Subject: when is a chickadee not a chickadee?
Date: Aug 31 11:51:37 1999
From: Hal Opperman - halop at accessone.com


Hi Tweets,

Here is a summary of a summary of an article in the latest *Science*, taken
from Henry Fountain's "Observatory" column in today's New York Times
science section. Researchers on Corsica studied two populations of the
Blue Tit (a close relative of our chickadees) over a six-year period. This
species moves around a lot outside the nesting season, and the two
populations -- which nest only 15 miles apart -- were expected to cross
over and generally get mixed together, eventually interbreeding. But they
didn't. One population inhabits a deciduous oak forest, the other
evergreen oaks. Both feed principally on leaf-eating caterpillars, which
become available a month earlier in the evergreen oaks than in the
deciduous oaks which leaf out later. The breeding cycle is keyed to
caterpillar availability. So when the evergreen birds are singing and
eager to mate, the deciduous birds aren't interested or available. The
situation is reversed a month later. Result: the two populations remain
distinct. Fountain notes that "the researchers suggest their work could
have implications for conservation policies that are meant to protect
diversity among species." And also, one might add, profound evolutionary
consequences. How many examples are there of populations of the same
species attached to different habitat niches in different parts of the
Northwest? Lots, probably. The trick is to heighten our observational
skills, and our awareness, to the point that we can begin to notice the
differences, and value them as much as we do gross differences among
species.

Hal Opperman
Medina, Washington
mailto:halop at accessone.com