Use of satellite and GPS telemetry is enabling researchers to track the movements of large raptors such as bald eagles. Current technology allows us to fix a bald eagle's location multiple times during a 24-hour period, identifying its home range; and track eagles over large areas, identifying seasonal distribution.
Since 2008, up to five eagles have been tracked at one time using satellite technology. Maps following the progress of Bethany, Dexter, Jesse and Rachel will be posted on this site at the beginning of every month. Click on a thumbnail to open a PDF map.
Top of the Food Chain
Catching and tagging a wild adult eagle is not without its challenges and excitement. Read more about the eagle capture and monitoring process in Top of the Food Chain (873 KB) from the Winter 2010 edition of Our Wildlife.
|Emily is a rehabilitated eagle from Salmonier Nature Park. She came into Salmonier's care after colliding with and shattering a six-foot, double-paned window at the St. John's Arts and Culture Centre in November 2011. After about three weeks of recovery, she was fitted with a transmitter and released near Paddy's Pond. This bird will provide information on the recovery success of rehabilitated wildlife and hopefully go on to breed this coming spring.|
|Dexter's remains were
found scavenged and
scattered in a bog near
Springdale in March 2011.
The cause of death is unknown.
Rachel's transmitter stopped moving at the beginning of October. Conservation Officers from the Department of Natural Resources in Clarenville investigated and found her remains. All that was left were some feathers and bones, so the cause of death is unknown, but Rachel was possibly taken by a predator.
Newfoundland has one of the highest populations of bald eagles in northeastern North America, with an estimated population about 300 to 600 eagle pairs in the province. They are popular among tourists and are highlighted by tour operators and tourism promoters.
The bald eagle is a large, conspicuous raptor that occurs exclusively throughout most of North America. It is considered at risk in parts of Canada, and has only been removed from the endangered species list in the United States.
A mature bald eagle has a distinctive white head and tail, and a yellow beak and talons. Colors range from all dark plumage as juveniles, to various phases of mottling as immature (two- to four-year-old) birds. As is typical of a relatively long-lived species, eagles lay up to three eggs, but usually fledge one or two young per nest.
Populations are generally considered secure over most of their range; however, like any birds of prey, bald eagles will normally occur in relatively low densities except where food might be abundant.
Eagles are both predators and scavengers, and are territorial during the nesting season. They take five years to mature and are considered to be a relatively long-lived species.
Bald eagles occur throughout most of Newfoundland and Labrador. On the Island, they are primarily found along coastal areas during the nesting season, but may also appear along the coast and inland for the rest of the year. They do not appear to migrate off Newfoundland during the winter, but seem to move around seeking ice-free coastal areas to find food. They have also been known to hunt and scavenge inland.
One of the larger concentrations of bald eagles in Newfoundland occurs in Placentia Bay. In Labrador, they are almost exclusively found inland near large water bodies during the nesting season. In fall and winter, bald eagles from Labrador migrate south to the eastern part of the USA.
The Wildlife Division has been monitoring bald eagle populations in Placentia Bay and elsewhere in the Province since 1983. The program first began by soliciting public information on active bald eagle nest sites. Early on it became evident there was a relatively substantial population in Placentia Bay, which became the prime area for monitoring.
In the late 1980s a long-term monitoring area was established around the larger islands of Merasheen Island and Long Island, as well as part of the bay's western coastline. Boat surveys of this area have been conducted at least 13 times since then. Most surveys were conducted in late June, when young bald eagles were 4-8 weeks of age; however, a number of early spring surveys were also conducted to determine territorial occupancy.
In addition to checking if nests are active or new nests have been established, these surveys have also gathered information about food habits and productivity rates. More than 100 eagle chicks have been banded, mostly in Placentia Bay, as part of an island-wide banding program that provides more information about dispersal.
In the 1990s the impact of existing and future industrial developments on Placentia Bay eagle populations became a concern. Bald eagles are top-level predators and scavengers, and toxins and heavy metals that can harm these birds and their long-term survival can bio-accumulate (become highly concentrated) in their bodies.
Bald eagles may also ingest oil, which can prove lethal. This occurrence was well documented in 1989 during the Exxon Valdez spill in Alaska, when more than 150 bald eagles died as a result of the spill. Over time the population did recover, but with a small pool of thousands of eagles to support recovery.
Since bald eagles are excellent bio-monitors of environmental health, the Wildlife Division sponsored a student through Memorial University of Newfoundland to study toxin levels and heavy metals in eagles in Placentia and Bonavista Bays, with Bonavista Bay chosen as a control because of its very low level of industrial activity.
The results indicate heavy metal and toxin levels were relatively low and within acceptable parameters in both bays, although levels in Placentia Bay were higher. This information has established a good baseline to monitor for future changes in toxin and heavy metal levels in bald eagle populations in Placentia Bay.
Our annual surveys have also helped establish 'hot spots' for nesting activity within at least part of the Bay, and have developed a long-term monitoring data set from which to detect changes at a population level. In some years, close to 30 eagle pairs are found nesting in the study area, which is only a part of the bay.
A number of important questions still need to be addressed regarding bald eagles' use of Placentia Bay, possible impacts of industrial development, and how such impacts can be mitigated. If, as we suspect, bald eagles do not migrate off the Island of Newfoundland, a limited pool of birds would have to support a recovering population if there was a significant mortality event. While we have some good information on breeding densities in part of Placentia Bay, we do not know the overall breeding picture.
We also suspect that areas of the south coast that are ice-free during the winter, including Placentia Bay, are important wintering sites for bald eagles from throughout Newfoundland. Also unknown is the home range bald eagles use during the breeding period. Such information is important when trying to assess the potential impact of industrial development, including accidental events such as oil spills.
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