Details

Bay-breasted Warbler
Setophaga castanea

The Bay-breasted Warbler breeds in the boreal forests across central and eastern Canada. It can be found in Tennessee during the fall and spring as it travels to and from its wintering grounds in Panama and northern South America. This large warbler benefits from spruce budworm outbreaks when the caterpillars provide abundant food. However, spraying to control the destructive outbreaks may have reduced populations of this warbler. In Tennessee it is an uncommon to fairly common spring migrant across the state and a fairly common fall migrant. It is generally present in the state from late April to mid-May and then again from early September to late October.

Description: The breeding male of this small songbird is striking, with a black face, a chestnut head and flanks, a gray back with black streaks, a yellow neck, and white under-parts. The breeding female looks similar to the non-breeding male and is grayish above, white below, has a weak face pattern, and the only chestnut marking are small flank-patches. Non-breeding birds are greenish above and yellowish below. Two white wing bars are present in all plumages. Juveniles look similar to females but lack the chestnut patches. Non-breeding males, females, and juveniles closely resemble Blackpoll Warblers.
Length: 5.5"
Wingspan: 9"
Weight: 0.44 oz

Voice: The song is a very high-pitched, thin seetzy, seetzy, seetzy.

Similar Species:

• Chestnut-sided Warbler has a white chest and a yellow-green crown, with the chestnut restricted to two lines on either side of the breast.
• In fall, very similar to Blackpoll Warbler. Blackpoll does not have buffy or chestnut on sides, has dark streaking on pale under-parts, white under the tail, a more defined eye-stripe, and yellow feet.
• Pine Warbler is unstreaked on the back and has a white under-tail.

Habitat: Found in woodland, and forest edge during migration.

Diet: Insects and spiders, fruit in winter.

Nesting and reproduction: The Bay-breasted Warbler has not been documented nesting in Tennessee.

Status in Tennessee: An uncommon to fairly common spring migrant across the state from late April to mid-May, and a fairly common fall migrant from early September to late October.

Dynamic map of Bay-breasted Warbler eBird observations in Tennessee

Fun Facts:

• Like the Tennessee and Cape May Warblers, Bay-breasted Warblers are able to take advantage of outbreaks of the spruce budworm (Choristoneura fumiferana). Spraying for the spruce budworm during the 1970s and 1980s, primarily in Canada, has partially controlled these outbreaks, but has also reduced Bay-breasted Warbler populations. During outbreak years, it was estimated that this species typically ate more than 13,000 budworms per hectare in a 41-day period!
• The migration routes of the Bay-breasted Warbler were not defined until the 1950s when observers learned to properly distinguish between Pine, Blackpoll, and Bay-breasted Warblers in their non-breeding plumages.
• Adult and juvenile Bay-breasted Warblers appear to take different routes on their fall migrations. More adults migrate west of the Appalachian Mountains than east of them, while first-year birds are more frequent along the coast.

Best places to see in Tennessee: In mixed-species foraging flocks in woodland habitats across the state during spring and fall migrations.

For more information:

Sources:

Robinson J. C. 1990. An Annotated Checklist of the Birds of Tennessee. Univ. of TN Press, Knoxville, TN.

Sibley, D. A. 2000. The Sibley Guide to Birds. A. A. Knopf, New York, NY.

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' Union, Washington, D.C.