Bird Banding On Brewster’s Wing’s Island: A Stop-Over For Scores Of Species On Migration

by Greg O'Brien

Sue Finnegan, a master bird bander of national acclaim who has coordinated a bird banding station on historic Wing’s Island in Brewster for a quarter century, gives new meaning to the moniker “bird brain.”

“Birds are highly intelligent,” says Finnegan, a certified North American Banding Council trainer with a master permit from the federal government and a state banding permit. “Birds have keen instincts. They have personalities, and they often talk and sing to one another, particularly during mating seasons, with the male trying to attract a mate. Birds have particular call notes to communicate with one another. You can hear them if you listen. Some species will even follow you around looking for food. And birds are protective of one another. If a predator is nearby — a coyote, fox, or other animal — birds will start vocalizing to alert the others that there’s danger on the ground.”

Before becoming a bird bander Finnegan was a radiation therapist who worked at top Boston hospitals through the Harvard Joint Center for Radiation Therapy. She moved with her husband Bill to the Outer Cape decades ago.

Over the years, Finnegan and her volunteer team of trained bird banders have banded more than 62,000 birds representing 154 species since 2000 on Wing’s Island, owned by the town of Brewster. The nearby Cape Cod Museum of Natural History has supported the effort over the years by helping to secure non-profit grants for the work that provides vital information on the health and welfare of the birds to the U.S. Geological Survey (USGS) and others. The USGS is deeply involved in the management and conservation of bird populations and depends on banding stations across North America to help accomplish the goal.

“Wing's Island is a biodiverse and ecologically significant area, and Sue’s bird banding program is particularly valuable,” says Bob Dwyer, president and executive director of the Cape Cod Museum of Natural History. “She addresses conservation planning and educates the public on the changes affecting our habitat. Her work, supported by volunteers, is invaluable and reaches far beyond the town of Brewster.”

Permission to operate the Wing’s Island bird banding station was granted years ago by the Brewster Select Board. Wing’s Island is a key stop-over for scores of species during their spring and fall migrations from as far away as the Arctic and South America. The many fruits and berries on Wing Island’s 122 acres help sustain migrating birds on their long journey.

Wing’s Island, says, Finnegan, is also a perfect habitat to encourage breeding for gulls, terns, hawks, blackbirds, sparrows, catbirds, warblers, orioles, chickadees, titmice, wrens, cardinals and scores of other species.

Banding involves a gentle catch-and-release close observation of a bird for telltale signs of species, age, sex, and overall health, then the attachment of a small, light aluminum band with nine digits on it carefully secured to the bird’s leg — different numbers for each bird. Computerized data is then entered for each bird and sent to the bird banding laboratory at the USGS and made available to avian experts worldwide. Finnegan keeps the information on record as well.

“The importance of bird banding cannot be overstressed,” says Finnegan. “In order to save bird species in decline we must have as much knowledge as we can gather. Banding provides critical information on the number of birds in a given area, and answers questions as to their general condition. Being able to age a bird accurately is important in order to answer questions if a species is in decline. Is the population declining because the young aren’t surviving or are the adults not producing young? Banding can help answer these questions, which in turn helps land managers know what type of habitats need to be protected to increase the survival of a species in peril. When a habitat disappears, birds will not move to another area; they will just stop breeding. Long-term banding stations are vital because they show changes in bird populations, behaviors, and environments over time, especially with the ongoing threats of climate change. This is why it’s so important to preserve Wing Island and to continue monitoring the bird species.”

Here's how bird banding works:

“Mist Nets” made of soft, mesh-like material, each about 40 feet long and eight feet high, are used to carefully “catch” the birds, says Finnegan. “One needs to be specially trained to take the birds safely and gently out of the nets,” she adds, noting the birds are then put into a cotton bird bag and taken to a banding table where they are identified as to species, age, health, weight and the like.

Bird species are identified visually with expertise. In discerning the age of a bird, Finnegan says, one can tell by the pattern, quality and color of their feathers. “An adult bird will molt every year and lose all feathers, which grow back with feathers looking uniform. If you look at a bird’s wing, you can see differences in the age of the bird in terms of the color and quality of the feathers. A young bird, for example, will molt only part of its feathers. So it’s easy to ascertain the difference between a juvenile bird and an adult bird.

“We also look for fat on a bird to assess its health, determining whether its underweight or not doing well,” she adds. “And we look for ticks on the bird; ticks won’t get birds sick, but birds often can pass tick diseases along. So we remove the ticks.”

In addition, sometimes a tail feather is carefully removed to map where species are wintering. “Tail feathers have DNA,” Finnegan notes. “Similar to a human genome project, the study of avian DNA offers valuable information and is shared with research experts at the Bird Genoscape Project, working to map where species are wintering.

How long does it take to capture all this information?

“Just minutes,” Finnegan says.

Finnegan has a trained volunteer staff of as many as seven on site at Wing’s Island. In spring, she says, an average of 20 birds a day are usually banded. “In the busier fall during migration season, we may get more than 200 birds a day,” she says.

But not all birds migrate. Birds born on Wing’s Island tend to stay — like some Cape Codders they never cross the bridge, adds Finnegan. Migrating birds are likely born in other places. And even some birds — mockingbirds, cardinals, titmice, and Carolina wrens, which used to be southern species, have moved north due to climate change, and are now resident birds.

Why do some birds migrate and others don’t?

“It’s instinct, the way the species has evolved,” says Finnegan.

The environment has a significant impact on birds on Cape Cod.

“It’s a tough time for birds,” Finnegan says. “Birds are declining here in distressing numbers. I can see it in the 25 years I’ve been bird banding on the Cape. You just don’t get as many birds migrating. Over development, pollution, climate change, and sea level rise all have major consequences on the bird population. Sea level rise, for example, is flooding salt marshes and other wetlands where many species nest. Scientists think saltmarsh sparrows and other species will be extinct in over the next 50 years.

“And any time forests or upland is being developed, you’re losing birds that require acres of land in order to breed,” she adds. “These birds don’t move to another place to breed; they just don’t produce more young and die off.”

So the good work of Sue Finnegan and her volunteers on Wing’s Island in their bird banding and their educating the public is critical to preserving such a fragile yet remarkable population on this fragile land we call Cape Cod.

Greg O’Brien has been a board member of Cape Cod Museum of Natural History for close to 25 years. A career journalist, he’s also an author and scriptwriter. He lives in Brewster’s Stony Brook Valley, not far from Wing Island.