By Dr. Becker
The University of Minnesota’s Raptor Center has seen an influx of injured eagles in recent months, but no one is able to explain why. In 2014, the Center took in 114 eagles.
In 2015, this rose to a record 145 eagles by November. Some of the eagles were poisoned by lead ammunition after eating deer organs, while others were brought in as juveniles after an onslaught of summer storms.
The birds require ample space, and the center’s 12 eagle cages were at capacity, prompting the need to make makeshift housing for 13 additional eagles. The birds were also consuming an extra $5,000 to $10,000 in food, not to mention the extra expenses for medical care and staff time.
Juvenile Eagles May Require Long-Term Care
If a juvenile eagle becomes injured, long-term care is often required. Without their families, the birds can’t fend for themselves in the wild until they’re older. In the video above, you can see a 5-month-old eagle preparing for free flight after being rehabilitated.
Before being released back into the wild, the birds must be capable of flying with proper form and endurance. Birds will be given test flights while attached to a long tether, which allows volunteers to assess their condition and flight position of their wings, tail and feet during flight.
If the bird starts to favor gliding over flapping, it’s a sign they may be tired and need to build up their strength before being released. Clinic manager Lori Arent explained to MPR News:1
“A lot of times they do power out on their first flight, but then they get tired as time goes on … So their strength is really indicated by how many flights they can do before they need a rest. So we'll wait and see."
Lead Poisoning Is Common Among Minnesota Bald Eagles
Exposure to lead ammunition has long been recognized as a risk to bald eagles. The Raptor Center collaborated with the Minnesota Department of Natural Resources (DNR) to compile data showing bald eagles were being poisoned by eating lead shot-crippled or lead-poisoned waterfowl.
Their study led to the passage of a 1991 Federal law banning the use of lead ammunition for waterfowl hunting. In 1997, the Center conducted additional research that showed eagles were still suffering from lead poisoning, even after the ban.
They then conducted another study, from 1996 to 2009, to determine if lead ammunition used in the hunting of white-tailed deer could be to blame. A significant association was found. According to the Center:2
“A statistically significant seasonal and geographical association … was established between deer hunting season onset and hunting zones, with the incidence of eagle poisoning.
The majority of cases occurred during late fall and early winter, with significantly higher number of poisoned bald eagles recovered from the deer hunting rifle zone.
… The kidney copper concentration was significantly higher in lead exposed eagles … implying the ingestion of fragments from copper-jacketed lead bullets.
The results from these four epidemiological parameters strongly support the hypothesis that spent lead from ammunition is an important source of lead exposure for bald eagles.”
Manmade Obstacles Are Putting Raptors at Risk
Lead poisoning is only one man-made threat facing bald eagles and other raptors. Bald eagles almost went extinct in the 1960s due to the pesticide DDT, habitat destruction and hunting.
In the early 1960s, there were under 500 nesting pairs remaining in the U.S., and the species was listed as endangered in the late ‘60s. After DDT was banned in the early 1970s, bald eagle populations began to slowly recover, but they still face threats to this day. According to the Raptor Center:3
“Humans worldwide are plowing up habitat at an alarming rate to make room for food and biofuel crops, as well as urban development. Avian malaria and blood parasites have increased and diseases are spreading geographically.
Raptors also continue to suffer trauma injuries from man made obstacles and poisonings on an almost daily basis.”
If you want to get involved to help eagles and other raptors in your area (along with other birds), the Raptor Center recommends the following:
Make your windows safe for birds Keep cats inside Turn off the lights when you leave a room (artificial lights may disorient migrating birds) Enjoy birds from a distance. Approaching birds may make them nervous, causing them to deplete their energy reserves. Clean your bird feeders, as dirty feeders may spread disease. Avoid the use of rodent poisons, as birds may eat the poisoned rodents and get a dose of poison themselves.