Figures 284, 285 (above, below). From 1972 through 1975 the CBRC reviewed records of the Bay-breasted Warbler. As with the Cape May Warbler, California records of the Bay-breasted have decreased steadily since the mid 1970s, although it remains a rare, regular transient, primarily in autumn. This first-fall male at Furnace Creek Ranch, Inyo County—sketched on 27 November 1999 (Andrew Birch) after being photographed three days earlier (Jon L. Dunn)—shows an unstreaked breast, olive back with faint streaks, and cinnamon flanks .

 

Figure 285.

 

 

 

 

BAY-BREASTED WARBLER Dendroica castanea (Wilson, 1810)

Accepted: 9 (100%)	Treated in Appendix H: no
Not accepted: 0	CBRC review: records from 1972 through 19751
Not submitted/reviewed: NA	Color images: see Figures

This denizen of North America’s boreal forests breeds across a range very similar to that of the Cape May Warbler. The northern breeding limit extends from extreme southeastern Yukon, the southwestern Northwest Territories, and northeastern British Columbia east to western Newfoundland. The southern limit stretches from northern Minnesota east to northern New England and Nova Scotia. The species migrates through the Caribbean and along the Atlantic coast of Middle America to wintering grounds that extend from Costa Rica to northwestern South America. The species occurs casually to rarely through the West Indies to northeastern South America, and in Labrador. Vagrants occur casually across the West—from central Alaska south to Clipperton Atoll and the Islas Revillagigedo—and accidentally in Greenland and Great Britain.

The state’s first Bay-breasted Warbler was a first-fall male collected on 6 October 1956 approximately 21 nautical miles southeast of San Clemente Island, Los Angeles County (Arvey 1957, MVZ 134974). California now claims more than 300 records, roughly 70% in fall (21 August–21 December, peaking in late September/October) and 30% in spring (20 May–9 July, peaking in early June). A female found on 10 April 1982 in Goleta, Santa Barbara County, was thought to be an early spring vagrant, perhaps one that wintered somewhere along the coast of California or northern Mexico (Lehman 1994). A female present from 22 to 25 July 1997 on Southeast Farallon Island was either an odd summer wanderer or a very early fall vagrant. Three birds, two of which definitely overwintered, have been recorded later than 21 December: 10 January–9 April 1982 in Long Beach, Los Angeles County (AB 36:332, 895); 30 December 1983–10 April 1983 in San Diego, San Diego County (Unitt 2004); and 29 December 2001–7 January 2002 in Long Beach (NAB 56:225).

As with the Cape May Warbler (see that account), the Bay-breasted’s rate of occurrence in California has dropped off since around 1980, with both trends linked to a reduced frequency of Spruce Budworm (Choristoneura fumiferana) outbreaks on the breeding grounds (Patten and Burger 1998).