Well, in our corner of Alaska our data suggest some cyclical fluctuation, possibly a bit down in parts of the peninsula, but within the 40 year range of the ongoing population. Numbers are actually up in some areas.
According to my friend George Divoky, the polar bear population at the other end of the state is making its presence known.
Cooper Island 2024 - the 50th Field Season
The colony of Mandt’s Black Guillemots on Cooper Island has been declining for over 30 years, from a high of over
200 pairs in 1989. Loss of summer sea ice has been the major factor affecting colony size as decreasing ice has
reduced breeding success and survival of birds breeding on Cooper Island, as well as the rate of immigration of
birds from colonies in the Chukchi Sea. A paper including an analysis of the demographic and environmental
variables affecting the colony’s growth was recently published in the journal Ecosphere. Last year, in 2023, there
were only 24 breeding pairs, the lowest number since the 1970s. The 2024 field season saw the decline continue,
with only 20 pairs laying eggs.
Catherine and I arrived on Cooper Island on June 21 and the first eggs were laid on June 22. On July 2, shortly after
egg laying was over, a female polar bear with two nearly fully-grown young visited the island. Polar bears were rare
on Cooper Island during our first 25 years on the island but since the early 2000s have become regular visitors, as
decreases in summer ice have forced bears to land, primarily during August. This year’s early July visit was
noteworthy due both to its timing, when sea ice and ice seals were still visible north of the island, and to the
behavior of the bears, which were extremely thorough in locating active nests and manipulating them to extract
adult guillemots incubating eggs.
These early July bears broke eggs in ten (half) of the active nests and captured and ate four of adult guillemots
attending nests before moving off to the sea ice. The remainder of July was relatively uneventful. Replacement
clutches were laid in eight of the ten disturbed nests in mid-July, with two of the four birds widowed by the polar
bears breeding with previous nonbreeders. Hatching success for the undisturbed nests was high, as was nestling
survival. Scattered ice floes persisted north of the island and Arctic cod was the primary prey fed to chicks.
Unfortunately, on August 11 another polar bear visit occurred, again a female bear with two large young. As with
the early July visit, the bears were highly efficient in locating and disturbing active nests. By the morning of August
13, all the active nests had their eggs broken or nestlings eaten. I packed up camp and returned to Utqiagvik with
Catherine, who had come back to the island on August 10. Loren Holmes, a photojournalist from Anchorage Daily
News who had come out to the island with Catherine, documented much of the activity of this last group of bears.
We will be comparing his images with those obtained in early July to try to determine whether they are the same
bears.
The continuing decline of the colony and the activity of bears this past field season will change the activities and
duration of future field seasons on Cooper Island. The colony can still provide important information on
demographics and nonbreeding movements in the Chukchi and Bering seas, using geolocators. But we can
anticipate that hatching and fledging success, previously indicators of the availability of the guillemots’ prey while
breeding on Cooper, will be regularly disrupted by polar bears.