Documenting an Extinction: George Divoky and Black Guillemots


It’s a little bit of a bummer to have two posts on extinction of bird species in one week. But bird extinctions are a crisis, and that crisis becomes more urgent every day.

Black Guillemot, Gambell, St. Lawrence Island, Alaska

Black Guillemot, Gambell, St. Lawrence Island, Alaska

Another poor quality photo, WC is afraid. But this is the best of the three photos of Black Guillemot that WC has been able to get. Black Guillemots have a much smaller range than their more common cousins, Pigeon Guillemots. They are consequentially much more difficult to photograph.

Black Guillemots are in desperate straits, especially in Alaska. The Alaska subspecies of Black Guillemot, sometimes called Mandt’s Black Guillemot, is a sea ice-obligate species. Its primary prey is Arctic Cod, which frequents the melting edges of sea ice. What has been happening increasingly often is that the edge of the sea ice is so far from the birds’ colonies on the barrier islands of the Chukchi Sea that the checks starve to death before their parents can get from the nests to the distant sea ice edge and back with prey for the hatchlings.

Sea Ice cover, August 2018 and August 2019, via AACAP

Sea Ice cover, August 2018 and August 2019, via AACAP

It’ an increasing severe problem.

Sea Ice cover near Alaska, 1979-2019, via AACAP

Sea Ice cover near Alaska, 1979-2019, via AACAP

Dr. George Divoky has been studying the Black Guillemot colony at Cooper Island, a barrier island in the Chukchi Sea, east of Prudhoe Bay, for 45 years. He reports that in the 1990s, fledgling survival – chicks that hatch, thrive in the nest and successfully fledge – was in the range of 75%. In 2019, it’s only 25%. Putting it another way, in 2019 three-quarters of the nests failed. The chicks are starving to death before they can fly.

Divoky has documented other new hazards facing the Cooper Island Black Guillemot colony: predation by polar bears, themselves starving because they cannot reach the ice; competition for nesting cavities with puffins, which are expanding their range; rising sea levels and the absence of ice causing flooding the lower levels of the island. But mostly, based upon careful tracking of chicks themselves, it’s starvation.

The Alaska populations of Black Guillemots evolved preying on the Arctic Cod at the ice edges. They so far have not been able to adapt to the changed habitat; anthropogenic climate change has occurred too quickly.

Black Guillemot are a circumpolar species. Populations in eastern North America are much less dependent on sea ice and aren’t in such imminent danger. But the future looks very grim for the Alaska populations.

Divoky supports his long-term study at Cooper Island in part through a nonprofit corporation, Friends of Cooper Island. The website for the nonprofit has Divoky’s bog, links to his research and published papers. It’s grim reading. It’s a grim problem.

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