[CT Birds] Plankton feeding gulls

greg hanisek ctgregh at yahoo.com
Thu Mar 1 13:06:31 EST 2012

Since a couple of people have raised the possibility of the gulls feeding on fish attracted to the plankton, I would add my own observations. A number of us have been watching these concentrations and feeding groups for a number of years. All the birds participating - which include gulls, ducks and sometimes brant - feed in a similar way. They daintily peck at the surface of the water. I've never seen them raise their bills with something visible in them. They feed in a manner very similar to accompanying non-fish-eaters such as scaup and Gadwall. The gulls dip the tips of their bills into the water as if taking items that are not trying to elude them. There is none of the aggressive plunging, grabbing and submerging that I would associate with taking fish. This often happens when the water is very calm, so its easy to see the method if not the prey. It's possible the concentrations of the food items are so dense that this isn't a matter of picking
 up a single tiny creature but numbers of them at one time.
It's also worth noting that this is different from the feeding at Hammo described by Keith Mueller. He got some terrific pictures last year of the gulls with creatures in their bills that were easy to see. I don't personally know anything about the Slippershell ID, which Keith mentioned recently, but clearly those creatures were in that size range. This was different from the surface feeding in the wetsern end of the Sound.
Greg Hanisek

--- On Thu, 3/1/12, paul cianfaglione <pgcianfaglione at gmail.com> wrote:

From: paul cianfaglione <pgcianfaglione at gmail.com>
Subject: [CT Birds] Plankton feeding gulls
To: "CT Lists" <ctbirds at lists.ctbirding.org>
Date: Thursday, March 1, 2012, 11:48 AM

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

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
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