Subject: [Tweeters] Feeding frenzy
Date: Oct 3 14:39:22 2004
From: Guttman, Burt - GuttmanB at evergreen.edu


For an hour or more, we've had a sort of feeding frenzy around our house here on the west shore of Long Lake, just outside Lacey. When I walked out of the house around noon, even my poor ears (my principal limitation in birding) could hear that the trees were full of birds making a heck of racket. After getting out my binoculars, I could see that most of the birds were Starlings, Robins, and Band-tailed Pigeons. Most of the activity centered on a few Mountain Ash trees in neighboring yards and on the tall Douglas-firs surrounding the house; the berries on the local Pacific Madrones always attract some birds, especially the pigeons, but they may not be ripe yet. Anyway, birds were moving around like crazy, little flocks moving into a spot and back out again, a tremendous amount of chasing, calling, and random feeding. But the poor lighting was very frustrating, having to look at too much of the activity high in the trees against a gray sky with no direct sunlight, and you know how difficult it can be to catch a good look at a little bird hiding in the boughs of the firs under those conditions. By the time the sun burned off the clouds and provided a blue-sky background with good lighting, the excitement was over. Flickers, Steller's Jays, and a few other common birds very active, also, and several smaller passerines looking like warblers that I just couldn't get a decent look at. An exciting time, anyway.
It occurred to me, though, that I would expect a good feeding strategy for birds that eat berries (and similar foods) would be to stay on one tree and feed until all the berries are gone. But they don't do that. Several birds will come to a tree, feed for a while, and then fly off and feed somewhere else for a while, and then some will fly back to the first tree and feed. Of course, I can't tell which birds in a large flock are moving where, but it all seems very random and inefficient. A strategy for varying the diet might be built into their behavior, or maybe I'm seeing the effects of birds being scared away from a site for a while (though I saw no other humans and nothing else that might scare birds during the time I watched them.

Burt Guttman guttmanb at evergreen.edu
The Evergreen State College
Olympia, WA 98505 360-456-8447
Home: 7334 Holmes Island Road S.E., Olympia 98503