06/03/2007

On the Wing

Migration is both magical, risky

By Kay Charter
Local columnist

Read past On the Wing columns here

A few weeks ago, a call came in from my friend Mick Pfeiffer, who spent spring break with his family in Florida. He was on his cell phone from seven miles offshore from Fort Myers, where he was fishing with his daughter, Becca.

"Hi Kay!” Although fishing had been slow, his voice was filled with excitement.

"I need you to help me identify this little bird. It's got a black mask with a band of white above it and an olive back and yellow breast.”

It was a common yellowthroat, a warbler that breeds across North America and winters along the southern states down through Mexico and Central America. Mick's oceanic visitor was undoubtedly an exhausted migrant that simply found a resting place out of the drink before collapsing into it.

Once ashore, Mick sent an e-mail about the bird:

"He looked lethargic and sickly as he barely clung to the side of the boat. After what appeared to be a short nap in the sun, my normally sloppy housekeeping aboard seemed to be a blessing for this guy. He moved about the boat on foot, finding each spider web and feasted on the remains in them. I recall one particular funny moment when we were questioning what he found so interesting in one of the many storage crevices he was investigating, then a miller escaped. It became apparent this bird was hungry and looking for food.

"We enjoyed his company for over an hour. He really perked up during his visit. While we motored to shore, he found a comfy spot in the shade behind the protection of a downrigger ball on the floor, and seemed to nap as we neared the Florida coast. We stopped to drift-fish about 3/4 of a mile offshore, and the bird came out for a last inspection around the boat, headed up to the antenna for a brief watch, then took off.”

A week or so later, an e-mail from a bird-based listserv arrived with the following subject heading: Ten Billion Songbirds Arrive in North America.

Imagine 10 billion songbirds crossing the Gulf of Mexico every spring and fall. It goes without saying that many do not make it; they run out of gas, like my friend's tiny visitor did, or they meet a cold, rainy front that drives them into the water.

How does a bird that weighs half an ounce or less (about half an ounce for the yellowthroat and a tenth of an ounce for hummingbirds) have enough energy to carry it 400 or 500 miles across open water?

They fundamentally do it the way we get around — they fuel up for travel. As we prepare to make a long trip, we head to a service station to fill our tanks. Birds, however, move into appropriate habitats where they forage like crazy, packing on weight in the form of balls of fat under the skin on their breasts. These miniscule butterball-looking masses are their gas tanks, which the birds use exceedingly efficiently.

Noted author Scott Weidensaul once said of migrating blackpoll warblers (who travel more than 2,000 miles over open water) that if these birds were burning gasoline instead of their own body fat, they would be getting 720,000 miles per gallon.

Although some birds (orioles) build fat by tanking up on fruit, and others (bobolinks) do so by chowing down on seeds, many birds — especially warblers, vireos and thrushes — depend on insects for this crucial fat-building foraging period. It is important to remember that these insects are largely hosted by native trees, shrubs, flowers and grasses.

Birders who venture out into the Gulf during migration often have experiences like Mick's. My son, who has made numerous trips into the Gulf, often saw birds land on the vessels he traveled on.

Once, when he was off the Yucatan Peninsula, he watched as a marathon migrant blackpoll warbler, clearly exhausted, dropped lower and lower to the sea. The bird headed briefly toward the boat my son was on, as if considering that as a possible landing spot. Then, at the last moment, he turned away and flew to an island half a mile away with just the right habitat.

Kay Charter is executive director of Saving Birds Thru Habibat, an organization that teaches people how to help migrating birds whose habitats are declining.