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Wednesday, September 28, 2011

Shorebird Migration and Banded Red Knot

Over the last couple of weeks Heydi and I have been searching Brooklyn's shorebird habitats with the hope of locating the last of the southbound stragglers and, possibly, something new for the year. North America's breeding shorebird species have a very brief nesting period and actually begin their "Fall" migration as early as July, so we've been periodically checking several spots for over 2 months.

Plum Beach** is a narrow stretch of beach and marsh habitat just east of Sheepshead Bay. At low tide there is a fairly extensive mudflat where shorebirds congregate and feed until the tide change. Unfortunately, pet owners illegally unleash their dogs and allow them to chase the birds. To have any chance of seeing shorebirds here one must show up when low-tide is right around first light. So far this season we've managed to see Black-bellied Plover, Semipalmated Plover, Piping Plover, American Oystercatcher, Solitary Sandpiper, Willet, Ruddy Turnstone, Sanderling, Semipalmated Sandpiper, Least Sandpiper, White-rumped Sandpiper and Short-billed Dowitcher. I'm sure that this important stopover for migrating shorebirds would be a lot less stressful for animals that are traveling, sometimes, thousands of miles if they weren't being harassed by dogs.

Other good spots to look for shorebirds in Brooklyn are Gerritsen Creek (Marine Park), Dead Horse Bay and Floyd Bennett Field. On the one weekend morning that I decided to sleep late, I got a call from Heydi who was at Gerritsen Creek. At that moment she was looking at a Black-necked Stilt. This shorebird with obscenely long, thin legs is extremely rare in New York City and their range is, more typically, Florida and other locations far south and west of Brooklyn. Anyway, the bird flew in, fed for a few minutes then took off flying to who-knows-where. You can see more of Heydi's photos here.

The grasslands of Floyd Bennett Field are a good place to look for migrating "grasspipers". Grasspiper is not an official taxonomic term, but rather a designation given by birders to shorebirds that are mostly found feeding and nesting in grassy habitats. Two species that fit that category are Buff-breasted Sandpiper and American Golden-Plover. In addition to the attraction of the grassland habitats at Floyd Bennett Field, rain puddles that form on and around the old runways act as bird magnets. The season hasn't completely passed us by yet but, so far, we've struck out finding these two shorebirds at Floyd Bennett. It hasn't been a complete loss, however, because we did just stumble on a Dickcissel perched on the long grass at the edge of one of the fields. These birds are rare, but regular visitors during migration. There has also been an interesting array of butterflies and grasshoppers to keep our attention.

In addition to shorebirds, we've also been looking for marsh sparrows. There are 3 species of these beautiful, elusive birds that can be found around Brooklyn - Nelson's Sparrow, Saltmarsh Sparrow and Seaside Sparrow. Four Sparrow Marsh is a barely accessible, but wonderful habitat for seeking out these birds. As we quickly discovered, though, at this time of year it is also a great place for mosquitoes and horse flies. Despite an oil slick's worth of Deet glistening on our skin, we only managed a few minutes at the marsh before the biting insects drove us off.

Dead Horse Bay is just across Plum Channel from Plum Beach. This strange shoreline habitat is littered with broken glass that is spilling from the old landfill that once dominated what was formerly known as "Barren Island". Usually the only people one finds here are beachcombers collecting artifacts or the occasional birdwatcher. It is for this reason that I think relatively large flocks of migrating Black-bellied Plovers can be found resting along the shore here. I assume that when they are chased from the mudflat at Plum Beach they just fly the short distance across the water for some respite and horse bones. Where there are flocks of Black-bellied Plovers there can sometimes also be American Golden-Plovers. Over the last two weekends Heydi and I have counted an ever expanding group of plovers here, but haven't yet spotted the golden prize. The flock has grown from around 50 on our first visit to 90 at last count.

On one of our trips to Dead Horse I spotted a Red Knot within the plover flock. Red Knot populations are closely tied to Horseshoe Crab abundance (they feed on their eggs) and as the crab numbers have plummeted, so have the Red Knots. When we noticed that the knot had been banded, I tried to take a photograph so that I could report it to the proper organization. As you can see from this photo, I was somewhat successful.

In the close up it's clear that the left leg has an orange "flag" and the right has a yellow lower band and an upper metal (or silver) band. Sean directed me to the USGS "North American Bird Banding Program" website where they have a forms page for entering banding information. Since I wasn't able to read the code on the upper right leg, the resulting data will be a bit limited. I also found a website which lists the country codes for the flags. Orange means that the bird I spotted at Dead Horse Bay was banded somewhere in Argentina. A straight line from Dead Horse Bay to Buenos Aires is 5,263.24 miles! That's pretty impressive for an animal that weighs, on average, 4.7 ounces. Many Red Knots overwinter in Tierra del Fuego, another 1,500 miles south of Buenos Aires.

PBS produced a great program on the plight of Red Knots and Horseshoe Crabs entitled "Crash: A Tale of Two Species". You can watch the entire episode online here. I highly recommend it.

**Plum Beach is sometimes spelled "Plumb". On the 1873 Beers map of Gravesend Coast it lists the area as "Plum Island", but on an 1891 map of coastal Brooklyn it lists that location as "Plumb Beach". Even the NYC department of park and the National Park Service are inconsistent in their spelling.

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