Tennessee warbler (Vermivora peregrina)
Alexander Wilson had a penchant for naming warblers after the place where he first collected them instead of the place where they typically occurred. He described this rather nondescript warbler in 1811 from a specimen taken during migration along the banks of the Cumberland R. This species doesn’t breed anywhere near its namesake state. Rather, it nests in boreal forests from Yukon Territory east across Canada to Newfoundland and south to the n. parts of Maine, New Hampshire, Vermont, New York, Michigan, Wisconsin, Minnesota, and Montana. It winters from se. Mexico to Venezuela, Colombia, and n. Ecuador.
Status and Occurrence: Fairly common to common migrant, especially east of the Continental Divide, and presumed uncommon to rare breeder in the nw. part of state. Most records are from May and Jun in spring (earliest 7 May near Glendive) and Aug in fall (latest 1 Oct near Billings). No nests documented, but records of singing males from mid-Jun to mid-Jul suggest that breeding occurs in Sanders, Lake, Lincoln, Flathead, and Glacier Cos. An 1843 specimen taken near Fort Union may be from Montana (USNM 1879). R. S. Williams collected two migrants near Great Falls on 23 May 1888 (MCZ 189468, 189469). Presumed breeders were taken at Bigfork on 29 Jun 1904 (Silloway 1905) and at the se. end of Flathead Lake on 2 Jul 1958 (UMZM 4982).
On 22 May 2002, tens of thousands of passerines were grounded by a storm that brought high east winds, rain, snow, and cold temperatures to much of the state. Tennessee Warblers made up the largest number of birds seen, with several observers reporting “hundreds” in small groves of trees and along roadside shoulders. The fallout appeared to be greatest east of the Continental Divide, with concentrations of birds seen at Giant Springs SP in Great Falls and along the Highway 2 “High Line” from Havre to Glasgow.
Habitat: Breeds in deciduous and mixed coniferous-deciduous boreal forests, especially areas with dense shrubs and brush, sapling clumps, and grassy openings (Dunn and Garrett 1997, Rimmer and McFarland 1998). Also nests in riparian willows and alders. In Montana, uses riparian woodlands, shelterbelts, isolated tree groves, and wooded parks during migration.
Conservation: No information for Montana. An abundant species, with a global population estimate of 62,000,000 birds (Rich et al. 2004), but BBS data indicate a survey-wide decline in numbers from 1980-2007.
Historical Notes: In Jun 1873 while en route to Montana Territory, Elliott Coues (1874b: 53) met with a wave of migrant Tennessee Warblers in present-day North Dakota: “Standing in the heavy timber near the bank of the river, I easily procured a dozen specimens in an hour, without moving from my tracks, as the birds came fluttering past in the tree-tops, almost in a continuous band, associating with several other Warblers and with small Fly-catchers.” Perley Silloway found several territorial males and a female carrying nest material in a willow swamp near Bigfork in 1904. Returning to the place where he had seen the female, Silloway (1905: 22) found a pair, noting that “During the hour I spent searching the shrubbery near the place, the two birds manifested much uneasiness, though chirping in their quiet fashion. I am as certain that there was a nest in the neighborhood as anyone can be without ocular demonstration, but I failed to find it....It seems perfectly safe to assume that this warbler nests in Montana in the Flathead region, and further observation will verify this assumption.” The Tennessee Warbler builds a well-concealed nest on the ground, perhaps explaining Silloway’s failure to find a nest by searching in shrubbery.
Contemporary Work: No formal studies have been conducted in the state, but students from the University of Montana Biological Station reported Tennessee Warblers nesting in a marshy area at the se. corner of Flathead Lake in 1958 and 1959 (P. L. Wright, unpubl. data). The Landbird Monitoring Program at the University of Montana’s Avian Science Center detected only eight singing males in w. Montana from 1994 to 2008 (J. Young, pers. comm.).
Sponsored by Rose Leach, Missoula
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