“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.
Fall.—The myrtle warbler is one of the latest of its family to move southward and is also one of the most leisurely in migration; the migration covers practically the whole of September and October and much of November, the earliest arrivals sometimes reaching the Gulf States before the last ones have left Canada. Abundant in the spring, it is much more so in the fall, when it can often be seen in enormous numbers. As the birds drift along southward, many stop along the way where food is abundant and some spend the winter at no great distance from the southern limits of the breeding range. In Massachusetts, we usually look for them during the latter half of September or during those golden October days when woods are ablaze with the gorgeous autumn colors. As we stroll along the sunny side of the woods on some bright morning after a frosty night, the air is full of pleasing bird music. The robins, now wild woodland birds, are twittering or uttering their wild autumn calls as they drift through the trees; the white-throated and the song sparrows, from the brushy thickets below, give forth their faint, sweet notes like soft echoes of their springtime songs; and the myrtle warblers mingle their distinctive call-notes with these other voices as they glean for aphids on the birches. In the open grassy fields and weed patches, too, we find many myrtle warblers associated with the scattered flocks of juncos and field and chipping sparrows, feeding on the ground. And later in the fall, we find them in the bayberry patches near the seacoast, or even on the salt marshes or among the sand dunes with the Ipswich and savanna sparrows.
Southward along the Atlantic coast the flight is heavy; Dr. Stone (1937) says that, at Cape May, N. J., “on October 13, 1913, Julian Potter encountered a great flight of Myrtle Warblers which he estimated at 3,000. * * * October 31, 1920, was a characteristic Myrtle Warbler day. All day long they were present in abundance. The air seemed full of them wherever one went. Thousands were flittering here and there in the dense growth of rusty Indian grass (Andropogon), in the bayberry thickets, in pine woods and in dune thickets.”
From their breeding grounds in the northern interior these warblers continue to drift southward during October, not in compact flocks but straggling in a continuous stream, some alighting while others are moving on. In Ohio, according to Trautman (1940), “the numbers continued to increase rapidly until approximately October 5. Between October 5 and 20 the species was more numerous over the entire land area than it was at any other season, and thousands were daily present. It was particularly abundant on Cranberry Island, where it fed upon insects, cranberries, poison sumac, and other berries. On several occasions an estimated number between 1000 and 1200 individuals was seen within an hour on this island. After October 20 there was a rather gradual decline in numbers. By November 1, comparatively few remained, and in some years the birds had disappeared.”