In a Brief Communication in this week’s Nature, researchers from Harvard, Johns Hopkins and UC
Davis collaborated on a study of how pigeon color patterns affect whether peregrines targeted
them for predation and how often the falcons were successful.

In the original (wild-type) coloration, Columbia livia, the “Rock Pigeon” (FKA “Rock Dove”), had a
white rump patch.  Due to selective breeding by pigeon fanciers, resulting populations of feral
pigeons have a variety of color patterns.  The researchers captured and classified 5,235 pigeons
from around Davis into color groups Wild-type, Blue-bar, Checkered, Red, Splash and White.

Over a 7-year period, they observed and recorded 1,485 attacks by five adult peregrines and 309
attacks while 3 of the adults were juveniles.  They found that adults chose to attack the wild-type
(white rump patch) pigeons far less frequently than the Blue-bar (dark rump) variety.  Their
success rate for capturing all types was about 40%; of those, about 2% were wild-type and >90%
were Blue-bar.  As youngsters, the success rate for captures was only 19%, perhaps due to the fact
that young falcons went after any and all of the pigeon color patterns.

The researchers explained their data thusly: When a pigeon is trying to elude a plummeting
peregrine, it goes into a sharp roll that flashes the white patch, which then abruptly disappears.
The falcon, moving at speeds around 157 meters/second, can be thrown off its target by the
abrupt color change in the wild-type roll. Pigeons without the color change during their evasive
roll get bagged more frequently.

The authors note that due to the comeback of falcon populations, there is now a greater selective
advantage for the wild-type coloring, although the conspicuous white patch could be a negative
factor for predation by accipiters, who chase at level flight.

The two page paper is by Alberto Palleroni, Cory T. Miller, Marc Hauser and Peter Marler, and
appears in Nature 434:973-74, 21 April 2005

I think a group of scientists who happen to be birders got a grant to have lots of fun in the field
and got a nifty publication out of it….

Mary LaMarca, Silver Spring, MD