Thousands of Dunlin visit Cobourg Harbour

Nature Notes for May 30, 2014

“Want to see a couple thousand Dunlin?” My husband greeted me with this question when he came in from work last Monday evening.

“Where?” I responded.

“Cobourg Harbour” he replied, “but there are none in Port Hope. I checked.”

Off we went to Cobourg. Away from the Atlantic coast, I don’t think that I have ever seen so many shorebirds. They lined the sand beach on the west side of the harbour, perched on the rocks of the breakwater and fed in several large flocks on the surrounding lawns. All were feeding furiously on midges. Joggers and walkers didn’t seem to bother them. They would fly up, wheel around and then settle back to eating. If one stood still, they would approach your feet.

Some of the thousands of Dunlin that visited Cobourg Harbour last weekend.

Photo © Rob Lonsberry

Dunlins are medium sized shorebirds. In breeding plumage, which they are wearing now, they have a gray face, rust coloured back and a large black patch on the belly. They have a relatively long bill, black and with a slight droop at the tip.

Close up of a single Dunlin

Photo © Rob Lonsberry

As with many shorebirds, it is necessary to learn them in several plumages. The juveniles are different from the breeding adults, which are different than the non-breeding adults. The same Dunlin migrating back south in early summer will look quite different than the ones seen this week in Cobourg Harbour.

Dunlins are a circumpolar species, occurring in Europe and Asia as well as in North America. The birds that were visiting Cobourg are probably the population that winters from the mid-Atlantic states in the U.S. to the Gulf of Mexico. This is further north than many shorebirds. Many other shorebirds travel to South America for the winter months.

These birds are en route to the tundra, where they will nest. The abundance of insects there provides lots of food on which to raise the young. Dunlins eat mostly insects, although they also feed on aquatic invertebrates.

The big flocks of Dunlin were first reported in Cobourg Harbour on Sunday, May 25. On that date, they were accompanied by a single Red-necked Phalarope, one Whimbrel, and a few each of Short-billed Dowitchers, Red Knot, Ruddy Turnstone, Sanderling and some “peeps”. Most of the latter were Semipalmated Sandpipers, although there was one Baird’s Sandpiper, a very unusual bird for the spring in Ontario.

On Monday, there were still about 2000 Dunlin, many Ruddy Turnstones, many Semipalmated Sandpipers and a few Whimbrel and Red Knots.

The birds came and went throughout the day. On several visits throughout a day, the mix of species could be quite different, although this week they were dominated by Dunlin.

Before we left Cobourg Harbour, several Dunlin flocks lifted off and headed north. We didn’t visit on Tuesday, but probably there were very few shorebirds left. Why they chose to visit Cobourg this week is a mystery. We could only enjoy the sight.