Cooper Island, Alaska, July 8, 2010 — This post, like the start of summer on the North Slope is a bit tardy. Once Black Guillemot egg laying finally started in the last week of June, I was busy checking every one of the 200 nest sites on the island to determine date of egg laying. The snow drift in front of my cabin persisted until the Fourth of July due to both the large amount of winter snow accumulation and the cool temperatures in May and June. Snowmelt in front of the guillemot nest sites was also slow.
Black Guillemot enjoying its snow-free nest site.
Guillemot females begin to form their egg only after they gain access to their nesting cavity so the timing of egg laying is dictated by the time snow melts from the entrances to their ground-level nest sites. Over the 35 years of my study there has been a trend to earlier breeding, but this year’s breeding initiation was later than last year. The first egg appeared on June 23 compared to June 18 in 2009. The colony had one hundred nests with eggs on June 30, whereas last year that occurred on June 27.
The difference between the two years demonstrates the importance of looking at the response of birds to weather vs. climate. A two-year database (if one can even call something that short a database) cannot show how a population is responding to changes in climate. The response of Cooper Island Black Guillemots to climate change is demonstrated by the long-term trend over the past 35 years whereas comparing this year’s egg laying with those of last year demonstrates the effects of annual variation in weather.
As I waited for guillemots to start laying their eggs in response to this year’s weather, I was preparing for the consequences of the loss of arctic pack ice over the past decade. These changes have driven polar bears to shore and Cooper Island where they are now regular visitors in late summer. Over the years I have had to make a number of adjustments to address the issues involved when one has the world’s largest terrestrial carnivore as a late summer neighbor. In 2003 I brought out a cabin after seeing a bear rip through my tent in 2002. In 2009 I installed a noise-making trip wire as bears began to approach my cabin on a more regular basis. This year, because polar bear behavior may become less predictable as their habitat and prey availability changes, I purchased an electric bear fence.
Destruction of tent by a polar bear
The one I am using came from the North Slope Borough’s Department of Wildlife Management and was used earlier this year on the ice off Barrow during the spring census of Bowhead Whales. Unlike last year’s noise-making trip wire, this fence, which is similar to those used on horse farms a little bit further south, should actively discourage polar bears from reaching the cabin.
My camp with bear fence
I currently have two visitors from the BBC’s Natural History Unit who are hoping to get footage for the “Frozen Planet” series that will be coming out sometime next year. My next post will provide some details about what they are hoping to obtain during their ten-day visit to Cooper Island.