Bay-breasted warbler

The bay-breasted warbler (Setophaga castanea) is a small species of songbird in the New World warbler family, Parulidae. It is one of thirty-four species in the diverse genus Setophaga. Like all songbirds, or passerines, the species is classified in the order Passeriformes.

Distribution
Bay-breasted warblers breed in the boreal spruce-fir forests of eastern and central Canada, as well as the extreme northern United States. The species winters in the wet lowland forests of northeastern South America, the Caribbean, and southern Central America, and may be seen during spring and fall migration across the eastern half of the United States in a variety of vegetative communities. Many individuals cross the Gulf of Mexico on their long-distance migration, although some travel north and south along the Mexican shore.

Diet and behavior
In the breeding season, bay-breasted warblers feed primarily on insects and spiders, especially the spruce budworm (Choristoneura fumiferana). These are gleaned from vegetation, never caught on the wing. To avoid competition with similar species, bay-breasted warblers concentrate their foraging on the breeding grounds to the interior middle portions of coniferous trees. On wintering grounds in the tropics, fruit forms a majority of the diet. Wintering bay-breasted warblers often form mixed-species flocks with other neotropical migrants and resident species. These flocks seek food in the forest canopy, and the bay-breasted warbler is often an aggressive member of the unit, bullying smaller species from potential food sources.

Breeding
Nests are typically constructed in the lower portion of a spruce or fir tree. The nest is cup-shaped and primarily composed of plant material, with spider silk often utilized as well. Average clutch size is 4-7 whitish eggs with dark spots. The young are altricial at birth, with limited down.

Description
Adult males in breeding plumage are primarily grayish above, with two white wing bars, dark streaks on the back, and a creamy neck patch. The face is black, and the crown, throat, and sides are a dark chestnut color. Breeding females are similar in overall pattern to the males, but are paler and duller. In the nonbreeding season, both sexes gain olive-green feathers on the back, nape, and head. The rufous on the flanks is limited and may even fade away entirely in nonbreeding females. The two white wing bars are present in all plumages.

Similar species
In breeding plumage, the bay-breasted warbler may be confused with the chestnut-sided warbler (Setophaga pensylvanica), which has similar chestnut coloration on the sides. Chestnut-sided warblers may be easily differentiated by the extent of the chestnut, which does not reach the throat or crown. Chestnut-sided warblers also have a bright yellow crown, dark mask, and white cheek and throat in breeding plumage. In fall, nonbreeding bay-breasted Warblers may look very similar to the blackpoll warbler (Setophaga striata). However, blackpoll warblers never have a hint of chestnut coloration on the flanks, and also have yellowish feet, unlike the black feet of the bay-breasted warbler.

Conservation
Although currently classified by the IUCN as least concern, bay-breasted warblers, like many songbirds, are facing population declines across their range. A loss of insect prey and global climate change are contributing factors to decline. The global population is estimated to be fewer than 10 million individuals.

Etymology
The genus name Setophaga is from Ancient Greek ses, "moth", and phagos, "eating", and the specific castanea is Latin for chestnut-coloured.

<!--==Further reading==


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


 * Reports
 * Cooper JM, Enns KA & Shepard MG. (1997). Status of the bay-breasted warbler in British Columbia. Canadian Research Index. p. n/a.
 * Norton MR. (2001). Status of the Bay-breasted warbler, Dendroica castanea, in Alberta. Canadian Research Index. p. n/a.


 * Thesis
 * Clarke M. M.Sc. (2005). Avian abundance and habitat relationships in a managed forest landscape in eastern Nova Scotia. Dalhousie University (Canada), Canada.
 * Greenberg RS. Ph.D. (1981). The Winter Exploitation Systems of Bay-Breasted and Chestnut-Sided Warblers in Panama. University of California, Berkeley, United States, California.
 * McMartin DW. M.Sc. (1996). Impact of insecticide applications on the foraging behaviour and diet of three boreal forest warbler species. University of Toronto (Canada), Canada.


 * Articles
 * Apfelbaum S & Haney A. (1981). Bird Populations before and after Wild Fire in a Great Lakes USA Pine Forest. Condor. vol 83, no 4. pp. 347–354.
 * Caroline G, Marcel D, Jean-Pierre LS & Jean H. (2004). Are temperate mixedwood forests perceived by birds as a distinct forest type?. Canadian Journal of Forest Research. vol 34, no 9. p. 1895.
 * Cumming EE & Diamond AW. (2002). Songbird community composition versus forest rotation age in Saskatchewan boreal mixedwood forest. Canadian Field Naturalist. vol 116, no 1. pp. 69–75.
 * Drolet B, Desrochers A & Fortin M-J. (1999). Effects of landscape structure on nesting songbird distribution in a harvested boreal forest. Condor. vol 101, no 3. pp. 699–704.
 * Ellison K, Sykes PW, Jr. & Bocetti CI. (2002). Re-evaluating the Bay-breasted Warbler breeding range: Nine years of presence in Lower Michigan. Wilson Bulletin. vol 114, no 3. pp. 415–416.
 * Ferguson D. (1997). Bay-breasted warbler in Cornwall: New to Britain and Ireland. British Birds. vol 90, no 10. pp. 444–448.
 * Graves GR. (1996). Hybrid wood warblers, Dendroica striata X Dendroica castanea (Aves: Fringillidae: Tribe Parulini) and the diagnostic predictability of avian hybrid phenotypes. Proceedings of the Biological Society of Washington. vol 109, no 2. pp. 373–390.
 * Greenberg R. (1983). Role of Neophobia in Determining the Degree of Foraging Specialization in Some Migrant Warblers. American Naturalist. vol 122, no 4. pp. 444–453.
 * Greenberg R. (1984). Differences in Feeding Neophobia in the Tropical Migrant Wood Warblers Dendroica-Castanea and Dendroica-Pensylvanica. Journal of Comparative Psychology. vol 98, no 2. pp. 131–136.
 * Greenberg R. (1985). A Comparison of Foliage Discrimination Learning in a Specialist and a Generalist Species of Migrant Wood Warbler Aves Parulidae. Canadian Journal of Zoology. vol 63, no 4. pp. 773–776.
 * Hobson KA & Bayne E. (2000). Effects of forest fragmentation by agriculture on avian communities in the southern boreal mixedwoods of western Canada. Wilson Bulletin. vol 112, no 3. pp. 373–387.
 * Hobson KA & Bayne E. (2000). The effects of stand age on avian communities in aspen-dominated forests of central Saskatchewan, Canada. Forest Ecology & Management. vol 136, no 1-3. pp. 121–134.
 * McMartin B, Bellocq I & Smith SM. (2002). Patterns of consumption and diet differentiation for three breeding warbler species during a spruce budworm outbreak. Auk. vol 119, no 1. pp. 216–220.
 * Meiklejohn BA & Hughes JW. (1999). Bird communities in riparian buffer strips of industrial forests. American Midland Naturalist. vol 141, no 1. pp. 172–184.
 * Morse DH. (1978). Populations of Bay-Breasted and Cape-May Warblers During an Outbreak of the Spruce Budworm. Wilson Bulletin. vol 90, no 3. pp. 404–413.
 * Potvin F & Bertrand N. (2004). Leaving forest strips in large clearcut landscapes of boreal forest: A management scenario suitable for wildlife?. For Chron. vol 80, no 1. pp. 44–53.
 * Rodewald PG & Matthews SN. (2005). Landbird use of riparian and upland forest stopover habitats in an urban landscape. Condor. vol 107, no 2. pp. 259–268.
 * Sealy SG. (1979). Extralimital Nesting of Bay-Breasted Warblers Dendroica-Castanea Response to Forest Tent Caterpillars. Auk. vol 96, no 3. pp. 600–603.
 * Stewart PA. (1986). Fall Migration of Twelve Species of Wood Warblers through Coastal Virginia USA. North American Bird Bander. vol 11, no 3. pp. 83–88.
 * Venier LA, McKenney DW, Wang Y & McKee J. (1999). Models of large-scale breeding-bird distribution as a function of macro-climate in Ontario, Canada. Journal of Biogeography. vol 26, no 2. pp. 315–328.-->