Sue,

in the central valley of California, Swainson's nest in the middle of
cities with populations of 50-100,000 people, without seeming to be
bothered by the activity. Speculation has been that they choose these sites
because they prefer to nest in tall trees, and many of the taller trees in
the surrounding areas have been cut down. But they definitely don't seem
averse to human activity.

As for i.d., the diagnostic field mark of Swainson's in flight are light
underwing coverts and dark flight feathers, like a reverse turkey vulture.
This will be quite striking on light morph birds, but even full on dark
morphs will show darker flight feathers than underwing coverts, in my
experience. Like red-tails, though, there are many plumage variations
intergrading between light and dark morphs. Swainson's are also, at least
in CA, very vocal, frequently calling with a repeated, upslurred "kree"
while soaring. I've often heard them before seeing them.

Hope this is helpful, keep us posted...

Rob Saecker
Olympia