Cliff Swallow (Petrochelidon pyrrhonota)
   
 
Narrative and Science Lens
 

   Audubon places an egg on the rock surface. Why show it? Was he aware that these birds can get out of rearing a complete brood by carrying an egg--or even laying it--next door to have a neighbor involuntarily incubate and rear it? Such brood parasitism reduces parental effort a cost to competitors.

But Audubon might not have seen many of these birds nesting, for this is a western species whose range expanded eastward, presumably much later with the building of highway culverts that provide sites for colonies to nest. Audubon may simply have wanted viewers just to know what the eggs of these birds look like. Still, he did another interesting thing: He placed a male at the entrance of one of the nests. Both males and females incubate the eggs, but will respond to an alarm call by moving to the entrance. Might this bird's mate have called him when spotting another female nearby—one who might be looking for an unguarded nest to parasitize?
 
  Campus Locations
This small, dark-throated, square-tailed, pale rumped, short-billed, long-winged stocky songbird is a common resident from spring through fall, foraging aerially throughout campus. Large colonies in the Main Quad comprise most of the campus's breeding population, although a few pairs build their mud nests on residences and other structures. Nests are occasionally appropriated by House Sparrows.
 

Campus sustainability

  These birds prefer nest sites with an overhang and formerly nested within the arcade. Now they are more apt to nest on the Quad gates, as seen here, which share characteristics with the cliffs that give these birds their name. Why did they move? A number of years ago the arcade ceiling was stained and may be a factor. Also, years ago droppings beneath the nests were considered a nuisance and the policy was to deter nesting by washing away the mud nests. Campus biologists succeeded in having the nest-hosing practice curtailed, but the birds may have dispursed. The swallows of Capistrano, stopped returning to the mission after their nests were removed during rennovations. Only a swallow vocalization project using speakers playing swallow courtship calls enticed the birds to return.

Another factor may be involved: The birds are thought to get the mud for their nests from Lake Lagunita, puddles below sprinkler heads, and other sources of reliably damp soil. Lower lake levels and drought, may make mud a limiting resource.
       What you can do
  1. Report mud-gathering activity to help determine favored "mud puddles".
  2. In dry springs see if “mud puddles” can be maintained during nesting (the birds need to repair nests from time to time).
  3. Survey areas near the Quad that might provide good alternative nesting sites.
  4. Design a nest support that could be evaluated and tested to encourage nest-building in an area with low foot traffic.
  5. Help determine if nesting in the arcade should be encouraged to return, at least in part, to its historic role.
  Science
       Essays from The Birder’s Handbook:
            Parasitic Swallows; Parent-Chick Recognition; Coloniality; Brood Parasitism
       References:
       Videos:
  Art
       Photos:
            Tom Grey (gathering mud, nesting)
          Carel (nesting above Common Raven nest)
       Drawings and Paintings:
            DW drawing after Audubon
          DW watercolor of Cliff Swallow in Quad
 
  To add reports or images please submit them via the Art at Exits home page