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Birds in Pipes

A wildlife biologist in Idaho responded to an unusual call a few years ago - an owl was trapped in a campground toilet. When Joe Foust looked down into the holding tank of the toilet and saw a little boreal owl peering back up at him, something started that has likely saved the lives of thousands of birds.

Vault toilets are found in campgrounds on public lands across the country. Typically a cinder-block-and-cement-pad kind of outhouse, without plumbing, the waste is stored in a tank (or vault) underground. A vent pipe through the roof allows air to flow. And it allows cavity nesting birds like that boreal owl access to a space they can't escape.

Foust conducted a messy and successful rescue, and his spread. That was in 2010, and awareness has been growing about the threat open pipes pose to cavity nesting birds like owls, kestrels, bluebirds, and flickers. In Alaska, cavity nesting ducks like mergansers and goldeneyes use natural openings for nesting and roosting. An open vent, pipe and chimney can become trap, as the smooth sides and tight confines prevent escape.

The Teton Raptor Center in Wyoming has been instrumental in spreading the word and developing a solution - a screen that allows the air to flow through the vent, but prevents birds from getting in. More than 8,000 campground vault toilets have been screened across the country, including Alaska, and other types of pipes are being capped.

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A bald eagle swoops low just off the beach. Its talons brush the water and it snatches a ten-inch fish, which wiggles and twists as the eagle flies away. Nearby, another eagle lands on a spawned-out chum salmon and begins to feed. It has no intention of flying off with the fish because it can't.

Every few years a story makes the rounds that an eagle has swooped down and carried off someone's small dog. These stories never check out, and there's no documented case of a bald eagle in Alaska carrying off a dog or cat. Eagles are strong, aggressive raptors, but like everything that flies they are governed by the laws of aerodynamics. The wings of an eagle need to support the 8 to 12 pound bird itself, as well as whatever it might be carrying. An adult eagle can only carry about five pounds - but it's not quite that simple. Aerodynamic lift is based on wing size and air speed. The faster something flies, the greater the lift potential. An eagle that lands on the beach and then lifts off again is limited to a smaller payload than a bird that swoops down at speed and snatches something.

Eagles are alert and curious and they might watch a small pet, but they are also cautious and unlikely to approach a pet near people. And they are fish eaters and scavengers, by and large preferring herring size fish. They might scavenge a road-killed pet, but in reality, those furbabies are safe from eagles.

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Eagle eyes

A pair of hungry bald eagles sits in a big spruce tree overlooking a wetland. They're scanning the estuary for any sign of food - a duck or gull that might be a little impaired by an injury, or any ripples in the water revealing a fish. A small flounder in a shallow intertidal slough changes position, and one of the eagles drops from the tree in a fast glide, skims the water with outstretched talons, and scoops up the fish.

Eagles have remarkable eyes. Generally speaking, their eyesight is about eight times better than ours, in terms of visual acuity and perception. They are highly sensitive to motion and have excellent depth perception. One reason for this is they have two focal points, called fovea, on the back of each eye instead of one, like we have, for a total of four. With four fovea the eagle has the superior depth perception needed to make high speed dives and snatch up prey without missing or crashing.

An eagle's eyeball is about the same size a human eyeball, impressive considering we are basically ten to 20 times bigger than an eagle. It doesn't look as big because it is set deeper in the eagle's skull, capped by a bony ridge and surrounded by muscles. That protects the eagles' eye but limits its movement, so the eagle must turn its head to look in different directions. The eagle's eye is also protected by a second, translucent inner eyelid called a nictitating membrane that closes involuntarily when the eye needs extra coverage.

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Eagle Nest

On a rainy southeast Alaska afternoon, I've taken some friends to see an eagle nest near my house in Juneau. The nest is 75 feet up in a broken-top spruce tree and has been used every year for the past 15 years. Since it's on a slope, we hike uphill from it and look down into it. On this afternoon in early August, a raven-size chick is sitting on the edge of the nest, with an adult perched on a branch nearby. The big chick can't fly but stretches and flaps its wings every few minutes. The adult breaks into its chirping call and is answered by its mate returning to the nest with food. I've assumed the same pair of eagles has used the nest for years, but I have no way of knowing. But every spring a pair of adults raises a brood of eaglets here.

The female sits on eggs in April and May, periodically fussing with the nesting material, and around early June she starts perching on the side of the nest, indicating the eggs have likely hatched. Soon the dark chicks are visible and by mid-July they are often sitting on the edge of the nest. About this time one or two disappear. I've can't recall the pair ever fledging more than one chick, because eagle chicks will often kill their smaller siblings. In late August the giant brown chick - now the size of an adult - will fledge and the nest will be empty until next spring.

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Golden eagles

A golden eagle swoops low near a rocky cliff in Denali National Park. She flares her seven-foot-wings and sets down on a ledge. Golden eagles are extraordinary raptors, and this eagle is special - she's equipped with a satellite tracking device, and biologists have tracked her migration and movements over the past year.

Golden eagles use their powerful wings and long, sharp talons to catch prey such as ground squirrels, hares, ptarmigan, and even young caribou and sheep. They nest on cliffs across Alaska, from Southeast to the North Slope.

State wildlife biologists, collaborating with federal partners, have conducted long-term monitoring of golden eagle populations, using satellite telemetry to follow their migrations; and conducting annual spring counts of returning eagles to gain insights into the size and status of Alaska's golden eagle populations

The findings should provide a statewide population estimate. Preliminary results suggest that Alaska may support one of the largest populations of golden eagles in the US. Biologists have learned where golden eagles that nest in Alaska spend their winters, and have identified important migration corridors and wintering areas. This can improve management of resource development, such as wind farms, minimizing impacts on eagles.

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Hawk Owl

An unusual bird is hunting on the Mendenhall Wetlands in Southeast Alaska. Cruising low over the flats it seems to be part hawk and part owl. It's a northern hawk owl.

The northern hawk owl is a fairly common bird of the boreal forest in Alaska. It does not migrate and although it's not generally found in Southeast Alaska, a scarcity of food can bring it outside its normal range. The hawk owl occurs throughout the forested areas of the interior, southcentral, and southwestern parts of the state, including the Kodiak archipelago. The species has a circumpolar distribution from Norway across northern Europe and Asia through Alaska and across Canada.

The owl is atypical of most owls because it hunts during daylight, using sight more than hearing to locate its prey. The hawk owl is named for its similarities in behavior and appearance with typical hawks. The crow-sized owl is about 13 inches long with a 30-inch wingspan. Unlike most owls it has a very small facial disk which is abbreviated in the brow region over the bright yellow eyes. The wings are large and, unlike those of most owls, pointed at the ends. The tail is very long for an owl and tapers at the end. When the bird flies, the pointed wings, long tail, and swift flight appear hawk-like.

The northern hawk owl does not build a nest. It lays its eggs in cavities in the broken tops of rotten trees or in large holes in trees. Only the female incubates the eggs; the male hunts and brings food to the female. Usually the male will perch within 100-200 yards from the nest. The persistent presence of a single owl during late April is usually an indication that a nest is somewhere nearby.

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Old Eagle

In the spring of 2012, an adult bald eagle was found dead on a beach on Douglas Island near Juneau. Because the bird had a band on its leg, the people who found it called the US fish and Wildlife Service. Eagle biologist Steve Lewis picked up the bird and tracked down its story.

Lewis was unsure about the cause of death, but said some trauma on its head and beak suggested it wasn't old age. The bird was old, however, and a unique find in Southeast Alaska. The eagle was 30 years old, banded as a nestling in its nest on July ninth, 1982, near Point Couverden, about 15 miles west of where it was found on north Douglas.

Lewis said while that isn't the oldest bald eagle documented (the Bird Banding Laboratory has one from Maine that was 32 years old, and several captive bald eagles have lived to be about the same age) it is the oldest documented in Alaska. "My guess is that many adult eagles can get to be that age, or older, Lewis said. We just don't have a way to determine how old they are unless they are banded as nestlings and then the band is recovered." Banding marks a bird as a unique, identifiable individual, and that enables biologists to learn about its movements and migrations, reproductive behavior, and life history.

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Osprey

Early in summer, a large raptor calls from a tree near a river. It looks like a small, mature bald eagle, but closer inspection with binoculars reveals it's an osprey. This is a female and she's sitting on a nest, a platform of sticks and branches. Her mate soon appears with a ten-inch fish clutched in his talons and delivers it to the nestlings.

Osprey are raptors that specialize in catching and eating fish. They have uniquely curved claws that circle like a fishhook, and rough pads on the soles of their feet to help hold their catch. From flight or from a perch, an osprey will plunge talons-first into the water, sometimes completely submerging, to catch fish. An osprey erupts from the water clutching its prize and as it rises from the surface, wings pumping, it will pause to shake vigorously like a dog, spraying water from its feathers.

Osprey look a bit like bald eagles, but have a distinct dark stripe on each side of its white head. An unlike the brown-bellied eagle, the osprey has a white belly and breast.

Osprey were endangered in the 1950s and '60s because of poisoning by the widely used pesticide DDT. After DDT use was discontinued in the US, young osprey were transplanted into areas where birds had been extirpated, and since then ospreys have made a remarkable comeback in the lower 48. Ospreys are not abundant in Alaska but can be found along lakes, rivers and coastlines south of the Brooks Range. Bald eagles will harry osprey and force them to drop their fish, stealing the smaller raptors catch.

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What eagles eat

The bald eagle's diet is mostly fish, mainly herring, flounder, and salmon. Eagles are opportunistic and will also eat ducks and seagulls, small mammals, shellfish and carrion. Spawning salmon are important in late summer, when large hungry chicks are in the nest, and when those novice hunters first strike out on their own.

Eagles travel great distances to reach abundant food sources, and can sometimes be found in remarkable numbers. In the Chilkat Valley, 80 miles north of Juneau near Haines, thousands of bald eagles gather in the late fall to feed on spawned-out salmon. A short unfrozen section of the Chilkat River supports a late run of chum salmon, which attracts eagles from hundreds of miles away.

Eagles on the Chilkat are known to have come from as far away as Prince William Sound, 600 miles to the west; from Willapa Bay in Washington State, 1,000 miles to the south, and from Besnard Lake, in Saskatchewan 1,300 miles east.

A spring run of hooligan, a fish related to herring, in Berners Bay north of Juneau draws hundreds of eagles and other birds. Like the fall run of Chilkat chums, it's particularly attractive and important because it comes at a time when other food sources are scarce.

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