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New England Seabirds

 Wilson's Storm-petrel  Dave Jones

Seabirds


Jaegers and Skuas

 

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Jaegers and Skuas

 

Pomarine Jaeger

Parasitic Jaeger

Long-tailed Jaeger

South Polar Skua

Great Skua



Parasitic Jaeger by Leonard Medlock

Jaegers and Skuas Rather Different Seabirds

The sighting of any jaeger or skua can certainly add excitement to a pelagic trip or seawatch. Five species are possible in North America and the identification challenges endear them to veteran seabirders. They are often seen at sea associated with gulls to which they are closely related.They qualify as seabirds in this presentation because they spend most of their time at sea except during breeding season and because they are usually seen in our area from pelagic trips.

Evolution of Jaegers, Skuas and Relation to Gulls

Jaegers, Skuas  and Gulls belong to the family Laridae. Scientific evidence indicates that the Jaegers and Skuas diverged from the gulls some 10 million years ago.  Both groups  evolved in the northern hemisphere and later expanded into the southern hemisphere.

Characteristics of Jaegers and Skuas

They have strongly hooked claws like raptors and webbing between their toes like gulls. Unlike gulls they are able to drink salt water but they prefer fresh water.

They prey upon other seabirds forcing them to drop or reguritate food they are taking back to feed their mates or offspring (kleptoparisitism).  They prey upon other seabirds at sea and on the breeding ground including the world's most popular seabird, the puffin. These bully tactics do not endear the skuas and jaegers to casual birders.

They do not have a keen sense of smell and find food by sight. Pelagic trips often chum to attract gulls to the boat hoping to attract a jaeger or skua as well. Unfortunately attracting gulls sends small Alcids away including Common Murres guarding a chick. If Alcids are the target species do not attract gulls. Never attract gulls to breeding islands or coastal breeding areas.

They breed in loose colonies, and show mate and site fidelity (except Pomarine Jaeger). Females are larger than males.

Breeding
Male feeds the female before and after eggs are laid and continues to participate in the feeding of the chick after hatching. Usually lay two eggs with only one surviving especially in lean years. One chick hatches before the other and is therefore bigger. In lean years this older chick may eat the younger. Tundra breeding birds lose eggs and chicks to Arctic foxes.

Taxonomy
Members of the family Laridae which includes the gulls.

Stercorariidae - Skuas and Jaegers

Genus Catharacta -Skuas
Skuas are primarily southern hemisphere breeders except for Great Skua which breeds in the north east Atlantic. The skuas show less difference in plumage between breeding and non-breeding adults. Adults tend to hang around the breeding area rather than migrate long distances. In the north Atlantic we are concerned with two species: The northern breeding Great Skua and the southern hemisphere breeder the South Polar Skua which spends the off season in the north.

Genus Stercorarius - Jaegers (Known as Skuas in Europe)
This genus contains three species that all breed in the northern hemisphere and are called Skuas in Europe and Jaegers in North America. They are smaller than the Catharacta and migrate to the southern oceans for the winter. Long-tailed Jaeger is a more western breeder and infrequently seen in New England waters. Pomarine and Parasitic Jaegers are seen in small numbers on Stellwagen Bank and Jeffreys Ledge.

Why are Jaegers and Skuas so hard to identify?
Birds that exhibit many different plumages are always an identification challenge. Although they are not the only birds to do so, skuas and jaegers show variation in plumage in three circumstances.

  • Adults exhibit breeding plumage and non-breeding plumage
  • Young birds take several years to achieve adult plumage
  • Adults are polymorphic - dark and light  morphs

When you are ready to tackle jaeger and skua identification you should certainly purchase and study the book:

Skuas and Jaegers A Guide to Skuas and Jaegers of the World by Klaus Malling Olsen and Hans Larsson. (1997)



Seabirds | Jaegers & SkuasPomarine jaeger | Parasitic JaegerLong-tailed JaegerSouth Polar Skua | Great Skua   Top of Page  Comments to webmaster

           

Harrison, Peter (1983) Seabirds an identification guide Houghton Mifflin Company; Boston

Olsen, Klaus Mailing & Larsson, Hans (1997) Skuas and Jaegers A Guide to the Skuas and Jaegers of the World Yale University Press New Haven and London