Blackbumian Warbler Dendroica fusca

The Blackburnian Warbler is closely associ­ ated with mature coniferous trees. The spe­ cies prefers old-growth stands that contain either exclusively coniferous growth or mixed conifer-deciduous stands, but will oc­ cupy territories within northern deciduous forests that contain only a single tall red spruce or hemlock. Habitat studies indicate that the species prefers to forage and nest in conifers. MacArthur (I9 58) indicated that because of this warbler's preference for for­ aging in the topmost branches, it places a premium on tall, mature forests for habitat. He also hypothesized that because of over­ tached to the supporting limb with spider lap in foraging behavior, this species may webbing, and lined with black rootlets, hair, compete with the Black-throated Green or fine grass. Nest heights of five Vermont Warbler (D. virens). nests averaged 7.9 m (26 ft) above ground; A treetop bird that possesses a sibilant this is probably low, as most accounts indi­ song, the Blackburnian Warbler is difficult cate that nest heights are generally more to detect. The most reliable way to locate than IO m (33ft) up. Egg dates for Vermont this bird is by its voice. Its song consists of (three nests) extend from June 9 to June 22. a rapid series of high, "stitching" notes, Clutch sizes range from 3 to 5 eggs, with 4 followed by a normally upward-inflected being most frequent by far. Young have been note that trails off beyond the range of hu­ detected in the nest as late as July I3. Fledg­ man hearing. Variations on this theme are lings have been reported only as late as July many, including unadorned sibilant, slurred I4; in New York, fledged young have been high notes, and a version that ends in a noted into early August (Bull 1974). Black­ downward-inflected note. The nest is ex­ burnian Warblers depart from Vermont in ceedingly difficult to find because it is placed late August and early September; occasional high among coniferous greenery, which individuals may remain into early October. camouflages it. Nests may be sometimes This species is common in Vermont, located by watching parents fly back to though often highly localized. In much of them. The most frequent confirmation code Vermont's northern hardwood forest the used by Atlas Project workers for this spe­ species is represented by scattered pairs cies was FY (parents with food for young), whose territories center on one or more tall which accounted for more than 72% of all hemlocks or red spruces. The coniferous confirmations. species with which the Blackburnian War­ Blackburnian Warblers typically arrive bler is found vary with the physiographic from central and northern South America in regions it occupies. It inhabits stands of bal­ the first weeks of May; the earliest record is sam fir and black spruce in the Northeast for April 30. The species begins nesting in Highlands, red spruce in the Green Moun­ late May, and is single-brooded. The nest is tains, hemlock and spruce in the Eastern usually saddled on a side branch well out Foothills and Taconic Mountains, and even from the trunk of a conifer; sometimes it is tall, open stands of white pine on occasion placed in a trunk fork near the top. It is in the Connecticut River valley and Cham­ constructed of twigs and plant fibers, at- plain Lowlands. The historical status of the

298 Species Confirmed as Breeders in Vermont No. of priority blocks in which recorded

TOTAL I40 (78%) Possible breeding: 30 (22% of total) Probable breeding: 48 (340/0 of total) [!]~~- ~- Confirmed breeding: 62 (44 % of total) e -e[!] [!] e • [!]!]n • ~ [!]- [!] 0- .... - Physiographic regions in which recorded •• % of C!J-..o ~·eP % of species' no. of region's total l!J • • priority priority priority D~ blocks blocks blocks .. ­• Champlain Lowlands 13 42 9·3 I:illIJ Green Mountains 53 98 37·9 o North Central 15 79 10·7 - Northeast Highlands 16 100 11,4 '0 20 30 40 o , , ,,' East Central 16 84 11.4 Taconic Mountains 9 56 6·4 20,,30 Eastern Foothills 18 75 12·9

,,' species, as indicated by such authors as Mountains. In western Vermont the region Perkins and Howe (I90I) and Davenport of absence is roughly bounded by the 200 C (I907), has changed little; the species was (68 0 F) isotherm (the mean temperature for considered common, if local, before the ex­ July), indicating this species' need for conif­ tensive reforestation of much of the state erous trees that are scarcer in this warm during the past IOO years. If anything, region. Because eastern Vermont offers a the species has probably increased with wider selection of microclimates as a re­ reforestation. sult of its high land relief, the species does The distribution of the Blackburnian not become sporadic until below the 2IO C Warbler presents a familiar pattern found in (700 F) isotherm in the southern Connecti­ most of the state's boreal warblers. It is no­ cut River valley. ticeably widespread in eastern Vermont and WALTER G. ELLISON along the spine of the Green Mountains, is absent from more than half of the Cham­ plain Lowlands, and is local in the Taconic

Blackburnian Warbler 299