Tiny Birds Make Big Trips


Written by Jon Mercer in Biology
Viewed by 77 readers since 02-26-2009

In their annual migrations between the Americas, tiny songbirds like martins and thrushes can travel as far as three-hundred and eleven miles per day. This is three times as far as researchers previously believed the tiny migrating birds could travel in a single day. Biologist found out the distance of the birds flights when they conducted the first-ever study to track several species of birds to their wintering grounds and back.

Another interesting discovery was made during the research: the birds actually fly two to three times faster when they are heading north in the spring than they do heading south in the fall. Scientists believe that the birds may be in competition to reach the best breeding sites and attract the fittest mates.

One industrious female martin flew the four-thousand-six-hundred and sixty mile trek from the Amazon basin to Pennsylvania in only thirteen days — with four of days spent on stopovers! This data was obtained using miniature geolocators about the size of a dime and weighing just a few ounces. Scientists attached the tiny locating devices to the bird’s backs, sort of like a school child’s backpack.

The new geolocators make the research possible for the first time. Never before have scientists been able to log the speed of flight and distance as accurately. The device was invented by James W. Fox and his colleagues at the British Antarctic Survey. Each of the self-contained devices weighs about 1.3 grams and carries a computer chip and a light sensor mounted on a small stalk that sticks up above the feathers. The devices also measure and record the times of sunrise and sunset.

The concept is a simple one: for any given place on the planet they can match up the time of the sunrise and sunset and then determine the bird’s exact location. When the birds return to their original breeding ground they are captured and the data from the geolocator is downloaded to computers where researchers can examine it. The preliminary studies show that the devices do not interfere with the bird’s flight or their ability to catch prey, mate or feed their offspring.

On the return flight, most of the birds stopped on the Yucatan Peninsula before making the thirteen to fourteen hour non-stop flight across the Gulf of Mexico to return to the United States. However, one of the birds wearing a tracking device took the “long way home” and arrived back at the breeding grounds very late. Researchers are still unsure about why this particular female was taking an alternate route but they speculate that maybe she didn’t have the proper body fat in store to sustain her during the long trip.


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