Bay-breasted Warbler    Dendroica castanea

Migratory Status: Neotropical migrant

PIF Population Estimate: 3 100 000

Percent of western hemisphere population breeding in boreal forest: 82%

BAM Effective Detection Radius (m) : 45.86

PIF Maximum Detection Distance (m) : 80

Canadian BBS Population trend: -2.6 n.s. (-5.8 to 0.5)

Life History

The adult male Bay-breasted Warbler is easily distinguished during the breeding season by its striking chestnut crown and upper breast, black face, and cream-coloured hind neck. Females are much duller than males, though they retain many of the same plumage characteristics. In fall, this species can be easily confused with other, morphologically similar members of the genus, namely the widespread Blackpoll Warbler (D. striata) and the Eastern Pine Warbler (D. pinus).

The species’ breeding range extends over most of the southern boreal forest, from western Newfoundland to north-eastern British Columbia and the Liard Valley of the Northwest Territories. The distribution on the breeding grounds closely approximates the distribution of white spruce (Picea glauca) and balsam fir (Abies balsamea). The distribution on the wintering grounds includes Panama and northern South America.

The Bay-breasted Warbler is known to track highly irruptive outbreaks of the spruce budworm (Choristoneura fumiferana) and can undergo large population fluctuations during major outbreaks. Apart from local changes in breeding population density during peak years, very little is known of the larger spatial and temporal impacts of these highly localized outbreaks, on this and other breeding bird species.

The song of the Bay-breasted Warbler is one of the quietest and highest pitch songs of all North American wood warblers. Combined with its strong association with dense conifer forests, the species is one of the most difficult to hear, and when heard, it is often extremely difficult to pinpoint. This may present a potential detection bias on many surveys and may complicate studies that attempt to determine fine-scale habitat associations.

Reference(s)

Williams, J. M. 1996. Bay-breasted Warbler (Dendroica castanea), The Birds of North America, No. 206. A. Poole and F. Gill, eds. The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists's Union, Washington, D.C.