Today a pair of stellars jays were clearly dominating my bird feeder. Lots
of very aggressive behavior which drove other birds away. I counted 14
actions where the jays did what I call replacement behavior, they flew
directly at another bird, and landed in the spot just vacated by the rapidly
departing bird. While the jays were enjoying their uncontested access to the
feeder, a platoon of varied thrushes flew in under the feeder in a tight
formation, banked together then landed, all 9 birds together in about a foot
square space. There was a brief moment, where the two jays hopped around,
about a meter from the thrushes, but the thrushes stayed together and the
jays flew away. Within a minute of their departure the feeder was a traffic
jam of chickadees, and the rest of the winter crowd, with the thrushes
forming sort of what I thought of as a perimeter guard below the feeder.

After about five minutes or so, the thrushes were pretty disbursed, and one
of the jays returned, and did a displacement behavior on one of thrushes,
who flew out of the way but landed in close proximity to two other thrushes.
The Jay picked at the ground a bit then flew up to perch above the feeder.
The chickadees and smaller birds sort of hesitated going to the feeder but
then went about their usual business. I noticed that the three thrushes in
the small group had been joined by a couple others which came out of the
bushes, so now there were five thrushes more or less within 4-8 inches of
each other. There was no further displacement behavior from the jay over the
next several minutes other than it flying to the feeder a few times. I could
not help but imagine that the thrushes, in their militaristic orange and
black uniforms, were the cops, who were charged with keeping the order at
the feeder....:)

I began to wonder if groupings of birds like this are indeed what I
supposed, a defensive measure to aggressive behavior. I had to go get
ready for work at this point and of course when I returned after several
minutes away, All the birds were gone and that was the end of today's lesson
at the feeder. As I drove to work I pondered how bird feeders, which are
extremely rich and important survival resources, might skew behavior in all
kinds of interesting ways, and of course would be very visible. I wonder if
anybody has done research into the behavioral changes induced by feeders? Or
for that matter, the ecology of feeders as a resource. I can not think of a
natural resource which could rival the food value of a bird feeder, since it
is potentially inexhaustible, assuming us bird feeders keep up on the job.
And what are the consequences, social and ecological when we don't? Does the
sudden removal or loss of a rich ecological food resource have measurable
impacts. And how could you measure them? Yikes, so many interesting
questions from so simple a thing as a bird feeder.

Rob Sandelin
South Snohomish County at the headwaters of Ricci Creek
Sky Valley Environments <http://www.nonprofitpages.com/nica/SVE.htm>
Field skills training for student naturalists
Floriferous at msn.com