A persue to juvenile Skuas identification

Written by Menno van Duijn

Strong winds from the west brings seabirds closer to the mainland of the Netherlands and brings seabird loving birders to the shores. From the months August to September one can expect to see even four species of skuas with these conditions in a single day. The only problem is that most of the time they are observed at a fair distance and a good telescope is a necessary tool.

Adult birds are striking and can be a challenge but even more challenging are the juveniles that look very similar to inexperienced birders. Therefore we summed-up some of the key features of this plumage to look for.

One of the biggest pitfalls in our experience is to identify skuas based on their jizz (size, structure). It’s tempting to identify skuas that fly to far to see any plumage features based on their jizz. If you put the skuas in line you would say that Great Skuas is the largest, followed by Pomarine Skua, Arctic Skua and Long-tailed Skua being the smallest. But we experienced that in the field birds that were identified as Pomarine Skuas even turned out the be Long-tailed Skuas and visa versa looking back at the photos.

Best sites to observe skuas during autumn storms are Westkapelle, Maasvlakte, Scheveningen, Katwijk, IJmuiden, Camperduin and the Wadden Islands.

Great Skua (Stercorarius skua)

  • Dark belly;
  • Minor to none extended central tail feathers (streamers);
  • No banding on the under- or upper tail coverts;
  • Single large clear white patches on the under and upper wings;
  • No banding on the underwings;
  • In good light conditions contrast brown body with darker underwings.

Photo Jan Dekker (left) and André van Dam (right).

Pomarine Skua (Stercorarius pomarinus)

  • Two white patches on the underwing, a lager at the pase of the primaty and smaller at the base of the primary coverts;
  • Dark belly;
  • Banded under- and upper tail coverts;
  • Banded feathers on the axila;
  • Minor white patch at the upperwing, only the primaries have a white center;
  • Medium extended central tail feathers, (steamers)

Photos light morph by Piet de Poorter (top), intermediate morph by Rene van Rossum (middle) and dark morph by Danny Bregman (bottom).

Parasitic Skua (Stercorarius parasiticus)

  • Large single white patch on the under- and upper wing;
  • Contrasting light belly, marked by a light breast band;
  • Medium extended central tail feathers (streamers);
  • Banded under- and upper tail coverts but not as neatly as Pomarine or Long-tailed;
  • Light head, some have a darker cap, contrasting with a dark back.

Photos brown morph by Rene van Rossum (top), grey morph by Gerard Visser (bottom).

Long-tailed Skua (Stercorarius longicaudus)

  • Longer extended central tail feathers (streamers);
  • Single large white patch on the underwing;
  • Minimal white patch on the upper wing, only white center outer primary;
  • Light head, without a cap, (beside dark morph) that’s not as contrating with the darker back as in Arctic Skua.;
  • Light belly with darker breast band (beside dark morph)
  • Strongly barred upper and under tail coverts;

Photos light morph by Peter Soer (top), intermediate morph by Kris de Rouck (center left), Tomas Luiten (center right), dark morph by Jan van Holten (bottom left) and Karel Hoogteylingen (bottom right).

Many thanks to all the photographers for use of their photos.
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