The bald eagle was on the brink of extinction in the second half of the 20th century, but over the decades, its population has been declining again due to one of the most successful conservation efforts in history.
Recent data collected in New Jersey has revealed that the number of vultures in the state is soaring to new heights—nearly 250 active nests were identified last year.
That’s more than double the number counted a decade earlier—and in stark contrast to 1970 when the state had only one pair of breeding eagles.
Throughout the 1970s, there were fewer than 1,000 breeding pairs in the United States, by and large because of The spread of the toxic pesticide, DDT, which weakened eggshells and reduced hatching probability.
But after a federal ban on DDT was imposed in 1972, the Eagle population saw a gradual resurgence. In 2007 the government finally managed to remove the bald eagle from the endangered species list.
According to the latest national census, conducted by the US Fish and Wildlife Service in 2021, there are now more than 315,000 individual bald eagles in the United States.
The population of bald eagles is in every state in the United States. Midwestern states close to Canada, including Wisconsin, Ohio, Minnesota and Michigan, host some of the largest populations of breeding bald eagles.
Florida stands out as one of the few Southern states with more than 1,000 breeding pairs. Unlike other migratory eagles that fly south for the winter months, some Florida eagles have been known to migrate to the Chesapeake Bay
The numbers are likely to increase further, said Tom Wittig, coordinator of the US Fish and Wildlife Service for the Northeast.
“The population almost certainly continued to grow in the next four to five years in which that data was collected,” he said. “In most states, the number of nests continues to rise which is a sign that the population is still increasing.”
There are various ways in which a population can be measured. Ornithologists and conservationists often like to think in terms of “breeding pairs.”
A breeding pair describes a pair of male and female eagles that have begun to build a nest for hatching eggs.
Historically, there has been a lot of focus on bread pair counts because of how DDT affects vultures. We know this affected their ability to raise young, which became a major factor in their recovery.
Bald eagles also have a unique migratory behavior, which makes it difficult to attribute populations to specific nations. Therefore tracking active nests is more applicable.
“Different populations (of the bald eagle) in the United States and Canada will have different migration patterns,” he said. For birds in general, migration is driven by the availability of food. In particular climates – rivers will freeze over and limit access to food.
For decades, the US population of bald eagles has been bouncing back due to one of the most successful conservation efforts in history. In 1967 they were protected as endangered but 40 years later in 2007 they were removed from the list.
North American bald eagles are considered “partial” migrants with some living “year-round” in one location, while others migrate during the winter season to escape those frigid conditions.
It is likely that individual eagles will have a general preference and consistent behavior but may vary from year to year. If you’ve had harsher winters, they might be more inclined to go. “It’s all a calculation, at a certain point it makes more sense to stay put rather than travel.”
Many migratory bald eagles breed in the northern parts of Canada during the summer before heading south into the United States to avoid a cold winter with little food.
Illinois is a unique state in that it only shelters about 40 bald eagle nests but sees huge numbers of migratory birds in the winter—over 3,000 at some points in the year.
Midwestern states close to Canada, including Wisconsin, Ohio, Minnesota, and Michigan, host some of the largest populations of breeding bald eagles.
In the Northwest states including Oregon and Washington, there are also many nesting eagles. Florida stands out as one of the few Southern states with over 1,000 breeding pairs year-round.
While the ban on DDT was partly to blame for the increase in vulture numbers, conservationists have taken other measures to help increase their numbers.
Eagles were transferred from healthy populations in Alaska, Canada and the upper Midwest. As the population began to recover, some of that was attributed to these reintroduced birds.
A bald eagle (pictured December 2021) in Pembroke Pines, Florida, calls for its mate while resting in the nest building. The vulture, part of a nesting pair, has returned to the area to mate and raise their young
While the number of bald eagles in the United States is still on the rise, this trend is not expected to continue indefinitely.
It will eventually produce a plateau, it’s an environmental law, but it’s hard to guess when that will happen. There’s a strong case, Wittig said, that they’re getting closer to that point in the Chesapeake Bay and Maine.
Bald Eagles were running out of real estate and had to compete with each other. They can now reach six or seven years without breeding.
This means that more “floating” eagles are also taking to the skies. Those eagles fly around, migrate between countries, but they don’t settle in a specific place.
“For roughly the second half of the 20th century, any intact adult bald eagle would likely end up reproducing,” he said. Interestingly, we have seen a trend in the past few years that reaching this age does not guarantee that a bald eagle will be able to claim a territory.
Recently, the younger adult birds are unable to establish territories for themselves and are therefore unable to reproduce. Some of these pairs will hopelessly build nests in the wrong places and at the wrong time of year.
In the latest Fish and Wildlife Service report for 2021, the total bald eagle population is divided between different ‘passes’
We call them flight paths. Bald eagles will always stick to their flight path, Wittig said — it’s relatively rare for a bird to go significantly east or west.
“Every time a bird’s compass gets stuck,” he said, “that’s how you get rare birds in new locations.”
Of the approximately 320,000 bald eagles in the lower 48 U.S. states, about 40,000 are found in the westernmost “Pacific Flyway,” and 30,000 were in the “Central Flyway just to the east. To the east of that is the “Mississippi Flyway.” Which has the largest number of eagles – 160,000. Finally in the easternmost “Atlantic flight path” there were about 85,000 birds.
The following table approximates the number of breeding pairs of bald eagles in each US state, according to the most recent data from various government sources:
|state||The number of breeding pairs|
|Louisiana||three hundred fifty|
|nv||less than 5|
|New Mexico||less than 5|
|Rhode Island||less than 10|
|Utah||less than 5|