Saturday, June 22, 2013

Tundra Swan

Tundra Swan


Cygnus columbianus
Photo: Tundra swan swimming in water
The graceful tundra swan feeds not only on underwater flora and shellfish but has developed a taste for grains and corn, much to the chagrin of farmers.
Photograph by Bates Littlehales
The snowy white tundra swan breeds in the Arctic and migrates many miles to winter on North America's Atlantic and Pacific coastlines, bays, and lakes. The eastern population frequents the Chesapeake Bay and North Carolina, while the western population typically winters in California. These animals fly some 3,725 miles (6,000 kilometers) round-trip between their distant habitats, and make the daunting journey twice each year. Tundra swan subspecies also winter in Europe and Asia.
Tundra swans are often confused with trumpeter swans, and indeed the two species are very similar in appearance. They are most easily distinguished by their calls.
Tundra swans winter on the water and sleep afloat. They are strong and speedy swimmers that take to the air with a running start, clattering across the water's surface with wings beating. In flight, the rhythmic flapping of the swan's wings produces a tone that once earned it the name "whistling swan."
These large birds feed by dipping their heads underwater to pluck aquatic plants, tubers, and roots. They also eat shellfish and are developing an increasing taste for grains and corn found in farmland areas.
Believed to mate for life, these swans actually pair up for nearly an entire year before breeding. Though in their winter grounds they gather in huge flocks, they breed as solitary pairs spread out across the tundra. Each couple defends a territory of about three-fourths square miles (two square kilometers).
The bird's tundra nests are large stick dwellings lined with moss and grasses. Ideally, they are situated close to a pond or other water source.
Females typically lay about four eggs and incubate them for 32 days while males guard the nest. Young chicks are protected from cold and predators, including swarms of voracious Arctic mosquitoes. Tundra swans can be nasty when aroused, and the birds may even be able to fend off predators like foxes and jaegers.

Friday, June 21, 2013

Osprey

Osprey 

Pandion haliaetus
Photo: An osprey preparing to dive
An osprey preparing to dive
Photograph courtesy NASA
Ospreys are superb fishers and indeed eat little else—fish make up some 99 percent of their diet. Because of this appetite, these birds can be found near ponds, rivers, lakes, and coastal waterways around the world. Ospreys hunt by diving to the water's surface from some 30 to 100 feet (9 to 30 meters) up. They have gripping pads on their feet to help them pluck fish from the water with their curved claws and carry them for great distances. In flight, ospreys will orient the fish headfirst to ease wind resistance.
Ospreys are sometimes confused with bald eagles, but can be identified by their white underparts. Their white heads also have a distinctive black eyestripe that goes down the side of their faces. Eagles and ospreys frequent similar habitats and sometimes battle for food. Eagles often force osprey to drop fish that they have caught and steal them in midair.
Human habitat is sometimes an aid to the osprey. The birds happily build large stick-and-sod nests on telephone poles, channel markers, and other such locations. Artificial nesting platforms are common in areas where preservationists are working to reestablish the birds. North American osprey populations became endangered in the 1950s due to chemical pollutants such as DDT, which thinned their eggshells and hampered reproduction. Ospreys have rebounded significantly in recent decades, though they remain scarce in some locales.
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