Back in the Gulf: Our Nautical Hitchhikers

May 11, 2011

A cattle egret, courtesy of Bob O'Connor, USFWS

For several days, indeed much of this entire spring season, winds here in the southern Gulf of Mexico have blown strongly from the east. For land-birds that are trying to island-hop back to their North American breeding grounds through the Caribbean, this can pose a bit of a hazard, especially if their normal routing is up through Cuba and then over the relatively short 90-mile gap over to southern Florida and the Keys. Before they reach land, the strong winds can blow them far to the west, where only open water awaits the tired travelers.

Today on the Gordon Gunter we witnessed both tragedy and triumph for these exhausted migrants. After dawn, a cattle egret showed up, its gleaming white plumage, buff streaks, and brilliant yellow bill indicating a bird in full breeding status. After circling the ship, it finally landed, and ducked into a quiet alcove on the forward deck. By mid-day, another cattle egret had joined the first. Whenever disturbed by our work, these two would fly off temporarily, as if on a short scouting trip looking for land, but then come back. At the end of the day, at least three of the white birds had found refuge on our ship. At last they found a deserved rest perched high on the aft superstructure, hunkered down on some railing and faced into the howling wind.

Such an opportunistic strategy goes a long way in explaining how these land-birds got to the New World in the first place. Originally natives of Africa, it is believed that cattle egrets arrived in South America under their own power, and from there spread rapidly northward. Watching these egrets today, it occurred to me that those first immigrants might well have been assisted by the occasional rest (if not an entire free passage) afforded by a ship. My theory got some support the next day: when I looked for our hitchhikers, each had continued on with their flights sometime the previous night.

Those were not our only terrestrial visitors. A few solo barn swallows winged by, deviating only slightly from their route, and kept heading north. One merlin, a species of small falcon, dive-bombed past the pilot-house, then rocketed off. A group of shorebirds flew in tandem low over the water, steadily beating their way to a distant landfall. The high drama, however, was provided when a peregrine falcon stalked a hapless warbler flying low over the water.

Peregrine falcon in flight, courtesy USFWS

I saw the falcon first: a stocky profile bulleting around the stern of the Gunter, its flight path twisting and turning. As it came up the port side toward the bow, I saw it was actually chasing something. A tiny olive bird, a warbler flying only inches off the waves, was in its crosshairs. For a while the warbler’s tighter turning radius kept it out of the predator’s reach; I silently hoped it would stay that way.

But the peregrine climbed higher, zeroed in, and then shot down, striking a blow that knocked the warbler into the water. The falcon then circled around, deftly plucked the warbler off the ocean surface, and then flew past the pilot-house bridge. Right in front of me, using the wind for lift, the falcon flew so as to plane its wing into a near stall, and then proceeded to first pluck and then eat the warbler grasped in its talons. All of this occurred in flight, on the wing, over the open ocean, a hundred or more miles from land. And not content to stop there, the peregrine started diving-bombing the ocean again, scaring the flying-fish into a potentially fatal mistake of flushing out of the safer water below and into the far more dangerous air above.

Even now I can scarcely believe what I saw. Peregrines are famously powerful flyers, not at all intimidated to cross very large expanses of open sea. And why should they be, if they can hunt, capture, and eat on the wing?