Eagle by nature

Firstly, what is an eagle? There are noted differences between eagles, hawks and falcons, which you can read about in one of our earlier posts here, but unlike most birds categorised according to genetic markers, eagles are not what’s known as a “natural group”.

Birds that are classed as eagles in the family Accipitridae are in fact any bird of prey that is large enough to hunt vertebrate prey that is at least 50 cm long or more. To be part of this gang, these birds will have several things in common.

Aside from the size of their wingspan, which can range from 40 cm to 250 cm high, the females are always larger than the males. They have big heavy heads and fierce hooked beaks, and large, broad wings suitable for high altitude soaring, ending in flight feathers that can span out like fingers for reacting to the slightest breeze and increasing manoeuvrability. Their feet and legs are exceptionally strong, often yellow, muscular and thick, and end in sharp talons.

Their eyes are immensely powerful and can be up to five times better than ours, enabling them to spot prey from great distances. Due to the size and power of many eagle species, they are ranked at the top of the food chain as apex predators in the avian world.

The females are always larger than the males.

They also have another curious characteristic: unlike all other birds of prey, eagles don’t look back over their shoulders before striking their prey. I mean, why would they? Who is going to take on an eagle?

There are 60 species of eagle in existence today and most of them are Old World birds, with only 14 living outside of Europe, Asia and Africa: two in North America, the bald and golden, nine in Central and South America, and three in Australia.

Eagles are usually split off into four groups for ease of identification: harpy or giant forest eagles, (the largest ones), fish or sea eagles, snake or serpent eagles, and booted eagles, the smallest ones.

Bald and proud

Many people focus on the bald eagle, and you can understand why. This particular sea eagle does stand out for very good reasons. Firstly, it is iconic, the emblem of the USA, adopted as the national symbol in 1782.

Secondly, it looks magnificent. The name “bald” actually refers to the whiteness of the head feathers, rather than a lack of them. That striking white head with bright yellow eyes and beak, atop the deep, rich chocolatey hue of the body and wing feathers, stood proud and strong, on strong, bright yellow legs.

It has endured centuries of persecution and sanctuary, a forever oscillating bell-curve of existence, with the first major decline beginning in the mid-1800s and continuing over the years, mostly from habitat destruction, illegal shooting, and toxic chemicals.

Two of the collective nouns for eagles make reference to their numbers: a convocation, or a congress of eagles. This brings to mind great flocks of these large birds, which at some point in the past could be seen all around the world, certainly when collective nouns were first popular in the 15th century.

Alas, 73 of the top 100 birds on 2020’s latest published list of critically endangered or near extinction bird species are eagles, and their numbers have been declining at rapid rates since the 1970s. But there have been successes over the years as the conservation pendulum swings, and it’s important not to forget those and get bogged down with how bad things can potentially be.

Edge of the mountain

One criminally overlooked champion of birds of prey was already a fierce advocate for justice, whose campaigning efforts in 1920s New York helped secure the 19th amendment, granting women the right to vote.

But over the decades Rosalie Edge has been all but forgotten. Thankfully a recent resurgence in interest and admiration of her activism will help others learn about the fantastic exploits of this woman.

This level of hypocrisy was more than Edge could bear.

After being horrified to learn about the slaughter of 70,000 bald eagles in Alaska, she became interested in birds and environmental issues, and soon enough happened upon a pamphlet called “A Crisis in Conservation” whose 16 pages disclosed the connections between trophy hunting, gun manufacturers and professional conservationists.

Several high-flying members of the Audubon Society were said to be taking backhanders to essentially look the other way with respect to protecting certain species which rich hunters wanted to shoot for sport.

This level of hypocrisy was more than Edge could bear and she proceeded to focus her ire in their direction, frequently publicly calling them to account and only becoming more incentivised when they failed to answer any questions, instead resorting to personal attacks. Rather than wither under their presumed superiority she correctly concluded she must have been doing something right.

In 1934 at the age of 57, her focussed gaze fell upon a photograph of hundreds of dead birds lined up after a shoot in the Appalachians; not wasting any time Edge set out for this specific ridge and learned that every autumn recreational hunters would amass on Hawk Mountain, Pennsylvania, and from the spectacular viewpoint, shoot any migrating birds that came into sight.

Determined to stop this appalling practice, she did the obvious thing: she bought the mountain. Hiring two wardens to police the 1,400 acres, the hunters never came again, and bird populations recovered. Over time her land became the Hawk Mountain Sanctuary, which is now regarded as the world’s most prolific site of raptor conservation.

Among her friends and advocates was Rachel Carson, a woman whose powerful writing would go on to influence one of the most famous environmental laws.

Didn't DDT do it?

Dichloro-diphenyl-trichloroethane, more commonly known as DDT, is a cheap-to-manufacture and long-lasting insecticide that was used – and still is in parts of Asia – in the battle against mosquito infestations[S1]  and the attendant thousands of deaths each year from malaria.

Lauded by Winston Churchill for saving the lives of soldiers and mass produced across the world where it was highly effective in agriculture, the tide of public opinion began to turn against its use in a culmination of concern and fear fuelled by one very well-written book published in 1962, The Silent Spring, by Rachel Carson.

Awareness over the profligate use of insecticides and the potential for toxic build-up in soil and water aroused much suspicion and outcry. Conservationists, again noting that numbers were falling, found that bald eagles were laying eggs that had very thin shells, unable to withstand the weight of an incubating adult.

WHO currently classifies it as a “probable” human carcinogen.

This once hailed insecticide was blamed, and DDT was banned in the USA in 1972 and many places thereafter.

For nearly 50 years controversy has reigned about the ban and whether DDT really was the cause. It is thought that whilst DDT itself was not lethal to the adult bird, it interfered with their calcium production.

But there is a view that a combination of many factors including oil spills, lead and mercury levels rising in the nation’s rivers, stress from increased noise, logging, dehydration from seasonal rises in temperature, human and predator intrusion, nutrient deficiencies and so on all had their part to play in the malformation of eggs.

Detractors of the DDT argument are keen to point out several things, these among them: bald eagles had already suffered severe losses and were declared near extinct in 1921, 25 years before widespread use of DDT; a survey of bald eagles some 15 years after DDT had been used everywhere found that populations had increased by 25%; no-one to this day has been able to demonstrate the mechanism by which DDT causes the thin shells.

A year before DDT was banned an investigation by the Environmental Protection Agency concluded it did not affect shell thickness – indeed one study cited as conclusive proof that it was to blame found that the DDT-laced food one researcher had been feeding his caged subjects also turned out to be low in calcium anyway, so all results had to be scrapped.

More recently, in 1998, a study found that eggshell thinning of some bird species had begun 50 years before the introduction of DDT. The WHO currently classifies it as a “probable” human carcinogen, but now endorses indoor use in parts of Asia where malaria has reached epidemic proportions. Only time will tell.

Soaring for the moment

At the moment, bald eagles are not on the above list – they are currently classed as Least Concern, with population numbers increasing, and they are once again filling the skies above North America.

Nationally, there are more than 71,400 breeding pairs in the lower 48 states, according to researchers from the Service’s Migratory Bird Program, a huge increase since the days of the DDT suspicions when the species had reached an all-time low of 417 known breeding pairs in 1963.

Lovers of the bald eagle at least can again be hopeful that humans can undo damage to nature, but we must remain ever vigilant: recent research has found rat poison in eagle carcasses in America. Thousands of golden and bald eagles found between 2014 and 2018 died as a result of exposure to anticoagulant rodenticide. Rats are a major source of food for eagles.

A zoology professor at Harvard University, Scott Edwards has said the use of poison as rodent control is unnecessary, and urges people to understand the damage these chemicals can wreak when they get out into the environment. Since the 1960s, eagle numbers have quadrupled. As Rosalie Edge said, “the time to secure a species is while it is still common”.