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Arctic Wings: Miracle of Migration

Did you know?
Interesting facts from the pages of Arctic Wings

194 bird species have been recorded in the Arctic Refuge.

26 species of birds live in the Arctic Refuge year round, even in the depths of winter at minus 50 and 60 degrees F. The include the Common Raven, Gray Jay, American Three-toed Woodpecker, Spruce Grouse, Rock and Willow Ptarmigan, White-winged Crossbill, Gray-headed and Boreal Chickadee, and the American Dipper. Many of these birds have special adaptations that allow them to survive the frigid conditions.

Even in temperatures of 50 and 60 degrees below zero, there are river locations in the refuge where there is open water in winter–allowing a water bird, the American Dipper, to survive and thrive in these frigid conditions.

Birds are drawn on death-defying migrations to the Arctic Refuge every year by an explosion of rich food sources produced by the intensity of 24-hour Arctic summer daylight. The long days allow for continuous foraging, necessary for feeding of the young as well as for building up fat reserves in preparation for the long journey back to wintering grounds at the end of the short Arctic season.

What does it take for a bird to succeed in a long nonstop migration? Fat. To imagine eating enough to double your weight in only a month, consider this: An average human male weighting 160 pounds would be required to consume about 560,000 extra calories that month—on top of a normal diet. This is about the equivalent of eating 1600 cheeseburgers—that's 53 every day for a month!

How determined are birds to reach the Arctic Refuge?

  • The Arctic Tern makes the longest annual migration of any bird on the planet. They fly a minimum of 24,000 miles a year, essentially from the north polar areas to the south polar areas and back. They might spend three months during the Arctic summer nesting and raising their young in the north, and then take three months to make the long journey back to their northern summer home in the Arctic. They spend most of their lives on the wing and in daylight.
  • An American Golden-Plover travels approximately 9,000 miles each way between the Arctic and Argentina, for a total round trip of 18,000 miles or more each year.
  • The one-ounce Semipalmated Sandpiper makes a nonstop flight from Nova Scotia to South America, traveling 2,400 miles in 72 hours and burning fat equal to about half its body weight.

How crowded is the Arctic Refuge at the height of breeding season?

  • There are an estimated 230,000 shorebirds nesting on the coastal plain during the breeding season.
  • There are somewhere between 9,000 and 22,000 American Golden Plovers that nest in the Refuge, which is about 5 to 11 percent of the population thought to exist.

Some bird species live very different lifestyles during their summer breeding season on the Arctic Refuge than they do the rest of the year in other climes:

  • The Long-tailed Jaeger, Sabine's Gull, and Arctic Tern live, nest, and hunt on land during their Arctic summer; they then head south for the open ocean south of the equator for the rest of the year—with striking modifications in their behavior and the prey they seek.
  • Because of the long summertime daylight hours in the Arctic, owls in the Arctic Refuge hunt by day during much of the breeding season only to return to a more nocturnal lifestyle during the fall and winter seasons.
  • Like other birds that fall silent in winter, shorebirds do not vocalize much during migration or on their wintering grounds. But when they arrive on their Arctic breeding grounds in late May, they burst into song, vividly advertising for mates and staking out their territories.

Bird species that winter on the Arctic Refuge exhibit special adaptations that help them endure frigid conditions:

  • Chickadees roost in tree cavities in a state of "regulated hypothermia," in which their body temperature drops as much as twenty degrees F below their normal daytime body temperature. As a result, they don't have to expend as much energy, stored in fat reserves, to heat their bodies. They also have other cold-weather adaptations: By shivering their muscles, they use stored fat reserves to generate heat and to regulate their body temperature when cooling down at night
  • The White-winged Crossbill has an enlarged crop know as a gular pouch. They store extra seed in the gular pouch as they eat, especially toward nightfall and at the onset of inclement weather. This "lunch box" of extra food will carry the birds through the night and the cold by allowing them to slowly digest while resting in a sheltered spot. Another way they cope with the Arctic cold is by growing more down features in the fall and fluffing up these feathers as they remain completely still in the their snow-enclosed spruce shelters.
  • Ptarmigan not only grow very thick, downy body plumage to hold in warmth, but their feet are also heavily featured to the tips of their sharp claws and act as snowshoes to allow them to walk more easily on the surface of the snow. On cold winter nights they burrow into the snow to sleep, allowing the insulating value of the snow to keep them warm. They, too, have a gular pouch in which they store food for digestion during the night or a winter snowstorm.
  • The American Dipper, a water bird that thrives in river locations on the Arctic plain where there is open water in winter, has added insulation; it has more contour feathers than other passerines of similar size—approximately 4,200 feathers compared with 3,000 or fewer in other birds. Dippers also have a heavy layer of down between their feather tracts, and their eyelids are covered by tiny wisps of feathers. Dippers have a metabolic rate that is 35 percent lower than other passerines of the same size, so they can function well at very low temperatures.
  • The feathers of the Snowy Owl have been shown in laboratory experiments to protect the owls to ambient temperatures reaching minus forty degrees F.
  • The asymmetrical ear positions of the Great Gray Owl enable it to locate prey under several inches of snow. It then plunges down through the snow to capture its prey.
  • Many species of owls are known to kill prey and cache it for future use. During extreme cold, some species of owls are known to "incubate" frozen prey that had been previously cached in order to eat it.

What are some possible effects of development on the Arctic Refuge?

  • On average, there are more than 400 spills of oil and other toxic substances in and around North Slope oilfields annually.
  • The effects of oilfield infrastructure extend far beyond the immediate footprint of the facilities. For example, dust from roads can speed snowmelt in the spring, which may encourage early nesting by small birds, possibly to their detriment. Roads and placement of gravel pads on the tundra can alter the flow of water and create ponds or deeper water, which then affect birds in and around those habitats.
  • One key difference between the Prudhoe Bay/central Arctic oilfield area and the Arctic Refuge is that there is much less coastal plain habitat in the Arctic Refuge. Hence, for birds dependent on low, wet habitats, there is less available in the way of alternative habitats.
  • The U.S. Department of the Interior estimates that oil development could displace Snow Geese from as much as 45 percent of their preferred feeding habitat within that portion of the Arctic Refuge that is proposed for oil development.
  • The Spectacled Eider is listed formally under the Endangered Species Act—most of the US Arctic population nests where oil leases are likely to be developed.
  • According to the National Research Council, increased predation is the most apparent effect of oil development on birds that nest in oilfields. For example, at Howe Island, near the Endicott Causeway northeast of Prudhoe Bay, predation by foxes and bears drawn by human habitation (and the resulting garbage produced) appears to be responsible for low nest success and even complete failures in a colony of Snow Geese from 1991-2001.

 

Northern Wheatear feeding young, Arctic National Wildlife Refuge
Photo by Hugh Rose