Tracking Tiny Birds Using Tiny GPS Backpacks

To track a tiny songbird, you need a tiny tracker. This has been a problem plaguing ecologists who wished to study the movements of small animals for years, until now.

Researchers at the Smithsonian Conservation Biology Institute's migratory bird center have managed to precisely track the migration patterns of tiny ovenbirds as they flew south for the winter by equipping the birds with barely-there GPS chip "backpacks." They published their findings Wednesday in a study in Scientific Reports.

"Tracking an animal this small, with a device of this size, and with this degree of precision has never been done," Peter Marra, head of the migratory bird center, said in a press release. "Now we can identify the exact territories these birds occupied on their tropical wintering grounds. Miniaturizing technology so we can track animals throughout their annual cycle is an essential ingredient of effective conservation."

Other tracking devices have been used to successfully track the movements of larger animals, but with the smallest similar option weighing about 12 grams, they were too heavy for the delicate, little ovenbird, according to the study. Ovenbirds are about the size of tennis ball and weigh the same as four quarters. Strapping them with a bulky, heavy GPS tracker would mean they wouldn't be flying very far at all. And many of the other tiny trackers were imprecise, only able to track the animal's location within about half a mile, and expensive, costing upwards of $3,000 per unit.

In the spring of 2013, the researchers at the bird center tested out the latest in micro GPS trackers: a miniaturized tracking chip that weighs just 1 gram but is able to pinpoint an animal's location within 32 feet. The chips were programmed to begin collecting data on July 1, and switch on for 70 seconds during the night eight to 10 times throughout the year to grab location data.

The next spring, 24 of the tagged birds returned to the same location to breed, but nine of the birds' chips were either damaged or lost. Still, the researchers were able to collect location data from 15 birds, revealing better-than-ever details about exactly where the birds go during the winter months and how the species behaves.

Even this small slice of data already has significant implications for conservationists. Though general migratory patterns are known—scientists already knew, for instance, that the oven birds head down to Mexico, Central America, Florida, and the Caribbean in the winter—the exact locations have been a bit of a mystery. The location data revealed for the first time that ovenbirds from different parts of North America didn't hang out together when they got down south: birds from Maryland settled down in Florida and Cuba, while those from New Hampshire chilled in the Dominican Republic. This knowledge can help conservationists do more accurate population estimates and understand how different groups of the same species interact.

And since some little songbird populations have been declining for decades without any explanation, this technology will be crucial for future conservation efforts. Bonus: tiny birds look pretty cute wearing tiny microchip knapsacks.