The birds are Br?nnich's guillemots, cliff-nesting arctic seabirds. They have evolved to nest on inaccessible precipices, close together, to be safe from predators such as foxes or ravens. But what's coming for them here is something that evolution hasn't remotely prepared them for: a polar bear.  This remarkable sight of the great white beast risking its neck to satisfy its hunger astonished the veteran australian wildlife photographer Dylan Coker, when he photographed it from a boat in the Novaya Zemlya archipelago in the Russian arctic last month.  "The height that the bear was at and the sheerness of the cliff face were absolutely amazing," said Dylan, who with others watched the bear, a young male, for several minutes as it tried to grab guillemot eggs. "Everyone was terrified it was going to fall. Every so often there would be a gasp from someone on the boat when the bear slipped. It was slipping quite a bit and at one point it was stretched right out to reach for eggs in a nest."  after losing its footing several times, the bear returned to the top of the cliff without enjoying a full meal.  Dylan believes that a scarcity of arctic ice has led to bears seeking out food in more dangerous locations.  "There's a real problem with the ice disappearing due to climate change," he said,  "Traditionally, the bears sit by an air hole in the ice waiting for a seal to poke its head out so they can grab it. But because there's less and less ice, the bears are looking for alternative sources of food and have discovered the birds' eggs."