Pomarine Jaeger in Cobourg Harbour

Nature Notes for November 25, 2011

                            Pomarine Jaeger, Cobourg Harbour. Photo© Bruce Parker.

There were two phone messages waiting for us when we arrived home for lunch. Both were about a Pomarine Jaeger which had been spotted in Cobourg Harbour in mid-morning. One message also said that the bird looked like “it was on its last legs”.

This was not an encouraging message.

The Ontario Field Ornithologists were having an outing that morning (November 13) which had included Cobourg Harbour. Ian Shanahan, the leader of the trip, had spotted this bird, a rare one for Ontario. Cell phones began to hum and soon the word was out into the birding community.

Pomarine Jaegers are marine birds which, at this date, should be out in the middle of the Atlantic or Pacific Oceans. They usually come to land only in the high Arctic in the breeding season.

In the fall, some jaegers migrate over land from Hudson’s Bay to the Atlantic. Some of these birds show up in the Great Lakes, usually as the result of inclement weather.

The Pomarine Jaeger is a bit smaller than a Herring Gull with quite a stocky build. The one in Cobourg was a dark young-of-the-year, mostly dark chocolate brown with some pale barring on the undertail coverts. The bill had a gray base with a dark tip.

Pomarine Jaegers come in two colour morphs – light and dark. The dark form adult is all chocolate brown. The light form adult is light underneath and light on the back of the head and neck. Both forms have light colour at the base of the primaries, but this is only visible in flight. The central two feathers in the tail are considerably longer than the rest of the tail and twisted.

Unlike many marine birds, they nest singly, not in colonies likes gulls and terns. They would be unwelcome in colonies of other species, since they would eat the eggs and young and try to rob food which the parent birds were bringing back to the nest.

Pomarine Jaegers are quite eclectic in their food choices. On the breeding grounds, they feed mainly on lemmings. Their population fluctuates with the lemming population. In years of low lemming populations, they may not breed at all.

Most of the year they spend on the open ocean. They often harass other seabirds to try to rob them of their prey. If they can catch them, they will also eat adult birds. In addition, they feed on carrion and the offal discarded from fishing trawlers.

Jaeger is the German word for hunter. The British name for this species is Pomarine Skua.

We went to Cobourg as quickly as possible after we received the message. There were no other birders in the parking lot. (Birders can be easily identified by their binoculars and spotting scopes). This didn’t look good.

On scanning the beach on the west side of the harbour, we sighted a large brown lump. Unfortunately, the bird had died. It probably succumbed to Type E botulism, a bacterial disease which is present in the Great Lakes ecosystem. Large die-offs of other water birds have been reported recently from the Durham waterfront.

Since this is such an unusual visitor for this area, we collected the body. When prepared as a study skin, it will make its way into the collection of the Royal Ontario Museum in Toronto.

I hope that my next encounter with a Pomarine Jaeger is with a live one.