Thank you Steven. Very interesting.

Along those lines, there have been 3 barn swallows at Sikes Lake in
Carnation every day since, at least, Thursday.

Mike Wile
Redmond, WA
mike.wile at attws.com <mailto:mike.wile at attws.com>
425-503-5766

-----Original Message-----
From: SGMlod at aol.com [mailto:SGMlod at aol.com]
Sent: Sunday, January 20, 2002 12:56 PM
To: Tweeters at u.washington.edu
Subject: Swallows


Greetings Again

I read some swallow discussion on OBOL and arranged my thoughts on the
swallow incursion more carefully. See below

The swallow phenomenon is most interesting. It is important to note that
these can occur at any time during winter, that the birds are virtually
never stationary (ie, they almost never linger at one location), and that
Barn Swallows predominate. It is also important to note that Barn Swallows
are considered casual to very rare during winter even in Santa Barbara and
Orange Counties in southern California.

Given the above, I think we can be pretty certain about the following:

1) With the possible exception of some early December birds, the winter Barn
Swallows are not lingering fall or early spring migrants, in the sense of a
daylength inspired latitudinal movement.

2) These birds are not overwintering.

That does not leave many options. The leading contender is that these birds
are moving north on persistent southerly winds. These conditions are not
rare in the Pac NW and are often associated with heavy rainfall. To PROVE
the wind/swallow relationship, a careful analysis of this year, and past
years, would be necessary.

More interesting, and less answerable, is WHY. Unlike bluebirds and robins
that sometimes wander north as the weather warms, Barn Swallows are in a
much more precarious position. They are not frugivores to any significant
extent (Tree Swallows, and I believe, VG Swallows can survive on fruit for
periods of time - hence their tendency to winter further north and arrive
much earlier in the spring). When a Barn Swallow wanders a thousand miles
north of its normal winter range, it is in a very tenuous position. It is
hard to imagine that these birds are not doomed. Furthermore, why are these
northward movements mostly Barn Swallows. Why not the more northerly
wintering Tree/VGs? Why not Cliff Swallows, which share a similar winter
range?

Interestingly, Common Swifts nesting in northern Europe, are known to leave
their nest sites for days or more following the leading edge of low pressure
systems, returning to their nest sites after the storm has left. The young
are adapted to these long absences, and if the adults remained during the
storm, they would be unable to feed. This escape movement allows the adults
to continue feeding while the storm passes. I don't think that the winter
Barn Swallow incursions are analogous, however, and I can't see an advantage
for a midwinter visit to the dangerous (for a swallow) northwest. It would
be most interesting to know where they are coming from and if any survive to
return south.

Cheers
Steven Mlodinow