The Extraordinary Bald Eagle: See What You Know

December 17, 2019  •  Leave a Comment

We all know there’s something special about bald eagles – the United States’ national symbol. They represent strength and determination; they’re strong and independent; they’re incredible survivors; they’re majestic, bold, and faithful; and they’re unique to North America. The bald eagle is a perfect symbol for our nation. This year (2019) I encountered bald eagles on a few of my photography travels. Some I came across in their typical habitats in tall trees along coasts and shorelines. Others were spotted in unexpected and atypical habitats, like at the top of a water tower in Middleburg Virginia (below). They graced me with their presence and motivated me to share a bit of their story.

Let’s start with some of the basics on these incredible birds.

 

Eagles are one of the largest birds of prey found in North America. They are also considered raptors, like hawks and owls.

 

These are big birds. They stand about 30 inches high, and that’s 2 ½ feet. Their wingspan is 72-84 inches, and that’s 6-7 feet. One thing a lot of us don’t know is that for all that physical size, bald eagles aren’t necessarily heavy. They typically weigh between 8 and 14 pounds. Hollow bones and adaptations for flying keep them light.

 

Mature bald eagles are easily identified by their brown bodies, which actually can sometimes look black depending on the lighting and distance from us. Their white heads and tails, and their bright yellow beaks also make them easy to identify.

 

Male and female bald eagles look identical, except the female is usually about a third larger and heavier than the male. This size difference – with females bigger than males --  is seen in a few other raptor species, including red- shouldered hawks.

 

One fact that’s a little less commonly understood about bald eagles is that they don’t get their white head and tail until they’re five years old. That’s when they reach sexual maturity. Immature bald are mostly a chocolate brown with varying amounts of white over the body, tail, and underwings. Because of their coloring, juvenile bald eagles are often mistaken for immature golden eagles. I’ve also seen people mistake immature bald eagles for vultures.

 

The primary prey for bald eagles is fish, though they will take other birds, some mammals, waterfowl like ducks, seabirds, and dead animals, especially during winter. Their vision is off the charts compared to humans. An eagle can see something the size of a rabbit running three miles away. Their eyesight is estimated at 4 to 8 times stronger than that of the average human, they can see more colors than us, and can see in the ultraviolet spectrum. That enables them to see things like the urine trail of prey they may be hunting. Eaglets and immature bald eagles have brown eyes which turn lighter and more yellow in color as they mature. By the time a bald eagle reaches maturity at five years of age, it will have completely yellow eyes. My photo below shows a nearly mature bald eagle with still cream-colored eyes and some patchy brown mixed in with white head feathers.

VigilantVigilantNearly mature, four-year-old North American Bald Eagle, Chincoteague National Wildlife Refuge

In the wild, bald eagles can live more than 30 years. They mate for life, returning to nest in the general area from where they were raised. Once a pair of bald eagles selects a nesting territory, they typically use it for the rest of their lives. Because bald eagles are primarily fish eaters, nests are built near water in tall sturdy trees with a clear view of the surrounding area. The same nest may be used year after year. It can be over five feet in diameter and weigh hundreds of pounds. Bald eagles are day-hunters; however, some wildlife cameras have captured them feeding on carrion at night and taking food back to the nest.

 

Bald eagles are North American birds. They’re currently found in every state except Hawaii, and throughout Canada. On a recent trip to Nova Scotia, Canada I saw more bald eagles than I’ve ever seen in the wild. Some Nova Scotian bald eagles were sent to the United States to help re-establish the bald eagle populations in New Jersey and Massachusetts in the 1980s. This was the period after U.S. bald eagle populations plummeted and were nearly wiped out due to human-created pollution and habitat destruction. The photo below of two adult bald eagles perched on rocky Atlantic coastline was taken in a remote coastal area in northern Cape Breton Nova Scotia.

Bald Eagles Perching - Cape Breton Nova ScotiaBald Eagles Perching - Cape Breton Nova Scotia

Today, bald eagles are no longer believed to be endangered although they remain protected by federal, state and municipal laws. At the federal level, bald and golden eagles are protected by the Eagle Act, the Migratory Bird Treaty Act, and the Lacey Act. Eagles feathers and parts, their nests and nest trees, and their winter/nighttime roosts are all protected by federal laws. You can read more about laws that protect eagles and penalties for breaking those laws at the US Fish and Wildlife Service.

 

I’m thankful that I live in a country that has the know-how and will to establish and enforce laws that protect wildlife. But did you know that despite the existing legal protections for bald eagles, they still face serious and sometimes lethal danger from lead poisoning, due to our own actions?

 

We learned years ago that lead was toxic to humans. A few decades ago, the federal government successfully phased out leaded gasoline and lead paint. Although dangers from lead paint in older structures, and from lead pipes that transport drinking water still exist; there are laws or practices in place to reduce or completely remove the risk to humans from lead in those sources. Not so for our national symbol, and other wildlife that face the same risk.

 

Wildlife health officials have documented many cases of lead poisoning in eagles caused by their ingestion of lead bullet fragments. The fragments are ingested when eagles feed on the remains of hunted animals, like deer, that were shot with traditional lead bullets. Lead core rifle bullets can fragment into hundreds of pieces upon impact. These fragments are often found several inches from the site of the bullet hole in large game mammals.  After butchering an animal, many well-intentioned hunters leave the remains --- sometimes called the "gut pile" out in the field for other wildlife to consume. When avian predators, like eagles and hawks, and other scavengers consume the remains, the bullet or its fragments may be ingested and can result in lead poisoning. Most hunters are law-abiding wildlife enthusiasts and are not intentionally leaving poison out for eagles. However, lead from bullets has sadly become a common source of bald eagle poisoning.

 

The University of Minnesota Raptor Center shared some startling statistics on lead poisoning in bald eagles

  • For the past 40 years lead exposure and lead poisoning have been major health issues for bald eagles received by or admitted to their clinic.
  • 90% of the bald eagles received each year for all types of problems had elevated lead residues in their blood
  • 20–25% percent of these eagles had sufficiently high levels to cause clinical lead poisoning.
  • In the last 24 years, over 500 eagles received or admitted to the clinic had either died or had to be euthanized due to lead poisoning.
  • Data on the location and seasonal timing of lead poisoning events in eagles clearly indicates that lead ammunition from both shotguns and rifles is the source of lead exposure.

 

The University of Minnesota Raptor Center also conducted a 13-year (1996-2009) retrospective study of lead poisoning in bald eagles. They tested the hypothesis that lead from ammunition in carcasses and gut piles of white-tailed deer is an important source of lead exposure.

Their results:

  • “A statistically significant seasonal and geographical association (p<0.01) between the incidence of eagle poisoning and the onset of deer hunting season and hunting zones was present.
  • A majority of cases occurred during late fall and early winter, with a significantly higher number of poisoned bald eagles recovered from the deer hunting rifle zone
  • Most of the paired blood-fragment samples have a closely matched isotopic signature, thereby demonstrating that ingested lead was the source of lead found in eagles’ bloodstream.
  • The majority of the blood and fragment samples collected from lead-exposed eagles was within the isotope ratio from ammunition samples reported by Church et al. (2006).
  • The kidney copper concentration was significantly higher in lead-exposed eagles (p=0.002), implying the ingestion of fragments from copper-jacketed lead bullets.”
  • About 75% of the lead-poisoned eagles were adult, or breeding-age, birds.
  • There’s conclusive evidence that spent ammunition in deer remains a significant if not primary source of toxicity. There’s also direct evidence that some cases of poisoning are due to shotgun pellets that may be embedded in small, upland game such as pheasants, squirrels, and rabbits that may be wounded and subsequently consumed by eagles.  There is also anecdotal evidence that lead residues left in the carcasses of coyotes may be yet another source.”

 

Other wildlife rehabilitators that are licensed to care for injured bald eagles have documented many cases of lead poisoning in bald eagles, and even other raptors. Here are just a few:

  • From the Wildlife Center of Virginia: “Lead poisoning is a significant – and preventable – health issue for Bald Eagles.”
  • From the Blue Ridge Wildlife Center: “ >90% of the eagles we treat are positive for lead - a metal that should never be in the blood at all.”
  • From Saving Our Avian Resources (SOAR): Data on lead levels from bald eagles admitted to wildlife rehabilitators in Iowa from 2004-2014 showed that 136 of the 273 eagles tested, or 50%, had an elevated lead level. Lead concentrations were highest during October–January, which coincides with the hunting and trapping seasons in Iowa.
  • From Cornell University, College of Veterinary Medicine: “….in over 300 bald eagles tested for lead over the last 22 years, 17% had lead levels high enough to cause death from lead poisoning. Overall, 83% had exposure to lead. Eagle populations have rebounded, but lead is still a risk particularly to the adult, breeding-age birds.”

 

The United States Geological Survey (USGS) has also issued a fact sheet on lead poisoning in eagles and birds. USGS notes that lead is a potent, potentially deadly toxin that damages many organs in the body and can affect all animals.

 

Not only are eagles and other wildlife at risk from lead ammunition, a recent study showed that “human consumers of wildlife killed with lead ammunition may be exposed to health risks associated with lead ingestion. This is based on published studies showing elevated blood lead concentrations in subsistence hunter populations.

 

Educating hunters and related organizations on the poisoning risk to wildlife from lead ammunition is a critical step in eliminating wildlife suffering and death. Such work is being done by many wildlife health officials, rehabilitators, and others, including the Humane Society, and some National Parks.  

 

I discovered one wildlife center in California – Ventana Wildlife Society -  that’s advanced protections for wildlife by implementing a program that voluntarily allows hunters to trade their lead ammunition for free non-lead ammunition. There’s lots of very important details to this program, and an important backdrop on this is that in July 2019 the state of California’s ban on the use of lead ammunition for all hunting took effect.  But, based on its website, Ventana Wildlife Society still runs its trade-in program. It’s a very innovative way to partner with hunters and protect wildlife from the dangers of lead poisoning.

 

I’ve learned a lot about bald eagles from watching and photographing them in the wild, and from my wildlife rehabilitation experience and research.  Here’s a few final thoughts, facts, and myths that I find interesting and not always commonly known about our amazing national symbol:

 

I hope that all your eagle sightings are happy and inspiring! However, if you see someone harassing or injuring an eagle, or if you spot destruction of eagle habitat or find an injured or dead eagle, report it to your state fish and wildlife agency. Here’s a list.  If it’s a time urgent issue, call 911, take as many photos of the situation as you can, and record the location of the abuse. If your area isn’t equipped to handle wildlife or animal emergencies, contact the Humane Society.


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