Geolocator

A Helldunkelgeolokator or short Helldunkellokator is a scientific device that was designed to track the routes of elephant seals and (after miniaturization of devices) the routes of migration of small birds.

For small birds such as the wheatear, which weighs only 25 g, it is not possible to provide them with a satellite transmitter. The device would be too heavy for the bird, whose population in Alaska across northern Russia, Asia, the Caspian Sea to East Africa (Sudan and Kenya) and flies back and twice as 15,000 annual miles traveled by.

Modern Helldunkellokator weighs less than 1 g, and is mounted on the back of the bird. It consists of a photoelectric cell that measures the light intensity, a clock and a chip for recording the light intensity over time. The results can be read out later. From the time of noon ( maximum brightness ) and midnight can be the longitude, from the day-length and night length to calculate the latitude. From these values ​​, the migration route can be determined.

The Wheatear, as could be ascertained, flying for hours at a speed of 50 km / h, depending on the wind sets per night 450 km on its long-haul route back.