler is its habit of “wagging” its tail (actually, the tail is jerked downward and then: more slowly: retu~’ns). The mannerism is more pronounced when the warbiers are disturbed or excited, but it is quite conspicuous at all times.
Although they nest in a very dry habitat, often miles from any surface water, they nevertheless take water-baths. One June 21, 1944, an hour after sunrise, I watched a male about 6 feet up in a small oak among the pines take repeated baths by splashing among the heavily dew-laden leaves: singing in the intervals between baths. (The temperature was 470 F.) He finally flew over to a jack-pine and began to shake himself and preen his feathers: still singing at regular intervals.
On June 15, 1943, about 3 hours after sunrise, I watehed a female sun bathe. Perching about 5 feet above the ground on the southeast side of a small jack-pine, she tilted her body sidewise, fluffed her feathers, and thus basked in the sun for a minute or two.
Voice: Song is an important factor in this warbler’s life and also in our efforts to study the species. The males sing so loudly and so persistently that they are easily found even in the thick cover they usually frequent. Fortunately, Axtell (1938) has published a good account of t.he song and of the warbler’s habits while singing. He writes:
Even at * the nest-building season, there were frequent periods ï * * when no sound was heard for several minutes from ï ï * the six or more males. If any one individual was observed constantly for some time, it was noted that there were frequent intervals of silence 0 0 ï even in the early morning. * * After a period of silence lasting from half a minute to an hour or more, a bird might sing two or three repetitions of its song or might remain vocal for more than half an hour. During the singing period the song, itself less than two seconds in length, was commonly repeated with considerable regularity at intervals of from eight to twelve seconds. But here, also, some irregularities might frequently be injected. ï ï ï At this season, each male did a great deal of his singing while patrolling his territory, sometimes alone, at other times accompanied by his mate. Her presence or absence on these tours did not seem to determine whether or not he sang. I observed one singing from a stick within a foot of the ground and another nearly fifty feet up in the tip-top of one of the tallest trees in his territory. The greater part of the singing was done from the branches of the dense growth of ten-foot-high jackpines, perhaps several songs from one branch and only one song from the next, while the bird fed between. One individual interspersed preening with rather evenly timed singing while perched nonchalantly almost within arm’s reach of me. Any dead tree, rising above the level of the pinetops, seemed often to influence a bird to perch and sing from one of its higher branches, sometimes for several minutes, whether the tree were near his nest or in the farther reaches of his territory. On a later trip through the same part of his domain, the bird might choose to do his singing from a diUerent dead tree nearby, or might ignore such high perches In that vicinity until a later round.
It is remarkable how persistently the males will’sing in spite of all sorts of unfavorable factors. On a clear day at the height of the season they may begin singing as much as 40 minutes before sunrise, and they may sing until sunset. They will sing in spite of temperatures as low as 250 F., and even a pouring rain may not stop them. They sing wherever they are: in the trees, on the wing during a flight from one tree to another (though their mouths may be full of insects they are taking to the young), on the ground (though this is rare), and even on a perch within a foot of their nest and young. When singing most steadily, they commonly repeat the song about seven times a minute. Early in the morning I have counted, during such singing, 237 to 250 songs per hour.
None of the various syllabifications that have been used to describe the song is very satisfactory. Perhaps this is not remarkable, for (as shown by the sound-film record made by the Cornell party) there may be. more than 100 up or down slurs in one second, and pitch changes of several tones in less than one-hundredth of a second. Axtell (1938) very rightly compared the song with that of the northern waterthrush (Se jurus noveboracensi~) and the house wren (Troglodytes a~don), saying that they “are the most likely sources of confusion” in the identification of Kirtland’s warblers by song. “The Water-thrush’s song starts high and descends; the Kirtland’s starts low, goes higher, and may end either high or low. As compared with the wren, the warbler’s song is shorter, of fewer notes, and has a more definite beginning and ending.” “The loudness of the song is one of its most outstanding characteristics. In the bird’s desolate jack-pine haunts it may be heard from a quarter to a half mile. Its liquid, bubbling quality, and its lively, emphatic manner of delivery seem to be invariable features.” Axtell adds that the Kirtland has the lowestpitched song of any of the eastern Dendroicas.
I have sometimes noticed a Kirtland change his style of song, but only rarely after the early part of the season. Most individuals have quite characteristic songs, and after spending a few days in a given area of the nesting range, one can recognize by his song the owner of every territory within earshot.
A strange characteristic of Kirtland’s warbler is its habit of singing incomplete songs. Occasionally a song will be broken off abruptly at any point and for no apparent reason. Sometimes an incomplete song is followed almost immediately by a complete one.
Rarely I have found a male that has an extremely aberrant song: quite unrecognizable as that of a Kirtland. Two males that I noted in Oscoda County (June 16, 1941, and June 6, 1944) had songs that were harsh, completely unmusical “rattles,” reminding me somewhat of a cowbird. Another male (noted June 1, 1945) gave a simple trill. very like that of the field sparrow (Spizella pusilla) except that it suddenly increased in speed toward the middle and dropped slightly in pitch near the end.
Kirtland’s warbiers usually scold very little unless the provocation is great. They use a note for scolding described by Axtell (1938) as varying from tayip to tsliyook, and like the “common scolding note of the Oven-bird” (Seiwrua aurocapillus). Adults use a low churk to arouse the nestlings at feeding time. On the Kirtland’s wintering grounds in the Bahamas, Maynard (1896) heard only a “harsh chirp.
Unlike many warblers, this species continues to sing throughout the incubation period and even while raising the young. However, most individuals have stopped entirely, or almost entirely, by mid July; late records are July 24, 1939 (Verne Dockham, Oscoda County), and August 1, 1932 (Leonard Wing, Crawford County).
Field marks: Kirtland’s warbler is a large, rather slow-moving warbler, described by Peterson (1939) as “gray above and yellow below, with some large sparse spotting on the breast and sides. * * * The bird wags its tail much like a Palm Warbler; no other graybacked Warbler has this habit.” (As previously noted, the “wagging” is an up-and-down motion.) After their first winter, the two sexes are easily distinguished even in the field; males, especially if fully adult, are more blue above than females, and the black in front of their eye and about the base of their bill (absent in females) always gives the appearance of a dark mask. Kirtland’s warblers are usually discovered by hearing the song, and a study of Axtell’s excellent description (1938) should enable an observer with previous experience of bird song to recognize a Kirtland readily.
In fall, even the adult plumage is very brown above, and all plumage markings are less distinct; few people are able to identify a fallplumaged Kirtland in the field.
Enemies: There have been oddly contradictory statements about the adverse factors in the life of Kirtland’s warbler. In his first paper on the species, N. A. Wood (1904) mentioned the fires that sweep the jack-pine plains, and in a later paper he (1926) stated that “fire is without doubt the greatest menace to the Kirtland warbler colonies, since it destroys the habitat as well as the nests of the birds.” It is, of course, quite true that a fire, if it occurs in their breeding area before mid July, will destroy the nests in its path. However, since this warbler nests exclusively in the dense stands of jack-pine that spring up after a fire, one can truly say that fires are the Kirtland’s greatest need. Not only do fires in the older jack-pine stands result in suitable nesting conditions, but fires that occur in areas largely covered with red and white pine (never inhabited by the Kirtland’s) promote the spread of jack-pine. Completely successfuL fire prevention can actually extirpate Kirtland’s warbler from a given region: as happened recently in Alpena and Kalkaska Counties.
Leopold (1924, p. 57) was probably correct in considering the cowbird the most important enemy of Kirtland’s warbler. As indicated, a very large number of Kirtland nests are parasitized by the cowbird; frequently the competition is too great, and the warbler young do not survive. However, there seems to be no reason to share Leopold’s fear that the cowbird “may soon” exterminate this warbler. It is probable that the major changes that have been observed in the number of Kirtland’s are the result of changes in the amount of suitable habitat in Michigan or in the Bahamas.
I have seen a female cowbird spend hours apparently watching a female Kirtland building a nest. The nest was entirely unguarded when the warbler was not actually working on it, and as soon as the main structure was finished: even before the lining was added: a cowbird (presumably the one that had been watching the nest-building) came early in the morning and laid in it. After watching many hours at recently completed, or nearly completed, Kirtland nests, I would judge that cowbirds laying in a Kirtland’s nest during this early part of the cycle, which is the period most favorable for the cowbirds’ chances of producing young, run very little risk of detection and attack. But after the warbler has begun incubation, the nest is rarely left unguarded, and the female warbler will attack violently and drive away any cowbird she finds in the vicinity.
The only predator I have actually observed to kill a Kirtland’s warbler is the sharp-shinned hawk (Accipiter striatus veloa~), although the conditions were not natural in that instance, for the warbler was in a trammel net. However, this hawk, as well as Cooper’s hawk (Accipiter coo pen) and, more frequently, the marsh hawk (Circus cyaneus hud.sonius), occur regularly in the habitat of Kirtland’s warbler, and they undoubtedly take an occasional warbler. Crows (Cor1.flts brachyrhynchos) and blue jays (Cyanocitta cristata) , common in jack-pine areas, presumably rob the nests of this warbler as well as of other birds. Red foxes (l7ulpes fu~va), red squirrels (Sciurus /tudsonicus) ,spermophiles (Citellus tr~decem~i~atu~) ,and masked shrews (Sorex cinereus) are potential mammal enemies that occur regularly in the warbler habitat. I have some reason to attribute a few cases of nest destruction to red squirrels or to spermophiles. Nesting female Kirtland’s, under observation from a blind, have shown great excitement at the approach of a shrew, and have attacked it and driven it away.
Ants seem to be a serious enemy of the nestlings. The parents, especially the female, pay much attention to guarding the young against ants and can be seen frequently picking the ants from the nestlings’ bodies. If parent birds are kept away from a nest for more than a few minutes when the temperature is fairly high and the ants active, the biting ants cause the young to squirm and jump about violently. Ants collected from a Kirtland’s nest near Clear Lake, Montmorency County, June 27, 1935, were identified by Frederick M. Gaige as Cremate gaster lineolata. Kirtland’s warbiers seem to be very free of external parasites. It is rare to find even Mallophaga on them.
Fall: Soon after the postnuptial molt begins, the males cease to sing, and this, as well as the inactivity of both adults and young during the molt, makes them extremely difficult to find. Few observers have ever seen a Kirtland’s warbler later than July. Verne Dockham believes that after July they largely leave the jack-pine habitat; he has several times seen them in August, always near the ground, in the adjoining hardwood. The only known Michigan specimens taken later than September 1 are several in the Max M. Peet collection found in jack-pine near Luzerne September 5 to 9, 1916, and one male found September 28, 1919, in jack-pine seven miles south of Houghton Lake village. Kirtland’s warbler has never been recorded in Michigan in the fall south of the jack-pine plains.
Winter: Charles B. Cory (1879), who discovered the winter home of Kirtland’s warbler when he collected a female on Andros Island in the Bahamas on January 9, 1879, reported that its actions resembled those of the myrtle warbler and that it seemed to prefer the thick brush. Its stomach contained insects. However, most of our knowledge of the winter habits of this species is derived from C. J. Maynard’s account (1896) of his experience with it in the Bahamas in 1884:
Kirtland’s Warblers are shy birds of solitary habits, for never in any case did I find two together. They inhabit the low scrub, preferring that which is only three or four feet high, but retire at night to roost in the higher, more dense sbrubbery near the spots which they frequent during the day. Those taken were, with one or two exceptions, found in an exceedingly limited area, within a mile or two of the city, and always in old fields grown up to low shrubbery. I have never heard Kirtland’s Warbler sing, the only note that they uttered was a harsh chirp, with which they greeted me when alarmed at my approach. When one was not secured at first sight, it generally retreated into the bushes and silently disappeared. The thick and tangled character of the scrub rendered any quiet or swift pursuit impossible, thus a retreating bird was never seen again that day, and a number seen escaped In this way.
As with many shy birds, however, these warblers presented strange exceptions to the usual rule; twice at least as I was making my way through the thickets in search of the Greater Yellow-throat, I was confronted by a Kirtland’s Warbler. In both instances the birds appeared from out of the thicket within a yard of my path, remained a few seconds then darted off into the scrub.
The earliest autumn record for the Bahamas seems to be November 13 (1891, Eleuthera) ; and the latest spring record, April 25 (1887, New Providence).
Twomey (1936) has made the interesting point that the temperature and rainfall conditions in the Bahamas during the period December through April are very similar to those in the Kirtland’s range in Michigan during the breeding season.
Breeding range: Kirtland’s warbler breeds in Michigan north to Montmorency County (Clear Lake), east to Alpena County (southwest of Alpena) and losco County (west of Oscoda), south to Ogemaw County (west of Rose City) and Clare Count.y (northwest of Harrison), and west to Wexford County (north of Manton) and Kalkaska County (northeast of Kalkaska).
Winter range: The winter range is restricted to the Bahamas. The species has been recorded from: Abaco, Little Abaco, Berry, Eleuthera, New Providence, Athol, Andros, Watling, Green Cay, and Caicos Islands.
Migration: Early dates of spring arrival are: Florida: West Jupiter, April 27. Georgia: Cumberland Island, April 12. South Carolina: St. Helena Island, April 27. Missouri: St. Louis, May S. Ohio: Avondale, May 4; Columbus, May 8; Cleveland, May 13. Illiiiois: Glen Ellyn, May 7. Indiana: Wabash, May 4. Ontario: Toronto, May 16. Minnesota: Minneapolis, May 13. Michigan: Ann Arbor, May 6; Oscoda County, May 8.
Fall dates are: Ontario: Point Pelee, October 2. Ohio: Holland, September 22; Columbus, September 11. Virginia: Fort Myer, September 25. South Carolina: Chester, October 11; Mount Pleasant, October 29; Charleston County, October 4.
Egg dates: Michigan: 40 records, May 28 to June 30 (July 17 in the case of a second nesting after the destruction of the first set of eggs).