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Stercorarius longicauduslong-tailed jaeger

By Michael Garcia

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. (Wiley and Lee, 1998)

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. (Andersson, 1976; Wiley and Lee, 1998)

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. (Wiley and Lee, 1998)

  • Sexual Dimorphism
  • female larger
  • Range mass
    280 to 310 g
    9.87 to 10.93 oz

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. (Andersson, 1971; Andersson, 1981; Wiley and Lee, 1998)

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. (Andersson, 1971; Andersson, 1976; Andersson, 1981; Meltofte and Hǿye, 2007; Wiley and Lee, 1998; Andersson, 1971; Andersson, 1976; Andersson, 1981; Meltofte and Hǿye, 2007; Wiley and Lee, 1998)

  • Breeding interval
    Long-tailed jaegers breed once yearly if adequate food resources are available.
  • Breeding season
    Long-tailed jaegers breed between June and August.
  • Range eggs per season
    0 to 2
  • Range time to hatching
    23 to 25 days
  • Range fledging age
    22 to 28 days
  • Range time to independence
    1.5 to 2 months

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. (Andersson, 1971; Andersson, 1981; Wiley and Lee, 1998)

  • Parental Investment
  • precocial
  • male 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. (Wiley and Lee, 1998)

  • Range lifespan
    Status: wild
    8 to 9 years

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. (Wiley and Lee, 1998)

  • Range territory size
    1 (low) km^2

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. (Wiley and Lee, 1998)

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. (Andersson, 1981; Wiley and Lee, 1998)

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 (Andersson, 1971; Andersson, 1976; Andersson, 1981; Meltofte and Hǿye, 2007; Wiley and Lee, 1998)

  • 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. (Wiley and Lee, 1998)

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.

Contributors

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

Glossary

Arctic Ocean

the body of water between Europe, Asia, and North America which occurs mostly north of the Arctic circle.

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

migratory

makes seasonal movements between breeding and wintering grounds

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pelagic

An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).

piscivore

an animal that mainly eats fish

polar

the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tundra

A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.

visual

uses sight to communicate

young precocial

young are relatively well-developed when born

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..

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