For as long as we’ve seen birds flying overhead, they have begged a question: Where are they going? Some birds are known to travel over 40,000 miles, but measuring those distances can be tricky. In the past, researchers had to rely on banding birds or using GPS units that communicate with satellites. Because of the heavy battery packs required, only large birds like eagles and vultures could be used in these studies until fairly recently.
Joshua Horns is a graduate student at the University of Utah, and he uses a different sort of device to find where birds go, one that records sunrise and sunset times. It’s called a light-level geolocator.
“They [the geolocators] don’t talk to satellites at all," said Horns. "All they do is measure how much light there is, how much ambient light. So by looking at that timing of sunrise, and that timing of sunset, you can get a good idea of how long the day was.”
Considering that the length of day changes as you move north to south, these devices can find a bird’s latitude by measuring how long the day was. Similarly, sunrise and sunset times are specific to a certain longitude. By putting these together, researchers can get a rough idea of a bird’s location, and the best part is that they don’t require heavy battery packs, so they can be attached to much smaller birds, like the great reed-warbler, which migrates from Turkey to sub-Saharan Africa each year.
Joshua and his colleagues have been studying this species for several years, and are learning the places that birds need throughout their migrations. The research team has learned that the birds rely on wetlands, and that many of the wetlands they need are unprotected.
“Right now, the Turkish government is planning on constructing this dam that will flood the wetlands as well as several villages in the area," Horns said. "So we’re working to put a stop to that dam construction, not just for the conservation of these wetlands and all the animals that rely on them, but also for these old historic farming villages.”