Eagles continue to flourish in Minnesota
On a late winter day in Central Minnesota, a bald eagle sat atop a small hillock in a farm field, looking to anyone driving by as though he was just watching the cars go by. The carcass of a medium-sized deer lay nearby.
“That may have been an eagle that had just eaten,” said Gail Buhl, education program manager at the University of Minnesota’s Raptor Center. “Perhaps he or she had just gorged themselves on the deer carcass and was waiting to process all that food before they flew away. Alternatively, it could have been the dominant eagle.”
When feeding, eagles often take turns filling up on a carcass, with the dominant eagle going first, the submissive mate or young eagle taking a turn next. “The dominant eagle would have basically said to the submissive partner, ‘Wait till I’m done,’” Gail explained, pointing out that a large meal could add quite a bit of weight to a bird that generally only weighs between 7 and 10 pounds. “They may need to take a break when they’re full,” she said.
According to the Raptor Center, eagles usually eat fish during late spring and summer, as well as hunting small mammals and waterfowl. But their diet changes – especially in northern climates – in the late fall and winter, when lakes and rivers freeze over, and fish are not available. Then, the eagles turn to scavenging deer carcasses and gut piles. Bald eagles are birds of prey, but they do not turn down easy meals, such as animals that are found dead. They even steal food from other birds, such as osprey. The word “raptor” essentially means “a carnivorous (meat-eating) bird,” which can also be called a bird of prey. There are about 482 species of raptors across the world, including eagles, owls, falcons, hawks, and even turkey vultures. The Raptor Center’s main focus is on caring for and healing eagles, owls, falcons and hawks that have been injured. But they also educate people about large birds of prey, both at the center in Minneapolis and in schools and community centers across the state, often bringing one or more of their large birds when putting on a program so that attendees can see them up close.
“Eagles need large, open areas of water – big lakes, big rivers…” said Gail, “…and large trees. They want to be high – they want to be on one of the higher trees in the area,” she continued. Eagles’ nests are huge and made out of sticks. Gail described their creation as part of a courtship ritual in which, “the females arrange, the males rearrange, and then the females rearrange” until they have the nest just how they like it. The nest starts out 3 to 4 feet across, but then may get larger over the years, since eagles reuse their nest from one year to the next. Many sources suggest that eagles’ nests are usually at least 6 feet wide and 6 feet tall.
The Minnesota Department of Natural Resources (DNR) states that the most common trees selected for bald eagles’ nests in Minnesota are red pines, white pines, large cottonwood trees and aspens. Occasionally, eagles’ nests can be found on artificial structures, such as poles used for power lines and osprey nest platforms.
Since eagles are only “partial migrants,” (they only migrate to find open water), they return in late winter to their nesting site. In Minnesota, a pair of eagles usually begins nesting in late February or early March. The female will lay one to three eggs; the pair will then take turns sitting on the nest. When the baby birds, called ‘eaglets,’ hatch, after an incubation period of 35 days, the parents take turns at catching prey and feeding the young birds. The baby eagles are ready to leave the nest at about 10 to 12 weeks old.
The Minnesota DNR usually operates a webcam so that people can see baby bald eagles as they are hatched and until they leave the nest. Unfortunately, this year, the camera failed before the birds had grown large enough to fly. Since disturbing the eagles during this formative time would be harmful to the eagles, the DNR put any repairs or replacements of the camera on hold until next season, also requesting donations for the repair or replacement of the webcam. A recent post on the DNR’s website proclaims that they have received enough donations to purchase a new camera, and they expect it to be installed and available by next winter.
Melonie Shipman, a naturalist who has spent many years educating the public about eagles, explained that when eagles establish a nest, they often return to the same nest each year. Although they may decide not to use it one year, they will likely come back to the nest “even two to three years later.” According to Melonie, eagles may leave a nest for a variety of reasons, such as bugs, pests or lice. “Lice can be a big issue for birds of prey,” stated Melonie. In fact, she said, “Eagles often use spruce boughs in their nests because they are a natural pesticide.”
Melonie, who began her career as a science teacher in public schools, lived for many years in Alaska, where she was the education coordinator for the Alaska Maritime National Wildlife Refuge, educating the public about eagles and other wildlife. She continued to work with raptors after moving to Minnesota, where she spent time as co-director of the Audubon Center of the Northwoods in Sandstone. She currently offers informational naturalist programs in Minnesota and Wisconsin (scheduled through her website at http://travelingnaturalist.org) and often teaches classes through community education programs. An upcoming class she will be offering through St. Cloud’s Community Education Department is called, “Bald Eagles: Beyond the Basics.”
Eagles have made a strong comeback after dropping to near-extinction numbers in the 1970s. With the outlawing of DDT, as well as other conservation measures, their numbers are now soaring. Alaska has the largest number of eagles in the United States. Minnesota has the second-largest population of eagles, with Florida coming in third. Off the endangered species list, bald eagles are much more common than they were just a generation ago.
But eagles are still in need of protection, as both Melonie and Gail hasten to point out. Since the Raptor Center’s main focus is rehabilitating injured birds, Gail has seen many eagles and other birds of prey with trauma-related injuries, such as being hit by a car, being shot, or getting caught in a trap. But the most common injury she sees is lead exposure.
“Ninety percent of eagles come in with some exposure to lead,” said Gail. “And 25-30 percent of those have lead toxicity.” According to the Raptor Center, most of the birds brought in with lead toxicity die or must be euthanized. At the Raptor Center, all eagles are given a blood test to check for lead poisoning. The eagles that show exposure to lead are injected with a “binding agent,” which allows the eagle to excrete the lead from their system. Eagles are fairly sensitive to lead, which is still commonly found in fishing tackle and ammunition.
Since eagles are both fish eaters and scavengers of mammals or at gut piles, they can pick up a piece of lead easily in a fish or a dead animal.
“That’s why it’s so important to use non-lead fishing tackle,” said Gail, “and copper, not lead ammunition!”
For both Gail and Melonie, the most important thing for people to know is that our national bird still continues to need our assistance in order to survive. Removing lead from the environment would make a huge difference in their continued existence.
“Just one BB can kill them,” exclaimed Melonie. “If you want to protect eagles, collect all your fishing lines. And don’t use lead shot.”