Subject: [Tweeters] Buoyancy in ducks, gulls, etc.
Date: Dec 8 15:59:02 2010
From: Al Wagar - jalanwagar at gmail.com



A few weeks ago someone asked why gulls float higher in the water
than gulls. Thought I?d share ideas occurring in idle moments since
then:

Ducks need heavy muscles for long, sustained, flights and nearly all,
including dabblers, dive for at least some of their food, with excess
buoyancy a handicap for diving. Other diving birds also seem to float
low in the water?loons, cormorants, alcids, etc.

By contrast gulls stay aloft mostly by soaring. When stuck at a long
traffic light on a blustery day, I was fascinated to watch a gull
work its way upwind with very little flapping, riding up on eddies,
then diving through the headwind. For soaring, light weight is
advantageous.

Al Wagar
Shoreline