Bay-breasted Warbler

Bay-breasted Warbler

Bay-breasted Warbler Male 

The Bay-breasted Warbler (Dendroica castanea) is from the big family, Parulidae.  Dendroica is the largest and most diverse genus in that family with 29 species, 21 in North America and 8 in the Caribbean.  Most species in this genus are similar in behaviour and diet but show a vast array of colouration.  

In breeding plumage the male Bay-breasted Warbler is very pretty with a black  mask, chestnut coloured throat, sides and cap, cream neck patch, white belly, two white wing bars, and an olive and black streaked back.  The female is much duller with a mottled blackish cheek, paler chestnut cap and sides and a buffy split eye ring.  In the fall in non-breeding plumage they are much duller and more yellowish olive-green with indistinct black streaks and grayish upper tail coverts and rump.  Immature birds look like the fall female.

Bay-breasted Warbler [Internet Photo]

Fall warblers can be notoriously difficult to identify.  Fall Bay-breasteds can be confused with fall Blackpoll Warblers.  The Bay-breasteds have greyish legs and feet and buffy under tail coverts and flanks and an unstreaked breast.  The fall Blackpoll has yellow feet, whitish under tail coverts and a faintly streaked breast.  

Bay-breasted Warbler

The song of the Bay-breasted Warbler is a high-pitched, rapidly repeated seetzy, seetzy, seetzy.  This species breeds across Canada east of the Rockies from Alberta to Newfoundland, including New Brunswick.  It spends its winters in the tropics from Costa Rica through Panama to Columbia and Venezuela.  It feeds on insects while on the breeding grounds but also eats fruit in the south.  Bay-breasted Warblers, like all warblers, are an essential part of our ecosystem, keeping the insect population numbers balanced and protecting our trees from outbreaks of insect devastation.

This species nests mainly in the boreal forest but also may be found in mixed forests.  The female lays 4 to 6 brown or purple marked white, green or blue eggs in a loosely built nest of twigs, grass and tree needles, lined with hair.  The nest is usually in a conifer tree about 46 m/50 ft above the ground.

The population of Bay-breasted Warblers varies depending on outbreaks of insect pests in the forest, being abundant during outbreaks.  In 1979 during a spruce budworm outbreak in NB there were more than four singing males per hectare in a spruce stand in Fundy Park.

Bay-breasted Warblers are closely related to Blackpoll Warblers and sometimes hybridize with them.  They are also known to hydridize with Yellow-rumped Warblers and with Blackburnian Warblers.