Cool Facts:
Infamous as a destroyer of eggs and nestlings, Blue Jays actually derive only a small percentage of their annual food needs from these sources. Its diet is mostly vegetarian, including especially acorns, beech nuts, and seeds. Blue Jays also eat a variety of animal foods including grasshoppers, beetles, caterpillars, and small vertebrates. Blue Jays are intelligent and adaptable, taking advantage of almost any food resource, and will readily take to back yard bird feeders. In an extensive study of Blue Jay feeding habits, only 1% of jays had evidence of eggs or birds in their stomachs. Most of their diet was composed of insects and nuts. Their fondness for acorns is credited with helping spread oak trees after the last glacial period.
Blue Jays are disliked by many people for their aggressive ways, but they are far less aggressive than many other species. In one Florida study, Red-bellied Woodpeckers, Red-headed Woodpeckers, Florida Scrub-Jays, Common Grackles, and gray squirrels strongly dominates Blue Jays at feeders, often preventing them from obtaining food, and Northern Bobwhites, Mourning Doves, White-winged Doves, Northern Mockingbirds, and Northern Cardinals occasionally dominated them as well. Sometimes Blue Jays mimic hawks when approaching feeders, especially the Red-shouldered Hawk. These calls may provide information to other jays that a hawk is around, or may be used to deceive other species into believing a hawk is present. This may also deceive other birds into scattering, allowing the Blue Jay to take over the feeder, but most birds quickly return after the jay starts feeding. Blue Jays have a wide variety of vocalizations, with an immense "vocabulary." Captive Blue Jays sometimes learn to imitate human speech and meowing cats. and sometimes other species.
Thousands of Blue Jays migrate in flocks along the Great Lakes and Atlantic coasts, but much about their migration remains a mystery. Some are present throughout winter in all parts of their range. Young jays may be more likely to migrate than adults, but many adults also migrate. Some individual jays migrate south one year, stay north the next winter, and then migrate south again the next year. No one has worked out why they migrate when they do.
The pigment in Blue Jay feathers is melanin, which is brown. The blue color is caused by scattering light through modified cells on the surface of the feather barbs. The black bridle across the face, nape, and throat varies extensively and may help Blue Jays recognize one another. Both sexes are similar in appearance.
Blue Jays are known for their intelligence and complex social systems, and have tight family bonds.They often mate for life, remaining with their social mate throughout the year. The oldest known wild, banded Blue Jay lived to be at least 17 years 6 months old.
Only the female incubates; her mate provides all her food during incubation. For the first 8–12 days after the nestlings hatch, the female broods them and the male provides food for his mate and the nestlings. Female shares food gathering after this time, but male continues to provide more food than female.
Some individual nestlings begin to wander as far as 15 feet from the nest 1-3 days before the brood fledges. Even when these birds beg loudly, parents may not feed them until they return to the nest; this is the stage at which many people find an "abandoned baby jay." If it can be restored to or near the nest, the parents will resume feeding it. The brood usually leaves the nest together usually when they are 17-21 days old. When young jays leave the nest before then, it may be because of disturbance. The jays are usually farther than 75 feet from the nest by the end of the second day out of the nest. Young remain with and are fed by their parents for at least a month, and sometimes two months. There is apparently a lot of individual variation in how quickly young become independent.
Blue Jays communicate with one another both vocally and with "body language," using their crest. When incubating, feeding nestlings, or associating with mate, family, or flock mates, the crest is held down; the lower the crest, the lower the bird’s aggression level. The higher the crest, the higher the bird’s aggression level; when a Blue Jay squawks, the crest is virtually always held up. Blue Jays lower their crests when they are feeding peacefully with family and flock members or tending to nestlings.
Blue Jays carry food in their throat and upper esophagus—an area often called a "gular pouch." They may store 2-3 acorns in the pouch, another one in their mouth, and one more in the tip of the bill. In this way they can carry off 5 acorns at a time to store for later feeding. Six birds with radio transmitters each cached 3,000-5,000 acorns one autumn.
The Blue Jay populations have been slightly decreasing throughout their range since 1966, according to the North American Breeding Bird Survey. Partners in Flight estimates the global breeding population at 13 million, with 87 percent living in the U.S. and 13 percent living in Canada. They rate an 8 out of 20 on the Continental Concern Score and are not on the 2012 Watch List. The most frequent cause of death associated with humans comes from attacks by cats and dogs.
Despite being common, conspicuous birds that have been studied by many researchers, much about Blue Jays remains a mystery.
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