Sunday, September 19, 2010

Pirate of the seas: South Polar Skua

South Polar SkuaSouth Polar Skua, off Newport, Oregon on 11 September 2010 by Greg Gillson.


The big brute in the photo above is a South Polar Skua. I obtained this photo recently as the bird circled our boat, 35 miles offshore.

What is a skua? Skuas are dark seabirds with white wing patches. They are related to gulls. They have webbed feet and strong hooked bills. They are the size of the largest gulls, but heavier. South Polar Skuas differ from the other 3 or 4 species of skuas by being evenly dark, except for golden spangles on the hind neck.

Skuas are powerful and aggressive loners, attacking other seabirds. They steal fish from other seabirds--even if already swallowed!

More than once I have seen a skua pounce on a swimming Pink-footed Shearwater, grab it by the shoulders, and repeatedly dunk it underwater, trying to force the poor exhausted bird to regurgitate its last catch. In such a case, the skua may actually drown the shearwater and eat it instead.

Skuas are larger, bulkier, and more deliberate than the similar smaller aerobatic jaegers. While the Parasitic Jaeger reminds some of an ocean-going Peregrine Falcon, the South Polar Skua is more like a Red-tailed Hawk in comparison.

These birds are highly pelagic (found in the open ocean) and very rarely seen from shore in the Pacific NW. Most sightings here are at least 8 miles offshore, and most seem to be 20-40 miles distant from land.

The worldwide population of these birds is very small, only 5,000 - 10,000 breeding pairs. And their name is apt. They nest on the shores of Antarctica, where they victimize penguins.

While most of the population seems to remain in the southern hemisphere, some (perhaps mostly younger birds) undergo a migration around the entire Pacific Ocean. In spring they are found primarily in seas around Japan. They then circle around the Gulf of Alaska and show up off the coasts of the Pacific Northwest from August to early October. Then they are back in Antarctica to lay eggs in December and January.

Pacific NW ocean-going bird watching tours, called pelagic trips, rarely encounter more than half-a-dozen birds on a single day trip. In fact, one bird is probably the most frequent number seen, if any. That is why, though aggressive, it is always exciting to see one winging by.

And, if you're lucky, it may even circle the boat and allow you better views, and maybe a photo....