[CT Birds] composition of plankton upon which gulls are feeding
charles barnard jr
chbarnjr at gmail.com
Wed Feb 29 15:07:54 EST 2012
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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