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Home > Wildlife > Species Information > Maine Endangered Species Program > Maine's Bald Eagle > Recovery in Maine
The Comeback of Bald Eagles in Maine
Charlie Todd and Amy Meehan, Wildlife Biologists –
An Emerging Success Story
Bald eagles have been listed as Endangered or Threatened in Maine (and throughout the lower 48 states) since 1978. Federal and state wildlife agencies are evaluating species recovery and a current proposal to remove bald eagles from this special designation under the U.S. Endangered Species Act: see http://www.fws.gov/migratorybirds/BaldEagle.htm
We’ve been working towards this milestone event for decades and developing safeguards to ensure that the comeback of Maine’s bald eagles is lasting. Those who live in or visit our state should be able to enjoy them regularly as a reminder of Maine’s special wildlife heritage … now and in the future. We want you to be familiar with bald eagle recovery. Your understanding and active support are crucial to endangered species conservation. This presentation details recovery in Maine: the stronghold for bald eagles in the northeastern U.S. We will:
Historic Insights: One account suggests at least 50,000 breeding pairs of eagles lived in the lower 48 states before European settlement! Historic numbers are unknown in Maine, but eagles were widespread in the state and locally abundant in some coastal regions. Eagles were fed to hogs by Casco Bay settlers in the 1700's! In 1806, there was a bounty on eagles in a Knox County town. Nesting “colonies” were reported along the Maine coast from Swan Island (Sagadahoc County) to Roque Island (Washington County). Arthur Norton, an early naturalist noted 15 eagle pairs on a 12-mile reach of the lower Kennebec River around 1900.
Frequent place names like Eagle Lake, Pond, Stream, Point, and Island (as well as corresponding references to Swan Island, etc. = from the Abenaki word “sowangan” translated as “bald eagle”) infer a widespread presence in Maine. Dramatic declines of eagles became evident during the 1950's - 1970's.
1967: Bald eagles south of the 40th parallel were listed under the Endangered Species Preservation Act, the 1966 statute that preceded today’s U.S. Endangered Species Act. A comparative study of eagle nesting during the 1960s in Alaska, Florida, Maine, Michigan and Wisconsin revealed relatively low numbers and chronically poor reproduction, especially in Maine’s remnant population and the subpopulation along the immediate Great Lakes shorelines.
In 1962, Charlie Brookfield and Frank Ligas (biologists with the National Audubon Society) began annual monitoring of bald eagles in Maine. Early efforts were limited, but their counts could only document 21-33 pairs of nesting eagles and only 4-15 eaglets fledged each year between 1962 and 1970. Average productivity among Maine eagles during the 1960s was only 0.34 eaglets per nesting pair: at least 60% lower than rates considered normal.
1978: On February 14, the Bald Eagle was listed as Endangered in 43 of the lower 48 states under the federal Endangered Species Act. It was designated a Threatened Species in the remaining 5 states in the continental U.S.: Michigan, Minnesota, Oregon, Washington and Wisconsin. This listing triggered an automatic recognition as Endangered under Maine’s new Endangered Species Act.
Nationwide inventory efforts were not yet comprehensive, but only 791 pairs could be documented across the lower 48 states in 1974. Aerial reconnaissance of Maine’s population replaced previous, ground-based inventories. Charlie Todd completed his M.S. research in 1978: the first of six graduate research studies on bald eagles at the University of Maine. Intensified surveys boosted Maine’s baseline index to 62 nesting pairs: still a vestige of former numbers.
Eagles continued to decline in western Maine through the 1970's. By 1979, only two pairs remained in the western half of the state’s vast coastline. None were in northernmost Maine. Only easternmost coastal regions of Washington County (adjacent to Canada) supported viable eagle numbers and productivity.
A “Waterloo” moment occurred at this time as agencies anguished over a $1,000,000,000 oil refinery proposal in this last stronghold in the Northeast, worst case scenarios from theoretical oil spills, and potential jeopardy for Maine’s endangered bald eagles. The project was never initiated and eagle numbers began to rebound in Maine from this point onward.
Meanwhile, nesting eagles were absent from all other New England states, New York could only account for a single nesting pair, and New Brunswick (on Maine’s eastern border) was the only Canadian province to ever recognize bald eagles as Endangered.
Population Enhancements: In the 1970's and early 1980's, biologists in Maine worked to increase eagle productivity and survival. Egg transplants attempted to bolster productivity at nests with chronic failure, especially in western Maine where the population was nearly extirpated. Greater success was achieved with eaglet fostering in subsequent years. A limited supply of eggs or eaglets from Minnesota, Wisconsin, and a captive breeding program at the Patuxent Wildlife Research Center (Maryland) fuelled these drastic efforts.
Public outreach, educational initiatives, and intensified law enforcement sought to reduce human-caused mortality: illegal shooting was the leading cause of documented eagle mortality in this era. Incidental trappings, poisonings, and electrocutions also took a toll. Bart (a debilitated bald eagle from a Hancock County nest) went on the lecture circuit to strengthen public support and understanding for the plight of eagles. Thanks to collaboration with chapters of the Maine Audubon Society, Bart visited every classroom in eastern Maine (several times!) and many more across the state.
1987: A total of 2,239 nesting pairs of bald eagles are documented in the continental U.S. Increases in the last decade reflect an initial comeback of eagles and better monitoring. Most growth occurred in remnant populations. There was little evidence yet of range re-expansion without aggressive recovery efforts. However, optimism prevailed as eagles began moving towards goals set in 5 national recovery plans. Maine and parts of 23 other states were under the jurisdiction of the Northern States bald eagle recovery plan: see http://ecos.fws.gov/docs/recovery_plans/2006/060309b.pdf
By this time, there were 90 pairs in Maine. Yearly increases of Maine’s population averaged 7% during the 1980s, and reproduction in Maine improved to 0.77 eaglets per nesting pair: more than twice the average two decades ago, but still suboptimal and a handicap to faster recovery. Most gains were localized in eastern Maine. Virtually all of Maine’s eagles nested on private lands and were protected only by voluntary agreements.
In the late 1980's, the Maine legislature twice amended the state Endangered Species Act to address growing problems eagle recovery: prohibitions against harassment and illegal baiting as well as regulatory options for habitat protection. The “Essential Habitat” provision enabled MDIFW oversight of all projects permitted by, licensed by, funded by, or carried out by municipalities and other state agencies. Inconsistent decisions in the late 1980s had led to more litigation on development pressures near nesting eagles without consistent, objective decision-making. By March 1990 MDIFW had mapped 109 bald eagle nest sites and ¼-mile buffers as Essential Habitats; legal debate was put to rest. In 2006, 569 Essential Habitats are mapped for Maine eagles, and more than 240 environmental reviews have since been conducted without controversy. For more information, see Introduction to Essential Wildlife Habitat.
Survivorship Studies: During 1974-2006, biologists have banded 1,190 eagles (mostly nestlings) in Maine. Traditional studies of bird survival rates and movements rely on band encounters with dead or injured birds. In 1986, Mark McCollough completed his Ph.D. research at the University of Maine on bald eagles. He provided carrion to eagles wintering across Maine and spent countless hours in observation blinds to identify live birds by reading leg bands with high power optics. He found a 73% survival of fledglings in their first year. Survivorship improved to 85% survival among 2nd and 3rd year birds and to 95% survival of older birds.
Comparable measures of eagle survival in Alaska, Florida, Maryland, Montana and Saskatchewan eventually helped validate this important parameter: the most important influence on eagle population dynamics. The oldest encounter of a Maine eagle is one aged 27 years – 6 months: second only to a 28-year old eagle from Alaska holding the longevity record for the species in the wild.
1995: There were 4, 712 pairs of eagles in the continental U.S. Modest range expansion has led to the return of nesting eagles in many states where they had been extirpated. Bald Eagles were reclassified under the U.S. Endangered Species Act as “Threatened” in all lower 48 states. This event symbolized significant recovery progress but did not diminish legal protection. For more information, see: http://www.fws.gov/endangered/fr95580.html
In Maine, the population has risen to 203 nesting pairs! Growth rates have averaged 8% annually over the last 8 years. Modest range expansion is now evident. Historic nesting areas are increasingly reoccupied in central, western, and northern Maine. Nesting bald eagles returned to Kennebec County in central Maine (home to the state capital, Augusta) this year after a 21-year absence. In the 1990s, the average productivity of Maine’s eagles was 0.86 fledglings per nesting pair.
2006: The eagle population in the continental U.S. has surpassed 7,000 nesting pairs and (with less intensive monitoring in some states) may be closer to 8,000. Breeding eagles are now present in all 48 states! The recovery is so advanced that agencies are reviewing proposals to “delist” bald eagles from its current status as “Threatened” under federal legislation. Two states have delisted bald eagles within their jurisdictions and reverted to periodic population monitoring: Minnesota (1996) and Wisconsin (1997). Several other states are considering this reclassification on a state level. Florida is now drafting a state management plan in response to a petition for delisting this year.
In Maine, the breeding population has rebounded to 414 eagle pairs! Continued growth in density is evident statewide and significant range expansion is finally evident. Bald eagles now breed in all 16 counties: newly arriving in Franklin County in 2004 and York County in 2006. The average productivity in the 2000's remains 0.87 fledglings per nesting pair: a level adequate to sustain annual population growth but not to accelerate the recovery to rates achieved in many other population centers.
Recovery Trends (1962-2006): No significant improvements of Maine’s isolated, remnant population emerged until the 1980's. Annual increases since are still hindered by relatively low reproductive rates. In many populations (notably the robust Chesapeake Bay region), eaglet production dramatically exceeds 1.0 fledgling per nesting pair (so the blue trend line lies well above the red line). Inclement weather, inadequate foods, disturbances near nests, and lingering contaminant influences are all plausible explanations for slower recovery in Maine. The years 1996 and 2005 illustrate dramatic setbacks in eaglet production (= blue line) due to poor nesting success stemming from prolonged adverse weather during the spring breeding season. In 1997, an actual drop in the count of breeding pairs (= red line) coincided with an unusually high rate of deaths among adult eagles.
Obviously, there are many challenges to endangered species recovery. While one or a few factors may have led to the original jeopardy for a species, other problems and challenges often arise.
Statewide Carrying Capacity: How many nesting eagles can Maine support? The state’s extensive coastline and widespread lakes and rivers could host many more nests: perhaps 1,000 or more overall based on physical habitat availability. However, suitable food supplies and nesting habitat set the functional limits. As these combatant eagles in central Maine illustrate, disputes over territories erupt when balances with available food or optimal spacing between nests are broached.
Based on nearest nest separations, Maine currently has a low breeding density. For example, the mean separation of eagle nests in Florida is 0.9 miles, while separations in Maine average 4.1 miles. In Cobscook Bay, a stronghold for eagles in Maine, average nest separation distance is 1.0 mile. Clearly eagle numbers can further expand, and the Maine Department of Inland Fisheries and Wildlife set a 15-year planning goal of 600 nesting pairs by the year 2019; see Bald Eagle Species Plans.
Carrying capacity can be boosted with continued efforts for other resources: improved water quality, better fish passage, and conservation efforts for seabirds/waterfowl. The limits of future eagle populations can be diminished if human development pressures and patterns of sprawl do not accommodate suitable eagle habitats on the waterfront.
Environmental Quality: An array of organochlorine contaminants, PCB's (polychlorinated biphenyls), dioxins, furans, mercury, and lead appear in Maine bald eagles. Exposure levels are not preventing eagle recovery but may be slowing the eagle’s comeback in Maine. Most of these contaminants persist for decades. Future eagle monitoring is likely to focus partly on populations with potential toxicology concerns. As a top-level predator of complex aquatic food webs, bald eagles are a sensitive environmental indicator.
The diminished influence of DDE (a persistent by-product of the insecticide DDT) is broadly correlated with the comeback of the bald eagles. Some local populations may have other contaminant problems. Linda Welch and Angela Matz both completed graduate research on this topic at the University of Maine during the 1990's. Chris DeSorbo (BioDiversity Research Institute/Antioch College of New England) has been investigating mercury exposure among Maine eagles since 2004.
Federal Delisting: All formal delisting criteria have been achieved in national recovery plans. Bald eagle futures may vary widely amongst states, but overall abundance in the lower 48 states and a broad distribution of regional population centers are a testament to the eagle’s general comeback and a pending success story for the Endangered Species Act.
The U.S. Fish and Wildlife Service proposed to remove bald eagles from the list of federally Threatened Species on February 16, 2006: see http://www.fws.gov/migratorybirds/issues/BaldEagle/Reopening.Comments.06.pdf
An earlier (1999) proposal to delist eagles was tabled until regulations from the Bald Eagle-Golden Eagle Protection Act related to “take” prohibitions were better defined. For more information on this topic, see http://www.fws.gov/migratorybirds/issues/BaldEagle/DisturbEA.pdf
The U.S. Fish and Wildlife Service and U.S. Geological Service are developing a monitoring plan to track eagle populations after delisting.
Maine’s Delisting Criteria: Most biological thresholds for bald eagle recovery have been surpassed during the last 10 years. The criteria for reclassification from its current status of a state Threatened Species are:
If federal delisting of the bald eagles is promulgated later in 2006, no immediate changes will be realized under state law. Essential Habitat regulations for bald eagle nesting habitat will not be affected. When all of Maine’s recovery criteria are achieved, MDIFW will recommend reclassification of bald eagles to the state legislature, which retains ultimate listing authority under Maine’s Endangered Species Act.
Breeding Population Abundance in the Northeast - 2006: For the foreseeable future, the regional outlook for bald eagles nesting in the northeastern U.S. is tied intimately to the fate of Maine’s population.
Habitat Conservation: Maine is notable for its widely admired natural resources. We are fortunate to have an array of highly effective conservation partners that have contributed greatly to conservation of eagle habitats: generally acknowledged as the best insurance for a lasting recovery. Major conservation investments on behalf of bald eagles have been made by: MDIFW, U.S. Fish and Wildlife Service (Moosehorn, Maine Coastal Islands, Sunkhaze, and Lake Umbagog refuges), Maine Bureau of Parks and Lands, The Nature Conservancy, Maine Coast Heritage Trust, Forest Society of Maine, New England Forestry Foundation, and the Maine Land Trust Network.
Bolstering conservation status of key habitats for bald eagles and promoting effective stewardship by private landowners are the current management priority for bald eagles in Maine. Your support to any of our conservation partners is a big help!
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