Part 25

_Eggs._--Three eggs seems to form the usual set for the mangrove warbler; in the Thayer series there are five sets of three and one set of two. Ed. N. Harrison (MS.) says that "it seems that one egg is a set as often as two." Most of the eggs in this series are ovate, but some are short ovate; they have only a very slight gloss. They are white or creamy white, speckled, spotted or blotched with shades of "mummy brown," "bone brown," "Prout's brown," or "clove brown," with undertones of "light mouse gray," "deep mouse gray," "Quaker drab," or "drab-gray." The browns are frequently so dark as to appear almost black, but some eggs are spotted with lighter shades, such as "cinnamon brown" and "snuff brown." On the more lightly marked types the most prominent markings are the grays, with only a few scattered brown spots. Often a loose wreath is formed around the large end, where the spots are usually concentrated.

The measurements of 32 eggs average 17.9 by 13.4 millimeters; the eggs showing the four extremes measure =19.5= by 13.2, 17.9 by =14.6=, =17.0= by 13.2, and 18.3 by =12.9= millimeters (Harris).

_Plumages._--Although I have examined a large series of mangrove warblers, I have seen no downy young and no summer birds in juvenal plumage. But Dr. Chapman (1907) describes the young female as "above grayish olive-green, rump brighter; tail blackish, externally greenish, webs of all but central narrowly margined with yellow; wings and their coverts blackish, quills margined, coverts tipped with dull greenish; below whitish more or less washed or obscurely streaked with yellow, the under tail-coverts pale yellow."

Young males in the fall are much like adult females, but brighter in color and often with traces of chestnut on the head. Apparently young males wear this femalelike plumage all winter; young males in March show a variable amount of chestnut on the head and throat, and show further progress toward maturity during April, May, and June, indicating a first prenuptial molt. A specimen described by Brewster (1902) is apparently undergoing this molt. "It has the head dull chestnut, very pale and mixed with whitish on the throat, mottled with greenish on the crown; the jugulum, sides of the neck and the middle of the breast _white_ with occasional small patches or single feathers of a pale yellow color and numerous fine, chestnut-rufous streaks on the breast; the remainder of the under parts pale primrose yellow mixed with whitish. The back, wings, and tail are nearly as in the adult female. The upper mandible is of the usual dusky horn color, but the basal half of the lower mandible of a pale flesh color. The plumage, generally, has a worn and faded appearance."

This would seem to indicate that the first prenuptial molt is quite extensive, and that young birds become nearly adult after their molt. Adults probably have a complete postnuptial molt sometimes during the summer, but the following descriptions indicate that the prenuptial molt of adults is less extensive. Ridgway (1885) describes the type male, taken December 16, 1882, as follows: "Head rich chestnut, lighter or more rufous on the throat. Upper parts olive-green, the wings dusky, with broad greenish yellow edgings; outer webs of rectrices dusky, edged with yellowish olive-green, the inner webs chiefly primrose-yellow. Lower parts bright gamboge-yellow, the jugulum and breast with a few very indistinct and mostly concealed streaks of chestnut-rufous." And of an adult female, taken December 29, 1882, he says: "Above grayish olive-green; wings grayish dusky, the feathers edged with olive-grayish; rectrices dusky, outer webs edged with olive-green, the inner with primrose yellow. Lower parts dull pale olive-yellowish."

From Dr. Chapman's (1907) descriptions of spring adults it appears that there is very little seasonal change. Male: "Head all around and throat reddish chestnut; back yellow olive-green, the rump brighter; inner webs of all but central tail feathers largely yellow; wings black margined with yellow; underparts, except throat, rich yellow faintly streaked with reddish brown." Female: "Above olive green, much darker and greener than [M]; tail black the two outer feathers with large yellow patches on the inner web near the tip; wings black margined with greenish yellow; below uniform pale, dull yellow."

Laurence M. Huey (1927), referring to the bird life of San Ignacio and Pond Lagoons, on the west coast of Baja California, states that mangrove warblers were found there--

in isolated pairs and gave evidence of early nesting by their singing and by the condition of the sex organs of the specimens collected. This warbler was one of the most interesting species observed. The song of the male was usually delivered from a hidden position amid the dense mangroves, though occasionally the bird was seen perched on a dry twig projecting above the level tops of the thicket. The song was pleasing in tone, and of good volume, suggesting that of the Yellow Warbler, but less shrill. Unlike the song of the Yellow Warbler, it was given with a steady rising inflection. The alarm note is a sharp chirp, audible at some distance even during a brisk wind. This note is uttered at intervals and always in the same tone, much as are the chipping notes of the Orange-crowned Warblers. In searching for food, Mangrove Warblers resemble others of the genus _Dendroica_ in their habit of searching each leaf and stem with most careful scrutiny. At times, however, they were seen to launch forth into the air, in true "flycatcher" fashion, after small insects. These aerial sallies were seldom for a distance of over 10 feet, and the bird nearly always returned to the same perch from which it started.

_Enemies._--The following remarks by Dickey and van Rossem (1938) about the El Salvador race of this species are of interest:

As the entire lives of these birds are spent in an environment which renders them immune from attack by the great majority of the predators which harass species inhabiting the land forest, one is at first inclined to be surprised at their relative scarcity. Raccoons (_Procyon_) are extremely common in the mangroves and were often found prowling through the branches at night. They, as well as carnivorous iguanas, undoubtedly take toll of many nests, but aside from these two it is difficult to conjecture what natural enemy operates to limit the mangrove warbler population. Certainly no "saturation point" has been reached, for pairs may be separated by as much as a mile even in the areas which appear most favorable.

DENDROICA MAGNOLIA (Wilson)

MAGNOLIA WARBLER

PLATES 26-28

HABITS

Wilson secured only two specimens of this pretty warbler, one of which was shot among some magnolia trees near Fort Adams, Miss. He gave it the scientific name _Sylvia magnolia_ but called it the black and yellow warbler. This stood for many years as the common name. Nuttall, who had seen it only occasionally in Massachusetts, regarded it as rare. Audubon, on the other hand, found it quite common and even abundant in several places, as we now know it to be. His lively plate of this beautiful bird, one of his best, has always been a favorite of mine; and it seems to me that in the magnolia warbler, more than in any one of the many beautiful species of American wood warblers, are best combined daintiness of attire with pleasing combinations and contrasts of often brilliant colors. Particularly are these qualities apparent when this warbler is seen amongst the dark green firs and spruces of its summer home, where its brilliant array of colors are displayed to advantage as it flits about, sometimes within a few feet of us.

_Spring._--From their winter quarters in Mexico and Central America, some magnolia warblers migrate straight across the Gulf of Mexico to the Gulf coast between Louisiana and western Florida; they seem to be accidental in Cuba and very rare anywhere in Florida. Another migration, probably of some importance, occurs along the coast of Texas from the mouth of the Rio Grande to Louisiana; I saw a few magnolia warblers in the great migration wave noted on an island in Galveston Bay on May 4, 1923. Professor Cooke (1904) remarks: "The dates of arrival of the magnolia warbler in spring furnish the best evidence yet available in support of the theory that birds migrating across the Gulf of Mexico do not always alight as soon as they reach the shore. The species is a common spring migrant from the Mississippi River to the Atlantic, between latitudes 37° and 39°. South of this district it becomes less and less common, except in the mountains, until in the Gulf States it is rare." It is significant that the earliest date of arrival at Atlanta, Ga., is the same as at the lower Rio Grande in Texas, April 20.

William Brewster (1877) writes:

The Black-and-Yellow Warbler arrives in Massachusetts from the South about the 15th of May. During the next two or three weeks they are abundant everywhere in congenial localities. Willow thickets near streams, ponds, and other damp places, suit them best, but it is also not unusual to find many in the upland woods, especially where young pines or other evergreens grow thickly. Their food at this season is exclusively insects, the larger part consisting of the numerous species of _Diptera_. The males sing freely, especially on warm bright mornings. They associate indifferently with all the migrating warblers, but not unfrequently I have found large flocks composed entirely of members of their own species, and in this way have seen at least fifty individuals collected in one small tract of woodland. By the first of June all excepting a few stragglers have left.

On its migration as well as on its breeding grounds the magnolia warbler seems to avoid the taller tree-tops and to prefer the lower levels in the forests and in the thickets along the borders of woodlands; it is sometimes seen in garden shrubbery and in orchards, where it adds a brilliant touch of color to the blossoming fruit trees. When it reaches its breeding haunts it prefers low hemlock thickets, or more especially, where these can be found, the dense thickets of small spruces or balsam firs that spring up thickly in old clearings, or grow profusely along the more open woodland paths; the density of the forest depths seems to be avoided in favor of the more open spaces.

In Allegany Park, N. Y., according to Aretas A. Saunders (1938); "Magnolia warblers seem to have territory and a definite singing location, but I have seen no animosity toward each other or other species of warblers, such as the black-throated green and blackburnian, birds that have very similar habits and live in the same habitat and sometimes sing regularly in the same tree. * * * Territories are evidently vertical as well as horizontal, that is measured in volume rather than area, so that a clump of big hemlocks furnishes space for several pairs and several species of hemlock-loving warblers."

_Courtship._--William H. Moore (1904) says: "During the mating season the males are pugnacious little fellows, and many fights do rivals have. They attack each other with much fierceness, seizing hold with their beaks, and hitting with half-opened wings they sprawl about on the ground, until thoroughly overcome. When pressing his suit to the female of his choice, the male displays his colors to great advantage, as they show in fine contrast among the bright green foliage of the trees."

_Nesting._--All the 14 or more nests that I have seen, in Maine, New Brunswick, Quebec, and Newfoundland, have been in small spruces or balsam firs growing in old clearings, in reclaimed boggy pastures, or along the edges of coniferous woods. These little trees were often less than 6 feet high and generally stood in dense thickets. The lowest nest I find recorded in my notes was only 12 inches above the ground in a tiny fir, and the highest was 8 feet up in a slender balsam in a thick clump of these trees in rather open woods; more nests were below 5 feet than above it. The nests usually rested on horizontal branches or twigs and against the trunk but in a few cases they were placed a few inches or a foot out on a branch.

Similar nesting habits seem to be characteristic of the magnolia warbler in other parts of northern New England, Nova Scotia, and southern Canada according to information received from others; and most of the nests have been placed at similar low levels, though Mr. Brewster (1938) found one near Lake Umbagog that was 25 feet from the ground. In this northeastern region an occasional nest has been found in a cedar, a larch, or a small hemlock, but at a height usually less than 5 feet.

In New York and Pennsylvania hemlock seems to be the favorite tree, and the magnolia warbler more often places its nest at a higher level and well out toward the end of a horizontal branch, where it is usually shaded and sometimes well concealed in dense foliage. Verdi Burtch, of Branchport, N. Y., wrote to Dr. Chapman (1907) that he found nests "in hemlocks usually on a horizontal limb from eight to twenty feet up and over an opening in the woods. Several nests were found in the top of little hemlock saplings from one to five feet from the ground. One nest was found by Mr. C. F. Stone in a birch sapling, this being the only instance to my knowledge of its nesting in a tree other than a hemlock." He has sent me a photograph of a nest in a wild blackberry bush.

T. E. McMullen has given me the data for 14 nests of the magnolia warbler found in the Pocono Mountains, Pa.; 10 of these were located in hemlocks from 30 inches to 30 feet above the ground and from 6 to 12 feet out on the branches; one nest was 30 feet up and one 18, but the others were all less than 10 from the ground. The other 4 nests were in rhododendrons, in woods, or along the banks of creeks, and were from 2 to 3 feet up.

Edward A. Preble (Todd, 1940) says that "all but one of more than fifty nests of this warbler that R. B. Simpson has examined near Warren [Pa.] were placed in hemlocks. One nest was at the exceptional height of thirty-five feet; another was only a foot from the ground in some low hemlock brush." Mr. Simpson's other nest was in a witch-hazel, and Mr. Saunders reported one in a pin cherry, both under hemlocks.

The magnolia warbler is a poor nest builder; its nests are apparently carelessly built and are very flimsy affairs, much like poorly built nests of the chipping sparrow; and they are usually insecurely attached to their supports. Brewster (1877) gives the following good description of a typical nest: "The framework is wrought somewhat loosely of fine twigs, those of the hemlock being apparently preferred. Next comes a layer of coarse grass or dry weed-stalks; while the interior is lined invariably with fine black roots, which closely resemble horse-hairs. In an examination of more than thirty examples I have found not one in which these black roots were not used. One specimen has, indeed, a few _real_ horse-hairs in the lining, but the roots predominate. This uniform coal-black lining shows in strong contrast with the lighter aspect of the outer surface of the nest."

Miss Cordelia J. Stanwood, of Ellsworth, Maine, who has sent me some elaborate notes on the magnolia warbler, gives me this description of one of her best nests: "In this some hay and the fine tips of cinquefoil served as a foundation, but the greater part of the nest consisted of a fine black, vegetable fibre, resembling horsehair. So much of this hair-like material was used that, when the rim was frescoed with down from the willow pod, a person looking at the dainty abode in its setting of fir twigs could see nothing but the jet-black lining and the fluffy, silvery plant-down around the throat of the nest. The structure was partly pensile, being bound with spiders' silk to the two branches at right angles to the main stem.

"The front part of the base rested on the branches beneath. It was placed in a small fir, 2 feet from the ground, surrounded by a growth of fir and gray birches. * * * The nests were about 2 inches wide at the top on the inside and 1-1/4 deep. The wall at the top was 3/4 inch thick."

A series of eight nests now before me vary considerably in size, compactness, manner of construction, and in the materials used. The largest two measure 4 inches and 3-3/4 inches, respectively, in outside diameter, and the smallest ones measure from 2-3/4 to 3 inches. The inner diameter seems to be more constant, varying from 1-3/4 to 2 inches. All of my nests are shallow, hardly more than an inch deep internally in most cases. Some of them are fairly well made, but most of them are very flimsy and more or less transparent. The neatest nests have the sides and rims well built up with dry grass or weed stems of varying degrees of fineness and density. In some there is no grass, but the sides are well made of the very finest hemlock or larch twigs interwoven with fine, red, fruiting stems of mosses and many fine, black rootlets; they are often slightly decorated or camouflaged with a few weed blossoms or bits of wool or plant down. The lining of black rootlets is present in these and in all other nests of the magnolia warbler that I have seen; it seems to be characteristic of the species and will distinguish the nests from those of other warblers. This jet-black lining forms a fine background against which the handsome eggs are shown in striking contrast.

Miss Stanwood gives in her notes the following account of nest building: "The birds fly with much jolly chattering through the trees and examine any nesting sites that appear desirable. The dainty female, after fitting her little body into many spaces among the twigs, finds one that is entirely adapted to her prospective domicile, and the birds proceed to fashion a basketlike frame of long, fine potentilla or cinquefoil runners, or culms of fine hay. These they fasten to the twigs and needles around the selected space with spiders' web, or tent caterpillar silk, leaving the long ends free. Around the top of the basketlike frame on the interior is laid a culm of hay in the form of an imperfect circle, which is secured to the frame with spiders' silk; many of the long ends are then turned down within, or crumpled into the space for the foundation of the superstructure. In the frame is fashioned the cradle, which is symmetrical and cup-shaped on the inside, but may be formed like the bowl of a spoon on the outside, according to the space which it is designed to fill. The preferred lining materials appear to be a jet-black, hair-like vegetable fibre, and horsehair, but on occasion, the dull orange setae of the birdwheat moss, or the brown fruit stems of maples are used for this purpose.

"Both twittering birds bring the materials while it is damp, if possible, and place it, but being very timid, they work little while an observer is near. At such times the birds come silently, one at a time, deposit the bit of cinquefoil or hair-like fibre hurriedly, the female who is oftentimes less timid than the male, doing most of the modelling, turning around and around in the tiny dwelling and shaping it with her breast. Two birds that I timed carefully spent 4 days building their habitation, and another pair 6 days in doing the same work. The amount of time occupied by the task is determined by the abundance or scarcity of materials and the weather; continuous, heavy, cold and retard the work greatly."

_Eggs._--Four eggs almost always form a full set for the magnolia warbler, but sometimes there are only three and occasionally five. They vary in shape from ovate to short ovate, or rarely to elongate ovate, and are only slightly glossy. The ground color is white or creamy white and in some instances greenish white. Their markings vary considerably, some being very lightly speckled, while others are boldly spotted, blotched or clouded with "buffy brown," "cinnamon-brown," "Mars brown," "Prout's brown," "mummy brown," "Brussels brown," "chestnut," "auburn," or "tawny-olive," with occasional scrawls of "bay" or black, and with undertones of "vinaceous-drab," "deep brownish drab," or "Quaker drab." There is a tendency for the markings to be concentrated at the large end, where they often form a wreath, or sometimes a solid cap. Many interesting effects are found on the boldly marked eggs, where the large brown blotches are superimposed on the drab undertones. The measurements of 50 eggs average 16.3 by 12.3 millimeters; the eggs showing the four extremes measure =17.9= by =13.2=, =15.0= by 12.0, and 15.8 by =11.6= millimeters (Harris).

_Young._--The period of incubation for the magnolia warbler is said, by different observers, to be 11, 12, or 13 days, and it is evidently performed by the female only. Miss Stanwood tells me that incubation sometimes begins after the second egg is laid. One egg is laid each day until the set is complete. The young remain in the nest from 8 to 10 days, usually the latter. The eyes of the young are opening on the third or fourth day. On the sixth day, the feathers are breaking the sheaths, and by the eighth or ninth day the young are well feathered. The female does all the brooding of the young, of which Miss Stanwood writes in her notes:

"At first the mother bird covered the young much of the time, as the infant birds were fragile and the weather was cold and damp. Every few minutes the brooding bird moved back on the nest far enough to feed the nestlings regurgitated or digested food, and to cleanse the nest of biting pests such as ants, which might endanger the lives of the baby birds. The father bird sang gaily, far away and near at hand, throughout the long summer day. When he came to the nest with food, he flirted his tail, fluttered his wings, quivered all over and twittered very prettily to his mate, who responded in like manner.

"He presented his first tender moths and juicy caterpillars to the mother bird, who ate part of them, but the remainder she crushed and mixed with digestive juices in her mouth and placed well down the throats of the baby birds.

"The little ones were not many hours old before the male insisted on presenting to them a few tidbits himself; and in a few days the parents fed the young almost exclusively on fresh insect food, which grew larger and tougher as the days went by."

She mentions two attempts of the parent birds to draw her away from their young: "Once I accidentally flushed a brooding magnolia. The bird disappeared into the underbrush, but soon attracted my attention to herself by calling from the top of a second-growth fir, a few yards from where her precious secret was concealed. Then she fell from branch to branch, striking the boughs with a thud, like a dead weight, and dragged an apparently helpless leg or wing over the ground, but always away from where her treasures were hidden. On another occasion, when I visited a family of magnolias that were quite ready to fly, the little ones spilled over the side of the cradle into the surrounding grasses and ferns. Both parent birds, with spread wings and tail, tumbled from all the seedlings in the vicinity and trailed around in widening circles, calling piteously. At last the male bird poised himself in air on fluttering wings between me and a callow youngster, but the moment I lessened the distance between us he vanished."

Henry Mousley (1924) recorded his observations on two nests of magnolia warblers, and found that during a period of 15 hours, at one nest containing very young birds, the male fed the young 34 times and the female 58 times; the average rate of feeding was once in 9.8 minutes; the female did all the brooding for a total of 6 hours and 19 minutes; the faeces were eaten 9 times and carried away 17 times, about equally by each sex.