Tuesday, December 27

Pomarine jaeger

   ›      ›   Pomarine jaeger - Stercorarius pomarinus.

The pomarine jaeger (Stercorarius pomarinus) belongs to the family of jaegers and skuas, Stercorariidae.

These jaeger species are highly migrant and breed in the far north of Europe, Asia and North America. The wintering population of pomarine jaeger species is distributed in the tropical and subtropical coasts of all major oceans. The breeding population is specialized in catching lemmings, which are the main diet of breeding jaeger. The pomarine jaeger is a monotypic species.

Overview & Quick Facts Description & Identification
Pictures of Pomarine jaeger Distribution & Range
Ecosystem & Habitat Diet & Feeding Behavior
Breeding Habits Migration & Movement Patterns
Conservation & Survival IUCN Status
Taxonomy & Classification Bird World

Pomarine jaeger - Overview

  • Scientific name: Stercorarius pomarinus
  • Species author: (Temminck, 1815)
  • Synonyms/Protonym: Lestris pomarinus Temminck, 1815
  • Family: Stercorariidae › Charadriiformes › Aves › Chordata › Animalia
  • Vernacular names: English: Pomarine jaeger, Chinese: 中贼鸥, French: Labbe pomarin, German: Spatelraubmöwe, Spanish: Págalo pomarino, Russian: Средний поморник, Japanese: トウゾクカモメ, Malay: Burung Pelangi Pomarin
  • Other names: pomarine skua, pomatorhine skua, Pomatorhine Jaeger
  • Distribution: breeds far north of Europe, Asia and North America; winters in coastal Americas, Africa, Europe, India, Southeast Asia, Australia
  • Diet and feeding habits: lemming, fish, carrion, scrap fish, smaller birds
  • IUCN status listing: Least Concern (LC)
The pomarine jaeger (Stercorarius pomarinus) is closely related to the great skua (Stercorarius skua).

Appearance, physical description and identification

The pomarine jaeger (Stercorarius pomarinus) is a large-sized bird, measuring 45 to 50 cm in length and weighing 550 to 900 grams.
The jaeger wingspan is 120 to 140 cm and the wing is long and broad. The overall plumage is grayish brown. There are three morphs. The light-morphs have brown back with white under parts. The dark morphs have dark brown plumage and the intermediate morphs have dark backs with somewhat paler underparts.

All these jaeger morphs have a white patch in the underwing, which flashes during flight. In breeding adults, there are two central tail feathers streamers, which are long and spoon-shaped. The irises are black. The pomarine jaeger call is a chattering noise and also "which-yew" sound.
Indian birds - Picture of Pomarine jaeger - Stercorarius pomarinus
Birds of India - Image of Pomarine jaeger - Stercorarius pomarinus
Birds of India - Image of Pomarine jaeger - Stercorarius pomarinus
Indian birds - Photo of Pomarine jaeger - Stercorarius pomarinus by Ronald Woan
Photo of Pomarine jaeger - Stercorarius pomarinus
Birds of India - Picture of Pomarine jaeger - Stercorarius pomarinus

Origin, geographical range and distribution

The breeding pomarine jaegers occur in far north Arctic tundras in Europe, Asia and North America. They undertake transequatorial over land migration and move to tropical and subtropical coasts, especially of Australia and Argentina.

The pomarine jaegers also occur in coasts of countries bordering Indian Ocean, Arabian Sea, South Pacific Ocean, South Atlantic Ocean, southern part of North Atlantic Ocean, southern part of North Pacific Ocean and South China Sea.

The Important Bird and Biodiversity Areas (IBA) of pomarine jaeger species in United States are Barrow Canyon & Smith Bay, Beaufort Sea Shelf Edge 152W71N, Bering Sea Shelf 168W62N, Bering Sea Shelf 169W60N, Chukchi Sea Nearshore, Eastern Kodiak Island Marine and Icy Cape Marine. The IBAs of pomarine jaeger in Norway are Slettnes and Varanger Peninsula. The IBA in Russia is the Valley of the Yorkutayakha river.

Ecosystem and habitat

These jaeger species do not normally occur in forests. They inhabit various natural, open, wetland, Arctic and tundra ecosystems. The pomarine jaeger inhabit tundra grassland, shallow seas with macroalgae, seagrass or kelp, coastal upwelling regions, neritic subtidal areas with loose pebble, gravel, sand or mud and tundra wetlands.

Diet and feeding behavior

Outside the breeding season, the diet of these pomarine jaeger species is mostly fish. Lemmings are the primary food of the breeders. The jaeger is a specialist lemming hunter, in many instances digging open the burrows. The wintering birds feed on fish, carrion, fish scraps, smaller birds and rodents. Sometime the pomarine jaegers are kleptoparasitic, robbing gulls, terns and gannets of their catches.

Reproduction and breeding habits

The breeding season of these jaeger species starts from June in the Arctic tundras. Breeding sites are widely scattered over tundra. The pomarine jaeger nest is a scrape on the ground, rarely lined with grass. The clutch may consist of two or three olive-brown eggs. The jaegers are highly territorial and fly at the head of any intruder approaching their nest. The parents incubate and the eggs hatch in about 25 days.

Migration and movement patterns

These jaeger species are highly migratory and the breeding populations from northern Europe, Asia and North America move to tropical and subtropical coasts for wintering.
After the transequatorial migration, much of the population is distributed along the coastlines of Australia and Argentina. These jaeger species also migrate over land and disperse along the coasts of countries bordering Indian Ocean, Atlantic Ocean and Arabian Sea. Post breeding dispersal of the juveniles takes place. They may make local movements for feeding and breeding in their range.

Conservation and survival

The global population size of the pomarine jaeger (Stercorarius pomarinus) is estimated to be about 400,000 individual birds. The overall population size of these jaeger species is considered to be stable. Throughout its ranges it is reported to be common to uncommon. The generation length is 13.5 years.

The pomarine jaeger (Stercorarius pomarinus) does not approach the thresholds for being Vulnerable either under the range size criterion or under the population trend criterion or under the population size criterion.

There are no substantial threats that may endanger the survival of these species. Climate change, severe weather and habitat shifting and alteration may affect the survival, especially of the hatchlings and fledglings.

IUCN and CITES status

The IUCN (International Union for Conservation of Nature) has categorized and evaluated the pomarine jaeger species and has listed it as of "Least Concern". CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora) status is ‘Not Evaluated’ for the pomarine jaeger (Stercorarius pomarinus).
Taxonomy and scientific classification of Stercorarius pomarinus
Kingdom:Animalia
Phylum:Chordata
Class:Aves
Order:Charadriiformes
Family:Stercorariidae
Subfamily:-
Genus:Stercorarius
Species:S. pomarinus
Binomial name:Stercorarius pomarinus
IUCN status listing:
Least Concern
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1.Image source: https://en.wikipedia.org/wiki/File:Stercorarius_pomarinusPCCA20070623-3985B.jpg
Image author: Patrick Coin | License: CC BY-SA 2.5
2.Image source: https://www.flickr.com/photos/rwoan/28415787752/
Image author: Ronald Woan | License: CC BY-NC 2.0 (as on 2016-12-26)
3.Image source: https://commons.wikimedia.org/wiki/File:Pomarine_Skua_from_the_Crossley_ID_Guide_Britain_and_Ireland.jpg
Image author: Richard Crossley | License: CC BY-SA 3.0
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