Bald Eagles: An Update on Population Status

by: Peter MacDonald
WINTER 1994/95

During the past three decades, Department of Lands and Forestry surveys and annual Christmas bird counts in eastern Kings County have documented an occurrence obvious even to the most casual observer. The number of bald eagles (Haliaeetus leucocephalus) visiting the Annapolis Valley during the winter has increased dramatically. Travelling the roads of this area during January and February, one can easily count several hundred eagles and may see more than 30 perched in a single tree.

During a one-day eagle count each year, observers record the number of eagles seen within an assigned area for one hour. In the winters of 1993 and 1994, the totals for eastern Kings County were 442 and 408, respectively. In contrast, the sight of a single eagle over this same landscape was uncommon in the 1960s and earlier.

At the time of early European settlement, bald eagles were likely abundant throughout most of North America. Since then, human encroachment has subjected them to widespread loss of nesting and feeding habitat, disturbance, accidental poisonings, persecution, and pollution. The bald eagle evokes a considerable amount of admiration, interest, and concern from the public. As a bird of prey at the top of the food chain, it is an important indicator of the health of other wildlife species and the environment generally.

The need for more information on eagle population status and distribution in Nova Scotia led to a number of DNR projects on eagles during the 1970s and 1980s. One example is the survey of nesting eagles conducted by biologists since 1977 to determine how successfully they are reproducing. All known nest locations have been documented and most active nests are surveyed each year by helicopter during the breeding season. A flight is normally made in late April to identify occupied nests through the presence of fresh nesting material, eggs, or incubating adults. A second flight in late May determines the number of hatched young in the nests. This provides the department with information on the number of young birds produced each year. In 1975, it was estimated that Nova Scotia had a minimum of 65 breeding pairs of bald eagles. Today, there are well over 200 active bald eagle nests in the province. Reproduction has been at a healthy rate in recent years, with an average of 1.2 young produced for each nest.

Most Nova Scotia eagle nests are found on Cape Breton Island, concentrated around Bras D'or Lake in areas of shallow water and irregular coastline. Nests are also common along the coast of Antigonish and Pictou counties, and they are scattered throughout the rest of the mainland on lakes, rivers, and coastal bays. Historically, there have been only a few nests in southwestern Nova Scotia. This has changed in recent years, as eagles continue to expand their breeding range. The location of known or suspected eagle nests in the western counties should be passed along to your nearest DNR district office.

Our provincial flag is prominent at this "hack" site in Massachusettes, where a number of Nova Scotia eaglets were kept and released during the 1980s. Credit: Jack Swedberg

Nova Scotia has the highest concentration of breeding bald eagles in northeastern North America. In contrast, populations in the northeastern United States and other provinces were severely hit by pesticide pollution and habitat loss. During the 1980s, wildlife biologists in Nova Scotia took part in a cooperative program that relocated young eagles to help rebuild former populations. Between 1983 and 1988, 40 eaglets from Cape Breton nests were transferred to artificial nest sites in the northeastern states, primarily Massachusetts. It was hoped that some would eventually nest in the vicinity where they were released. The program was a success and in 1989, the state of Massachusetts had its first eagle nest in 80 years. Two young were produced from a pair that included a female from Nova Scotia and a male from Michigan. As of 1993, there were nine pairs of bald eagles nesting in Massachusetts and neighbouring Connecticut. Most are believed to be Nova Scotia birds or their offspring.

When good fishing areas freeze over in late fall and early winter, many eagles leave their nesting grounds for wintering sites. They are more social with each other in winter and often congregate in areas with abundant food. Wild and domestic animal carcasses become an important source of nutrition throughout winter. Favoured wintering areas include Bras D'or Lake, the lower Tusket River area of Yarmouth County, and eastern Kings County. On the intertidal portions of the Shubenacadie River, wintering eagles are attracted to the area by spawning tomcod (frostfish). Many eagles spread out across the province, especially to coastal areas where they scavenge along shorelines and hunt wintering waterfowl.

DNR projects were also developed to monitor wintering eagle populations. Between 1977 and 1988, a series of road census routes were set up around the province to survey wintering eagle populations and their distribution. The eastern Kings County route continues to monitor population changes. The prescribed route is driven once a week through the winter, with two observers noting the numbers, locations, and age classes of eagles they see. The highest number of eagles seen during one survey provides a maximum for that season, which is compared to other years. Wintering eagles along the Shubenacadie River have been surveyed by helicopter since 1977 and they are still checked at least once each winter.

From 1977 to 1988, over 580 eaglets were banded in Cape Breton nests to provide information on survival and movement. Some were also captured for banding and marking at a few wintering locations in the late 1970s. As part of this overall population study, several winter feeding stations were set up during the 1980s to draw eagles close to observation blinds to identify individually marked birds.

Supplemental feeding during winter can improve survival in young and inexperienced birds, and allow adults to enter the breeding season (which begins in late winter) in excellent condition. One particular feeding site established along the Gaspereau River in Kings County in the early 1960s has played an important role in the present status of Nova Scotia eagles. Cyril Coldwell, a well-known naturalist, farmer, and curator of Acadia University's ornithology museum, originally established the site to bait ravens for a banding study and found that it attracted bald eagles. Only a few were observed at first, but use of the site increased gradually over the years. By the 1980s, over 50 eagles could be seen at the site at one time. More eagles began to forage across the surrounding countryside, usually in the vicinity of farms where the carrion of farm animals was available. Cyril maintained the site up to his death in 1994. The results of his efforts are visible across the landscape of eastern Kings County and elsewhere in the province.

Eagles have become conditioned to automobiles and curious onlookers after successive years of winter feeding close to human activity. Nesting eagles have traditionally been associated with isolated wilderness areas, but two breeding pairs have now established nests in the eastern end of the Annapolis Valley. These are presumably eagles that spent their adolescent years in the area and are now tolerant of human activity. Since they were discovered in the early 1990s, both nests have produced two to three young each year. It is estimated the number of adults, young of the year, and intermediate age classes (bald eagles require four to five years to mature) in Nova Scotia now exceeds 800 resident eagles and may be the source of breeding birds in other populations. In addition to winter feeding, changing public attitudes has resulted in reduced habitat destruction, shooting, and disturbance of nesting birds. The bald eagle has been protected under the Wildlife Act since 1987.

While fortunate to be the guardians of a thriving population of this majestic North American wilderness symbol, we need to ensure a positive future for our eagles by continuing to monitor reproductive success and population status. This can be accomplished by managing and protecting nesting, feeding, and roosting habitat, reducing nest disturbance, and emphasizing the ecological importance of our birds of prey through education.

Bald eagles congregate at a feeding area in Sheffield Mills in the eastern Annapolis Valley.
Credit: Rick Harley