Red-shouldered Hawk (Buteo lineatus)
   
 
Narrative and Science Lens
 

Audubon shows us a pair of Red-shouldered Hawks on tree limbs, reminding us, possibly, that these buteos hunt from a perched position. Many other buteos hunt while patrolling.

This is not a large hawk: It is just under two feet long and its wingspan about twice that. You’ll know it by its, yes, red-shoulders, and by its banded tail, reddish breast that gives way to reddish-white banding. When airborne the (white) crecent window“window“ toward the tips of its wings are great field markers. It

This hawk is not large, but it IS loud, repeatedly screeming, kee-ahh, even in winter, leading to a reputation as possibly California’s noisiest raptor. Allen Fish, who directs the Golden Gate Raptor Observatory (www.ggro.org) has suggested this may trace back to its early breeding season, which begins in December. Are theses birds on the rise in the Bay Area, or are they just more noticeable? Steve Rottenborn, a wildlife ecologist (and Stanford Ph.D) who has studied Bay Area birds since 1992, thinks it’s the former (see Sustainability.)

 
  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
  Around 1950, it is thought by many, Red-shouldered Hawks were less common in the Bay Area. In Marin County, for example, they were considered declining and actually rare. From the 1960s-1970s on, local annual counts showed increases, and by 1990, with the increasing availability of tall trees, the birds were becoming more evident in our area.

Steve Rottenborn’s work in the mid 1990s found that many in our county (52 of 85 nesting pairs) selected non-native trees, often eucalyptus, and nesting success was higher than for those selecting native trees, like this Red-shouldered photographed by Tom Grey, Sweitzer Professor of Law, emeritus.

By around 2010, numbers in some areas peaked. Lower numbers might be related to the felling of eucalyptus, which has been underway in many areas, but it thought by many that the upper limit of Red-shouldered Hawks in the Bay Area may simply have hit its natural peak between 2002 and 2008.

While the number of Red-shouldered Hawks changes year-to-year, in 2011 there were 248 sightings in the Bay Area, which is atypically low. Within this overall upward trend—now leveling out some—there are dramatic dips and rises from year to year. The reasons for such year-to-year variation are unknown. While the count of 248 sightings is well below average, it’s too early to say if it’s a dip or the beginning of a decline.
       What you can do
  1. Report any sightings—especially of nesting on campus. Keep a journal of sightings
  2. Check out trees that might make good nesting sites. 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:
            Tom Grey (pair, in flight calling )
          Carel (n)
       Drawings and Paintings:
            DW drawing after Audubon
 
  To add reports or images please submit them via the Art at Exits home page