Alaska Southeaster Magazine

The newly hatched eaglet is totally helpless. Her eyes are not open. She can barely move around, and she cannot feed herself. She will not be able to maintain her body temperature for several weeks. Right now she weighs about 3 ounces, but in three months she could well weigh 40 or 50 times that much. According to Mark V. Stalmaster, author of the fascinating book The Bald Eagle, she may eventually gain up to 6.3 ounces a day. That is the fastest growth rate of any North American bird.

Problems and Responsibilities of Parenthood

Raising young eaglets and preparing for them is a tremendous investment for bald eagle parents. It means about 6 months of hard work and staying almost constantly within a limited nesting territory.

If a female bald eagle has survived the winter in good condition, and if she and her mate have successfully built a nest together, she will lay one or more eggs (in most cases, two) in late April or early May. For the next 35 days, the female and her mate must incubate the eggs, keeping them warm, protecting them from predators such as crows or ravens, and turning them approximately every hour to keep them evenly warm and prevent the membranes of the embryos inside from sticking to the shells.

The male does not feed the female during this time, as some birds do. Instead, he forages to feed himself while the female is on the nest, then returns to relieve her so she can fly off and eat.

Even before the eggs hatch, eagle parents begin gathering food for their young. Perhaps alerted by the peeping sound as young eaglets work to break out of their shells, the adults begin caching food in the nest. They bring small fish—maybe herring or sand lance—and larger ones—a walleye pollock, perhaps—providing the same amount of food they will provide when the nestlings are older, as if to be sure there will be enough.

When the eaglets are young, the parents must tear the food into tiny bits, dangling it from their bills so the hungry chicks will gobble it down. As the eaglets get older, they may squeal and scream for food, grabbing at their parents’ bills, shoving and pecking at each other, and snatching sometimes enormous chunks of fish and gulping them down.

Nesting eagles usually bring food to their young at least once every few hours, and they will need to do so for some 11 to 12 weeks until the eaglets fledge and leave the nest.

The Challenge of Getting a Meal

Nesting eagles stay close to their nest sites—usually within about one square mile. Typically they perch on tall trees or snags where they can see large areas of water—and that is how we often see them, their white heads clearly visible against the dark green forest behind them. From their perches the birds may wait for hours for fish to swim by near the water’s surface, or for dead or dying fish to float by or wash up on the beach. Eagles have incredibly powerful eyesight. They spot fish and zero in on them from thousands of feet away.
But obtaining fish from the water is no easy task. Watching a bald eagle swoop down from its perch, snatch a large fish from the water, and grandly carry it to a waterside perch is one of the more exciting events Southeast residents and visitors are sometimes privileged to enjoy. (How eagles perform this difficult feat is described in text and photos in the October 1999 Alaskan Southeaster). Some eagles are better at it than others; immature eagles seldom succeed. The immatures nearly always miss their mark by a considerable distance and usually end up grabbing talonsful of air several feet above the water. It must take eagles years of practice to perfect this hunting technique.

Eagles may also pirate their meals from others. They steal fish from river otters, ospreys, mergansers, gulls, and, of course, each other. Several times we have seen an otter catch a flounder or a sculpin, then swim ashore to eat it. As the otter tore the fish apart for its meal, a bald eagle swooped down at it with such speed and surprise the otter dropped the fish and fell backwards into the water, while the eagle—still airborne—grabbed the fish and flew off with it.

Eagles also take fish injured by whales and sea lions, or driven to the surface by loons, seals, or salmon. Eagles follow feeding marbled murrelets, swoop to the water’s surface, and emerge with talonsful of sand lance that the murrelets had driven up from deeper water. We observed an eagle swoop down and steal a small duck shortly after it had been taken on the tidal flats by a northern harrier.

Southeast Alaska’s widespread commercial, sport, and subsistence fisheries must provide a considerable number of fish carcasses that eagles can pick up for food. Most fishing in Southeast takes place from May through August, the time when bald eagles are nesting and gathering food for their nestlings. Fish that are injured and thrown back into the water often swim about at the surface, where eagles could reach them. Fish that die usually sink to the bottom, beyond reach; but members of the cod family, such as walleye pollock, float because their gas bladder expands when they are pulled up quickly from deep water.

When researchers studied the stomach contents of some 325 nesting eagles (birds killed under Alaska’s predator control program, in effect from 1917 to 1952), they found pollock and cod in about a third of them. They also found that pollock were the most frequently consumed fish during May and June before salmon spawning began and during a critical time for eagles nesting and raising young.

Care Until Eaglets Leave the Nest

Besides feeding their youngsters several times a day, eagle parents also must “brood” them, or keep them warm. Even though they go through two different plumages of downy feathers, eaglets are unable to keep themselves warm for a number of weeks. For the first month, one or the other parent is seldom away from the nest. Once nestlings are about a month old, they begin sprouting flight and contour feathers amid their down, but still the parents must protect them if there is rain, wind, or too much sun.

When the parents are away from the nest, older eaglets seem to prepare for their adult life by playing. They may flap their wings, jump around in the nest, fight with one another, or play tug of war with sticks. Some eaglets are so aggressive they attack their parents when they bring food to the nest; in that case, the parents just fly by the nest and drop food off, faithful to their duties but unwilling to put up with their offspring!

Once eaglets have developed most of their wing and tail feathers (usually when they’re 11 to 12 weeks old), they are ready to fledge, or leave the nest. Some leave on their own. Others need to be lured away, perhaps by a parent flying overhead with food and calling to them.

In The Bald Eagle, Stalmaster estimates that perhaps half of all fledglings fall to the ground after their first flight. Whether they fall or successfully land in trees near the nest, the parents will often, but not always, bring them food. Some studies found that most fledglings stayed within a mile of the nest for six to eight weeks, and some eaglets returned to the nest to pick up food their parents had cached.
We can hardly overstate the value of spawned out salmon to juvenile eagles that have left the nest but are not yet very skilled at hunting. Juvenile eagles are probably very much dependent for their survival on salmon carcasses washed up on beaches or riverbanks, or dragged to shore and abandoned by bears.

As winter approaches, juvenile eagles tend to travel more widely than adults. Some young eagles travel as far south as British Columbia or Washington state in search of accessible food. Meanwhile their parents—relieved at last from their tremendous responsibilities—are free to forage beyond their nesting territories, perhaps even traveling to winter feeding grounds such as the Chilkat Valley near Haines. Those that are likely to nest again the next year, however, may remain near their territory or occasionally return to assert ownership throughout the winter.