[Fact box]

Landscape associations:

[BCR]

[Ecoprov.]

[BEC zones]

Print

Click on plot to view table of mean abundance

Characteristics and Range These black-and-yellow sparkles of beauty sing a soft summer song from high, hidden places. Townsend's Warblers breed in mature coniferous forests in the Pacific Northwest as far east as the Rocky Mountains. Birds breeding in coastal British Columbia winter along the Pacific Coast of Oregon and California, and are genetically similar to Hermit Warblers, with shorter wings (Morrison 1983) and earlier spring arrival times than the "pure" Townsend's Warblers of the Rocky Mountains. Research suggests that Hermit Warblers once inhabited the entire west coast of British Columbia; as the last ice sheets retreated, Townsend's Warblers moved from the Rocky Mountains to the coast, hybridizing with, and outcompeting Hermit Warblers, forcing them south almost 2,000 km. The contact zone is now south of British Columbia in the Olympic and Cascade Mountains, but coastal Townsend's Warbler populations in British Columbia retain much Hermit Warbler mitochondrial DNA (Krosby and Rohwer 2010). Rocky Mountain populations of Townsend's Warblers winter in the highlands of Mexico and Central America (Wright et al. 1998).

Distribution, Abundance, and Habitat Atlas records show no appreciable change in this warbler's range and distribution since the publication of The Birds of British Columbia in 2001. It continues to have a widespread distribution except on the drier plateaus of the central interior, and is largely absent from the Boreal and Taiga Plains northeast of the Rocky Mountains.

Probability of Observation and abundance is highest below 250 m elevation in the Coast and Mountains and Georgia Depression ecoprovinces, as described in Campbell et al. (2001). A secondary area of abundance is at higher elevation (1,000-1,750 m) across the Southern Interior, Southern Interior Mountains and the Sub-Boreal Interior ecoprovinces. The highest Atlas abundances were recorded in hemlock-, fir- and spruce-dominated biogeoclimatic zones, especially Coastal Western Hemlock.

Townsend's Warblers prefer tall coniferous and mixed deciduous-coniferous forest, from wet coastal types to drier subalpine types (Wright et al. 1998). Kessler and Kogut (1985) found Townsend's Warblers "in old-growth habitats, but nearly absent in younger forest stands and clear-cuts" in southeast Alaska. Townsend's Warblers occur in higher densities near salmon-rearing streams than near non-salmon streams. Salmon carcass nutrient cycling in and near streams increases both aquatic and terrestrial invertebrate prey concentrations, providing abundant food for passerine birds in fall and spring along British Columbia's coast (Gende and Willson 2001, Field and Reynolds 2011).

Conservation and Recommendations The Townsend's Warbler has undergone a moderate long-term decrease based on Breeding Bird Survey data (Environment Canada 2011). The cause is not known, but some studies show the species prefers older forests with taller trees (Wright et al. 1998). Cotter (2005) states "the most important conservation issue in the Tongass Forest (Alaska) is likely the harvest of large conifer trees; the association of Townsend's Warblers and large coniferous trees should be considered in land-use decisions". Predation by introduced American Red Squirrels (Tamiasciurus hudsonicus) on Haida Gwaii is a local threat.

Contact and hybridization with Black-throated Green Warbler occurs along the eastern foothills of the Rocky Mountains in British Columbia (Toews et al. 2011). Further studies west of Fort Nelson River where the Atlas shows the two species also overlap could determine whether a second contact zone exists.

Marguerita (Margo) E. Hearne

Recommended citation: Hearne, M.E. 2015. Townsend's Warbler in Davidson, P.J.A., R.J. Cannings, A.R. Couturier, D. Lepage, and C.M. Di Corrado (eds.). The Atlas of the Breeding Birds of British Columbia, 2008-2012. Bird Studies Canada. Delta, B.C. http://www.birdatlas.bc.ca/accounts/speciesaccount.jsp?sp=TOWA&lang=en [04 Dec 2024]