Eurasian jay

Name and taxonomy

Carl Linnaeus described the jay in 1758 as Corvus glandarius. Ernst Hartert narrowed the type locality to Sweden in 1903. Mathurin Jacques Brisson set up the genus Garrulus in 1760. Garrulus is Latin for chattering or noisy. The epithet glandarius is Latin for of acorns. The two words together describe a loud bird that lives on acorns.

Steve Madge and Hilary Burn sorted 33 subspecies into eight groups in 1994. The groups differ in the crown, the face and the amount of white in the wing. Birds in south-east Asia carry no white in the wing at all. Himalayan birds have a plain rufous crown and no white wing patch. The IUCN and BirdLife International now split the species into three. They treat the white-faced jay and the plain-crowned jay as separate species.

Evolution and relatives

The jay belongs to the Corvidae, the family of crows, magpies and jackdaws. Two other species share the genus Garrulus with it. It is about the size of a western jackdaw. Like other corvids it remembers where it put food and appears to plan ahead. It carries the tail higher than a crow or a magpie, so the tail feathers wear less.

Unlike most corvids the jay has only two plumages, juvenile and adult. It loses the juvenile plumage by the autumn of its first year. Birds seen in autumn therefore all look adult, which makes ageing hard. Across the range the forms differ so much that the extremes look like separate birds. Those differences probably reflect long isolation in separate forests.

Appearance

The body plumage is a light reddish or pinkish brown. The throat is whitish, and a black moustache stripe runs down each side of it. The crown and forehead are whitish, streaked with black. The bird raises the crown feathers into a crest when it displays. The rump is white and the tail is mostly black. A red-brown triangle marks the point where each wing joins the body.

The blue wing panel is the bird's best-known feature. Fine black bars cross the blue, and the patch widens when the wing opens. White bars on the wing show clearly in flight. The bill is black and the eye is pale. The feathers reflect ultraviolet light, so other jays see more colour than people do. Adults measure 34 to 35 centimetres and weigh about 170 grams. The wings span 52 to 58 cm.

Habitat and range

The jay is a bird of woodland with thick cover. It needs trees, bushes and undergrowth, and it forages on the ground as well. Oak woods give it the best feeding, and conifers give it the best nest sites. It avoids open ground, where hawks catch it more easily. In recent decades it has moved into parks and gardens in towns.

The range covers Europe, north-west Africa and most of temperate Asia. It reaches the Indian subcontinent, Japan and south-east Asia. GBIF holds occurrence records from 86 countries. iNaturalist carries 106,568 observations of the species. Most jays stay in one wood all year. When the acorn crop fails they move in numbers to find food elsewhere.

Home ranges are smaller in winter and spring than in summer and autumn. A range is larger where the habitat is varied. Neighbouring jays overlap a great deal and tolerate each other.

Diet and feeding

The jay eats almost anything it can handle. Acorns make up the largest part of the diet. It bites the shell and levers the pieces apart with the bill. It also takes beechnuts, other seeds, grain, blackberries and rowan berries. Worms, snails, slugs and insects fill out the summer diet. It robs eggs and nestlings, and it kills small birds, small rodents and even bats. Carrion is a regular food, and jays visit about half the carcasses in a wood.

The autumn store is the centre of the jay's year. One bird can bury between 4,500 and 11,000 acorns in a season. It hides them one at a time and can find them again up to ten months later. It usually carries one acorn in the bill and swallows the others into the crop. Jays have carried single acorns as far as 20 kilometres. They choose large, sound acorns and leave dead or damaged ones behind. Captive jays with no acorns will store stones of the right shape instead.

Behaviour and social life

The jay spends most of its time in trees but feeds on the ground too. It plays, and its chases resemble the way it flees from a hawk. Rank between jays shifts and does not depend on strength alone. A male usually ranks above a female, though a moulting male can lose that place. Contests sometimes end in grappling and pulled feathers, and often end without a fight. Jays are not very quarrelsome with each other.

The bird performs anting when wood ants are available. It drops onto the nest and rubs the tail, wings and body over the soil. The ants then crawl over it and spray formic acid into the plumage. This probably kills parasites in the feathers. A jay ants no more often than every other day and bathes in water several times a day.

Male jays take note of what their partner wants when they share food. They also hide food from other jays that might steal it. Like other corvids they appear to prepare for a need that has not arrived yet.

Communication and senses

The best-known call is a harsh screech. The bird gives it when it sees a predator, and also as an advertisement. The appeal note asks for something, and a young bird uses it to beg. An adult sometimes gives the same note while foraging alone. Jays also have calls for anger, play, affection and alarm.

The jay is a fine mimic. It copies the mew of a common buzzard and the cackle of a goshawk. It also copies crying babies, dripping taps and lawn mowers. A mobbing jay uses the alarm calls of blackbirds, magpies and tawny owls. A relaxed jay copies woodpeckers, sparrows and human whistling. Young jays practise a sound until the copy is exact.

Visual display matters as much as sound. A jay raises its feathers, spreads the wings and shifts its posture. A very submissive bird spreads the wings fully, and a bolder one only part way. Because the plumage reflects ultraviolet light, the display looks brighter to another jay.

Reproduction and life cycle

Jays pair for life and raise one brood a year. Unpaired birds gather in March and April to find mates. A gathering may hold three or four birds, or thirty and more. Males display more than females and chase them through the trees. A male crushes food and offers a piece to the female. The pair may pull the food back and forth before one of them eats it.

Both birds build a cup nest of sticks in a tree or a bush. The nest usually sits 2 to 5 metres up, close to the trunk. Twigs 3 to 15 millimetres thick form the base, and roots, grass, moss and feathers line it. The female lays 3 to 6 pale green or olive eggs with fine dark speckles. Each egg measures about 31.3 by 23.0 millimetres and weighs about 8.5 grams. The eggs hatch after 16 to 19 days.

The male feeds the female while she sits. Both parents feed the chicks, which hatch naked and blind. The young fledge after 19 to 23 days but stay dependent on the pair. The parents feed them until they are 6 to 8 weeks old. Most jays first breed at two years of age. The oldest known wild jay reached 17.9 years.

Predators and threats

Birds of prey take most adult and fledgling jays. Pine martens and cats take eggs and young. A jay that sees a hawk overhead freezes and gives a low moan. Mobbing is the usual answer to a predator on the ground or in a tree. A threatened jay may copy the call of a tawny owl to frighten the attacker.

A jay leaving its nest may fly out of sight and then imitate a carrion crow. A sitting bird crouches with the bill open as a predator comes nearer. If the danger is very close it spreads the wings and threatens. As a last resort it flies at the intruder and strikes with claws and bill. A poor acorn crop forces jays to leave the wood and search elsewhere. Loss of woodland and shooting also reduce local numbers.

Population and conservation

The IUCN lists the Eurasian jay as Least Concern. The range is enormous and the population runs into millions. No decline has been detected across the range as a whole. Britain holds about 170,000 breeding pairs. The bird is green-listed there, the lowest level of concern.

The species has moved into towns as woodland has been cleared. That move may soften the loss of forest. The three-way split proposed by BirdLife International changes how the range is counted. Under that scheme the white-faced jay and the plain-crowned jay probably need their own assessments. The jay is still shot as a nest robber in some countries.

Relationship with humans

The jay does no measurable harm to people. Gamekeepers once killed it because it takes eggs and chicks. It eats many pest insects in return. Foresters now value it for the oak seedlings it plants. The National Trust credits jays with spreading the holm oaks at Ventnor on the Isle of Wight.

Researchers in Sweden costed the work that jays do for nothing. They put hand planting in a 2,700 hectare park at 1 to 6 million kroner. A German study found oaks returning to a pine forest at 2,000 to 4,000 trees per hectare. No parent oaks stood nearby, so the jays probably carried every acorn in. A tame jay will beg from its owner and give the same submissive display it gives a jay.

In culture and myth

The jay appears in a classical fable about borrowed feathers. A bird dresses itself in feathers taken from others and is stripped of them. The Greek telling uses a daw, and the Latin telling a jackdaw or a jay. Phaedrus preserved the Latin form, and Jean de la Fontaine retold it in French. The moral warns against claiming a rank you have not earned.

Horace turned the story on a poet who borrowed from other writers. Robert Greene reached for the same image in his attack on Shakespeare. The fable gave English the phrase about strutting in borrowed plumes. Dutch painters and later cartoonists returned to the scene many times.

In British woodland tradition the jay is the planter of oaks. Foresters now describe the bird as a free labour force. The screech of a jay warns other woodland animals, and red squirrels react to it. In autumn the sight of jays crossing open ground with acorns marks the season.