COOPER ISLAND, ALASKA — I had no idea when I decided to provide 150 Nanuk plastic cases to protect the Cooper Island black guillemots how much the new nest sites would change the 2011 field season for both the birds and me. It was clear that I would need to arrive at the colony earlier than usual so that Penelope Chilton and I could dismantle the traditional wooden sites that were remnants from a 1950’s Navy camp and replace them with the new nest cases.
What I had not anticipated was the amount of individual variation the guillemots would demonstrate in their adoption and use of the nest cases. Some pairs moved into the sites within hours of their deployment while others visited the site once or twice and then moved off to prospect elsewhere in the colony — apparently looking for something that looked more like their traditional site. There was also an issue of asymmetry of response within a pair. In some cases one member of a pair quickly occupied the site but its mate was initially wary of entering and took several days to join its partner. The wide range of responses was reflected in the dates of egg laying with some late adopters laying eggs four weeks after the initial egg in the colony. That led to the unprecedented occurrence of having chicks hatching in some nests while eggs were being laid in others.
While the nest cases were obtained primarily to address the issue of late-season predation by polar bears, they have also greatly facilitated the capture of adults and my access to eggs and chicks. In the past the array of random wooden structures used to make the original nest sites on the island meant that nest access would frequently require a complicated series of maneuvers in moving multiple pieces of wood and then pivoting the structure the correct way to ensure the safety of eggs or chicks. Incubating or brooding parents would flush off the nest during this process so we kept nest checks to a minimum and would frequently wait until the nest was not attended. With the new nest cases, however, it is possible to lift the lid of the case just high enough to see the nest interior, with little or no disturbance of birds. Additionally, the parent birds feel so secure in the Nanuk cases that their bands can easily be read and, if they have not yet been banded, can be captured and given a combination of color bands. At this point only two of the approximately 240 birds on the island are unbanded, the highest percentage in the history of the study.
The security of the sites is also the reason why hatching success is apparently going to be very high. That has kept me quite busy for the past two weeks — and because of the protracted egg laying will keep me busy monitoring hatching for two more weeks. Having a large number of chicks on the island in August is important since that is when the pack ice now retreats well north of Cooper. Monitoring the prey that parents bring their young and nestling weight changes as the ice retreats provide important information on how the marine waters of the Arctic are changing during a period of unprecedented ice retreat.