Blue Jay (Cyanocitta cristata) - wiki
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[Photo] English: Blue Jay (Cyanocitta cristata) ??? Algonquin Provincial Park, Canada (Fran??ais : Geai bleu (Cyanocitta cristata) - Parc Naturel d'Algonquin, Canada). Date 2005 December. Author Mdf http://commons.wikimedia.org/wiki/User:Mdf
The Blue Jay (Cyanocitta cristata) is a passerine bird and member of the crow family Corvidae native to North America. It is adaptable, aggressive and omnivorous.
The Blue Jay is about 30 cm (10-12 in) in length from the bill to tail and 70-100 g (2.47-3.53 ounces), with a wingspan of 34-43 cm (13-17 in).  Its plumage is lavender-blue to mid-blue in the crest, back, wings, and tail, and its face is white. The underside is off-white and the neck is collared with black which extends to the sides of the head. The wing primaries and tail are strongly barred with black, sky-blue and white. They can be aggressive towards other birds. They are known to approach humans confidently. The bill, legs, and eyes are all black. Males and females are nearly identical; males are slightly larger.  There is a pronounced crest on the head, a crown of feathers, which may be raised or lowered according to the bird’s mood. When excited or aggressive, the crest may be fully raised. When frightened, the crest bristles outwards, brushlike. When the bird is feeding among other jays or resting, the crest is flattened to the head. 
As with other blue-hued birds, the Blue Jay's coloration is not derived by pigments, but is the result of light refraction due to the internal structure of the feathers; if a Blue Jay feather is crushed, the blue disappears as the structure is destroyed. This is referred to as structural coloration.
 Distribution and habitat
The Blue Jay occurs from southern Canada south to Texas and Florida. It breeds in mixed-wood forests, deciduous forests, parks, and residential areas from Canada in the north, through eastern North America, and south to Florida and northeastern Texas. The western edge of the range stops where the arid pine forest and scrub habitat of the closely related Steller's Jay begins. Recently, the range of the Blue Jay has extended to the Northwest so that it is now a regular but still-rare autumn migrant along the northern Pacific Coast. 
The Blue Jay is partially migratory. It may withdraw several hundred kilometres south in the northernmost parts of its range. It migrates during the daytime, in loose flocks of 5 to 250 birds. The Blue Jay occupies a variety of habitats within its large range, from the pine woods of Florida to the spruce fir forests of northern Ontario. It is less abundant in the heavier forests, preferring mixed woodlands with oaks and beeches.
The Blue Jay is generally aggressive toward other birds and it will chase birds from feeders or other food sources. It may chase birds of prey, such as hawks and owls, which occasionally prey on jays, and will scream if it sees a predator within its territory. It may also be aggressive towards humans who come close to its nest, and if an owl roosts near the nest during the daytime, the Blue Jay attacks it until it takes a new roost. The Blue jay is a slow flier and an easy prey for hawks and owls, when it flies in open lands. It flies with body and tail held level, with slow wing beats.
The Blue Jay is known to be a raider of other bird's nests. It may steal eggs, chicks, and nests. It appropriates American Robin nests. Young jays collect brightly coloured or reflective objects, such as bottle caps or pieces of aluminium foil, and carry them for a moment.
Blue Jays in captivity have been observed using strips of newspaper as tools to obtain food.
The voice is typical of most jays in being varied, but the most commonly recognized sound is the alarm call, which is a loud, almost gull-like scream. There is also a high-pitched jayer-jayer call that increases in speed as the bird becomes more agitated. Blue Jays will use these calls to band together to drive a predator such as a hawk away from their nest.
Blue Jays also have quiet, almost subliminal calls which they use among themselves in proximity. One of the most distinctive calls of this type is often referred to as the "rusty pump" owing to its squeaky resemblance to the sound of an old hand-operated water pump. In fact, they can make a large variety of sounds, and individuals may vary perceptibly in their calling style. Like other corvids, blue jays may learn to mimic human speech. 
Its food is sought both on the ground and in trees and includes virtually all known types of plant and animal sources, such as acorns and beech mast, weed seeds, grain, fruits and other berries, peanuts, bread, meat, eggs and nestlings, small invertebrates of many types, scraps in town parks and bird-table food.
The breeding season begins in mid-March, peaks in mid-April to May, and extends into July. Any suitable tree or large bush may be used for nesting, though an evergreen is preferred, and the nest is built at a height of 3 to 10 m.The adults build a cup-shaped nest of twigs, small roots, bark strips, moss, other plant material, cloth, paper, and feathers, with occasional mud added to the cup.
Both sexes build the nest and rear the young, though only the female broods them. The male feeds the female while she is brooding the eggs. There are usually 4???5 eggs laid and incubated over 16???18 days. The young are fledged usually between 17???21 days. Blue Jays typically form monogamous pair bonds for life. After the juveniles fledge, the family travels and forages together until early fall.
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