Seabirds are highly adapted to a marine lifestyle. They obtain all of their food from the ocean, even during the brief periods of the year when they do come to land in order to breed. Most Arctic seabird colonies reflect this trait in that birds choose to nest as close as they possibly can to reliably productive waters in which to feed themselves, and also forage for their chicks. In fact, in years when extensive ice cover forces birds to forage further away from their colonies, many species suffer reduced breeding success.
There are very few species of seabirds known to switch over to a terrestrial diet during the breeding season, but recent research from Nasaruvaalik Island suggests we can add one more to the list....Check out this fascinating paper from Isabeau Pratte et al. that neatly demonstrates how Sabine's gulls can take advantage of regular but unpredictable seasons in which terrestrial prey is readily available by supplementing their otherwise strictly marine diet by eating terrestrial invertebrates.