Birds Fly More Than 7,000 Miles Nonstop, Study Shows

Gill and his colleagues outfitted 23 bar-tailed godwits with satellite transmitters that periodically sent a signal detected by a satellite.

Female godwits are substantially larger than males. A one-ounce, battery-powered device was surgically implanted in them, with the antennas exiting their bodies just beneath the tail. The smaller males got a solar-powered device weighing less than half an ounce strapped to their backs.

Nine of the transmitters functioned well enough on the southward flight to provide evidence of sustained, nonstop flight.

One female flew directly from the Yukon-Kuskokwim Delta of Alaska to New Zealand in eight days. Other birds either landed short of their destination in the Solomon Islands and Papua New Guinea, or the signal was lost near those places. Four were later identified in New Zealand by leg bands.

The birds weigh no more than 1.5 pounds when they leave. Half of that is fat, which they burn off completely during the flight. Some of the males may have lost their transmitters in flight as their bodies shrank.

The starting and stopping places are not chosen by chance. The Kuskokwim Delta is rich in food supply, which the birds must consume in prodigious quantities before leaving. The wintering site in New Zealand is largely free of predators. When the birds arrive in early October, they molt almost immediately.

The birds leave from late August to late September, departing only with favorable tail winds. How much of their journey is wind-aided is something the researchers hope to determine by overlaying the birds' routes with day-by-day meteorological data.

A major mystery is how high the birds fly. Gill said that since word of his research has spread, researchers on boats in the Pacific have told him of seeing godwits 3,000 feet high and "smoking by at deck level."