Click on image for enlargement.

Figure 275. About 1000 Chestnut-sided Warblers have been found in California, and coastal fall vagrants account for roughly four out of every five. Many of the rest have been found inland, particularly during the spring passage. The Committee reviewed records of this species only from 1972 to 1974. This first-fall individual was photographed on 21 September 2001 at Point Reyes, Marin County (Edward D. Greaves).

 

 

 

 

 

CHESTNUT-SIDED WARBLER Dendroica pensylvanica (Linnaeus, 1766)

Accepted: 6 (100%)	Treated in Appendix H: no
Not accepted: 0	CBRC review: records from 1973 through 19751
Not submitted/reviewed: NA	Large color image: see Figure

This warbler’s northern breeding limit extends from central Alberta east to the Maritime Provinces. The southern limit extends from central Minnesota east to Delaware and south through the Appalachian Mts. to northern Georgia. Small, isolated populations exist around the margins of the main range south to Arkansas (Dunn and Garrett 1997). Migration is primarily through the East and the northern West Indies to wintering grounds that extend south along the Atlantic slope of Middle America, from southern Mexico to eastern Panama. The species winters casually in the southern United States and northern South America. Migrants occur rarely but regularly across the West (including the Baja California Peninsula) and casually or accidentally in Alaska, Barbados, western Ecuador, Newfoundland, Greenland, and Great Britain.

A settler of second-growth woodlands and neglected pastures, the Chestnut-sided Warbler was “largely unknown by the early writers on American birds” (Bent 1953) and may even have been “in the same league as the Bachman’s and Swainson’s warblers” 200 years ago (Morse 1989). It is undoubtedly among the native bird species that profited most from large-scale clearing of forests and other landscape-level manipulations that accompanied the conquest and taming of North America by Europeans. More recent trends are toward more forests, fewer overgrown pastures, and continuing urban and residential expansion, and so populations have leveled off and even experienced some declines since the 1960s (Richardson and Brauning 1995).

California’s first Chestnut-sided Warbler, a first-fall male, was collected on 21 September 1908 at Sherwood in Mendocino County (Marsden 1909, MVZ 31345). The state has since accumulated roughly 1000 records, about 80% in fall (2 September–2 December, peaking in late September and October) and 15% in spring (1 May–3 July, peaking in early June), with one to three birds typically found during winter, most of them in the southern half of the state. Although fall vagrants are seldom found far from the coast, numerous winter records come from the state’s interior. As an example, Patten et al. (2003) reported only four records of fall vagrants in the Salton Sink compared with 12 records of wintering birds.

¹On the review list 1972–1973