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Scientific name: Cyanocitta cristata
Common name: 
Blue Jay

(Information used in this Species Page was derived, in part from a paper researched by Bill Mentecky for a Biology 220W class in Spring 2000 at Penn State New Kensington)

The blue jay is an active, noisy, bright blue bird with a distinctive head crest, black necklace, gray-white underbelly, and white spots on both its wings and on its tail. The adult blue jay is 11 to 12 1/2 inches long (slightly bigger than a robin) and is absolutely unmistakable in any of its habitats. They are found naturally in forest edge communities but have developed such a tolerance of human beings that they occur in increasingly large numbers in almost any human inhabited or modified ecosystem. Male and female blue jays have identical plumages and can be absolutely identified only by their mating and nesting behaviors. Blue jays molt their feathers once a year, usually in July and August, and often appear rather ratty and drab just prior to molting.

The vocalizations made by blue jays are as distinctive and as definitive as their plumage. From a loud piercing "jeeah" scream to a rounded, flute-like whistle, the blue jay seems to spend a great deal of its time and energy communicating. Just to whom and for what purpose these communications are intended are not always obvious.

Social Groups
Blue jays are most often seen in groups. Some groups represent families (the adult mating pair and the three to five recently fledged individuals) which persist throughout the summer and fall following birth. Larger groups may form, though, from the merging of any number of these smaller familial groups. These multi-family groups are especially seen in habitats with very abundant sources of food. The onset of winter, though, breaks up these larger flocks into small groups of four to six birds that disperse themselves through the increasingly resource limited habitat. Blue jays do not characteristically migrate except in the most northern reaches of their North American range (southern Canada). Blue jays are remarkably tolerant of other blue jays and occupy widely overlapping ranges at all stages of their lives. Non-parental adults are even allowed to land near or on nests containing eggs, nestlings or fledglings. Complex visual displays including head bobbings, feather and crest fluffing etc. between individuals seem to be used to establish social positions, intent and degrees of dominance.

Courtship and Mating
Courtship in blue jays begins in February and, like most of the other aspects of their lives, involves complex group behaviors and displays. A group of three to ten individuals forms in the late winter. The focus of this group is a single female whose activities determines the behavior of the group. When the focus female flies, the group flies. When the focus females lands, the groups lands, etc. When the group is flying, its individuals make a staggering amount of noise. When they land, there is a moment of silence and stillness which is then broken by aggressive head bobbing and feather fluffing on the parts of the males. As the days pass the size of the courtship group gets smaller until there is a single pair of birds (the focus female and a single male) remaining. This pair then displays a quiet sequence of feather fluffing and ritualistic feeding behaviors away from the on-going noise of other courtship groups that are preludes to actual mating.

Mating pair individuals work together to build nests. These nests are located in the forked branches of almost any species of tree. The nest is cup shaped and is constructed of roots, sticks and a wide variety of human-made and natural materials. All of these building materials are then cemented together with mud. Initially, the male gathers sticks and other building materials and brings them to the female who assembles them first into a sequence of "practice" nests. After several of these partially constructed preliminary nests are begun and abandoned, the pair begins work on the actual breeding nest. During this final stage of the nest building project it is the female that does most of the actual gathering and building. It takes about a week for the nest to be built. Occasionally, a mating pair of blue jays will appropriate a nest of another bird species and then use it as their breeding nest. 

The breeding season for blue jays is quite long, from March to July. In a given locale mating pairs emerge from the courtship groups at any time during this five month season. Older birds seem to pair and mate earlier in the season than younger individuals.

The blue jay clutch consists of three to five eggs that will hatch after a sixteen to eighteen day incubation. The female does most of incubation and is fed and protected by the male during her nest sitting. Young jays will stay near their birth nests even after fledging and will, as mentioned previously, form familial groups with the parental birds that will persist until the onset of winter.

Blue jays react violently and in numbers to the intrusion of a potential predator. House cats and squirrels consume both eggs and nestlings of the blue jay and are each prime triggers for blue jay protection behaviors. When either of these animals enter a blue jay nesting area they typically mobbed by not only the nesting pair in the immediate area but also by adjacent nesting and non-nesting individuals. The mobbing behavior consists of both loud calling and swooping dives and even actual contact and physical injury to the intruder. Hawks are also mobbed by blue jays and are driven away from the nesting areas.

Feeding Behavior
Blue jays eat a great variety of foods from both plant and animal sources. Insects and other invertebrates, seeds, nuts (especially acorns), fruits, carrion, small vertebrates (including frogs, mice, and nestlings of other bird species), and the eggs of other bird species are some of the documented foods of blue jays. Bird feeding areas that have sunflower seeds or corn especially spilled onto the ground are also frequently visited by blue jays. This penchant of blue jays to consume both the eggs and the nestlings of other birds has been implicated as an important factor in the significant decline of songbird populations throughout North America. The increasing numbers of the extremely human tolerant blue jay greatly amplifies this deleterious ecological impact. This is a very serious consequence of the activity of this otherwise easily admired bird.

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