Have redshoulders saturated their nesting opportunities? Or are they encountering some urban challenge such as tree removals or the overuse of rat poisons? The jury is still out. This hypothesis is supported by the Christmas Bird Counts, five of which hit a clear redshoulder peak in the years 2002–2008. In either case, the apparent leveling trend may indicate that redshoulders have reached capacity in the Bay Area. While the count of 248 sightings from 2011 is well below the average, it’s too early to say if it’s a dip or the beginning of a decline. The reasons for such year-to-year variations are probably not possible to ferret out. Within this overall upward trend - now leveling out some - there are dramatic dips and rises from year to year. Twenty-five years of GGRO autumn red-shouldered hawk counts, expressed as five-year averages (to soften annual swings due to weather, etc.), show an upward trend. Although California redshoulders aren’t classically migratory - that is, all moving from north to south in autumn - they do disperse quite a bit, traveling dozens of miles in any direction in search of pockets of abundant prey. This pattern holds as well for the red-shouldered hawk fall migration counts by the Golden Gate Raptor Observatory (GGRO) in the Marin Headlands. Three counts (Mount Diablo, Palo Alto, Santa Rosa) actually show populations still rising as of 2010. For eight different Bay Area CBC circles, annual redshoulder counts increased starting in the 1960s or ’70s and peaked only in recent years. And these nonnative nest trees launched, on average, a greater number of fledgling redshoulders than did their native counterparts.Ī review of Christmas Bird Count (CBC) statistics, collected and compiled under the auspices of the National Audubon Society since 1960, backs up these more anecdotal observations. In 19, biologist Steve Rottenborn focused on the nesting redshoulders of the Santa Clara Valley and discovered that 52 of 85 nests were in nonnative trees, particularly eucalyptus. My own dear Woodside grandmother had a stuffed Cooper’s hawk on the mantel, the result of her swift trigger and eagle eye.Īre red-shouldered hawks more common in the Bay Area now than half a century ago? In the Marin County Breeding Bird Atlas, David Shuford notes that the species was rare by mid-century in California, due to the pressures of human growth and expansion, but by the early 1990s they were starting to reoccupy “the Los Angeles basin where mature trees provided nesting habitat in certain residential areas, parks, and cemeteries.” Not long after, that exact phrase could have been applied to the Bay Area as well. Regarding the first hypothesis, Dawson, in The Birds of California, notes that a particular nesting redshoulder “marks our distant approach and is ill-at-ease, fearing the gun.” It should be no surprise that any diurnal raptor pre-1960s was a chickenhawk first and a unique species second. It appears that redshoulders in abundance is a fairly recent phenomenon in the Bay Area, either because the hawks were more tight-lipped in historical times or they just weren’t common here. (Photo by Phil Robertson) A Rise in Redshoulders In their wonderfully descriptive book, Raptors of California, Hans and Pam Peeters put it bluntly: The red-shouldered hawk is perhaps “California’s noisiest raptor, often drawing attention to itself with its loud and repeated clarion calls.” A red-shouldered hawk calling from its perch in a creekside park in a suburban area north of Sacramento. Regarding the redshoulder song, Hoffmann called it “high and piercing.” William Leon Dawson described it as “a ringing series that sets the woods agog, kee-a!, kee-a!, kee-a!” Early naturalists called the redshoulder “the Singing Hawk,” more in reference to the species’ incessant noisiness than to the sweetness of its sound. It will often perch hunt, “not circle over open country as Redtails do,” to quote Ralph Hoffmann, author of the 1927 field guide Birds of the Pacific States. For instance, a redshoulder flaps in series, then glides on set wings much like a Cooper’s hawk. However, a redshoulder’s habits and habitats are accipiter-like. Morphology and genetics put them in the genus Buteo with red-tailed, ferruginous, and Swainson’s hawks.
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