The black guillemots of Cooper Island, at the western edge of the Smith Bay area, demonstrate how productive and diverse those waters are. These small seabirds come to the island each year to nest, lay their eggs, and raise their chicks, feeding offshore on small fish in the water column and invertebrates on the seafloor. Their abundance is a powerful indicator of the health of the ecosystem.
Divoky has spent more than 40 summers on Cooper Island, watching the birds mate and breed, weighing them, monitoring their food intake and their ability to feed their young, and studying how their welfare depends on snow, sea ice, and other features of their Arctic habitat. The result is an extraordinary set of data with few parallels anywhere.
The black guillemots come to Cooper Island because it provides good nesting habitat, sheltered from land-based predators, so long as no polar bears or arctic foxes remain on the island after the sea ice breaks up, and because it gives them access to the rich waters of Smith Bay. In brief, they come because they find food and a home.
And though the Arctic has always been variable — when it comes to breeding success, the record shows good and bad years — lately, the story has become more complex. In 2009, only one chick survived to fledge and leave the island. One cause of the decline has been a shift in the food web, with fewer of the rich, fatty Arctic cod that provide calories and nutrients for young guillemots. Instead, the adults feed on sculpin, which offer less of what the chicks need. And polar bears have become more likely to get stranded on the island, where they feed on eggs and nestlings. Puffins, too, have expanded their range northward to Cooper Island, and they also prey on the newly hatched birds. All in all, these changes are a big challenge for the guillemot colony.
read more: medium.com/@VitalArctic/what-we-can-learn-from-remarkable-smith-bay-alaska-ff3856d4f5df#.hipqsx971
article: Henry Huntington
photo: Katie Stafford