Siberian Jay

The species has a complex and unusual social structure. Siberian jays live in small flocks of 2-7 individuals, with the dominant breeding pair at the centre of the group; alongside retained multigenerational offspring and unrelated immigrants. Within a group, there is a dominance hierarchy; whereby males are dominant over females and breeders are dominant over non-breeders; with some male non-breeders being dominant over female breeders. Flock composition varies, with some comprising only family members, families associated with nonrelated immigrants, and others containing only nonrelated individuals. Immigrated unrelated individuals can be tolerated within the territory outside nesting areas. At least one offspring usually remains with the parents after successful reproduction and regularly accompanies the pair for at least a year before dispersing; although some retained offspring delay dispersal for up to five years. These are the dominant offspring, which out-compete and expel their subordinate siblings. The dispersed subordinate individuals (which disperse in their first summer) settle as non-breeding immigrants in other existing flocks and tend to disperse much further than their dominant siblings, which more often move straight into a breeding position in a new territory. Unusually for a group living species of Corvidae, group members do not help the parents raise younger siblings in future cohorts (there is no cooperative breeding) and so offspring retention is not explained by cooperative breeding. Groups also unusually stay together outside the breeding season. Retention of some offspring in the natal territory after fledging is probably explained by nepotism which parents show toward them. Parents provide retained offspring with reliable access to resources and antipredator protection, thereby imparting to them a survival advantage (in turn with an inclusive fitness advantage to the parents). Although delayed dispersal of offspring may be explained by “queueing” for available high-quality territories for the offspring to occupy, the influence of nepotism has been shown experimentally. In removal experiments in which a father alpha male in a group was replaced with a new male unrelated to the offspring, the offspring were more likely to disperse prematurely; probably because the new male did not impart the same nepotistic advantages to the now unrelated young. Although retained offspring may incur an initial cost of postponing breeding, this may be offset by enhanced breeding success later in life as a result of resource advantages gained from nepotistic parents; and late dispersers have been found to have higher lifetime reproductive success than early dispersers. Siberian jays also display nepotistic alarming calling and these calls may function as a warning to conspecifics of an approaching predator. Warning calls have been shown experimentally to decrease reaction time in response in an approaching predator and improve survival within non-breeding individuals. However, females seem more able than males to differentiate between kin and non-kin(Griesser and Ekman, 2004). Alongside direct warning to family group members, nepotistic alarm calling by a breeding female may also function to divert predator attention away from her offspring. Siberian jays are aggressive to non-related intruders on their territory. Two different aggressive responses from territory holders within feeding grounds have been observed:(1) the intruder is approached and forced away (2) or is chased in flight; although the latter behaviour is more costly to the aggressor. Although breeders show considerably more aggression toward immigrants than retained offspring, aggressive responses appear to be modified by social dominance within groups. For example, females have been found to receive notably more aggression than males because males show more resistance owing to their higher social dominance, therefore leading to higher energy cost by the aggressor. Siberian jays also appear to recognise their own young through associative learning as opposed to genetic cues, as shown by experiments in which Siberian jays did not differentiate between own and fostered offspring.

The Siberian jay is resident in the northern boreal forests of spruce, pine, cedar and larch stretching from Scandinavia to northern Russia and Siberia. It has an extensive range estimated at 19,300,000 square kilometres (7,500,000 square miles) and is native to Norway, Sweden, Finland, Russia, Mongolia, Kazakhstan and China. It is vagrant in Belarus, Estonia, Latvia, Poland, Slovakia and Ukraine. Although the species is largely sedentary, some individuals in the east of the range may move southwards in winter. This jay favours dense, mature forest habitat with closed canopy within lowlands and foothills. Spruce forest is the preferred foraging and nesting habitat because the denser foliage of spruce than other local conifers offers greater concealment from predators. Indeed, breeding success has been linked to higher foliage density; where eggs and nestlings are less likely to attract attention of predators. Additionally, the benefit of increased predator evasion through more hiding space would probably outweigh the cost of making predators more difficult to see by the jays within the dense foliage. The Siberian jay is notably selective in its choice of territory, with a typical territory comprising old dense spruce swamp with ample vegetation cover. Territories also tend to be structurally diverse, comprising variably aged scrub, groves and flood meadows; so that active territories may be regarded as an indicator of high ecological diversity within the forest.

The Siberian jay is evaluated as Least Concern by the IUCN because of the species’ exceptionally large range. Although the world population is decreasing, the magnitude of this decrease is not considered sufficiently large to render the species Vulnerable. The world population is very large and estimated at 4295000-7600000 mature individuals. Population declines have been reported to be strongest in the southernmost part of the range.