Los Farallones

Dispatches from Point Blue’s field station on the Farallon Islands National Wildlife Refuge

An ankle monitor for seabirds

No, this shiny piece of bling on this bird’s leg isn’t jewelry or an identification tag. It is more like an ankle monitor that police place on parolees to find out their location.
It is called a geolocation (GLS) tag and lets biologists track birds by recording light levels. The time of sunrise and sunset lets scientists calculate latitude while the time of midday lets them calculate longitude.
While this method of tracking is not as accurate as GPS, GLS devices are a lot lighter than GPS models and are able to be carried by smaller birds.
Many seabirds can be located in the spring and summer because they have to come to land to breed. But many of their whereabouts during the winter are unknown. Last year, Point Blue Conservation Science placed GLS tags on seabirds nesting on Southeast Farallon Island, and some of those birds have now come back to the island this year.
Point Blue would like to thank these birds for their service to science as the information they have brought back will be used to fill in our knowledge gaps in the birds’ life history.
photos: Kiah Walker
This post can also be seen on: No Such Things as a Seagull