Last month, in addition to our annual adult banding activities, we had the good fortune of having scientist Kate Shlepr on island to show us how to safely deploy solar powered GPS loggers on our birds. While Great Black-backed Gulls can be intimidating to work with, their large size means we can attach loggers with good size solar panels, allowing frequent pings to the satellites, and therefore a read on where the birds are every 15 minutes.
Since we deployed the loggers a month ago, we’ve been performing weekly downloads (thanks to our intern, Brett, for staying on top of that) and can visualize the data via Google Earth.
Each bird’s data is downloaded to a base station on Appledore whenever the bird is in range. At the end of the breeding season, once the gulls disperse, we will take down the base station since the birds will not be in its vicinity all winter. We will wait, with bated breath, until next May when we redeploy the base station and, hopefully, start to pick up signals from the tagged birds as they return to nest again. Return rates for adult gulls on Appledore are upwards of 80% each year, so our chances of seeing these individuals again are good.
While much of our choice on which birds to tag was opportunistic, we tried in at least some cases to select birds that have not been re-sighted previously anywhere off island. We are deeply curious about where these birds overwinter, roost, and forage.
So far, the loggers indicate that some birds are vastly more pelagic than others. In the past month, some of our tagged birds have not visited the mainland once, preferring to forage exclusively offshore. This would explain the dearth of sightings by humans on shore. Knowing that birds forage offshore is not sufficient in gulls, however, since they could either be fishing for themselves outright, or begging for scraps off fishing vessels. Brad Natti, lobsterman and gull re-sighter, has suggested that we use AIS data to see how the tracks of where ships have been traveling overlaps (or doesn’t) with our gull logger data, and we think this is a very exciting line of inquiry that we intend to pursue once the field season winds down.
There are so many questions these loggers can help us answer, and if you have any, we welcome yours too. Watch this space for more on these special gulls.