The bald eagle, with its snowy-feathered head and white tail, is the national symbol of the United States – yet for many decades eagles were hunted for sport and to ‘protect’ fishing grounds. Use of now-restricted pesticides like DDT wreaked havoc on eagle populations, as they collected in fish and moved up the food chain. Ingested by eagles, they weakened the bird’s eggshells, impacting their ability to reproduce. Since DDT use was curtailed in 1972, eagle numbers have rebounded significantly and have been aided by reintroduction programs. The result is a wildlife success story that is still unfolding.
Bald eagles are found in most of Canada, Alaska, continental US and northern Mexico. Though their num-bers have grown throughout their range, they remain most abundant in Alaska and Canada. These pow-erful birds of prey use their talons to fish, but they also get food by scavenging carrion or stealing the kills of other animals. (Such thievery famously prompted Ben Franklin to argue against the bird’s nomination as the United State’s national symbol!) They occupy a variety of habitats, from coastlines and open water, to inland lakes, marshes and bayous, to eastern forests and southern deserts. They thrive on fish but will also snare and eat small mammals, herons and other birds.
Bald eagles are believed to mate for life. A pair constructs an enormous stick nest – one of the bird world's biggest – high above the ground, and tends to one pair of eggs each year. The biggest nest on record was found in Florida in 1963, measuring ten feet across by 20 feet deep!
Immature eagles are dark and mottled in plumage, and until they reach five years of age they lack the dis-tinctive white markings that make their parents so easy to spot. Adult males and females are identical, with females outsizing their mates by about 25 percent.
As birders well know, bald eagles are expert flyers, soaring high on thermal convection currents. Reaching speeds of up to 70 km/h on a glide, an eagle’s dive speed can more than double to 160 km/h.