Thursday, 10 December 2009

Catch up with our grebes

Strange as it may seem, winter is a good time to catch up with the five species of grebe that either breed or winter within the county. When people think of grebes, they often have an image of the Great Crested Grebe, resplendent in its breeding finery and indulged in an elaborate courtship dance, or the Little Grebe – the dabchick of smaller waterbodies. Both species are less showy in their winter plumage and both may leave their breeding waters to winter elsewhere, where they may swim alongside Red-necked, Black-necked and Slavonian Grebes, all winter visitors to Norfolk.

A trip to the coast can provide views of all five species in a single day and, sometimes, at a single site. The Little Grebe makes use of brackish pools and saline lagoons, with Titchwell and the ditches at Cley both favoured sites. Great Crested Grebes may join them at Titchwell but are more often encountered just off the beach, making use of our inshore coastal waters. Here they mingle with much smaller numbers of the other three species, providing birdwatchers with an opportunity to practice their identification skills.

The Great Crested Grebes leave their breeding sites in the autumn, seeking out larger waterbodies and coastal waters on which to moult, a process which leaves them flightless for several weeks. While several dozen individuals may gather at favoured sites, our wintering population is dwarfed by the 30,000 that moult and winter on the Ijsselmeer in The Netherlands.

Both Black-necked and Slavonian Grebes have small breeding populations in northern Britain (roughly 40-50 pairs each), which are part of a much larger breeding range. While some of our breeders may be among the birds wintering around the Norfolk coast, other wintering birds will have arrived from elsewhere. The size of the arrival is influenced by weather conditions across more northerly waters. All of the species that make use of coastal waters prefer shallow, sheltered bays, which is why Holkham, Holme and Titchwell seem to hold birds to a greater degree than other sites around the county. Here they feed on crustaceans and small fish, often feeding alongside Red-throated Divers and Cormorants.

During the hardest of the winter weather, when bitter winds deliver ferocious storms to our shores, the birds may be forced inland, affording birdwatchers easier viewing than is typically the case when watching these birds at sea. The winter plumages of these birds are dull in comparison with their breeding finery and separation of the different species requires an understanding of the physical structure of each species as well as the plumage pattern. It is worth the effort, however, when you can see all five in a single morning.

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