Breeding Bird Atlas 1 Species Accounts
Number of Broods
The preferred habitat of this warbler includes moist thickets in woodlands of second-growth such as oak, beech, ash, gum, and Red Maple, which afford a fairly open understory over the shrubs and rather dense mixed vegetation below. In Massachusetts, Swamp Azalea, viburnum, Catbrier, and ferns figure prominently in the understory, and these plants are used advantageously to provide both support and cover for the nest.
The breeding of Hooded Warblers in southeastern Massachusetts was first documented in 1967 and 1968, when several nests were monitored in Westport. Unfortunately, human encroachment on the breeding territories during the ensuing years undermined the possibility of their continued nesting success. The Atlas failed to produce any confirmed nesting attempts, although singing males were occasionally heard and believed to be on territory.
Hooded Warblers generally arrive in southeastern Massachusetts in early May. Some authors have expressed the belief that males return in spring before females, but that conclusion may have been reached because the latter are inconspicuous and not usually sighted until the courtship singing of the male leads the observer to a pair’s nesting territory. Females are definitely more secretive than males, and they tend to move furtively about in habitat where observation is not easy.
Both male and female Hooded Warblers give a call note best described as the ringing chink of a silver spoon striking a thin china cup. The male’s note is stronger and louder than that of the female, whose note can be likened to the sweet little chip of a cardinal. The literature seems full of different descriptions of the male’s song, although all authors agree that it is uncommonly beautiful and that there are two versions that differ primarily in length. Most also agree that the next-to-last note is noticeably emphasized, while the final note falls away in a soft slur. The series of rapidly whistled phrases is usually given 3 times in succession, but occasionally only 2. The song is somewhat comparable to the vocalization of a Chestnut-sided Warbler but is delivered with greater velocity, clarity, and assertiveness.
Nests are usually located low in the undergrowth, not less than 1.5 feet and seldom more than 3 feet above ground. The cup is quite deep, given such a small resident, and is structurally very strong, albeit made of fine materials. The exterior of the wall is generally formed with thin strips of the outer layers of grapevine bark. In Westport, where a tidal river reached to within 300 feet of one nest site, some of the lower lashings of a 1960s nest were of eelgrass and the inside was finished with closely packed, horizontally curved fine plant fibers in a tightly structured cup. The coarser exterior is bonded and made water-resistant with a generous application of tough, adhesive cobwebs.
Nest building usually takes 6 to 8 days and may, ironically, contribute to the misfortunes that frequently befall nesting success. Cowbirds are notorious brood parasites of Hooded Warbler nests, a practice that seems remarkable because the little nests are so well concealed. One must suppose that gravid cowbirds see the countless comings and goings of the nest builder, thus learning the whereabouts of the nest. Also, such extended activity may arouse the curiosity of domesticated cats and dogs along with snakes, Raccoons, and Opossums. If predatory destruction interrupts the first nesting, the female will quickly rebuild then produce a second clutch. Unfortunately, the new nest may only be a few yards away from the first, thus contributing to a replay of the original scenario.
Hooded Warblers lay three or four eggs. The eggs are a creamy off-white in color, with modest speckling of cinnamon spots distributed around the larger end. Laid at the rate of one per day, the eggs are not incubated until the clutch is complete. Once incubation starts, the female may not leave the nest until hatching occurs. During hatching, the female remains on the nest, in a somewhat elevated position. She reaches down with her bill, pulls up the shell halves, and proceeds to break them down into bite-size pieces, which she swallows. Both parents feed the young a variety of small caterpillars, plus insects including crane flies, moths, mosquitoes, and gnats.
Fledging occurs when the young are 8 or 9 days old, although the wings of the juveniles are not developed enough for them to attempt flying. Their feet and legs, however, allow them to move about the thicket surrounding the nest for several days to a week. There, develop- ment of the young is remarkably accelerated and the parents remain in dutiful attendance. While the fledglings are still learning to use their wings in the underbrush, their mother may some- times undertake a second brood.
After nesting and before autumn migration, adults undergo a complete molt that results in a winter plumage similar to the breeding plumage except that there are usually some yellowish tips to the black feathers of the crown and throat. Juveniles also undergo a complete molt but often retain some of their juvenile flight feathers until their first spring, as well as exhibiting considerable yellowish feathering in the black hood and throat feathers. Fall migrants bound for wintering grounds extending from southern Mexico to Panama are on the move by mid-August. The species is rare in Massachusetts after mid-September. Small numbers also winter in the Bahamas and Greater Antilles.