Stercorarius longicaudus

Geographic Range

Long-tailed jaegers ( Stercorarius longicaudus ) have a breeding range which covers the North pole. This includes parts of North America, Greenland, Russia, and Canada. They can live as far south as 61° N latitude during the breeding season but are completely migratory birds. In the winter they migrate south off the coasts of South America and South Africa usually near continental shelf breaks, upwelling regions, and coastal waters in general.

• Biogeographic Regions
• nearctic nearctic
  • native native
• arctic ocean arctic ocean
  • native native
• atlantic ocean atlantic ocean
  • native native
• pacific ocean pacific ocean
  • native native

Habitat

During the breeding season long-tailed jaegers typically inhabit arctic tundra regions which are far from sea. These areas have some shrub coverage, are generally flat, and are populated by rodents of some type. On occasion they will dwell in marshy areas but they usually prefer wide open, rocky terrain.

Less is known about their wintering habitat. They are pelagic after breeding and spend little time near the land. They are often found over ten miles from shore, following schools of fish. They have been known to dwell at breaks in the continental shelf, regions with heavy upwelling, and fishing vessels.

• Habitat Regions
• temperate temperate
• tropical tropical
• polar polar
• saltwater or marine saltwater or marine

• Terrestrial Biomes
• tundra tundra

• Aquatic Biomes
• pelagic pelagic

Physical Description

Long-tailed jaegers are the smallest of the g.Stercorarius species. They can weigh anywhere from 280 to 310 g at adulthood with females generally on the heavier end of this distribution. In immature and basic plumage there are very few differences between long-tailed jaegers and the 3 other species of jaegers.

Juveniles of the species have central rectrices which are not much longer than the other ones. They have mostly brown plumage on their upper regions. The tips of feathers in juveniles are often white in coloration and have white barring on several body parts including the flanks and under-wing coverts. There are two juvenile plumage types: light and dark. Light type juveniles have grey heads and whitish abdomen with brown bars. Dark types are so called due to entirely dark underparts.

Adults with basic plumage are lacking the characteristically elongated rectrices. They have brown under-wing coverts and feature a mostly brown and barred plumage. This type of plumage is rare to see in the wild because they usually wear this plumage while out at sea. They closely resemble juveniles at this stage.

In alternate plumage adults lose their mostly brown coloration. In this plumage the upperparts are brownish gray. The remiges and rectrices take on a solid black color while the underparts become mostly white. Heads are primarily white but have a distinct black cap with yellow coloration on either side of the neck. In this plumage adults have two central rectrices which extend well beyond the rest (adding 15 to 20 cm to total length) which are characteristic and gave long-tailed jaegers their name.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger

Reproduction

Long-tailed jaegers are socially monogamous and form long-term pair bonds. Males will loudly compete for mates. Male long-tailed jaegers will also present food items to females and the females exhibit a hunched posture to accept the food. Pairs also perform aerial displays.

• Mating System
• monogamous monogamous

The breeding season usually begins around June and lasts through August. Breeding is dependent on food availability; if food is scarce they will choose not to breed and return to their pelagic lifestyle. Pairs lay a maximum of two eggs during a season. The eggs are laid directly on the ground, in a scrape nest constructed by both parents. It is speculated that long-tailed jaegers do not use nest materials because they use their highly vascularized feet to incubate eggs.

Eggs are incubated mainly by the female for 23 to 25 days. Eggs are carefully balanced on top of the feet of the incubating parent. Chicks are born downy and with eyes open but unable to feed themselves (semiprecocial). Hatchlings usually stay in the nest for one or two days before leaving. They typically take shelter under shrubs to remain hidden but never travel very far from the nest. Chicks will fledge at 22 to 28 days, but both parents continue to tend the young for up to 3 weeks post-fledging.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• oviparous oviparous

Both male and female long-tailed jaegers participate in nest building, but the females perform most or all of the incubation. Once eggs have hatched, females remain near the nest at all times to defend and brood the young while the males fly off and hunt. Upon returning the female, and chicks, assume the same hunched posture seen in courtship to request food. The male then regurgitates a food item for them and the female accepts it and shares with the young. Parents continue to tend the young until 3 weeks after they've fledged.

• Parental Investment
• precocial precocial
• male parental care male parental care
• female parental care female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • male
    • female
• pre-weaning/fledging
  • provisioning
    • male
    • female
  • protecting
    • male
    • female
• pre-independence
  • provisioning
    • male
    • female
  • protecting
    • male
    • female

Lifespan/Longevity

There are no known records of captive lifespan. Adults in the wild live from 8 to 9 years as recorded in several studies.

Behavior

Long-tailed jaegers are migratory birds that spend three-quarters of their lives on the open ocean. The remaining time is spent on land on the northernmost breeding territory of any bird. They are generally solitary and only come together briefly to breed or gather around a large school of fish. Long-tailed jaegers are active during the day.

• Key Behaviors
• flies
• diurnal diurnal
• motile motile
• migratory migratory
• solitary solitary

Home Range

Although they are the least aggressive jaeger, long-tailed jaegers do actively defend breeding territories. In the densest conditions, long-tailed jaegers defended a territory of 1 square kilometer. Both males and females will perform aerial displays to claim territory. Nest density has been recorded to range from 0 to 0.6 nests per square kilometer.

Communication and Perception

Long-tailed jaegers use three calls and a few postures to communicate with one another. The short versions of the kreck and kilu sounds are used in response to mammalian and avian intruders while longer versions are used to interact with conspecifics. Hatchlings also use kilu as a method of calling to parents.

The third call, kuep , is often used by parents for contacting young. It is typically used because of the hatchlings’ tendency to hide in shrubs near the nest. In this scenario it is the female using the call presumably to coax the chicks from their hiding places. She also uses it to in conjunction with the hunched posture to request food from her mate. Both males and females will use kuep in territorial disputes.

As previously mentioned, the hunched posture is used when females and sometimes chicks are soliciting the male for food. Occasionally females will also raise their tails in conjunction with the hunched posture, but it seems to have the same meaning as without.

An upright posture is usually seen when long-tailed jaegers are preparing to attack conspecifics. This, combined with long calls, is a good indicator of aggressiveness. A slow wing-beat display is seen used in conjunction with the kuep call to establish territorial boundaries when pairs first arrive at the breeding territory. There is also a rapid wing-beat display which is seen less frequently and is performed silently. It has been noted during territorial disputes and breeding. Long-tailed jaegers do not vocalize often when not on the breeding grounds. Like all birds, they perceive their environment through visual, auditory, tactile, and chemical stimuli.

• Communication Channels
• visual visual
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Long-tailed jaegers subsist primarily on rodents during the breeding season. They are known to eat lemmings and certain voles ( Arvicolinae subfamily) almost exclusively during this time. After a meal jaegers typically retreat to a source of water in which they clean themselves. During seasons where rodent populations are sparse, they will either not reproduce or one of their young will eventually lose weight and die.

Other foods of long-tailed jaegers include small birds, insects, and some berries. These items represent very little of the total dietary input of most individuals. When at sea it is presumed that long tailed jaegers feed on fish but less is known about their wintering habits in general. Some cases of kleptoparasitism have been seen in migrant populations but not at breeding sites

• Primary Diet
• carnivore carnivore
  • piscivore piscivore

• Animal Foods
• birds
• mammals
• fish

• Plant Foods
• fruit

Predation

Long-tailed jaegers have quite a few predators during their breeding season. These include mammalian predators, especially foxes , and many raptors that prey on juvenile birds. In response to mammalian predators, long-tailed jaegers use several quickly repeated diving attacks usually in conjunction with a call. Foxes have been known to receive the worst assaults but they will also attack humans who encroach upon their territory. In some cases a distraction display is used wherein adults fluffed feathers and ran away from the nest.

Most birds do not hunt adult long-tailed jaegers, but juveniles are vulnerable. In cases where the juveniles come under attack by raptors the adults often pursue the assailants in the sky. Their great agility in the air and fierce defense is usually enough to deter would-be avian predators. Many raptors have been known to climb very quickly to great heights in order to avoid being chased and harassed by long-tailed jaegers. At a certain height long-tailed jaegers usually abandon the chase and return to the nest.

Ecosystem Roles

Long-tailed jaegers likely have a significant impact on the populations of their prey species including many fish, lemmings, and voles. Feeding by kleptoparasitism also has a negative impact on the individuals that food is stolen from. Even if the jaeger is not successful in stealing the food item, the energy expended in avoiding the jaeger is probably significant and could be detrimental. Predators such as falcons and foxes likely depend to some degree on long-tailed jaeger chicks.

Economic Importance for Humans: Positive

There are no known economic benefits of long-tailed jaegers.

Economic Importance for Humans: Negative

There are no known adverse effects of long-tailed jaegers on humans.

Conservation Status

According to the IUCN Red List Long-tailed jaegers are of least concern.

Additional Links

Encyclopedia of Life

Contributors

Michael Garcia (author), Florida State University, Emily DuVal (editor), Florida State University.

References

Andersson, M. 1971. Breeding behaviour of the Long-Tailed Skua Stercorarius longicaudus (Vieillot). Ornis Scandinavica , 2/1: 35-54.

Andersson, M. 1976. Population ecology of the Long-Tailed Skua ( Stercorarius longicaudus Vieill.). Journal of Animal Ecology , 45/2: 537-559.

Andersson, M. 1981. Reproductive tactics of the Long-Tailed Skua Stercorarius longicaudus . Oikos , 37/3: 287-294.

Meltofte, H., T. Hǿye. 2007. Reproductive response to fluctuating lemming density and climate of the Long-tailed Skua Stercorarius longicaudus at Zackenberg, Northeast Greenland, 1996-2006. Dansk Orn. Foren. Tidsskr , 101: 109-119.

Wiley, R., D. Lee. 1998. The Birds of North America . Philadelphia, PA: The Birds of North America, Inc..