Subject: [Tweeters] Synchronous diving in scoters
Date: Jan 22 13:31:01 2007
From: fsharpe at sfu.ca - fsharpe at sfu.ca



Guy

Synchronous diving in surf scoters is thought to be both an anti-theft and
anti-predator tactic. By returning to the surface en mass, you presumably
dilute the likelihood that your food morsel will be snatch by gulls or other
"kelpto-parasites". Scoters and their allies often feed on bi-valves or
crustecea that require extended handling in the bill, thus increasing the
likelyhood of theft. Synchronous movements presumably reduces the
likelihood that a given bird will be snatched in the talons of a predator
(eagle).
There are also probably underwater benefits of to feeding in groups.
This includes utilizing the search efforts other individuals who have found
lucrative food patches. As birds return to the surface, successful
foragers could potentially leave debris trail of rendered prey items,
providing a cue for descending birds.
Where mussel patches have been torn open, they may have more
vulnerable edges where the next bird can come and more easily grasp these
tasty mollusks. Living in groups may also optimize chances for pair
bonding. Birds can also gossip about the latest Youtube videos.

Fred Sharpe
fsharpe at sfu.ca
Snowbirding in Benicia