The darker the color, the more favorable the climate conditions are for survival. The outlined areas represent approximate current range for each season. More on reading these maps.
This West Coast alcid is common, but generally seen well out at sea, and thus little known to most birders. Studies suggest its movements relate to changes in sea surface temperature, which can affect food availability. Research also suggests that short-term population fluctuations are connected to El Niño–La Niña phenomena. Audubon's climate model forecasts a substantial increase in the amount of climatically suitable areas for wintering birds, but only 17% of the current range remains stable. Unsurprisingly, much of this increase is predicted to be in the north. The key with the Cassin’s Auklet, and indeed with most if not all alcids, isn’t climate per se—these birds are hardy! Rather, it is whether their climatically sensitive prey will be able to adapt to and flourish in a changing climate, and whether the oceanic islands it needs for nesting will be in the new climate space.