Sunday, December 14, 2008

飛 a Couple of Common Goldeneyes, Lake Ontario Toronto Dec 13 2008

The Common Goldeneye (Bucephala clangula) is a medium sized sea duck of the genus Bucephala, the goldeneyes. Their closest relative is the similar Barrow's goldeneye.
Adult males ranges from 45-52 cm (18-21 inches) and from 888 to 1400 grams (1.9 to 3.1 lbs), while females range from 40-50 cm (16-20 inches) and from 500 to 1182 grams (1.1 to 2.6 lbs). The species is aptly named for its golden-yellow eye. Adult males have a dark head with a greenish gloss and a circular white patch below the eye, a dark back and a white neck and belly. Adult females have a brown head and a mostly grey body. Their legs and feet are orange-yellow.
Their breeding habitat is the taiga. They are found in the lakes and rivers of boreal forests across Canada and the northern United States, Scandinavia and northern Russia . They are migratory and most winter in protected coastal waters or open inland waters at more temperate latitudes. Naturally, they nest in cavities in large trees. They will readily use nestboxes, and this has enabled a healthy breeding population to establish in Scoltand where they are increasing and slowly spreading with the help of nestboxes. They are usually quite common in winter around lakes of Britain and some are being encouraged to nest in nestboxes which are put up to try and have them there all year round.
Often the natural tree cavities are made by broken limbs, unless they are made by pileated woodpeckers or black woodpeckers, the only tree-cavity-making animals who make a cavity large enough to normally accommodate a goldeneye. Average egg size is a breadth of 43.3 mm (1.7 inches), a length of 59.3 mm (2.3 inches) and a weight of 64 grams (2.3 oz). The incubation period ranges from 28 to 32 days. The female does all the incubating and is abandoned by the male about 1 to 2 weeks into incubation. The young remain in the nest for about 24-36 hours. Brood parasitism is quite common both with other common goldeneyes as well as other duck species and even tree swallow and European starling eggs have been found mixed with goldeneye eggs! The broods commonly start to mix with other females' broods as they become more independent. Goldeneye young have been known to be competitively killed by other goldeneye mothers, common loons and red-necked grebes. The young are capable of flight at 55-65 days of age.
These diving birds forage underwater. Year-round, about 32% of their prey is crustaceans, 28% is aquatic insects and 10% is molluscs. Insects are the predominant prey while nesting and crustaceans are the predominant prey during migration and winter. Locally, fish eggs and aquatic plants can be important foods. They themselves may fall prey to various hawks, owls and eagles, while females and their broods have been preyed upon by bears, various weasels, mink, raccoons and even northern flickers and red squirrels.
The common goldeneye is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.
Approximately 188,300 common goldeneyes were killed by duck hunters in North America during the 1970s, representing about 4% of the total number of ducks killed in the region during that period. The rate is probably similar today. Both the breeding and winter habitat of these birds has been degraded by clearance and pollution. However, this is the only duck in North America known to derive short-term benefits from lake acidification.

Thursday, December 4, 2008

猛禽 Watch-Vulture for the holy Crater, Condor Volcan Masaya Nicaragua 2005

Though the vulture looks ugly and even dum with bold head,
when you see them hover around high above the sky with the giant wings you might fall in love with them.

They are gregarious so they usually hover or flock together but now I see the very lonely one keep standing and watching down the hole of the fuming crater.
I like to call him Watch Vulture of Volcan Masaya..

It soars high while searching for food, holding its wings horizontally when gliding. It flaps in short bursts which are followed by short periods of gliding. Its flight is less efficient than that of other vultures, as the wings are not as long, forming a smaller sail surface. In comparison with the Turkey Vulture, the American Black Vulture flaps its wings more frequently during flight. It is known to regurgitate when approached or disturbed, which assists in predator deterrence and taking flight by decreasing its takeoff weight. Like all New World Vultures, the American Black Vulture often defecates on its own legs, using the evaporation of the water in the feces and/or urine to cool itself, a process known as urohydrosis. It cools the blood vessels in the unfeathered tarsi and feet, and causes white uric acid to streak the legs. Because it lacks a syrinx, the American Black Vulture, like other New World Vultures, has very few vocalization capabilities. It is generally silent, but can make soft hisses and grunts.
(Close Shot of the vulture: photo source : Wikipedia)
The American Black Vulture is gregarious, and roosts in large groups. In areas where their ranges overlap, the American Black Vulture will roost on the bare branches of dead trees with groups of Turkey Vultures. The American Black Vulture generally forages in groups; a flock of Black Vultures can easily drive a Turkey Vulture, which is generally solitary while foraging, from a carcass.
Like the Turkey Vulture, this vulture is often seen standing in a spread-winged stance. The stance is believed to serve multiple functions: drying the wings, warming the body, and baking off bacteria. This same behavior is displayed by other New World vultures, Old World vultures, and storks.