There is a very interesting article in the New York Times this morning.
According to a study just published in PNAS by Nottebohm and Barnea,
Black-capped Chickadees studied in New York State basically grow new brains
every Autumn. The birds showed a huge turnover of neurons in the hippocampus
(the area associated with memory storage and spatial learning), as old cells
died and new cells grew; this turnover peaked in October, when it was as
high as 2% per day! The researchers think this change happens because wild
chickadees increase their home ranges in the fall, switch from eating
insects to finding and storing seeds, and have to remember the location of
the seed stores (captive chickadees showed only half the turnover of the
free birds). The birds seem to be dumping last year's memories and making
room for new ones. Nottebohm and Barnea earlier had a similar finding in
canaries; the canaries showed annual neuronal turnover in the part of the
brain associated with song-learning as they forgot last year's songs and
learned new ones. Not all neurobiologists agree with this explanation, yet,
but it will be interesting to follow this topic over the years.

I also thought some of you environmental-minded Tweeters might be amused by
the following: The checkers at my neighborhood dress up for Hallowe'en.
This year, one came as a logger, complete with a battered hardhat bearing
the motto "Earth first---we'll log the other planets later".

Rachel Lawson
Seattle, WA
jbrown at halcyon.com