Mésangeai du Canada

Identification

The Canada jay is a relatively large songbird, though smaller than other jays. A typical adult Canada jay is between 25 and 33 cm (9.8 and 13.0 in) long. Its wingspan is around 45 cm (18 in). It weighs about 65 to 70 g (2.3 to 2.5 oz). Adults have medium grey back feathers with a lighter grey underside. Its head is mostly white with a dark grey or black nape and hood, with a short black beak and dark eyes. The long tail is medium grey with lighter tips. The legs and feet are black. The plumage is thick, providing insulation in the bird's cold native habitat. Like most corvids, Canada jays are not sexually dimorphic, but males are slightly larger than females. Juveniles are initially coloured very dark grey all over, gaining adult plumage after a first moult in July or August. The average lifespan of territory-owning Canada jays is eight years; the oldest known Canada jay banded and recaptured in the wild was at least 17 years old.<p>A variety of vocalizations are used and, like other corvids, Canada jays may mimic other bird species, especially predators. Calls include a whistled quee-oo, and various clicks and chuckles. When predators are spotted, the bird announces a series of harsh clicks to signal a threat on the ground, or a series of repeated whistles to indicate a predator in the air.

Taxonomie

In 1760 the French zoologist Mathurin Jacques Brisson included a description of the Canada jay in his Ornithologie based on a specimen collected in Canada. He used the French name Le geay brun de Canada and the Latin Garralus canadensis fuscus. Although Brisson coined Latin names, these do not conform to the binomial system and are not recognised by the International Commission on Zoological Nomenclature. When in 1766 the Swedish naturalist Carl Linnaeus updated his Systema Naturae for the twelfth edition, he added 240 species that had been previously described by Brisson. One of these was the Canada jay. Linnaeus included a brief description, coined the binomial name Corvus canadensis and cited Brisson's work.<p>William John Swainson named it Dysornithia brachyrhyncha in 1831. French ornithologist Charles Lucien Bonaparte assigned the Canada jay to the genus Perisoreus in 1838 in A geographical and comparative list of the birds of Europe and North America, along with the Siberian jay, P. infaustus. The Canada jay belongs to the crow and jay family Corvidae. However, it and the other members of its genus are not closely related to other birds known as jays; they are instead close to the genus Cyanopica, which contains the azure-winged magpie. Its relatives are native to Eurasia, and ancestors of the Canada jay are thought to have diverged from their Old World relatives and crossed Beringia into North America.<p>A 2012 genetic study revealed four clades across its range: a widespread "boreal" or "taiga" clade ranging from Alaska to Newfoundland and ranging south to the Black Hills of South Dakota, Wyoming and Utah in the west and New England in the east, a "transcascade" clade in eastern Washington and Oregon and ranging into Alberta and Montana, a "Rocky Mountains (Colorado)" clade from the southern Rocky Mountains, and a "Pacific" clade from coastal British Columbia, Washington, and southwestern Oregon. There was also a population of the boreal clade in the central Rocky Mountains between the Colorado and transcascade clades. Genetic dating suggests the Pacific clade diverged from the common ancestor of the other clades around three million years ago in the Late Pliocene.<p>The boreal clade is genetically diverse, suggesting that Canada jays retreated to multiple areas of milder climate during previous ice ages and recolonized the region in warmer times.<p>In 2018 the common name was changed from grey jay to Canada jay by the American Ornithological Society in a supplement to their Check-list of North American Birds. This change was also made in the online list of world birds maintained on behalf of the International Ornithologists' Union by Frank Gill and David Donsker.<p>Nine subspecies are recognized:<p>Two additional subspecies were formerly recognized:

Nom scientifique

Perisoreus canadensis

Autorité

(Linnaeus, 1766)

Ordre

Passériformes

Famille

Corvidés

Genre

Perisoreus

Répartition et habitat

The Canada jay's range spans across northern North America, from northern Alaska east to Newfoundland and Labrador, and south to northern California, Idaho, Utah, east-central Arizona, north-central New Mexico, central Colorado, and southwestern South Dakota. It is also found in the northern reaches of the states of Minnesota, Wisconsin, Michigan, the Adirondacks in New York, and New England. The Canada jay may wander north of the breeding range. In winter it travels irregularly to northwestern Nebraska, central Minnesota, southeastern Wisconsin, central Michigan, southern Pennsylvania, central New York, Connecticut, and Massachusetts. Fossil evidence indicates the Canada jay was found as far south as Tennessee during the last ice age.<p>The vast majority of Canada jays live where there is a strong presence of black spruce (Picea mariana), white spruce (P. glauca), Engelmann spruce (P. engelmannii), jack pine (Pinus banksiana), or lodgepole pine (P. contorta). Canada jays do not inhabit the snowy, coniferous, and therefore seemingly appropriate Sierra Nevada of California where no spruce occur. Nor do Canada jays live in lower elevations of coastal Alaska or British Columbia dominated by Sitka spruce (Picea sitchensis). The key habitat requirements may be sufficiently cold temperatures to ensure successful storage of perishable food and tree bark with sufficiently pliable scales arranged in a shingle-like configuration that allows Canada jays to wedge food items easily up into dry, concealed storage locations. Storage may also be assisted by the antibacterial properties of the bark and foliage of boreal tree species. An exception to this general picture may be the well-marked subspecies P. c. obscurus. It lives right down to the coast from Washington to northern California in the absence of cold temperatures or the putatively necessary tree species.

Migration

Resident species

Comportement

The Canada jay typically breeds at two years of age. Monogamous pairs remain together for life, though a bird will pair up with a new partner if it is widowed. Breeding takes place during March and April, depending on latitude, in permanent, all-purpose territories. Second broods are not attempted, perhaps allowing greater time for food storage.<p>Breeding is cooperative. During the nest-building phase of the breeding season, Canada jay breeding pairs are accompanied by a third, juvenile bird. A 1991 field study in Quebec and Ontario found that approximately 65% of Canada jay trios included a dominant juvenile from the pair's previous breeding season, and approximately 30% of trios included non-dominant juveniles who had left their parents' territory. Occasionally, two nonbreeding juveniles accompany a pair of adults. The role of juveniles is in allofeeding (food sharing) by retrieving caches and bringing food to younger siblings, but this is only allowed by the parents during the post-fledgling period. Until then, parents will drive the other birds away from the nest. This may reduce the frequency of predator-attracting visits to the nest when young are most vulnerable. The benefits of juveniles participating in subsequent brood care may include "lightening the load" for the breeding pair, which may possibly increase longevity, reducing the probability of starvation of nestlings, and detecting and mobbing predators near the nest. Dominant juveniles may eventually inherit the natal territory and breed, while unrelated juveniles may eventually fill a vacancy nearby or form a new breeding pair on previously unoccupied ground.<p>Breeding Canada jays build nests and lay eggs in March or even February, when snow is deep in the boreal forest. Male Canada jays choose a nest site in a mature conifer tree; the nests are found most commonly in black spruce, with white spruce and balsam fir (Abies balsamea) also used, in Ontario and Quebec. With the male taking a lead role in construction, nests are constructed with brittle dead twigs pulled off of trees, as well as bark strips and lichens. The cup is just large enough to contain the female and her eggs, measuring about 3 in (76 mm) wide and 2 in (51 mm) deep. Insulation is provided by cocoons of the forest tent caterpillar (Malacosoma disstria) filling the interstitial spaces of the nest, and feathers used to line the cup. Nests are usually built on the southwestern side of a tree for solar warming and are usually less than one nest diameter from the trunk. Nest height is typically 8 to 30 ft (2.4 to 9.1 m) above the ground. The average height of 264 nests surveyed in Algonquin Provincial Park was 16 ± 9.2 ft (4.9 ± 2.8 m) above ground.<p>A clutch consists of 2 to 5 light green-grey eggs with darker spots. The mean clutch sizes of Canada jays in Algonquin Provincial Park and La Verendrye Provincial Park were 3.03 and 3.18 eggs, respectively. Incubation is performed only by the female and lasts an average of 18.5 days. The female is fed on the nest by her partner, rarely moving from the nest during incubation and for several days after hatching.<p>Canada jay young are altricial. For the first three to four days after hatching, the female remains on the nest; when the male arrives with food, both parents help in feeding the nestlings. Nestling growth is most rapid from the fourth through the tenth day following hatching, during which time the female begins to participate in foraging. The parents carry food to the nest in their throats. The accompanying nonbreeding third bird does not help with feeding during this period but is driven away by the parents if it approaches the nest. Food is a dark brown, viscous paste containing primarily arthropods. Young Canada jays leave the nest between 22 and 24 days after hatching, after which the third bird begins to participate in foraging and feeding. Natal dispersal distance for the Canada jay is a median of 0.0 km for males, 2.8 km (1.7 mi) for females, and a maximum distance of 11.3 km (7.0 mi) for males and females.<p>After 55 to 65 days, juveniles reach full adult measurements and battle among themselves until a dominant juvenile forces its siblings to leave the natal area. The dominant bird remains with its parents until the following season, while its siblings leave the natal territory to join an unrelated pair who failed to breed. In a study by Dan Strickland, two-thirds of dominant juveniles were male.<p>In studies conducted in Ontario and Quebec, the mortality rate for dominant juveniles was 52%, and mortality was 85% for juveniles who left the parents' territory between fledging in June to approximately mid-October. From fall to the following breeding season in March, further juvenile mortality was 50%. Territory-holding adult Canada jays experienced low mortality rates (15.1 and 18.2% for males and females, respectively). The oldest known Canada jay recaptured in the wild was at least 17 years old.<p>Canada jays are omnivorous. They hunt such prey as arthropods, worms, small mammals including rodents, shrews, and juvenile bats, eggs, and nestling birds, and have even been recorded taking a magnolia warbler (Dendroica magnolia) in flight. They have been reported to opportunistically hunt young amphibians such as the western chorus frog (Pseudacris triseriata) in Chambers Lake, Colorado, and the long-toed salamander (Ambystoma macrodactylum) in Whitehorse Bluff in Crater Lake National Park, Oregon. Canada jays have been seen landing on moose (Alces alces) to remove and eat engorged winter ticks (Dermacentor albipictus) during April and May in Algonquin Provincial Park. Researchers also found a Canada jay nest containing a brooding female, three hatchlings, and three warm, engorged winter deer ticks. Because the ticks were too large for the hatchlings to eat, it was hypothesized that the ticks may have served as "hot water bottles", keeping hatchlings warm when parents were away from the nest.<p>Nestling birds are common prey, being taken more often from nests in trees rather than on the ground. Canada jays find them by moving from perch to perch and scanning surroundings. Avian nest predation by Canada jays is not necessarily higher in fragmented versus unfragmented forest. Evidence from studies in the Pacific Northwest suggest a moderate increase in nest predation in logged plots adjacent to mature conifer forest, which is the Canada jay's preferred habitat. Studies of nest predation by Canada jays in Quebec have shown that the birds prefer preying on nests in open forest with high prominence of jack pine, and greater rates of predation in riparian forest strips and green-tree retention stands versus clearcuts. This may be due to increased availability of perch sites for avian predators such as the Canada jay. Canada jays are suspected but not proven to prey on nests of the threatened marbled murrelet (Brachyramphus marmoratus) in coastal areas of the Pacific Northwest.<p>Carrion, fungi, fruits such as chokecherry (Prunus virginiana), and seeds are also eaten. They've been known to use bird feeders provided by humans. Two Canada jays were seen eating slime mold (Fuligo septica) near Kennedy Hot Springs in the Glacier Peak Wilderness, Washington. This was the first report of any bird consuming slime mold in the field. Risk and energy expenditure are factors in food selection for the Canada jay, which selects food on the basis of profitability to maximize caloric intake. Increased handling, searching, or recognition times for a preferred food item lowers its profitability. Canada jays wrench, twist, and tug food apart, unlike other birds known as jays (such as the blue jay, Cyanocitta cristata), which grasp and hammer their food. Canada jays commonly carry large food items to nearby trees to eat or process for storage, possibly as defense against large scavengers.<p>The Canada jay is a "scatterhoarder", caching thousands of food items during the summer for use the following winter, and enabling the species to remain in boreal and subalpine forests year round. Any food intended for storage is manipulated in the mouth and formed into a bolus that is coated with sticky saliva, adhering to anything it touches. The bolus is stored in bark crevices, under tufts of lichen, or among conifer needles. Cached items can be anything from carrion to bread crumbs. A single Canada jay may hide thousands of pieces of food per year, to later recover them by memory, sometimes months after hiding them. Cached food is sometimes used to feed nestlings and fledglings.<p>When exploiting distant food sources found in clearings, Canada jays were observed temporarily concentrating their caches in an arboreal site along the edge of a black spruce forest in interior Alaska. This allowed a high rate of caching in the short term and reduced the jay's risk of predation. A subsequent recaching stage occurred, and food items were transferred to widely scattered sites to reduce theft.<p>Caching is inhibited by the presence of Steller's jays (Cyanocitta stelleri) and Canada jays from adjacent territories, which follow resident Canada jays to steal cached food. Canada jays carry large food items to distant cache sites for storage more often than small food items. To prevent theft, they also tend to carry valuable food items further from the source when caching in the company of one or more Canada jays. Scatterhoarding discourages pilferage by competitors, while increased cache density leads to increased thievery. In southern portions of the Canada jay's range, food is not cached during summer because of the chance of spoilage and the reduced need for winter stores.

Conservation

Tendance de la population

declining