I agree with Dennis that birds are attracted to towns because they provide
food. Human habitats also provide warmth for wintering birds.

I think there is some location bias, however. Towns are almost always along
rivers. A comparison of bird density between town and grasslands or town
and forest isn't valid. A better comparison would be between towns and a
location next to a river or between a native grassland and a farm without an
above-ground source of water.

I live several miles outside of Pullman. There fewer birds here than in
Pullman in both summer and winter. I don't have a feeder, but that can't be
the only reason. I was particularly struck by how Violet-green Swallows
are common in Pullmn during the summer, but virtually absent out here on the
higher, windier, colder plains. Why? Certainly not feeders. The
explanation might be that Pullman has more nesting locations, but I think
it's because Pullman sits next to the Palouse River while our property sits
next to only a small, intermittant stream.

Another factor: The Columbia Basin Reclamation Project produced many new
lakes and marshes but the artesian wells that used to exist around Pullman
(and other parts of the Basin?) no longer flow because of pumping of water
from the aquifer. Any bird that once relied on springs to supply flowing
water in winter would have to find another source.

Kelly

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