The salmon die shortly after spawning, and their carcasses provide a feast for the eagles at a time of year when food is scarce elsewhere. This combination of open water and plentiful food brings over 3,000 eagles into the Chilkat Valley beginning in early October and lasting until January. The peak of the gathering usually occurs in mid-November. Eagles have a wing span of over six feet, and their average weight is thirteen pounds. Immature eagles are a mottled brown, and often appear larger than mature birds.
Females are somewhat larger than males.
They obtain the distinctive white head and tail feathers when they molt in the spring of their fifth year. Eagles can fly at 30 mph and dive for prey at up to 100 mph. Bald eagles mate for life and live 30 years or more. A pair of eagles renews their bond in spectacular aerial courtship displays, diving and somersaulting through the air with talons locked. They build nests that can reach twelve feet across and weigh over a ton, and return to the same nesting site each spring.