Figure 99. In California, Broad-winged Hawks have always been very hard to find away from the Marin Headlands—where dozens of migrants are recorded each fall—and during the last two decades only a handful have been found overwintering in the state. This first-winter bird was photographed in February 1978 in Santa Barbara, Santa Barbara County (Jim Greaves).

 

 

 

 

 

BROAD-WINGED HAWK Buteo platypterus (Vieillot, 1823)

Accepted: 3 (75%)	Treated in Appendix H: no
Not accepted: 1	CBRC review: 1972 and 1973 records1
Not submitted/reviewed: NA	Color image: none

This buteo breeds across most of southern Canada, from extreme southeastern Yukon and east-central British Columbia east to Nova Scotia, and across much of the United States east of the Great Plains. The main wintering grounds extend from western and southern Mexico south to southern Brazil. Small numbers winter in southern Florida, and resident populations exist in the West Indies. The species is a very rare to rare migrant across most of the West, and is especially scarce in spring. Small to moderate numbers of southbound birds are tallied every autumn at a few select hawk-watch sites, one of them at California’s Marin Headlands in Marin County (see below). Other productive sites in the West include the Goshute Mts. in northeastern Nevada, the Grand Canyon in northern Arizona, Commissary Ridge in southwestern Wyoming, and Rocky Point Bird Observatory on the southern tip of Vancouver Island, British Columbia.

California’s first Broad-winged Hawk was a first-winter male found on 11 December 1966 in the Tijuana River valley, San Diego County (McCaskie 1968a, SDNHM 36086). That none was found earlier must be attributed largely to identification difficulties. Another factor was the relatively late discovery of this species’ minor southbound migration route along California’s coast (Binford 1979). The overwhelming majority of California’s records come from the Marin Headlands, where hawk watchers recorded an average of 103 birds per fall—primarily in September and October—between 1995 and 2004 (Golden Gate Raptor Observatory data; www.ggro.org/research.html). The Committee reviewed only a few records before the species’ status as a regular migrant at this location became clear.

Broad-winged Hawks have never been encountered regularly in California anywhere away from the Marin Headlands, but during the 1970s and the first half of the 1980s small numbers were found infrequently during late fall and winter from the San Francisco Bay Area southward. Such records later became almost nonexistent, and the species is now very rare during the winter period, with most such records involving first-year birds along the central coast. Many December records, and perhaps even some in January, may pertain to late migrants rather than overwintering birds. For example, only four out of ten winter-period records from Monterey County involve birds thought to have overwintered there, and none has been found wintering there since 1986 (Roberson 2002). Only two Broad-winged Hawks have been found on California islands, both first-year birds photographed on San Clemente Island in Los Angeles County: 31 October 2001 to 10 October 2002 (Sullivan and Kershner 2005) and 22 March to 4 April 2006 (NAB 60:437).

Additional evidence of late fall/winter decline in southern California is provided by Lehman (1994) and Unitt (2004). See also Garrett and Dunn (1981), McCaskie et al. (1988), and Small (1994).

 

¹On the review list 1972–1976