Jody Victor : Bald Eagles first came under the wing of specific protective legislation in 1940 with the edict of the United Stated Bald Eagle Act. The Act, together with Ontario's Game and Fish Act, helped to protect eagles from direct persecution. However, over the next 30 years, the effects of persistent chemical contaminants presented an unprecedented threat, particularly in heavily settled areas like the Great Lakes region.

In the early 1970s, faced with overwhelming scientific evidence, Canada and the United States restricted the use of DDT and tightened regulations for disposing of industrial chemicals. These actions, together with the development of endangered species legislation and assessment programs to monitor the status of endangered wildlife, protected the animals themselves and the habitat they need to survive. Ontario passed its Endangered Species Act in 1973.

Committees for the assessment of the status of species use a scientific approach to evaluate animal populations believed to be at risk. They also recommend recovery plans to protect and augment the populations. Each assessment is reviewed periodically and either re-instated or changed, depending on the status of the species.

In the United States, Bald Eagles are listed nationally as "Threatened" in the lower 48 states. The U.S. Fish and Wildlife Service is reviewing a proposal to change the designation. Without a protective designation, however, measures are needed to continue protection of the birds' nesting sites.

Canada's national assessment body, the Committee on the Status of Endangered Wildlife in Canada, is known as COSEWIC. This group made its first designations in 1978. COSEWIC consists of distinguished scientists and wildlife managers from government and non-government positions, representing 20 member agencies. All provincial and territorial government wildlife agencies are represented, as well as four federal agencies: Canadian Wildlife Service, Parks Canada, Fisheries and Oceans, and the Canadian Museum of Nature.

Bald Eagles were considered "Endangered" at the national level from 1978 to 1984, when COSEWIC changed the designation to "Not at Risk Nationally". The more recent designation recognized the flourishing populations of eagles along Canada's west coast and in the northern boreal forests.

At the provincial level, Ontario continues to designate Bald Eagles as "Endangered" and protects the birds and their nest sites under the provincial Endangered Species Act, proclaimed in 1973. Currently, the province is reviewing this status in response to recent improvements in the Great Lakes population and the presence of apparently healthy populations on inland lakes.

Jody Victor

Jody Victor: It was a retired Canadian banker, Charles Broley, who first raised the alarm about the principal cause of the swift decline of the eagles.

Since 1947, DDT had been sprayed regularly to control a variety of insect pests in agricultural, urban and shoreline areas. A new generation of industrial chemicals had entered common usage in the late 1940s, consequent to the scientific discoveries of the Second World War. During this era, many industrial chemicals were discharged directly into waterways. Countless tons of an estimated 2,000 chemical compounds were deposited into the Great Lakes, either by direct application or via air and water, some transported over great distances.

Chemicals that were released into the Great Lakes system entered the aquatic food web - settling into the sediment of the lake bottoms and spreading first among the tiny aquatic plants and organisms, and then into the bodies of fish and fish-eating birds. Eating at the top of the Great Lakes food web, eagles absorbed the accumulated burden of these toxic substances, a load that amassed in their bodies throughout their lives. The chemicals affected not just individual health, but the production of young, too.

DDT and its breakdown product, DDE (dichlorodiphenyldichloroethyene), which is created when DDT degrades over time, affect eggshell development. The chemicals interfere with the deposition of calcium, a key component in the formation of eggshells. Eagles in the Great Lakes region - and some other birds - produced thin-shelled eggs that broke easily during incubation, killing the developing embryos.

Direct poisoning by DDT and DDE, as well as other toxic compounds, caused the deaths of some adults and hatchlings. As well, these contaminants tended to accumulate in the eggs' fatty yolk, which contains the nutrients that sustain development of embryonic birds. As the embryos grew inside the eggs, they absorbed contaminants, along with nutrients, from the yolk.

Canada and the United States restricted the use of DDT in the early 1970s. Even so, nearly 10 years later, persistent contaminants caused Bald Eagles along the shorelines of the Great Lakes to experience total reproductive failure. For instance, few active nests remained on the northern shore of Lake Erie and research showed exceedingly high levels of contaminant residue in their eggs and the blood of eaglets.

By the late 1980s, however, positive progress was emerging. DDE levels decreased by more than 50 per cent. Levels of PCBs, or polychlorinated biphenyls, decreased by as much as 80 per cent. The resulting reduction in contaminants in Bald Eagle eggs allowed reproductive rates to recover steadily. The number of active nests increased and the number of eaglets produced per nest improved. This progress was augmented by eaglet re-introduction programs, which supplemented the natural recruitment of young eagles into the population.

The sensitivity of Bald Eagles to toxic chemicals has led scientists and conservation groups to identify the birds as a bio-sentinel species, meaning that the health of eagles can be taken as a reliable indicator of the health of aquatic ecosystems in the Great Lakes region.

Jody Victor

Jody Victor: Prior to European settlement, Bald Eagles were common in the forests and along the shores of the Great Lakes region. Increasingly, as the landscape was transformed for agricultural and residential uses in the 1700s and 1800s, eagle habitat and food supplies were reduced. As well, settlers routinely killed Bald Eagles for the market value of their feathers, as predators of farm animals, or because the birds were considered to be "vermin". The eagle population declined as a direct result.

Uncontrolled persecution exacerbated the population crisis until, by the early 1900s, few eagles nested in the region. In Ontario, the Ministry of Natural Resources' Game and Fish Act, first enacted in 1890, offered protection for wild, native birds, including raptors. The United States government, prompted by wildlife conservationists, prohibited killing eagles via the Bald Eagle Act of 1940.

The respite, although effective, was short-lived. By mid-century, eagles were suffering from the insidious effects of synthetic chlorinated pesticides, such as DDT. Many years passed before the connection between the introduction of chemical pollutants into the Great Lakes and the decline of Bald Eagles was widely understood.

Jody Victor

Jody Victor : There are 59 species of eagles in the world, two of which inhabit North America: the Bald Eagle and the larger Golden Eagle.

Bald Eagles are found exclusively in North America. In Canada, the majority occur along the coast of British Columbia, with smaller populations located across the nation, such as in southern Ontario and New Brunswick.

The scientific name for this powerful predator is Haliaeetus leucocephalus. (Haliaeetus means "sea eagle" and leucocephalus means "white head".) Adult females are generally larger than the males, and both have the same characteristic plumage. The juvenile birds are a mixture of brown and white until they reach four or five years of age. At maturity, between four and eight years of age, the birds have dark brown feathers on their bodies and wings, snow-white feathers on their heads and tails, and yellow legs, eyes and beaks. As singular as their appearance, the eagles' call is a haunting series of high-pitched cries, similar to a gull's call but delivered more quickly and with more apparent urgency.

Mature Bald Eagles reach an average weight of three to six kilograms. Their wings are broad and may extend to more than two meters, enabling them to soar on columns of warm air, called thermals. Eagles can fly easily at 50 kilometers per hour.

Primarily, Bald Eagles feed on live or scavenged fish and aquatic birds, along with smaller mammals, amphibians and reptiles. Deer carcasses are a major source of food in winter. their keen vision allows them to see prey on the ground or in the water while in flight. Their strong beaks and sharp talons grasp and carry away their food: given the chance, they will "pirate" the kills of other birds, especially Ospreys.

Bald Eagles generally stay with one mate, unless the mate dies or disappears, which prompts the remaining bird to seek another. Adult females lay one to three whitish eggs in an enormous nest constructed of branches high in a tree. The eggs are incubated for 35 days by both adults. The newly hatched young are fed for 10 to 12 weeks until they have developed feathers and learned to fly, which is called fledging. Eagles can live up to 28 years in the wild and 36 or more years in captivity.

Jody Victor