Thursday, July 12, 2007

Brown Pelican

The Brown Pelican (Pelecanus occidentalis) is the smallest of the eight species of pelican, although it is a large bird in nearly every other regard. It is 106-137 cm (42-54 in) in length, weighs from 2.75 to 5.5 kg (6-12 lbs) and has a wingspan from 1.83 to 2.5 m (6 to 8.2 ft).
It lives strictly on coasts from Washington and Virginia south to northern Chile and the mouth of the Amazon River. Some immature birds may stray to inland freshwater lakes. After nesting, North American birds move in flocks further north along the coasts, returning to warmer waters for winter.
This bird is distinguished from the American White Pelican by its brown body and its habit of diving for fish from the air, as opposed to co-operative fishing from the surface. It eats mainly herring-like fish. Groups of Brown Pelicans often travel in single file, flying low over the water's surface.
The nest location varies from a simple scrape on the ground on an island to a bulky stick nest in a low tree. These birds nest in colonies, usually on islands.
Pesticides like DDT and dieldrin threatened its future in the southeast United States and California in the early 1970s. Pesticides also threatened the pelican population in Florida in this period. A research group from the University of Tampa headed by Dr. Ralph Schreiber conducted research in the Tampa Bay/St Petersburg area and found that DDT caused the pelican eggshells to be overly-thin and incapable of supporting the embryo to maturity. As a result of this research, DDT usage was eliminated in Florida and the rest of the country.
Along with the American White Pelican, the Brown Pelican is protected by the Migratory Bird Treaty Act of 1918.
There are four subspecies:
P. o. californicus (California Brown Pelican)
P. o. carolinensis (Eastern Brown Pelican)
P. o. occidentalis (Caribbean Brown Pelican)
P. o. thagus (Galapagos Brown Pelican)
The Peruvian Pelican, Pelecanus thagus, used to be considered a subspecies of the Brown Pelican (P. o. thagus). However, due to its well-defined allopatry and because it is much larger and heavier than its relatives, it was reclassified as a separate species.

Wednesday, July 11, 2007

Western Meadowlark

The Western Meadowlark (Sturnella neglecta) is a medium-sized blackbird, very similar in appearance to the Eastern Meadowlark.
Adults have yellow underparts with a black "V" on the breast and white flanks with black streaks. The upperparts are mainly brown with black streaks. They have a long pointed bill; the head is striped with light brown and black.
Their breeding habitat is grasslands and prairie, also pastures and abandoned fields, across western and central North America to northern Mexico. Where their range overlaps with the eastern species, these birds prefer thinner, drier vegetation; the two birds generally do not interbreed but do defend territory against each other. The nest is on the ground, covered with a roof woven from grasses. There may be more than one nesting female in a male's territory. The nest is sometimes destroyed by mowing operations with eggs and young in them.
Western Meadowlark will interbreed with the Eastern Meadowlark where their ranges overlap, though their offspring are infertile.[citation needed]
These birds are permanent residents throughout much of their range. Northern birds migrate to the southern parts of the range; some birds also move east in the southern United States.
These birds forage on the ground or in low to semi-low vegetation, sometimes probing with its bill. They mainly eat insects as well as seeds and berries. In winter, they often feed in flocks.
This bird has a flute-like warbled song, unlike the simple whistled call of the Eastern Meadowlark. They were considered to be the same species for some time; the western species, having been overlooked for some time, was given the species name neglecta.
This is the state bird of Kansas, Montana, Nebraska, North Dakota, Oregon and Wyoming.

Tuesday, July 10, 2007

American Goldfinch

The Eastern or American Goldfinch (Carduelis tristis), also known as the Wild Canary, is a North American bird in the finch family. It is migratory, ranging from southern Canada to North Carolina during the breeding season, and from just south of the Canadian border to Mexico during the winter.
The only finch in its subfamily which undergoes a complete molt, the American Goldfinch displays sexual dimorphism in its coloration; the male is a vibrant yellow in the summer and an olive color during the winter months, while the female is a dull yellow-brown shade which brightens only slightly during the summer. The male displays brightly colored plumage during the breeding season to attract a mate.
The American Goldfinch is granivorous and adapted for the consumption of seedheads, with a conical beak to remove the seeds and agile feet to grip the stems of seedheads while feeding. It is a social bird, and will gather in large flocks while feeding and migrating. It may behave territorially during nest construction, but this aggression is short-lived. Its breeding season is tied to the peak of food supply, beginning in late July, which is relatively late in the year for a finch. This species is generally monogamous, and produces one brood each year.
Human activity has generally benefited the American Goldfinch. It is often found in residential areas, attracted to bird feeders installed by humans, which increases its survival rate in these areas. Deforestation by humans also creates open meadow areas which are the preferred habitat of the American Goldfinch.