Plankton & Gulls by Boat

For some time I've wanted to get on the water to experience the annual Long Island Sound gull-plankton phenomenon, but I never really had late winter access to a boat until 2016. Still, last year I was a bit late and didn't get in the water until mid-April, which ended up being a few days late for the event.

This year was looking no better with a late-season blizzard and marina construction, both out of my control. But we got lucky with a break in the weather on a weekday I was was too good an opportunity to pass up. So I trailered the boat to the Birdseye Street ramp in Stratford for some LIS gull searching on Thursday morning (March 30th).

Joining me were Virginia Parker, Larry Flynn, Frank Mantlik, and Tom Robben...the latter two representing the Connecticut Ornithological Association's Research Committee. Tom and Frank brought plankton collection equipment in hopes of finding a flock of birds in the act of feeding. We were hopeful despite the low numbers of birds seen in recent days.

The Housatonic River held many COMMON LOONS in various stages of molt, which seemed to be feeding on crabs. I've seen them feed on European Green Crabs at this time of year, and these seemed about that size. The waters off Stratford Point were home to many SURF SCOTER and LONG-TAILED DUCK. We turned the corner towards the mouth of Bridgeport Harbor and spotted exactly what we were looking for - a raft of gulls picking at the surface.

The flock consisted mainly of RING-BILLED GULLS with lesser numbers of HERRING and BONAPARTE'S. Our estimate of 60 "Bonies" was encouraging, as this has been a down year for these sprightly birds. Total gull numbers reached 2,000+. This is actually a modest number for the date in this area; peak numbers in past years have reached over ten thousand.

part of the gull flock between us and the Bridgeport (CT) -Port Jefferson (NY) ferry

part of the ever so scenic Bridgeport coast in the background

Bonaparte's Gull (photo by VP)

Bonaparte's Gull (photo by VP)

Bonaparte's Gull (photo by VP)

Bonaparte's Gull (photo by VP)

Tom and Frank broke out their nets and we did a 5-minute tow through the heart of the flock in hopes of picking up whatever they were eating.

Tom monitoring the net being towed (photo by FM)
Tom and Larry
Larry handling the transfer

Very pleased with our plankton success, we decided to make a quick run further west to see if we could turn up other, larger flocks. We made it as far as Penfield Reef off Fairfield, not seeing much of anything, before we turned around to head back to that flock off Stratford. We were able to relocate the birds, though less concentrated this time. An adult "Kumlien's" ICELAND GULL stood out among the crowd.

"Kumlien's" Iceland Gull

We headed for the dock, but not before a quick check of a Greater Scaup flock off the Milford coast. Note to self: scaup do not like boats.

Greater Scaup

Tom took the plankton samples to UConn for analysis - please check out Tom's blog entries for updates and photos. Long story short, we pulled in lots of barnacle larvae (cyprid stage), copepods, and diatoms. Given that these gulls are calmly sitting on the water and constantly plucking at its surface, is it obvious to me that this plankton is what they are feeding on. If they were going after something more active, such as bait fish feeding on the plankton, their feeding behavior would be drastically different (and they would be seen pulling up larger prey).

This was a lot of fun for all of us, and I am grateful for Tom and Frank bringing their research gear on board. Extra thanks to Tom for pursuing the lab results and sharing them with us. I'm looking forward to doing this again...if not again this year before the show is over, then certainly next year.

 - Nick


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