Red-shouldered Hawk (Buteo lineatus)
   
 
Narrative and Science Lens
 
Audubon shows us a pair on tree limbs, reminding us, possibly, that these buteos hunt from a perched position, while many others hunt while patrolling. The upper hawk may be hunting, but judging from the protruding breast of the lower one, it looks as if it has consumed a large meal. Audubon has noted that the birds are known to gorge, consuming an entire squirrel in one meal.

This is not a large hawk: It's just under two feet long and its wingspan is about twice that. When airborne the (white) crescent “window“ toward the wing tip is a great field mark. Although not large, it’s loud, even in winter, leading to a reputation as possibly California’s noisiest raptor. Allen Fish, who directs the Golden Gate Raptor Observatory thinks this may reflect its early breeding season, with courtship beginning in December.

In recent decades, populations have increased throughout much of California (see Sustainability, below). Formerly restricted primarily to native riparian habitat, the Red-shouldered Hawk has expanded into more upland areas by nesting in a variety of non-natives, especially eucalyptus. A study in the South Bay (including birds on campus) found that they nested disproportionately in, and were even more successful in, eucalyptus than in native riparian trees, likely due to their more sturdy structure.
 
  Campus Locations
Resident virtually throughout campus, foraging for small vertebrates in fields and occasionally on lawns. The number of breeding pairs is only 5-10 due to large territory size and the paucity of trees large enough for nesting. Most pairs nest in eucalyptus trees, which provide sturdy support for nests and protection from predators.
  Campus sustainability
 
Image courtesy of Tom Grey

 Around 1950, Red-shouldered Hawks were less common in the San Francisco Bay area. In Marin County, they were considered declining and actually rare. From the 1960s-1970s on, local annual counts showed increases. By 1990, with the increasing availability of tall trees in our area, the birds were becoming more evident. Wildlife ecologist (and Stanford Ph.D) Steve Rottenborn, who has studied Bay Area birds since 1992, found that in our county many Red-shouldered Hawks (52 of 85 nesting pairs) selected non-native trees, often eucalyptus, for nesting. Keep your eye out for pairs, like this one photographed by Tom Grey, Sweitzer Professor of Law, emeritus.
       What you can do
       1. Share any sightings—especially of nesting on campus. Keep a journal.
       2. Check trees that might make good nesting sites and try to assess why they are not being used.
       3. Record which birds mob Red-shouldered Hawks
       4. If you often see one of these birds perching in the same spot, keep track.
  Science
       Essays from The Birder’s Handbook:
            Hawk-Eyed; Mobbing
       References:
          Bednarz and Dinsmore, 1981; Brown and Amadon, 1968; Henny et al., 1973; Wiley, 1975
       Videos:
  Art
       Photos:
            Johanna van de Woestijne's photo of Red-shouldered Hawks in tall tree habitat--Rancho San Antonio Park, Los Altos, CA. See more of Johanna's photographs.
       Drawings and Paintings:
            
 
  To add to the Science or Art links, submit bird sightings, comment on the exhibit or the web presentation, or ask questions, please use the web forms on the Art at Exits home page.