Part 4

Combat with other species found within the territories of these birds was observed. Combat with the Bluebird was most frequent but one or more indications of opposition was noticed with the Flicker, Downy Woodpecker, Acadian Flycatcher, Tufted Titmouse, Robin, and Cardinal.

The males sing persistently and energetically from the time that they arrive on their territories, hoping to attract their mates, but they are not always successful, especially in regions where the species is rare or not very common, and their nest-building brings no occupant. Edward von S. Dingle writes to me that, at Summerton, S. C., a male prothonotary warbler built a nest in a low stub, but no female was ever seen. He sang frequently and remained in the vicinity for several weeks. And Frederic H. Kennard, in far-away Massachusetts, mentions in his notes that he saw one and watched it for several days, June 16-20, 1890. "He sang loudly and clearly and sweetly, and seemed to like a particular place by the side of the river, for when I returned later in the day, he was still there, on the other side of the river." On June 19, he watched him for half an hour. He was always in the same locality. On a later search, no nest or no mate could be found.

_Courtship._--Brewster (1878a) gives the following full account of this performance:

Mating began almost immediately after the arrival of the females, and the "old, old story" was told in many a willow thicket by the little golden-breasted lovers. The scene enacted upon such occasions was not strikingly different from that usual among the smaller birds; retiring and somewhat indifferent coyness on the part of the female; violent protestations and demonstrations from the male, who swelled his plumage, spread his wings and tail, and fairly danced around the object of his affections. Sometimes at this juncture another male appeared, and then a fierce conflict was sure to ensue. The combatants would struggle together most furiously until the weaker was forced to give way and take to flight. On several occasions I have seen two males, after fighting among the branches for a long time, clinch and come fluttering together to the water beneath, where for several minutes the contest continued upon the surface until both were fairly drenched. The males rarely meet in the mating season without fighting, even though no female may be near. Sometimes one of them turns tail at the outset; and the other at once giving chase, the pursuer and pursued, separated by a few inches only, go darting through the woods, winding, doubling, now careering away up among the tree-tops, now down over the water, sweeping close to the surface until the eye becomes weary with following their mad flight. During all this time the female usually busies herself with feeding, apparently entirely unconcerned as to the issue. Upon the return of the conqueror her indifference, real or assumed, vanishes, he receives a warm welcome, and matters are soon arranged between them.

_Nesting._--The prothonotary warbler and Lucy's warbler are the only two American warblers that habitually build their nests in cavities, usually well concealed. The normal, and probably the original, primitive, nestling sites are in natural cavities in trees and most nests are still to be found in such situations today. The prothonotary is not at all particular as to the species of trees, nests having been found in many kinds of trees, although perhaps a slight preference is shown for dead willow stumps. Nor is it particular as to the size or condition of the cavity, or its location, though quite often choosing one over water or near it. The height above the ground or water varies from 3 feet or less to as much as 32 feet but there are more nests below 5 feet than there are above 10, the height of the majority being between 5 and 10 feet. The size and shape of the cavity are of little concern; if the cavity is too deep, the industrious little birds fill it with nesting material up to within a few inches of the top; sometimes a very shallow cavity is used, so that the bird can be plainly seen from a distance as it sits on the nest. The old deserted holes of woodpeckers or chickadees are favorite nesting sites; the entrances to these have often been enlarged by other agencies, or are badly weathered. In very rotten stumps, the warblers have been known to excavate partially or to enlarge a cavity.

The nests built by the males in early spring, referred to above, are probably rarely used as brood nests and might be classed as dummy nests. The family nest is built almost entirely by the female, with encouragement and a little help from her mate, who accompanies her to and from the nest and in the search for material; much of the soft, green moss used extensively in the nest is often obtainable from fallen logs and stumps in the vicinity.

Brewster (1878a) mentions a nest taken from a deep cavity that "when removed presents the appearance of a compact mass of moss five or six inches in height by three or four in diameter. When the cavity is shallow, it is often only scantily lined with moss and a few fine roots. The deeper nests are of course the more elaborate ones. One of the finest specimens before me is composed of moss, dry leaves, and cypress twigs. The cavity for the eggs is a neatly rounded, cup-shaped hollow, two inches in diameter by one and a half in depth, smoothly lined with fine roots and a few wing-feathers of some small bird."

In Dr. Walkinshaw's (1938) Michigan nests, "moss constituted the bulk of the nesting material in nearly all cases, completely filling the nest space whether it was large or small. On top of this the nest proper was shaped and a rough lining of coarse grape-bark, dead leaves, black rootlets procured from the river-banks, and poison-ivy tendrils was added. Above this a lining of much finer rootlets, leaf-stems, and very fine grasses was used."

In addition to the materials listed above Meyer and Nevius (1943) mention hackberry leaves, hairs, pine needles, horsehair, and cedar bark in their Tennessee nests. They say that from 6 to 10 days were required for nest construction, and that from 3 to 5 days more elapsed before the first eggs were laid. Their four nests were all in bird-boxes; one was in an orchard over plowed ground, one over a lotus pond in a wooded ravine, and two were over lily pools near buildings.

Dr. Walkinshaw (1938) publishes a map showing the location of 21 nesting boxes along the winding banks of the Battle Creek River, in Calhoun County, Mich., and writes: "Of the 28 nests found during 1937, 19 were in bird-houses over running water, 6 were in stubs over water (2 of which were over running water), and the other 3 were in natural holes back from the river bank. Of 44 nests found from 1930 through 1937, excluding the 21 in bird-houses, six were over running water in old woodpecker holes, one in a bridge-support in a slight depression, and nine in natural holes over standing water. Seven were in old woodpecker holes from two to a hundred and sixty feet back from the river-bank."

Many and varied are the odd nesting sites occupied by prothonotary warblers. Dr. Thomas S. Roberts (1936) writes:

The vagaries of this bird in choosing artificial nesting-places are shown by the positions of the following nests. On the La Crosse railroad bridge: in a cigar-box nailed on the engine-house on top of the draw; on one of the piers; in a metal ventilator-cap four inches in diameter, that had fallen and lodged just at the point where the draw banged against the pier, and close under the tracks; in a shallow cavity in a piece of slab-wood nailed to a trestle-support close under the road-bed of the railroad; these all far out in the middle of the Mississippi River. Still others are: in a Bluebird box on a low post by a switching-house and busy railroad platform; in a cleft in a pile in the river; in a tin cup in a barn, to reach which the birds entered through a broken pane of glass; in a pasteboard box on a shelf in a little summer-house; in an upright glass fruit jar in a house-boat; and other similar situations. In most cases the birds had to carry the nesting-material long distances, especially to the places on the bridge.

John W. Moyer (1933) relates an interesting story that was told to him by people living in a farm house along the Kankakee River. A pair of these warblers built their nests and raised their broods for three consecutive seasons in the pocket of an old hunting-coat, hung in a garage; each year the man cleaned out the nest and used the coat in the fall, and the next spring the birds used it again. M. G. Vaiden tells me of a similar case.

Nests have been found in buildings, on beams and other supports. Louis W. Campbell (1930) reports two on shelves in sheds, one in a small paper sack partly filled with staples and another in a coffee can similarly filled. Nests in cans in various situations have been found a number of times, and others have been reported in a tin pail hung under a porch, in a mail box, in a box on a moving ferry boat, in a Chinese lantern on a pavilion, and in an old hornets' nest.

Dr. Walkinshaw writes to me: "At Reelfoot Lake, Tenn., during July, 1940, I found 8 nests of the prothonotary warbler, all built a few feet above the water in small natural holes in cypress knees. Evidently these are regular late-summer nesting sites." The knees were farther under water earlier in the season. Most of his 76 Michigan nests were over water, or less than 100 feet from it; but 10 were 300 or more feet away from it and 2 were over 400 feet away. M. G. Vaiden tells me of a pair that nested in the tool box of a log-loading machine that was in daily operation, hauling logs.

_Eggs._--From 3 to 8 eggs have been found in nests of the prothonotary warbler, from 4 to 6 seem to be the commonest numbers, 7 is a fairly common number, and at least 3 sets of 8 have been reported; in the J. P. Norris series of 70 sets are 34 sets of 6, 15 sets of 7, and 2 sets of 8.

The eggs vary in shape from ovate to short ovate, and they are more or less glossy. The eggs are undoubtedly the most striking of the warblers' eggs, with their rich creamy, or rose-tinted cream, ground color, boldly and liberally spotted and blotched with "burnt umber," "bay," "chestnut brown," and "auburn," intermingled with spots and undertones of "light Payne's gray," "Rood's lavender," "violet-gray," and "purplish gray." There is quite a variation in the amount of markings, which are generally more or less evenly scattered over the entire egg; some are sparingly spotted and blotched, while others are so profusely marked as almost to obscure the ground color (Harris).

J. P. Norris (1890b), in his description of his 70 sets, describes 2 eggs in each of 2 sets as "unmarked, save for four or five indistinct specks of cinnamon." These were in sets of 6 eggs each. Pure white, unmarked eggs were once taken by R. M. Barnes (1889). Dr. Walkinshaw (1938) gives the measurements of 78 eggs as averaging 18.47 by 14.55 millimeters; the eggs showing the four extremes measured =20= by 15, 19 by =16=, and =17= by =13= millimeters.

_Incubation._--The eggs are laid, usually one each day, very early in the morning; Dr. Walkinshaw (1941) says between 5:00 and 7:00 a. m. in Michigan; Meyer and Nevius (1943), in Tennessee, saw the female enter the nest to lay as early as 5:00 a. m. on May 2, and as early as 4:44 on May 23, remaining in the nest from 28 to 36 minutes on different occasions. The period of incubation is recorded as 12, 13-1/2, and 14 days by different observers; about 13 seems to be the average, according to Dr. Walkinshaw (MS.), probably depending on conditions and the method of reckoning. Incubation seems to be performed entirely by the female, but the male feeds her to some extent while she is on the nest. Incubation starts the day before the last egg is laid.

_Young._--Meyer and Nevius (1943) write:

The adults shared feeding duties, and both removed fecal sacks. During the first three days the female steadily brooded the young. One female, observed from 4:55 to 8:10 a. m., when the young were one day old, spent a total of 70 minutes off and 155 minutes on the nest. Trips from the nest lasted an average of 8.6 minutes, while periods on the nest averaged 19.4 minutes. * * * At one nest when the young were eight days old, activities were noted during the eight and one-half hours from 8:30 a. m. to 5:30 p. m. The young were fed an average of 16 times an hour. * * * The adults were seen carrying spiders and insects, small green caterpillars frequently being used. Mr. H. P. Ijams saw a male offer a 10-day old nestling a may-fly. An incubator-hatched bird accepted egg-yolk, ants, ant larvae, crickets, earthworms, and spiders.

They say of the development of the young: "The young on the day of hatching had orange-red skin. The mouth lining was red. Down was distributed over the frontal and occipital areas of the capital tract, spinal tract, femoral, altar, and humeral tracts. Feather sheaths of the alar tracts penetrated the skin the first day after hatching. On the second day after hatching the eye-slits began to open. Feather sheaths of the humeral, femoral, and crural tracts emerged on the third day; those on the dorsal and ventral tracts emerged on the fourth day, and those of the capital and caudal tracts on the fifth day. On the fifth day the sheaths began breaking." During the next five days the young developed rapidly and became more and more active, and on the tenth day began to leave the nest.

Young observed by Dr. Walkinshaw (1914) at Reelfoot Lake "averaged 11 days of age when leaving the nest in 1939, while 21 young in Michigan during 1939 and 1940 remained in the nest for a period of 10-3/4 days." Of the comparative nesting success in the two localities, he says:

In Michigan from 1930 through 1940, 121 nests of the Prothonotary Warbler were observed. Only 28, or 23.14 per cent, were successful. Out of 413 eggs, 159 (38.47 per cent) hatched and 100 young were fledged (.87 per total nest; 3.78 per successful nest). The fledgling success was 25.66 per cent of eggs laid. More failures in Michigan resulted in more nestings by individual birds.

In Tennessee during 1939, 30 nests were observed until terminated or successful; 19 were successful (63.33 per cent) while out of 139 eggs, 78 hatched and all the young lived to leave the nest or 56.11 per cent fledging success of eggs laid; 2.6 young were fledged per total nest; 4.1 per successful nest.

He also notes that in Michigan the species is typically single-brooded if the first nesting is successful, but that in Tennessee it is typically double-brooded.

_Plumages._--According to Dr. Dwight (1900) the natal down, located as indicated above, is brownish mouse-gray. Ridgway (1902) gives rather the best description of the juvenal plumage as follows: "Pileum, hindneck, back, and scapulars dull olive-greenish; wing-coverts, tertials, rump, and upper tail-coverts slate-gray, tinged with olive, the middle and greater wing-coverts narrowly tipped with light olive-greenish, producing two very indistinct bands; secondaries, primaries, and rectrices as in adults; sides of head pale yellowish olive; chin, throat, and chest dull light grayish olive, darkest on chest rest of under parts dull white, passing on sides and flanks into olive-grayish."

In very young birds, according to Dr. Dwight, there is a variable amount of brownish wash on the back, which fades out to gray. And Dr. Chapman (1907) says that the white on the inner webs of the tail feathers is more restricted than in adults and more or less mottled with blackish. This first plumage is followed in June and July by a partial postjuvenal molt involving all the contour plumage and the wing coverts but not the rest of the wings or the tail. The young bird now becomes a golden swamp warbler, the young being nearly like the adults, the females being considerably duller in color than the males and having less white in the tail.

The crown and hind neck in both sexes, both old and young, are washed with dusky or olive in the fall. Spring plumages are produced by very slight wear without molt. There is one complete, annual molt in late summer.

_Food._--Very little seems to have been recorded on the food of the prothonotary warbler. It is evidently highly insectivorous, obtaining most of its food from the trunks and branches of trees and shrubs and from fallen logs. Brewster (1878) says: "This Warbler usually seeks its food low down among thickets, moss-grown logs, or floating débris, and always about water. Sometimes it ascends tree-trunks for a little way like the Black-and-White Creeper, winding about with the same peculiar motion."

Dr. Roberts (1936) lists "ants, and other insects and their larvae," as its food. Some of the food of the young is mentioned above, most of which is doubtless included in the food of the adults. Spiders, beetles, may-flies, and other insects should be included, as well as many caterpillars and the larvae of water insects. Audubon (1841) says: "It often perches upon the rank grasses and water plants, in quest of minute molluscous animals which creep upon them, and which, together with small land snails, I have found in its stomach."

_Behavior._--Brewster (1878a) observes:

When seen among the upper branches, where it often goes to plume its feathers and sing in the warm sunshine, it almost invariably sits nearly motionless. Its flight is much like that of the Water-Thrush (either species), and is remarkably swift, firm, and decided. When crossing a broad stream it is slightly undulating, though always direct. * * *

In general activity and restlessness few birds equal the species under consideration. Not a nook or corner of his domain but is repeatedly visited through the day. Now he sings a few times from the top of some tall willow that leans out over the stream, sitting motionless among the yellowish foliage, fully aware, perhaps, of the protection afforded by its harmonizing tints. The next moment he descends to the cool shades beneath, where dark, coffee-colored water, the overflow of the pond or river, stretches back among the trees. Here he loves to hop about on floating drift-wood, wet by the lapping of pulsating wavelets; now following up some long, inclining, half-submerged log, peeping into every crevice and occasionally dragging forth from its concealment a spider or small beetle, turning alternately his bright yellow breast and olive back towards the light; now jetting his beautiful tail or quivering his wings tremulously, he darts off into some thicket in response to a call from his mate; or, flying to a neighboring tree-trunk, clings for a moment against the mossy bole to pipe his little strain or look up the exact whereabouts of some suspected insect prize.

_Voice._--The same gifted writer and careful observer (Brewster, 1878) gives the following good account of the distinctive song of this warbler:

The usual song of the Prothonotary Warbler sounds at a distance like the call of the Solitary Sandpiper, with a syllable or two added,--a simple _peet, tweet, tweet, tweet_, given on the same key throughout. Often when the notes came from the farther shore of a river or pond we were completely deceived. On more than one occasion, when a good opportunity for comparison was offered by the actual presence of both birds at the same time, we found that at the distance of several hundred yards their notes were absolutely undistinguishable; nearer at hand, however, the resemblance is lost, and a ringing, penetrating quality becomes apparent in the Warbler's song. It now sounds like _peet, tsweet, tsweet, tsweet_, or sometimes _tweet, tr-sweet, tr-sweet, tr-sweet_. When the bird sings within a few yards the sound is almost startling in its intensity, and the listener feels inclined to stop his ears. The male is a fitful singer, and is quite as apt to be heard in the hot noontide or on cloudy days, when other birds are silent, as during the cool morning and evening hours. The ordinary note of alarm or distress is a sharp one, so nearly like that of the Large-billed Water Thrush (_Siurus motacilla_) that the slight difference can only be detected by a critical ear. When the sexes meet a soft _tchip_ of recognition common to nearly all the Warblers is used. In addition to the song above described the male has a different and far sweeter one, which is reserved for select occasions,--an outpouring of the bird's most tender feelings, intended for the ears of his mate alone, like the rare evening warble of the Oven-Bird (_Siurus auricapillus_). It is apparently uttered only while on the wing.

Although so low and feeble as to be inaudible many rods away, it is very sweet, resembling somewhat the song of the Canary, given in an undertone, with trills or "water-notes" interspersed. The flight during its delivery is very different from that at all other times. The bird progresses slowly, with a trembling, fluttering motion, its head raised and tail expanded. This song was heard most frequently after incubation had begun.

Dr. Roberts (1936) refers to this flight song, as delivered "after the manner of the Maryland Yellow-throat, * * * consisting first of the usual rapid monotone of five or six notes and ending with a pleasing, varied warble, full and strong in some of its notes and far sweeter than the usual utterance."

Dr. Walkinshaw (1938) says of the usual song: "Uttered at the rate of five or six times per minute, the song lasts slightly over one second. It is given all day long from the time of arrival until the young have left the nest and has been heard as late as the 16th of August (1931). The frequency is much greater during the early nesting season and during the earlier hours. During midday on warmer days the number of times per hour seems much less. Later, from four until near sundown, it again increases. During late nesting, when the young are about to leave the nest, the rate again decreases, but it is heard several days after the young leave the nest." Aretas A. Saunders tells me that the songs are pitched at C´´´´ or B´´´, and the call note, _tseek,_ at A´´´.

_Field marks._--The golden swamp warbler could hardly be mistaken for anything else. The rich, brilliant yellow of the head and breast, sometimes almost orange on the head, only slightly paler in the female, the absence of wing bars, and the large amount of white in the tail will distinguish it.

_Enemies._--Dr. Walkinshaw (1941) says that the house wren is a serious competitor with the prothonotary warbler in Michigan, contending with it for nesting sites in the bird-boxes.

The cowbird is a persistent enemy of this warbler in spite of its hole-nesting habits; perhaps if the warbler nested in deeper holes it might find some relief from this pest. Among 70 sets of eggs of this warbler in the J. P. Norris collection, 18 contain cowbirds' eggs. Dr. Friedmann (1929) found no less than 36 records of such parasitism in the literature, and says: "As many as four eggs of the Cowbird have been found in a single nest together with four of the Warbler's. There are several cases on record of doubled-storied nests of this bird, with a Cowbird's egg buried in the lower story. Such cases are, however, not common, and usually the Warbler seems to make no attempt to get rid of the strange eggs." E. M. S. Dale wrote to me of a nest, found near Toronto in 1933, that contained seven eggs of the cowbird and none at all of the warbler!

Snakes sometimes destroy the eggs or young.