[CT Birds] Plankton feeding gulls

Al Collins aecollins83 at hotmail.com
Thu Mar 1 13:24:02 EST 2012


I saw another example of opportunistic feeding on plankton I though I should add to this very interesting conversation on plankton.

On July 31 of last year while fishing off of a rock pile mid-sound between Greenwich and Oyster Bay, LI I saw many small animals feeding in the top few feet of the water column. They were swimming like squid, which is what I thought thew were until I caught a few in a bucket and realized that they were a sandworm (or similar polychaete). They were between 1/2 and 3/4 inches long and darting around. The school extended at least half a mile to the north and south of me. Here's a photo:

http://bit.ly/xp6noB

Feeding on them were many scattered gulls, including Greater Black-backed, Laughing and Herring; common and least terns; schools of filter-feeding menhaden (bunker); normally bottom-feeding fish including scup (porgy) and black sea bass; very small bluefish; and schools of small fish that looked like spearing. Feeding on the feeders were bluefish and striped bass. 

In the few hours I was in the area the worms were steadily drifting by; certainly many hundreds of thousands and probably millions went within a few yards of my boat. 

> Date: Thu, 1 Mar 2012 11:48:48 -0500
> From: pgcianfaglione at gmail.com
> To: ctbirds at lists.ctbirding.org
> Subject: [CT Birds] Plankton feeding gulls
> 
> I really enjoyed the discussion about plankton feeding gulls. At first, I
> had a hard time wrapping my mind around the idea of gulls with large bills
> feeding on microscopic organisms. But after reading about Herring Gull
> feeding habits, I guess it is certainly something to consider. Below is a
> small excerpt from The Birds Of North America Online regarding Herring Gull
> feeding habits;
> 
> *At sea, forages in large, widely scattered groups that coalesce quickly
> through rapid recruitment when prey concentrations located (**Hoffman et
> al. 1981*<http://bna.birds.cornell.edu/bna/species/124/articles/species/124/biblio/bib061>
> *, **Pierotti 1988*<http://bna.birds.cornell.edu/bna/species/124/articles/species/124/biblio/bib099>
> *). Often follows foraging humpback whales (Megaptera novaeangliae) or
> groups of delphinids. Hovers over feeding groups grabbing fish, squid,
> zooplankton concentrated at surface by mammals, diving birds, or large
> predatory fishes swimming underneath concentration (**Pierotti
> 1988*<http://bna.birds.cornell.edu/bna/species/124/articles/species/124/biblio/bib099>
> *).*
> 
> I understand that gulls may shift foraging patterns to take advantage of
> short-term fluctuations in food supply. It just seems inefficient for gulls
> to feed on microscopic plankton unless they are taking in massive amounts
> at a time.
> 
> As an alternative thought, could gulls that attend plankton concentrations
> be feeding on other prey items?? Many types of fry fish feed on plankton.
> What may appear to be plankton feeding,  could in fact be opportunistic fry
> fish feeding.
> 
> Paul Cianfaglione
> Canton
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