Interesting article noting that increasing numbers of Pacific Black Brant are choosing not to bother flying south from their breeding grounds in Alaska to warming climates during the winter:

Scientists have documented that increasing numbers of black brant are skipping that far southern migration and staying in Alaska instead. Fewer than 3,000 wintered in Alaska before 1977. In recent years, however, more than 40,000 have remained north, with as many as 50,000 staying there last year, during the most ice-free winter that Izembek had seen in more than a decade.