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Frozen Dinner
The Challenge of Finding Food in Winter

by Laura Erickson
Bald eagle on perch alert to any potential food below .
Credit Laura Erickson
 
Bringing home duck while mate watches from above
Credit Ray Foster

Imagine eating frozen meat without using your teeth. That’s something Bald Eagles do often in the winter.

When water is open in a good fishing river, of course, eagles don't have to worry about crunching through ice, either on the water’s surface or in their food. Even when the air temperature is 20 below zero, open water cannot be colder than 32 degrees Fahrenheit, so fish may be cold, but they’re not frozen.

But eagles don't live on fish alone, especially in the winter. In northern areas, eagles are often seen eating road-killed carcasses. During a cold spell, how can they possibly eat rock-hard, frozen meat?

"Help" From Other Animals
We humans are lucky. Like other mammals, we have teeth. Birds don't. Eagle beaks are designed to rip open fish and other kinds of meat, and their mouths and throats are designed to swallow big chunks, but “ripping” is hard when meat is frozen solid. So during winter, eagles often rely on other scavengers to hack into the carcass before the eagles can pick up and swallow loose chips of meat.

Ravens and wolves are usually the first to dine on a carcass. Ravens use their massive but straight, pointed beaks to hack away. Some carcasses are small enough to hack just anywhere, but some are just too thick. A sturdy deer hide is hard to break through even when the deer isn't frozen. So ravens usually eat a deer from the inside out, pulling out the guts from the opening under the tail. Once ravens start pecking at the carcass with their beak, nearby eagles can pick up and swallow flying chips of meat. And on sunny days, even when it's very cold, the inside of the deer will be warmer than the air, and is often not solid, so eagles can rip off chunks of the guts when the ravens pull them out.

Wolves gnaw their meat, and sometimes “play tug-of-war” while fighting over larger pieces, which helps to break them down into more chewable sizes. Again, Bald Eagles can take advantage of chunks they find.

Other Strategies
Eagles also eat chunks of fish (sometimes frozen ones) they find near dams. Swallowing a frozen fish chunk is like swallowing a piece of ice--it makes an eagle’s tummy cold! Fortunately, eagles have thick feathers to keep them well insulated, and they shiver. Shivering makes their muscles work hard, which produces extra body heat to keep them warm.

Eagles have other ways of finding food in winter. For instance, I’ve seen them hunting for mice in a field. And sometimes eagles find their food thanks to humans. When people are ice fishing, they often leave the fish sitting out on the ice to keep them fresh rather than bringing them inside their warm fishing huts. Sometimes eagles notice this and fly in to steal the fish the moment the anglers are back inside their huts! Some eagles come down to bait pots and take out minnows.

The oddest winter eagle feeding strategy I’ve ever heard of was from a man in Port Wing, Wisconsin. He attracted a Bald Eagle to his bird feeder! Every morning the man set out a couple of hard-boiled eggs, and the eagle flew down, ate the eggs, and flew off again.


Journaling Questions
  • How many different food items can you name that eagles eat? What do all of the foods have in common?
  • Other than hunting for fish, how many different hunting methods were described?
  • How do eagles do other animals in eagle habitats unintentionally help them get the foods they need?
  • What other animals can you think of that have special strategies (behavioral adaptations) for finding food in challenging conditions? Describe the strategies.

Try This! Scavenger Hunt for Eagle Food
Write a list of eagle winter food items for a “scavenger hunt” game. Which of the items on your list can you find in one day? An eagle eats 5-10% of its body weight each day. Do you think you could find that much food on your hunt? (First, find out what an average eagle weighs.) How much food would you need in a day if you were to eat the same percent of your weight as an eagle eats?

National Science Education Standards

  • Organisms have basic needs. They can survive only in environments in which their needs can be met.
  • Each plant or animal has different structures that serve different functions in growth, survival, reproduction.
  • All organisms must be able to obtain and use resources, grow, reproduce, and maintain stable internal conditions in a constantly changing external environment.
  • An organism's behavior patterns are related to the nature of that organism's environment, including the kinds and number of other organisms present, the availability of food and resources, and the physical characteristics of the environment.

 

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