[CT Birds] composition of plankton upon which gulls are feeding
aecollins83 at hotmail.com
Wed Feb 29 15:22:37 EST 2012
If anyone is interested, here's link to a photo of a sample I collected off of Stamford in March 2009. We pulled a plankton net right through a flock of dip feeding gulls and brant. We measured about 2000+ specimens per cubic meter and they were all this animal, which we (non-experts) identified as the cyprid stage of barnacle. In addition to these, we had a very small number of segmented worm larvae.
> Date: Wed, 29 Feb 2012 15:07:54 -0500
> From: chbarnjr at gmail.com
> To: ctbirds at lists.ctbirding.org
> Subject: [CT Birds] composition of plankton upon which gulls are feeding
> In answer to Bill Yule's questioning about the type of plankton upon which
> the birds are feeding: the zooplankton (it swims) has been collected
> numerous times from many locations and it is, almost without any doubt at
> all, almost entirely barnacle plankton. I know that Dennis Varza and
> Dr.Jack Barclay have pulled plankton nets behind Larry Flynn's boat (thank
> you to all of them) from Norwalk east to about the Bridgeport/Stratford
> town lines. They were far enough offshore to be right in the feeding
> lanes of the gulls and they identified the plankton as being composed of
> barnacle larvae. I will leave it to Dennis, Larry and perhaps Dr.Barclay
> to confirm the results.
> I tried unsuccessfully to get the Bridgeport School of Aquaculture out
> there to collect samples. The instructor with whom I met had no idea of
> what was taking place. At least she was interested in finding out and
> helping, but she and some of her class were about to leave for a fish
> aquaculture meeting in China. I never got around to talking with her again
> after she returned. My fault on that one.
> Anyway, I wound up collecting samples nearer inshore, from the end of
> jettys where gulls were feeding and sometimes right along the shoreline
> itself. I took the living zooplankton to Twan Leenders at the CT.Audubon
> location at Stratford Point and Twan passed it on for analysis. There was
> some disagreement as to what the plankton was in the samples which I took,
> with some people (with a minimum of a Master's degree in marine sciences)
> feeling that the plankton was mostly something called an ostracod. Others
> never even looked at the samples to the best of my memory.
> Here is a link to a good book on the subject. I think that you can read
> through quite a few sections online. Click on the photo gallery section and
> scroll down to the "copepods and lower crustaceans" subsection. Both
> ostracod and barnacle cyprid larva are pictured. For what it is worth (and
> it shouldn't be worth much) I agree with those who identified the larva as
> barnacle larva. I studied the book photographs and looked at the samples
> under a microscope myself, thanks to Twan having brought his own microscope
> to Stratford Point.
> "Zooplankton of the Atlantic and Gulf Coasts: A Guide to Their
> Identification and Ecology." It is by William S Johnson and Dennis M Allen.
> Incidentally, quite a few years ago, a group of us saw feeding gulls in
> multiple lines stretching from Russian Beach in Stratford all the way to
> the vicinity of Penfield Reef Lighthouse in Fairfield - as far as we could
> see with scopes set up. Each line contained thousands of gulls and we
> estimated well over 50,000 birds. There were most likely more birds to the
> west of our view, so 50,000 was probably a very low estimate.
> Charlie Barnard Jr.
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