This is a Cassin’s auklet nest box on Southeast Farallon Island. While not underground like the bird’s natural burrow, the covered shelter still provides protection from gulls as the tube is too small for a gull to to squeeze through to get at an egg or chick. But the gulls will poop on them — a lot.
Not only do the boxes provide a ready made shelter that the auklets do not need to create themselves, it helps biologists out as well. The top of the box has a lid that can easily be removed so scientists can peek in and grab the bird for measuring, banding and checking on the egg or chicks.
There is an extra covering shade on top of the box to keep the inside cool. The layer of air between the cover and the top of the box acts as great insulator to prevent the box from overheating. The rocks on top of the cover keep it from blowing away in the 30+ knot winds that frequently blow across the island.
Although they may look a little weird, the Cassin’s auklets seem to like the nest boxes just fine. In fact, over 75% of the nest boxes on the island are being inhabited by Cassin’s auklets and their young in the beginning of May.
Even rhinoceros auklets, which are over two times larger than Cassin’s seem to like them. There are larger next boxes placed around the island for them, but like true San Franciscans, they also seem to look for smaller, low budget dwellings.