Part 31

Forbush (1929) mentions two Massachusetts nests in tall white pines. A nest studied by Mrs. Nice (1930a), at Pelham, Mass., was "six feet up in a small red cedar on a branch next to the trunk. It was a rather shallow affair, composed of cedar twigs and bark, plant fibers, a piece of string and pine needles, and was lined with a few horse hairs and many Ruffed Grouse feathers."

Dr. Paul Harrington has sent me his notes based on the study of 44 nests of the myrtle warbler in Simcoe County, Ontario. He says that the white pine is generally chosen as a nesting tree, the nests being placed from 6 to 40 feet up, averaging 15 feet; "28 nests were built on horizontal limbs about two-thirds out from the trunk, but none at the outermost end. They were conspicuous from below but not from above, as clumps of needles overhung them in such a way as to afford good protection." Of the remainder, 2 were built in the top clump of needles in young trees; 5 were in small spruces, the lowest 3 feet, the highest 15, and all on horizontal limbs, 3 near the trunk and 2 halfway out on the limb; 5 were about 15 feet up in crotches of small cedars; 3 were found in red pines, in the outermost clumps of needles 10 to 15 feet from the ground; and 1 nest was 6 feet up in a small balsam. He says that the nest is lined thickly with feathers and a few hairs. "The feathers are so placed that, as well as lining the nest, they form a screen over the inside when the bird is not sitting. This is done by the shafts of the feathers being woven or imbedded into the inside of the nest and the vane lying free." At Petawa he found these birds nesting in small jack pines.

Dr. F. A. E. Starr, in his notes from northern Ontario, also says that any conifers are suitable nesting sites: "I have found only one exception to the use of a conifer. This nest was built in a hawthorn, and when I collected the nest, the birds moved to a cedar." A. D. Henderson writes to me: "The myrtle warbler is a fairly numerous summer resident at Belvedere, Alberta, and in the Fort Assiniboine District. It nests mainly in the muskegs in tamarack and spruce trees, but occasionally in deciduous trees close to a muskeg." The nests are mostly from 10 to 15 feet up. One nest was in a jack pine, "in a bunchy growth at the end of a limb." Baird, Brewer, and Ridgway (1874) state that MacFarlane found nests on the ground in the Anderson River region.

_Eggs._--Most observers agree that four or five eggs form the usual set for the myrtle warbler. Tufts (MS.) says that "five eggs are more commonly found than four." Dr. Starr says in his notes that "four eggs are rarely laid, two and three being the usual numbers, while sometimes only one is laid, along with those of the cowbird." This is probably an abnormal situation in which the cowbird fills the nest with its own eggs, leaving little room for those of the warbler.

The eggs are ovate to short ovate and slightly glossy. The ground color is creamy white and is speckled, spotted, or blotched with "auburn," "argus brown," "Brussels brown," "chestnut brown," or "cinnamon-brown," with undermarks of "light brownish drab," "vinaceous gray," or "purplish gray." Generally the spots are concentrated at the large end, forming a wreath, but some are marked all over and may also have a few scrawls of blackish brown. I think the handsomest are those having the rich creamy white ground almost immaculate except for a solid wreath, around the large end, of spots and blotches of the browns overlapping and intermingled with the undertones of gray, so that they resemble somewhat the eggs of the wood pewee. On lightly marked eggs the drab or gray spots are the most prominent. The measurements of 50 eggs average 17.5 by 13.3 millimeters; the eggs showing the four extremes measure =20.3= by 13.2, 17.9 by =14.8=, =14.8= by 12.9, and 16.0 by =12.4= millimeters (Harris).

_Young._--The incubation period for the myrtle warbler is from 12 to 13 days and the young remain in the nest normally from 12 to 14 days. Incubating the eggs and brooding the young is apparently done entirely by the female, but both parents are active in feeding the young and in cleaning the nest. Mrs. Nice (1930a), with the help of Miss Lucille Baker, watched a nest containing young for a total of 19 hours, over a period of 6 days. On the first day the female brooded 25 percent of the time, but less later on; the brooding periods averaged 9 minutes.

A great deal of her energy was expended in delousing the nest-- thirty-six minutes on July 28 and seventy-four minutes during the forenoon of the next day, but after that there was little trouble. Once, during thirteen minutes she made over 250 captures, all of which she ate. * * *

The male brought food sixty times, the female forty-eight times, so that the young were fed once in 10.9 minutes. About one-third of the time the male brought two insects, while the female did so on about one-sixth of her trips. During the fourteen hours of observation, the male brought food once In every nineteen minutes, the female once in every twenty-eight minutes. During the last five and one-half hours, the male brought food once in twenty-two minutes, the female once In eighteen minutes. * * *

Excreta were eaten by the female through July 29, but she carried one away at 7:05 P. M., July 28. She ate twelve sacs and carried eleven; her mate carried twenty-five and ate one. * * * He picked lice off his legs and gave them to the babies.

Mr. Knight (1908) says: "The female does most of the work of incubation, but on very rare and exceptional occasions I have found the male bird incubating and even engaged in song while on the nest. * * * The natal down rapidly dries and fluffs out on the young birds and is sepia-brown in color. At the end of six to seven days pin feathers begin to appear, and by the twelfth to fourteenth day the young are well advanced in their juvenal plumage and able to scramble out of the nest. Two to three days after leaving the nest they are able to essay short flights."

_Plumages._--Mr. Knight (1908) refers to the natal down as sepia-brown. Dr. Dwight (1900) describes the juvenal plumage, in which the sexes are alike, as "above, the feathers centrally dull black, edged with drab and buffy brown, producing a streaked effect. Below, much whiter but similarly streaked, a tinge of pale primrose-yellow on the abdomen. Wings and tail dull black, edged with drab, palest on primaries and outer rectrices. Two very indistinct buffy white wing bands. Upper and lower eyelids with dull white spots."

The first winter plumage is acquired by a partial postjuvenal molt in August, which involves the contour plumage and the wing coverts, but not the rest of the wings or the tail. This plumage is entirely different from the juvenal and the sexes are only slightly differentiated. Dr. Dwight (1900) describes the young male as "above, sepia-brown, grayer on the back and obscurely streaked with black, the rump and a concealed crown spot lemon-yellow, the upper tail coverts black, broadly edged with plumbeous gray. Wing coverts black, plumbeous edged and tipped with white tinged with wood-brown forming two wing bands. Below, dull white, washed with pale buff on the throat and sides and obscurely streaked on the breast and sides with black, veiled by whitish edgings. Sides of breast with dull yellow patches. Incomplete orbital ring and faintly indicated superciliary stripe white or buffy." He says of the young female: "The black streaking of this dress is less obvious both above and below than in the male, the plumage everywhere is browner, and the crown patch very obscure."

The extensive prenuptial molt begins early, usually in March, before the birds have left their winter quarters; a few new feathers may be assumed even in late February but most of the molt occurs in April while the birds are migrating; it is, however, generally completed by the time the birds have reached their breeding grounds. Dr. Dwight (1900) says this molt "involves most of the body plumage and wing coverts, occasionally a tertiary but not the rest of the wings nor the tail. The black and gray of the upper surface, the white wing bars and the yellow crown and rump are new, some of the old upper tail coverts and a part of the feathers of the abdomen and crissum being retained in many cases, those of the back and elsewhere less often. Young and old become practically indistinguishable although the young usually have browner and more worn wings and tails, obvious in the primary coverts, but the differences are not absolute." In the female, "the first nuptial plumage is assumed by a restricted moult, leaving behind many brown feathers. The brown feathers of the lores and auriculars are assumed by moult."

The adult winter plumage is acquired by a complete postnuptial molt, beginning late in July. In the male, this "differs little from the first winter dress, but the wings and tail are blacker with brighter gray edgings, noticeable especially in the primary coverts. The back is usually grayer and the lower parts whiter, with broader streakings above and below." In the female there are similar differences, the adult winter female resembling the young male at that season. Adults have a complete postnuptial molt in July and a prenuptial molt as in the young birds.

_Food._--Forbush (1929) sums up the food of this warbler very well as follows:

The Myrtle Warbler is one of the few warblers that can subsist for long periods upon berries and seeds, although undoubtedly it prefers insects when it can get them. Along the coast during the milder winters there are many flies rising from the seaweed in sheltered spots on mild days even in January, and there are eggs of plant-lice and some hibernating insects to be found on the trees, but the principal food of the Myrtle Warbler in New England during the inclement season is the bayberry. They can exist, however, on the berries of the Virginia juniper or red cedar and these seem to form their principal food when wintering in the interior; berries of the Virginia creeper or woodbine, those of viburnums, honeysuckle, mountain ash, poison ivy, spikenard and dogwoods also serve to eke out the birds' bill of fare. In the maple sugar orchards in early spring they occasionally drink sweet sap from the trees. In the southern Atlantic states they take palmetto berries. North and south they also eat some seeds, particularly those of sunflower and goldenrod. During spring and summer they destroy thousands of caterpillars, small grubs and the larvae of saw-flies and various insects, leaf-beetles, dark-beetles, weevils, wood-borers, ants, scale insects, plant-lice and their eggs, including the woolly apple-tree aphis and the the common apple-leaf plant-louse, also grasshoppers and locusts, bugs, house-flies and other flies including caddice-flies, crane-flies, calcid-flies, ichneumon-flies and gnats, also spiders.

To the above comprehensive list there is little to be added, although wild cranberries and the berries of the poison sumac might have been included. Myrtle warblers are doubtless instrumental in spreading the seeds of poisonous species of _Rhus_, which is not to their credit; they also help to disseminate the red cedar, as they digest only the outer covering of these three and the bayberries. These warblers are often seen on the beaches and sand dunes eating the seeds of the beachgrass, or in open fields feeding on grass seed and doubtless various weed seeds. They frequent the fresh holes bored by sapsuckers to drink the flowing sap and eat the insects that are attracted to it. In Florida, in winter, they drink the juice of fallen oranges in the groves and even the broken oranges on the trees.

They are somewhat expert as flycatchers, taking mosquitoes and gnats in the air. Knight (1908) writes: "During the fall months they enter the city gardens and orchards, climb over the roofs and along the gutters of houses, peering into every nook and cranny. They hover on beating wings about such crannies of the clapboards and finish where they may have spied some delicious, big fat spider, chrysalis or other delectable morsel, and such finds are speedily devoured. Now peering, now hovering, and now springing into the air after some winged insect, they stop about a building for a few hours or days, slowly but surely retreating southward."

_Behavior._--Much of the behavior of this friendly little bird has been referred to in connection with its activities about our homes and gardens and its nesting habits. Tilford Moore tells me that "these birds seem to have a tendency toward 'creeperism,' in that they are often seen hanging to the bark of a vertical trunk or branch, and are usually on the larger branches rather than among the smaller twigs. They often flutter a lot when hanging to the bark." And Wendell Taber sends me this note: "On May 5, 1940, Richard Stackpole and I watched a flock in West Newbury, Mass. The birds were running about on the grass near a stream. Again, they would alight at the base of a tree and run up it several feet. I think all the birds that performed this feat were females. They were most deceptive, and we kept thinking we were seeing brown creepers until we put field glasses on them."

William Brewster (1938) writes of the behavior of a female about her nest, 35 feet from the ground in a hemlock: "The female Yellow-rump was sitting and for some time she absolutely refused to leave her eggs. Watrous first shook the branch and then with a long stick poked and shook smartly the twigs within an inch or two of her head. At length she hopped out of the nest and stood for a moment or more on its rim looking about her. Then she fluttered down towards the ground with quivering wings and wide spread tail, moving slowly and alighting several times on a branch or cluster of twigs where she would lie prostrate for a moment beating her wings feebly and simulating the movements of a wounded or otherwise disabled bird."

Dr. Stone (1937) describes the flight of the myrtle warbler very well:

We soon learn to identify their rather jerky flight as they rise from the bushes, and with a series of short wing flips turn now to the right, now to the left, in their zigzag progress, rising somewhat with the beats, and falling in the intervals. Sometimes a bird will go but a short distance, flitting from bush to bush, while others will climb higher and higher in the air, drifting in their jerky way across the sky like wind-blown leaves. * * *

As soon as a Myrtlebird alights on a bush there is a short, sharp flip of tin tail, not a seesaw action, but one involving the body as well, and as it comes to rest the head is drawn in and the plumage ruffled up making the outline more nearly globular, while the wings are dropped slightly so that their tips are a little below the base of the tail.

Francis H. Allen has sent me the following notes on the behavior of this species: "Aug. 27, 1915, Mt. Sunapee, N. H. On the summit of the mountain an immature myrtle warbler, very tame, flitted and hopped about on the ground, over moss and rocks, and in bushes and trees, feeding industriously on small insects. It seemed to pay no attention to my companion and me, and at one time hopped between us when we stood about 6 feet apart, and came within 2 feet of my outstretched hand as I held a crumb out towards it. I followed it about a little and found it quite fearless, except when I made a sudden movement. The bird could fly well and seemed perfectly well able to take care of itself.

"July 5, 1931, Mt. Whiteface, N. H. One or more were seen flying up fifty or a hundred feet above the tops of the low spruces and darting about up there after insects--doubtless the black flies which were abundant on the summit.

"Oct. 25, 1941, Plymouth, Mass. A sizable flock were feeding actively, flying back and forth across the narrow Eel River, feeding among foliage, catching flies and eating bayberries. One came within 6 feet of me and calmly ate bayberry after bayberry."

_Voice._--Aretas A. Saunders contributes the following account of the songs: "The songs of the myrtle warbler show some differences from those heard from birds on migration or on the breeding grounds. The song in general is a series of short, rapid notes in a rather colorless simple, but musical quality. The number of notes, in my 41 records, varies from 7 to 21 and averages about 12. The songs heard on migration, however, average 11 while those on the breeding grounds average 14.

"The songs heard on migration are quite indefinite in form; the pitch rises and falls irregularly, and no two songs are much alike. An individual bird may sing many variations, each song it sings often being a little different from the others. The notes, however, are all about the same length and loudness, accented notes that stand out from the others being rare. This song shows indications of a somewhat primitive character.

"The song on the breeding grounds is somewhat more definite; the notes are often joined in 2-note phrases, the first note of each phrase higher in pitch than the second and each phrase successively higher, so that the song trends upward in pitch. This is true of 10 of my 13 records of the song on the breeding grounds in the Adirondacks. The other 3 have a slight downward trend. In addition to the more regular form, these songs have a somewhat brighter, livelier, and more musical sound than those heard on migration.

"Songs of this species vary from 1 to 2-4/5 seconds in length. There are usually about seven notes per second. Only 3 of my records show any irregularity in the time of the notes, that is having some notes that are shorter or longer than the others. Pitch of the songs varies from F´´´ to E´´´´, a half tone less than an octave. Single songs vary from one to four and a half tones, averaging about two and a half tones; only 5 records are greater in range, and only 16 are less, nearly half of the records having the average range.

"Since the myrtle warbler winters in Connecticut, I am able to get the first dates of singing. In 30 years of records the average date is April 13; the earliest April 2, 1923, and the latest April 25, 1920. In the Adirondacks the last date of singing noted was July 31, 1926.

"The call-note, _tchick_, is louder than in most warblers. I found it pitched on D´´. Another note is a fainter _tseet tseet_, usually doubled and pitched on F-sharp´´´."

Francis H. Allen (MS.) describes the song in a different way as follows:

"The only syllabifications I find in my notes are of a bird heard at West Bridgewater, Vt., June 19, 1907, which sang _whee whee whee whee whee whee whee whee hew hew_, sometimes with three or even four _hews_ at the end and sometimes with only one; and one of a bird at South Tamworth, N. H., July 23, 1942, whose song consisted of two trills, _ching ching ching ching ching weedle weedle weet_.

"The ordinary call-note is a hoarse _chep_, easily distinguished from the call of any other New England warbler. I have also heard occasionally a slight _tsip_ or _tsit_, suggesting a chickadee. The feeding call of the young out of the nest is a rapid succession of several explosive _chips_ or _pits_ with a rolling quality--a sort of chatter or chippering."

On June 7, 1900, in Washington County, Maine, I recorded the song of the myrtle warbler as _wheedle wheedle wheedle wheedle wheedle_, repeated five to seven times so rapidly as to be hard to count and all on one key, usually ending abruptly but occasionally in a little trill.

Few writers have accorded the song of the myrtle warbler much praise, but Bradford Torrey (1885) pays it this tribute: "For music to be heard constantly, right under one's window, it could scarcely be improved: sweet, brief, and remarkably unobstrusive, without sharpness or emphasis; a trill not altogether unlike the pine-creeping warbler's, but less matter-of-fact and business-like. I used to listen to it before I rose in the morning, and it was to be heard at intervals all day long."

_Field marks._--The male myrtle warbler in spring plumage is easily recognized at a considerable distance in its blue-gray, black, and white plumage, offset by conspicuous patches of bright yellow on rump, sides, and crown, and by the black sides and cheeks. The female is much duller and browner, the yellow being less conspicuous and the black cheeks lacking. Young birds and fall adults are much like the female, but the yellow rump, showing plainly as the bird flies away from the observer, will distinguish the species at any season or age.

_Enemies._--So much of the breeding range of the myrtle warbler is beyond the normal breeding range of the cowbirds that, until recently, it was supposed to be largely free from the imposition of this parasite. When Dr. Friedmann (1929) published his book on the cowbirds he had only three records of such molestation, but more have turned up since, particularly in the Middle West where the ranges of the two species overlap considerably. Dr. Paul Harrington writes to me from Toronto: "Sixty-five percent of the nests examined contained eggs or young of the cowbird; it would not be exaggerating to say that two-thirds of the initial nests are parasitized. The egg or eggs of the cowbird are often deposited before the nest is completed, leading to many a deserted nest. Twice I have found a cowbird's egg imbedded, as so often happens in the yellow warbler's nest, but in both cases yet another was in the nest with the owner's. Twelve percent of the nests with eggs of the cowbird were deserted, but none in which the owner's eggs were also present. Generally but one of the parasite's eggs was found, occasionally two and rarely three."

Dr. F. A. E. Starr says in his notes from Ontario: "Occasionally, when a cowbird usurps a nest, the birds continue building till the cowbird's egg is imbedded. This is all in vain, however, as out of 30 nests, I have yet to find one which did not contain from one to three eggs of the cowbird." And A. D. Henderson mentions in his notes from Belvedere, Alberta, a nest that held five eggs of the myrtle warbler and one egg of the Nevada cowbird, and another nestful consisting of four eggs of the warbler and two of the cowbird. Probably very few young of the warbler are likely to survive in nests with young cowbirds, which means that this parasite must seriously interfere with the normal increase in the warbler population.

Harold S. Peters (1936) lists two lice, two flies, and two mites as external parasites on the myrtle warbler.