Breeding Bird Atlas 1 Species Accounts
Number of Broods
First spring migrants are seen in late April; movement peaks in mid-May, and birds are in breeding habitat before June. Migrants may be found in any fairly dense cover, usually close to the ground. White-eyed Vireos are persistent singers; indeed, the many “probable” records on the map emphasize that this species is more often heard than seen, even on nesting territory. Songs consist of five to seven loud notes, the first and last often a clear, emphatic chick, the middle notes slurred together and delivered rapidly. Individuals may have several songs or seasonal variations plus a variety of calls described as short ticks, whistles, and harsh mewing notes.
Nest sites are generally in moist areas or close to water, in thickets, shrubs, hedge-rows, tangles of vines, or briers. For an apt description, one can hardly improve on Forbush’s, “among the umbrageous foliage of bosky thickets.” The rather bulky nests are suspended in typical vireo fashion from a forked branch 3 to 7 feet above the ground. An outer construction of leaves, bark, and coarse material is lined with fine fibers, grass, or hair. In eastern Massachusetts, nests have been found in brier thickets in swampy areas, but also occasionally in upland pastures in barberry and other bushes. Other state nests include one found in Rehoboth, also on dry ground, at 20 inches in a cherry sapling growing in a thicket among Arbor Vitae and one at 3 feet in a clump of Arrowwood (ACB). Minute, sparse, dark speckles cover the four to five white eggs, which are laid from late May to early June and are incubated by both parents for 12 to 15 days. One state nest contained a single egg on May 26, and another contained four fresh eggs on June 6 (ACB).
Nest predation is a major mortality factor in thicket-nesting species; thus, it is interesting to note that a strategy has evolved to minimize the dangerous preflight period for juveniles. Fledgling White-eyed Vireos leave the nest before their flight feathers are fully grown, advancing the crucial fledging date by 1 or 2 days. The adults are aggressive and noisy when potential predators are in their territories, particularly when the young fledge. White-eyed Vireos are solitary nesters, and indeed extremely territorial, but may be quite frequently encountered in suitable habitats, e.g., five pairs breeding in 20 acres of the moist coastal thickets of Rocky Point, Plymouth. Little specific information is available about nestlings or fledglings in Massachusetts. Adults are observed carrying food in late June and early July, presumably for nestlings, and an adult and immature were observed together on July 17 (BOEM).
From mid-August until early Septem- ber, adults replace all plumage in a complete postnuptial molt. Juveniles disperse and wander during this same period, and they also molt all feathers except the inner five or six primary and six outer secondary wing feathers. Fall migration is from mid-September to early October. A few stragglers have been recorded in November, but none have been reported to overwinter in Massachusetts. Normal wintering areas are in dense vegetation from the southern United States to Cuba and Nicaragua.