I've got to agree with Wayne on crow v. nighthawk. As Kelly pointed
out, the highest nighthawk densities occur in urban or semiurban areas
that have lots of flat, gravel-topped roofs for nesting and plenty of
night lighting to attract flying insects. Add to that an explosion
in crow populations in urban and semi-urban areas in the past 30 years,
and it seems downright *inevitable* that a lot fewer of those exposed
nests would succeed -- if the crows don't find the eggs, they'll find
the chicks. It's easy to imagine urban nighthawk populations getting
hammered this way, so the numbers are reduced to the relatively fewer
that survive the towns and cities and/or nest elsewhere. I'd love to
see a chart of crow densities plotted against nighthawk densities.

All of this, of course, doesn't mean there mightn't be other reasons
for the decline, but I gotta believe this effect is real. Nor does it
mean the decline will be ongoing. It seems reasonable that if the town
option was completely taken away from them, nighthawk populations might
simply stabilize at a lower level. I suspect that there isn't much
documentation of 18th-century nighthawk populations, but it wouldn't be
surprising if they were significantly lower before they began exploiting
the man-made environment. Does anyone have any old texts that might
shed light on the subject?

Jim McCoy
jfmccoy at earthlink.net
Redmond, WA



-----Original Message-----
From: Diann MacRae [mailto:tvulture at halcyon.com]
Sent: Friday, August 25, 2000 1:22 PM
To: Tweeters at u.washington.edu
Subject: Nighthawks, swallows, and crows . . .


Hi, Tweets

I generally try to stay out of most all discussions, but I must differ with
Wayne Weber's comments about nighthawks/crows/swallows - sort of a
collective disagreement from my perspective and my location. Many species
can be locally common or abundant, but practically non-existent elsewhere.
When I lived in New Hampshire for nine years (until 1981), we delighted in
watching the hundreds of southward-bound common nighthawks that would pass
by within a 2-3 day period - almost like clockwork, late in August, late in
the day, and often on the edges of a thunderstorm's front. The species was
in decline at that time in the northeast.

I also remember watching them here in the '60s, not in such large numbers,
but predictable at migration time. I haven't seen one in years, on a
casual, local basis.

Swallows: I think I've said this long ago, but when I moved to Bothell in
1983, I had two species of nesting swallows and saw one other swallow and
one swift species - daily, four species, in all. Now, in 2000, I'm lucky if
I see an occasional violet-green or tree swallow. I have seen other
postings that say the same thing. While swallows may be doing just fine in
certain areas, near certain bridges, etc., I would hazard a serious guess
that they are definitely declining.

All of these problems cannot be blamed on crows. Crows are what they are.
They eat baby birds, they clean up the environment much the same as some
other big black birds I've been associated with, but which some people also
think are awful. Crows are opportunists; so are people. I think that Toni
has the right idea - which is true in most declining species - it is a
combination of events. Habitat destruction has a far worse effect than any
corvid ever did, in my opinion.

So, to sum up this too-wordy message, I am glad swallows are doing well in
Vancouver, but they aren't everywhere; nighthawks have been declining for
many years, and crows have increased and are doing very well. Doing what
crows do. I certainly have no conclusions, just observations.

Cheers, Diann

Diann MacRae
Bothell
tvulture at halcyon.com