The Blue Jay (Cyanocitta cristata) measures 9–12 inches from bill to tail and weighs 2.5–3.5 oz, with a wingspan of 13–17 in. 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. They are widespread throughout Eastern and Central United States.
They are a noisy, bold and aggressive passerine. A moderately slow flier, it flies with body and tail held level, with slow wing beats. Due to its slow flying speeds, this species makes easy prey for hawks and owls when flying in open areas.
Blue Jays can be beneficial to other bird species, as it may chase predatory birds, such as hawks and owls, and will scream if it sees a predator within its territory. It will often sound an alarm call when hawks or other dangers are near, and smaller birds often recognize this call and hide themselves away accordingly. It may occasionally impersonate the calls of raptors, especially those of the Red-tailed and Red-shouldered Hawks, possibly to test if a hawk is in the vicinity, though also possibly to scare off other birds that may compete for food sources. 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 mobs it until it takes a new roost. However, Blue Jays have also been known to attack or kill other smaller birds. Jays are very territorial birds, and they will chase others from a feeder for an easier meal. Additionally, the Blue Jay may raid other birds’ nests, stealing eggs, chicks, and nests. However, this may not be as common as is typically thought, as only 1% of food matter in one study was compromised by birds. Despite this, other passerines may still mob jays who come within their breeding territories.
They are highly curious and are considered intelligent birds. Young individuals playfully snatch brightly colored or reflective objects, such as bottle caps or pieces of aluminum foil, and carry them around until they lose interest. While not confirmed to have engaged in tool use in the wild, blue jays in captivity have been observed using strips of newspaper as tools to obtain food, while captive fledglings have been observed attempting to open the door to their cages.