Tiny Migrating Birds Nabbed And Tagged As They Stop In Isles Of Shoals
If you visit Appledore Island during spring bird migration, consider wearing a helmet.
“Yeah I mean the herring gulls will hit you and it’s jarring, but the black-backs hitting you can do some serious damage,” says Sarah Courchesne, a sea-gull researcher with Tufts University, as she and her students suit up to go out and catch seagulls.
The gulls that nest around the research station get very protective this time of year
“They bite and they pinch and then they kind of lacerate you and then sometimes they twist and drag your flesh with them,” she says, noting that you have to be quick to clean out any injuries you receive, because “we know where those beaks have been.”
The things we do for the love of science.
When you think of migrating birds, you likely summon up the classic “vee” of Canada geese, honking as they fly past, but scores of New England bird species make the long trip to the tropics, including many that weigh no more than a triple-A battery. With the spring bird migration now coming to an end, researchers at this station in the Isles of Shoals (which is shared by Cornell and UNH) are working to figure out how these tiny animals make this titanic journey.
Dodging between nesting gulls is a necessary evil for the folks doing this work – like Lex Hetrick, a volunteer from Manchester. She’s extracting birds that have been captured in incredibly fine “mist nets” researchers string along paths through the brush.
“So what I’m just going to do is get ahold of the bird so that it’s nice and safe, bring it out of the net and I’ll start removing the net that it’s grabbed onto,” she says while demonstrating how this is done on a very “chatty” catbird. “What are you doing?” she asks softly as the bird chirps in response, “Yeah, tell me about it.”
This technique for catching song-birds is an important research tool for ornithologists. Since 1980, when this station opened, volunteers at Appledore have captured and banded 80,000 birds.
New Tech, New Discoveries
But these days, there’s a new technology on the block.
“This is a geolocator, it weighs about .36 grams, we’ve attached a harness to it, made of stretch magic jewelry cord,” explains Max Witynski, a sophomore at Cornell, who’s here as a research assistant, “and what we do is put it on the birds back, like a little backpack, the loops go over the bird’s feet and hopefully it stays comfortably on the bird for the whole year.”
With these geolocators they can learn everywhere that these tiny birds go. With bands researchers just see points in time: like when the bird is first caught, and when it’s found dead and the band number is reported.
But the geolocators are expensive – this team has just ten to deploy on Appledore – you still have to recapture the birds to collect the geo-locator data.
David Bonter, the Cornell professor running this experiment, says in the case of the bird he’s studying, the yellow warbler, the easiest way to do that is to use the male birds’ macho tendencies against them.
“They’re very defensive of their territory right now,” he explains.
He stands behind the nets and plays a recording of a male encroaching on another male’s territory.
“So you play the song, they come right in to chase out the intruder, the young punk,” he says
This new technology has led to some astonishing insights into the migrations song-birds make.
Take the black poll warbler, for instance. David Holmes, a veteran bird-bander on Appledore, says in the fall he can tell when he’s working on a bird that’s ready to migrate, just by the feel of the bird when he puts a band on its leg, because “they squish.”
Black polls double their body weight in the fall, and then make an incredible flight starting in the Northeast.
“And they took off at dusk. They [the researchers] tracked them: 14 hours later they were over Bermuda; 70 hours later they were at about 14,000 feet over Antigua; 82 hours later they were hitting the coast of South America,” explains Holmes.
Discoveries like these all start with the yeoman’s work of catching and banding birds, carried out mostly by volunteers. Not a bad way to spend a few weeks in the spring and the fall… except for the seagulls.