Just to add on to Dennis' excellent summation, while in Costa Rica, on the
Pacific Coast near Quepos I observed 4 large groups of frigatebirds. The
largest was 17 birds, which surprised me. Other groups were sized 12, 8, and
6. I had never seen this species in groups this size (17) before. Also saw
a group of 124 Brown pelican, all in a giant V shape soaring over the beach
just before sunset. The pelicans were constantly shifting positions in the
flock with the most movement occurring at the outer edges of the V. It
seemed like everybody wanted to be about the 5th bird from the end and there
was much movement in that area.

Rob Sandelin
Sky Valley Environments <http://www.nonprofitpages.com/nica/SVE.htm>
Field skills training for student naturalists
Floriferous at msn.com


-----Original Message-----
From: TWEETERS-owner at u.washington.edu
[mailto:TWEETERS-owner at u.washington.edu]On Behalf Of Dennis Paulson
Sent: Tuesday, March 04, 2003 1:16 PM
To: tweeters at u.washington.edu
Subject: frigatebird facts


Hello tweets,

I know anyone who's reading this is unlikely to be seeing
frigatebirds at this time, but an article just came out in Nature (23
Jan 2003) that tells an interesting story about them.

Magnificent Frigatebirds breeding on an island off French Guiana were
fitted with transmitters that recorded their flight altitudes and
locations. Some of these birds, when they left the nesting ground,
would stay in the air continually, night and day (the first birds
known to remain in the air at night besides swifts), for several
days. Their flight consisted of a constant series of ascents and
descents, presumably soaring up on thermals and then gliding down
again, only to repeat the same. Their average altitude at the top of
their oscillations was over 300 meters, and the highest altitude
reached was 2500 meters, well over a mile above the ocean's surface!
They flew hundreds of kilometers during that time and most of the
time didn't even approach the sea surface; apparently feeding is
quite infrequent, only during the day, and perhaps they locate their
prey visually from some altitude.

Frigatebirds have the lowest wing-loading of any birds, real flying
machines. Prey is scarce at the surface in tropical waters, so these
birds have evolved to move long distances and search for those scarce
resources efficiently. They feed their young infrequently, and the
young grow slowly and have an unusually long period of parental care.
They are supremely adapted to inhabit tropical oceans.
--
Dennis Paulson, Director phone 253-879-3798
Slater Museum of Natural History fax 253-879-3352
University of Puget Sound e-mail dpaulson at ups.edu
1500 N. Warner, #1088
Tacoma, WA 98416-1088
http://www.ups.edu/biology/museum/museum.html

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