Because the Arctic has fewer food resources than southern areas, birds living on the tundra have had to adapt their diets to what is available. Terrestrial birds that would normally eat only insects or seeds often have to feed on both, over the course of the summer, because there is not enough food for them to specialize. During the breeding season, female birds need lots of protein to form their eggs, which they get by eating insects – mainly midges, blackflies, and mosquitoes. Later in the summer, these insects die off and the birds switch to eating seeds, berries or other plant matter.

Rivers, lakes and ponds in the Arctic have far less vegetation than southern freshwater environments. Many birds that rely on aquatic plants in the south do not fare well in tundra lakes and rivers. In the Arctic, diving ducks that are adapted to feed on invertebrates – which are plentiful in arctic freshwater – have an advantage over dabbling ducks, which are herbivorous. In fact, only one of eight duck species in the Arctic – the northern pintail – manages to survive in the North solely on a diet of plants.