Monthly Archives: April 2018

When Do Eaglets Leave The Nest?

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Three weeks after hatching, eagle chicks, or eaglets, molt to a thicker, darker down which remains until the first set of feathers develop. At this stage, one of the parents remains near the nest to shelter the chicks from direct sunlight, inclement weather, and anything else that can harm them.

When an eaglet first hatches, its bill and eyes are dark-colored. Over the course of three to four years, the bill lightens to a swirl of shades of brown, then to yellow-brown, and finally to bright yellow. The eyes lighten to buff yellow by one-and-one-half-years, light cream by age two-and-one-half, and pale yellow by three-and-one-half.

As the chicks develop feathers and grow, the parents spend less time at the nest and more time hunting for food. The eaglets grow very rapidly as long as the parents can provide sufficient food. If the parents are unable to find enough food, the smallest chicks might die.

At one-and-one-half to two-weeks, most young eagles weigh one to two lbs. (500 to 900 grams). Between 18 – 24 days, chicks gain four ounces (100-130 grams) per day, a faster weight gain than at any other stage of their development. Eaglets begin feeding themselves around the sixth to seventh week, and by eight weeks, they can stand and walk around the nest. At sixty days, eaglets are well-feathered and have gained 90% of their adult weight. Large nestlings consume nearly as much food as adults.

Chicks remain in the nest for ten to twelve weeks. A week or two before they fledge, they can be seen on the rim of the nest exercising their wings and holding onto the nest with their talons. They flap their wings and may even lift off the nest. A chick can fall or be blown off a nest while exercising, and if it can’t make it to another branch, it might fall to its death. Biologists estimate one in seven eaglets fledges prematurely, either falling or jumping from the nest before it can fly.

Once their muscles and wings are strong enough, eaglets are ready to leave the nest. What prompts the chicks to fledge is a matter of speculation, but at some point, the parents cut back on the amount of food they provide their young, and they may even use food to lure the chicks away from the nest. Males fledge at an average of 78 days, and females fledge at an average of 82 days. Research in Southeast Alaska shows fledging there occurs on average in mid-August.

The first several flights of a fledgling are very clumsy, and their first few landings are usually crash landings. Juvenile birds have longer wings and tails than adults, and this makes learning to fly easier for them. As an eagle matures, its wings become shorter and narrower, and the tail gets shorter with each molt.

Immature eagles usually stay within a half-mile radius of the nest for the first six weeks after fledging, and they may even continue to receive food from their parents during this time. Eight to ten weeks after fledging, they seem to develop a stronger instinct to move further away from the nest.

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Robin Barefield is the author of three Alaska wilderness mystery novels, Big Game, Murder Over Kodiak, and The Fisherman’s Daughter. To download a free copy of one of her novels, watch her webinar about how she became an author and why she writes Alaska wilderness mysteries. Also, sign up below to subscribe to her free, monthly newsletter on true murder and mystery in Alaska.

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When do Bald Eagles in Alaska Lay Their Eggs, and When do the Eggs Hatch?

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Bald eagles lay their eggs in mid to late May in southern areas of Alaska, although one study in Southeastern Alaska indicated that they might lay their eggs as late as early June. The female lays between one and three off-white-colored eggs in a span of one to three days. The eggs range in size from 2.76 inches by 2.09 inches (70mm by 53 mm) to 3.31 inches by 2.36 inches (84 mm by 60mm).

The eagle pair begins incubating the eggs as soon as they are laid. The male and female share the incubation duties, and each mate hunts for its own food. Studies show that for 98% of the day, either the male or female sits on the eggs. The incubating bird stands up about once per hour and may change positions. A study at several nesting sites on Admiralty Island in Southeast Alaska found eggs were incubated for 95% of the daylight hours with females sitting on the eggs 53% of the time, and males tending the eggs 42% of the time. Brooding time dropped to 79% of the day for the first 10 days after the eggs hatched and by 41 to 50 days after hatching, the brooding time decreased to only 6% of each day. Brooding time increased when it was rainy and decreased when it was sunny. The incubation period takes 34 to 36 days. Since individual eggs may be laid a few days apart, they will not all hatch at the same time.

The hatching process is slow and arduous. It takes chicks twelve to forty-eight hours to fully emerge from the egg. The chick makes the first crack in the shell with its egg tooth, a small, hard bump on the top of the bill. After resting awhile, it then chisels around the large end of the egg. It eventually pushes off the end of the egg and wriggles out of the shell. The egg tooth dries up and falls off four to six weeks after hatching.

During hatching, a chick must undergo several physiological adaptations. Before it hatches, a chick absorbs oxygen through the mat of membranes under the shell. During the hatching process, it must cut the blood supply to these membranes and trap the blood within its body. At the same time, it must also inflate its lungs and begin breathing air once it has cracked the shell. The chick must also absorb the yolk sack into its body and seal off the umbilicus.

Newborn chicks are wet, exhausted, nearly blind, and extremely needy. Since a newly-hatched chick can’t regulate its body temperature, the parents must keep it warm. The chick is covered with pale gray down. The skin and scales of the legs are bright pink, the bill is a grey-black with a white tip, and the talons are flesh-colored. After the first week, the legs begin to turn yellow.

 

Eagles lay one to three eggs, but usually, only one or two chicks survive. Survivability is directly correlated to age. The first chick to hatch will be one to two days older than its siblings, so it will be larger and stronger and able to out-compete its nestlings if food is limited. If a brood has three chicks, the smallest chick usually dies within a week of hatching. Death is not normally caused by injuries from fighting with its siblings, but the chick simply starves to death because the older nestlings get all the food. The older chicks peck the young chick into submission to prevent it from eating enough to survive. By doing this, the older chicks ensure they have plenty of food.

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Robin Barefield is the author of three Alaska wilderness mystery novels, Big Game, Murder Over Kodiak, and The Fisherman’s Daughter. To download a free copy of one of her novels, watch her webinar about how she became an author and why she writes Alaska wilderness mysteries. Also, sign up below to subscribe to her free, monthly newsletter on true murder and mystery in Alaska.

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Bald Eagle Nest Building

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Spring is a time for nest building; whether it’s a new nest made from twigs or a hollow spot in a rock needing only a fresh supply of moss for padding, birds know they must prepare their homes for the eggs and chicks that will soon follow.

Our weather is slowly warming here on Kodiak Island. Most days we creep into the forties, but then we drop back into the low thirties at night. I see a few sprouts popping through the ground, but mostly, it still looks like winter here.

Animals are the one, true indication spring is right around the corner. I hear whales exhaling in the pass near our lodge, signaling they are following the krill and small fish into the bay. In turn, the krill and fish are here to feed on the phytoplankton which blooms as the water warms. Yesterday, kittiwakes arrived in a big swarm to repopulate the rookery in front of our lodge. Puffins and arctic terns should be here soon.

The surest promise of spring, though, is the circling eagles high in the sky as they perform their mating ballet. Soon, they will begin repairing their homes as they prepare for their young to be born.

Bald eagles build the largest nest of any North American bird. The nest may be as large as 8 ft. (2.44 m) across and weigh one ton (907 kg). An eagle pair often uses and adds to the same nest every year, causing the nest to grow over time.

Bald eagles build their nests in large trees near the water. In Alaska, nests are usually found along saltwater shorelines or rivers, and in many parts of Alaska, eagles nest in old-growth timber. On Kodiak Island, eagles prefer to nest in black cottonwood trees, but in areas where black cottonwoods are not available, nests can be found on rocky cliffs or at the bases of alder trees on cliffs along the coast.

The nest is usually built in the crotch of the last set of branches one-third to one-quarter of the way down from the top of the tree. Eagles tend to nest in trees with sparse foliage near the edge of a habitat, so they can fly to and from the nest without having to navigate through a canopy of trees.

The nests are built of sticks, and each year the eagle pair adds new branches and other vegetation to the nest to cover over food remains, feathers, and other debris left from the previous year. Branches and twigs are placed on the edge of the nest, while softer vegetation such as leaves, grass, and moss are placed in the center. An eagle pair continues to add branches, moss, and grass to the nest all summer until the chicks are nearly grown. Researchers believe the reason for this may simply be to keep the nest cleaner. Waste, rotting fish, and even the bodies of chicks that have died in the nest are not tossed out of the nest but are buried by moss, grass, and other greenery. It is important to keep the nest clean, so parasites don’t infest the chicks.

An eagle pair usually uses a nest until either the eagles die or something happens to the nest or the tree holding the nest. Mates may build two, three, or even four nests in their breeding territory, and scientists are unsure what the purpose is for these multiple nests.

The average distance between occupied nests is usually 1 to 2 miles (1.6 – 3.2 km), but nest sites are often closer to each other in areas where food is plentiful. A 2007 nesting and productivity study on the Kodiak National Wildlife Refuge identified 1141 nests with 439 (38%) of those nests active. This was down from a 55% occupancy rate found in a 2002 study. Of the 439 active nests in 2007, 208 of the nests (48%) were successful in producing young. The researchers suspected the harsh spring weather in 2006 and 2007 might have contributed to the reduction of nesting effort.

Nesting and breeding bald eagles are territorial and defend their nests from other animals, including other eagles. Adults spend much of the day perched in prominent trees near the nest, perhaps to make themselves more visible to intruders. A resident eagle will warn an approaching eagle with a loud call consisting of grunts followed by a high-pitched screech. Sometimes the resident eagle quietly escorts an intruder out of the area, but occasionally, one of the two birds will attack the other, resulting in a display known as cart-wheeling, where one eagle descends on the other eagle, and the other bird rolls onto its back while both eagles grasp talons. The two birds then tumble toward the ground, separating just before they crash.

I welcome the birds back after a long winter. They are often noisy neighbors, but their cries herald birth, life, and spring!

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Robin Barefield is the author of three Alaska wilderness mystery novels, Big Game, Murder Over Kodiak, and The Fisherman’s Daughter. To download a free copy of one of her novels, watch her webinar about how she became an author and why she writes Alaska wilderness mysteries. Also, sign up below to subscribe to her free, monthly newsletter on true murder and mystery in Alaska.

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Kodiak Bear Management

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Wildlife management most often involves managing humans. Research allows biologists to understand the needs and habits of wildlife, and this research hopefully leads to management policies to enable human populations to better coexist with wildlife. Wildlife management is never easy, and Kodiak is no different from anywhere else. Various user groups attempt to pressure wildlife managers into making decisions to further their particular interest, and managers struggle for a balance to try to accommodate a variety of users while protecting the wildlife and the habitat.

On the Kodiak Archipelago, I am proud to say the management of bears and their habitat is not only done well, but it is done so well, it is considered one of the best models of wildlife management in the world. The Kodiak National Wildlife Refuge managers, the Alaska Department of Fish and Game, the native corporations, and the citizens of Kodiak work well together to safeguard bears and protect their habitat.

History has shown us that protecting wildlife habitat is often the most difficult aspect of wildlife management, whether there is oil to be drilled, copper to be mined, trees to be cut, or roads and houses to be built, economics often wins while wildlife loses huge chunks of critical habitat. Brown bears require large tracts of wilderness to survive, and as the human population grows, it becomes more and more difficult to protect the bears’ home from economic and residential development.

The Kodiak National Wildlife Refuge is the largest intact, pristine island ecosystem in North America. The Refuge encompasses 16 lakes, 117 salmon streams, wetlands, grasslands, shrublands, Sitka spruce forest, tundra, and alpine meadows. This habitat supports 250 species of fish, birds, and mammals, including 400 breeding pairs of bald eagles. It supports 3000 bears, and an estimated 3500 bears live on the Kodiak Archipelago.

One of the stated purposes of the Kodiak National Wildlife Refuge is to conserve fish and wildlife populations and habitats in their natural diversity, including, but not limited to, Kodiak brown bears, salmonids, sea otters, sea lions, and other marine mammals and migratory birds.

The Kodiak National Wildlife Refuge was established in 1941 in response to concerns by bear hunters for the health and survival of the Kodiak brown bear population. The original mission of the Refuge was “to protect the natural feeding and breeding range of the brown bears and other wildlife on Uganik and Kodiak Island.” Without the strong lobbying efforts of hunting groups, it is doubtful the Kodiak National Wildlife Refuge would have been formed. The sale of bear hunting licenses and bear tags on Kodiak generates over $250,000 annually, and much of this money is used for research and habitat protection.

Bear hunting on Kodiak today is very tightly regulated. Each year, 4500 people apply for the 495 available bear-hunting permits. Of these 495 hunters, approximately 175 are successful, and 75% of the bears killed are male. All hunters must check in with the Alaska Department of Fish and Game office in Kodiak before going into the field, and they must check out with Fish and Game before leaving the island. Every bear killed must be inspected by an Alaska Department of Fish and Game biologist before it can be taken off the island. Because these strict regulations have the overwhelming support of guides and residents, illegal bear hunting on Kodiak is rare.

Perhaps the most telling fact proving the Kodiak bear and its habitat are well managed is the 3500 brown bears currently living on the Kodiak Archipelago. Biologists believe this is the largest the Kodiak bear population has ever been.

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Robin Barefield is the author of three Alaska wilderness mystery novels, Big Game, Murder Over Kodiak, and The Fisherman’s Daughter. To download a free copy of one of her novels, watch her webinar about how she became an author and why she writes Alaska wilderness mysteries. Also, sign up below to subscribe to her free, monthly newsletter on true murder and mystery in Alaska.

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Have Kodiak Bears Changed Their Feeding Behavior?

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Last week, I discussed a recent scientific study chronicling Kodiak bear feeding behavior during the summers of 2014 and 2015. I pointed out that while the study fascinated me, I was less enthusiastic about the flood of inaccurate leaps in logic following the publication of the research. Please refer to last week’s post if you haven’t read it, so my post this week will make sense to you.

I invited most of the authors of the study, Kodiak National Wildlife Refuge officials (the research was in part supported by the Refuge), and other biologists and guides on the island to read my post and share their thoughts on the study. I was curious to know what others who work in the field on Kodiak thought about the flood of publicity over the past few months stating as our climate warms, Kodiak bears are changing their feeding behavior and are abstaining from salmon while they eat their fill of elderberries. While I didn’t get many replies here on my website, I did receive several e-mails, and without mentioning any names, I will share some of those with you.

I know I just said I wouldn’t mention any names, but I do want to state that Dr. Deacy, the lead researcher on the project, sent me a very nice e-mail soon after I asked him to look at my post. He was on a deadline for another project but said he would respond in more detail when he had time. He couldn’t have been nicer, and I exhaled a long, slow breath when I read his response because Dr. Deacy has been generous with his time in explaining this as well as other, recent bear research to me. I didn’t want to anger him or anyone with my critique of the study.

One of the other researchers on the study was not as thrilled with me, and he seemed to think I was personally attacking him and the other biologists. I admit I am partially to blame for his anger because I stated scientists sometimes seem as if they are in a bubble. He equated this statement with me saying scientists never come down from their Ivory Towers – a term I did not, nor would not, use. After his message, I was afraid to look at my e-mail for the next few days, but the rest of the replies I received were positive.
Biologists and guides alike felt the conclusions stated in this study opened the door to the wild, speculative media reports following it. Two people mentioned an important point. Some Kodiak bears spend most of their lives in alpine regions on the island and eat neither elderberries nor salmon. As with humans, what bears eat varies from one area to another and from one individual to the next.

I hope most people who read articles with titles like, “Kodiak bears go vegetarian,” will stop for a moment and question such a wild claim. I applaud wildlife research and think this research is necessary, not only to understand the magnificent wild animals who share this planet with us but also because this research points the way to appropriate wildlife management decisions. I don’t, however, believe research should ever be done to prove a case. The point of research should be the search for truth.

Speaking of wildlife management, next week I will write about bear management on Kodiak Island. Thank you for reading my post.

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Robin Barefield is the author of three Alaska wilderness mystery novels, Big Game, Murder Over Kodiak, and The Fisherman’s Daughter. To download a free copy of one of her novels, watch her webinar about how she became an author and why she writes Alaska wilderness mysteries. Also, sign up below to subscribe to her free, monthly newsletter on true murder and mystery in Alaska.

Mystery Newsletter

Sign Up for my free, monthly Mystery Newsletter about true crime in Alaska.