Seabirds of Stellwagen: Skuas & Jaegers

Monday, Feb 11 2013 12:41 PM | Cape Cod, jaeger, Hyannis, whale watching, bird research, whale watchers, whale watch, Stellwagen Bank National Marine Sanctuary, skua, birdwatching | Permalink



Skuas & Jaegers

Welcome back to  Hyannis Whale Watcher Cruises seabird blog series where we hope to introduce whale watchers to the types of seabirds we most often encounter in the waters off Cape Cod. Today we will talk about some little known cousins of the gulls: the skuas and jaegers.  As top predators, this group of species is an important component in the ecology of Stellwagen Bank National Marine Sanctuary and a real treat to see on our whale watches! 


A light phase long tailed jaeger in flight.
Beautifully patterned, they are the smallest of this group.
Photo: NOAA- Rich Stallcup
Skuas & Jaegers are a group of seven to ten species worldwide. The largest species, the brown skua of the southern hemisphere has a wingspan of five feet, while the smallest species, the long-tailed jaeger, is about the size of laughing gull. Characteristically, they more closely resemble gulls than terns in form, but generally have stockier bodies with thicker necks. Like gulls, they are good at walking and swimming, but cannot dive underwater. They also have narrower and more pointed wings than gulls, which provide incredible maneuverability in flight. 

Like gulls, skuas and jaegers will eat just about anything they can, dead or alive, but skuas and jaegers are more predatory than gulls. Posessing a sharp, hooked bill, they are equally adept at hunting small rodents on their breeding grounds, plucking a fish from the surface of the open ocean, or preying on the young of other seabirds, from puffins to penguins. The larger skuas are well known for downing and killing other birds at sea. It's probably fair to say that skuas and jaegers are the raptors of the open ocean world. 

Though five species of skua have been sighted at Stellwagen Bank National Marine Sanctuary, the most frequently sighted is the parasitic jaeger (parasitic skua in U.K.). Roughly the size of a laughing gull, whale watchers often notice them when they are engaging in their namesake behavior, parasitizing other seabirds through aerial robbery.   Dipu Karuthedathu at Hornbill Media captured the action in this video, complete with  soundtrack! 



Kleptoparasitism is the behavior of stealing food from other predators. With their highly maneuverable form skuas and jaegers give chase to other seabirds and harass them to the point where they drop or regurgitate their prey. In defense of skuas and jaegers, it must be noted that not all individuals choose a life of crime. Some birds do not engage in piracy, supporting the idea that the behaviors for effective kleptoparasitism are acquired through observing other birds and learning the right moves. Additionally, some studies suggest that less than 25% of attempts at piracy are successful suggesting that this behavior augments, rather than dominates, their hunting strategy.  

Skuas and jaegers nest in the circumpolar regions of the earth. They lay claim to a couple square feet of nesting space which they defend ferociously. Like the terns, skuas will often defecate while dive bombing intruders, but unlike terns, skuas will also try to take a chunk of you with them! Their attacks can be debilitating. Just ask wildlife photographer Mattias Klum who was attacked in Lapland. This incident happened during the filming of the documentary film The Linnaeus Expedition. The filmcrew was several hundred meters away from the birds nest and took great care not to disturb wildlife.


On whale watches, picking out a single parasitic jaeger among hundreds of gulls is challenging. Adding to the challenge is the fact that there are two separate patterns of coloration or phases, one light and one dark, that observers need to note and the highly variable plumage in juvenile birds.  Nonetheless, a couple of tips for spotting skuas and jaegers include scanning for larger birds harassing other seabirds, particularly the terns we often encounter  just off Race Point in Provincetown in August and September. Also look for flashes of white in the long outer flight feathers, or primaries, of any large seabirds, Though not always prominent, especially light phase birds, they are a good diagnostic mark for in-flight birds at a distance. 


Great Skuas in courtship. Note the white in the primary feathers
a good field mark for all skuas and jaegers.
Photo: Stella Sutherlend

Though not seen everyday, skuas and jaegers  are present at Stellwagen Bank throughout the whale watch season and are exciting birds to watch. Many a birdwatcher has boarded the Whale Watcher hoping for good looks at these seldom seen seabirds. Again, the best time for parasitic jaegers is in the end of August and into September. South Polar skuas are very rare, but increasingly annual sightings. 

 We hope this finds everyone in New England safe and warm in the wake of this weekend's terrible, yet impressive, blizzard! Stay strong, whale watching season is just around the corner! Join us next time for a new group of seabirds.
Jonathan Brink
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Our vessel operates in compliance with NOAA's Northeast Whale Watching Guidelines and are active WhaleSENSE participants.