Wednesday, July 11, 2012

Black Terns

Black Terns -- © Dave Spier

The cattails grew denser and denser. Long poles would have been more effective than paddles as we grabbed clumps of emergent leaves and pulled our canoe deeper into the marsh. We passed an opening at the targeted GPS coordinates, but there was no sign of a nest. "Okay, turn the canoe around," Frank said. Easier said than done. Should have worn chest waders and just gotten out of the canoe. It was more effective to back out.

To shorten the story, we did relocate the "nest." Talk about well camouflaged. Three hard-to-see eggs on a tiny mat of cattail leaves... Another declining bird species has turned up in the Northern Montezuma Wetlands outside of the federal refuge in Seneca County, and we were part of an ongoing state survey. 

Black Tern nest on Howland's Island, part of the Northern Montezuma WMA, Savannah, NY, on July 1.

Black Terns (Chlidonias niger) specialize exclusively in inland freshwater marshes. Most tern species are at least partially coastal and nest in salt marshes. Black Terns utilize cattail marsh openings created by feeding Muskrats and often build their nests on a floating Muskrat feeding platform, usually not much more than a mat of cut leaves an inch or two above the water. This nesting behavior makes them vulnerable to two things: invasive Purple Loosestrife and motor boat wakes. The loosestrife crowds out the cattails forcing the Muskrats to move elsewhere, whereas boat wakes can destroy the nest. Motorized boating is not permitted in the Northern Montezuma Wildlife Management Area and the loosestrife appears to be under control, at least for the moment. The presence of another aquatic plant, bur-reed, is a good indicator of Black Tern nesting potential. Since Black Tern eggs and chicks are preyed upon by Great Blue Herons, choosing a nest site in deeper water (preferably two feet deep) with a thick growth of yellow bladderwort will discourage the long-legged wading birds.

Terns are related to gulls, but have pointed bills for catching small fish. Terns also have forked tails and long, narrow wings. They fly gracefully and hover with bills pointed down when searching for prey. In addition to a few small fish, frogs and crustaceans, Black Terns eat a lot of spiders and insects (such as mayflies, water scorpions, and unfortunately, dragonflies).

Adult Black Terns in breeding plumage are unmistakable. The head and body are charcoal with white undertail coverts and they are uniformly gray across the wings, back and tail. The underwing linings are lighter. Young birds and winter adults have white underneath and white on the forehead and sides of the neck.

Black Terns breed from the lake plains of New York and the upper St. Lawrence Valley westward through the Great Lakes Region, across the upper Great Plains and into the Rockies and Cascades. They winter along the northern coasts of South America and during migration, they can show up anywhere in between. There is also a Eurasian subspecies. For a range map, go to eBird [or look in eBird under "Explore Data," then "Range and Point Maps"]. There is also a generalized map on All About Birds.

Agitated parent as we relocated the floating nest.

Corrections, questions, and comments are always welcome at


July is a slow month for eBird reports. There's a huge swath of counties from the upper great Plains down and across to the Southeast with zero checklists [red on the map] for the month. As eBird approaches its 100 millionth record, they're having a contest [complete checklists only] and it would help greatly to fill in some of the gaps at the same time!

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