Speaking of Bird Banding

Early Sunday I travelled up to the Bronx with the Brooklyn Bird Club (despite an exhausting day on Saturday) for some bird banding along the Bronx River. Chad Seewagen and Eric Slayton are in the third year of a study on feeding habits of migrants passing through urban parks. They’re concerned that the same factors that make urban parks so great for birders may make bad sites for birds: many birds in a small area full of lots of invasive and ornamental plants.

Northern Parula trapped in a mist net at the Bronx Zoo

To do this, they’re measuring the birds two ways. First they estimate the fat content of the bird from on a scale of 0 to 5; 0 equals no fat, 5 equals maximum fat. If they recapture a bird a few days later, its fat reserves should have increased if it’s feeding well. If, on the other hand, the fat reserves haven’t increased much or have even decreased, then the bird is burning fat instead of getting calories from the environment. Ideally fat should only be burned on the long overnight journeys to the next site.

Secondly, they take breath samples from the birds. They can then analyze these with a mass spectrometer to tell whether the bird’s been eating or burning fat.

Taking a breath sample from a Swainson's Thrush

The birds like the Northern Parula above are captured in mist nets. Then they’re placed in soft bags for a few minutes until they can be banded, weighed, sexed, and breathalyzed. Then they’re released.

Having the birds in the hand is quite different than trying to identify them with binoculars. You can do things like compare the exact amount of white on tail feather R6 and to the white on tail feather R5 to get a really good estimate of the bird’s age, and be really, really certain that a bird is a Northern Waterthrush and not a Lousisiana Waterthrush. There are all sorts of things that you just can’t reliably determine through binoculars.

If you’re interested, Chad Seewagen will be talking about this work Thursday, June 1 at the Audubon Center in Prospect Park at 6:30. The event is free and all are welcome.

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