Celebrating the Nation's Icon
The bald eagle soared off the endangered species list in 2007, rebounding from 417 breeding pairs in the continental United States in 1967 to over 10,000 today. The recovery and delisting of the nation's symbol marks a major achievement in conservation. Idaho’s breeding bald eagle population has experienced a 20-fold increase, growing from about a dozen known nesting territories in 1979 to more than 250 today.
Uniquely North American, the bald eagle has a long and symbolic history in the United States. It first appeared on an American coin in 1776, and became the national emblem in 1782 when around 100,000 nesting pairs lived throughout the United States ranging from Alaska to northern Mexico. But by 1963, the U.S. Fish and Wildlife Service estimated that only 417 nesting pairs remained in the lower 48 states.
Beginning in 1940, Congress attempted to protect the bald eagle by passing the Bald Eagle Protection Act, which made it a crime to take or sell the eagles. But it was the chemical DDT, developed after World War II as the first of the modern synthetic insecticides, which really took a toll on the bald eagle and other raptor species. DDT accumulated in the birds and caused them to lay eggs with thin shells. Concerns about the bald eagle resulted in its protection in 1967 under the predecessor to the current Endangered Species Act (ESA). As a result, the bald eagle was one of the first species protected by the ESA when it was enacted in 1973.
Two important factors made the recovery of the bald eagle possible, the most critical being the federal government’s ban on the use of DDT in 1972. Second, listing under the ESA has reduced threats to bald eagle habitat, including nesting sites and summer and winter roost sites. In addition, federal and state agencies, tribes, private landowners and others played a vital role in restoring populations by protecting important habitat, reintroducing the bald eagle back into the wild, monitoring species recovery and conducting extensive public education efforts.
Nesting in Idaho
Since monitoring began in 1979, the number of known bald eagle nesting territories in Idaho has increased from about a dozen to more than 250 today. Statewide, recovery population goals have been exceeded by approximately150%. As part of the post-delisting monitoring period, IDFG now coordinates statewide monitoring of all known bald eagle nests every five years. Because 2014 is an “on” year for the survey, many nests are probably being checked this week; once all the data are in, results will then be compared to the last complete survey conducted in 2009.
Nest sites are usually located in the tallest trees (sometimes on cliffs or rock outcroppings), from which the birds have a clear view of their surroundings. Eagles generally use the same nests year after year. In Idaho, if wintering conditions permit, pairs remain on their territories year-round, constructing new nests or adding to existing ones between October and the end of February. Females lay one to four eggs (usually just one or two) in late February to early April. After 35 days of incubation, eaglets hatch in mid-April or early May. During the nesting season, eagles usually carry prey to a perch or deliver it to the nest to feed their young. Adults feed chicks by tearing off pieces of food and holding the pieces to the beaks of the eaglets. The nestlings begin to feed themselves at about seven weeks of age.
Bald eagles are especially visible in the winter when migrant eagles begin to appear on their traditional Idaho wintering grounds near sources of food—rivers, lakes and shorelines. Populations peak during January and February. Large groups of eagles gather at roosts—perching sites where birds spend the night. Stands selected for roosting are usually made up of mature trees with strong limbs high above the ground. Roosts provide physical protection, views of the surrounding area and any approaching danger, and serve various social functions.
In winter, the birds are primarily concerned with feeding and conserving energy. Although fish are the bald eagle's primary food, a fish need not be alive to attract a bird’s attention. Winter die-offs of salmon at some of Idaho's lakes and rivers, such as Lake Coeur d’Alene in northern Idaho, attract bald eagles. Eagle Watch is an annual event near Coeur d’Alene where people gather to view hundreds of bald eagles feeding on salmon. Other important winter foods include waterfowl, small mammals, winter-killed deer and, occasionally, upland birds or mammals when severe winter weather causes dependable sources to become unreliable.
In addition to Lake Coeur d’Alene, large concentrations of wintering bald eagles are found along Lake Pend Oreille, and sections of the Snake, Salmon and Boise Rivers. Although some nesting pairs remain in Idaho year-round, the winter population is supplemented by migrants from Canada.
Every year, volunteers and agency biologists participate in a mid-winter statewide survey counting eagles along specific routes. The intention is to monitor bald eagle numbers throughout the state. The count’s total has ranged from 480 to 832 birds.
Idaho’s count is part of a national effort called the Annual Midwinter Bald Eagle Survey. The survey is a true public-private partnership with hundreds of volunteer citizen scientists taking part, in addition to federal, state, and non-governmental agency biologists. Forty-three states actively participate, with over 740 standardized survey routes across the country.The data are collected during a two-week window every year; then sent to a national database set up to monitor eagle populations in the lower 48 states.
So as you are spending time outdoors this Fourth of July weekend, look for our nation’s icon and relish this great conservation success story… the return of our country’s national symbol from the brink of extinction.