Thursday, 11 May 2017

The complications of migration

Walking around Corby in the last 10 days or so, the sweet song of the Blackcap has been much in evidence from gardens, parks and woodlands, along with the very similar song of the closely-related Garden Warbler.

The latter's song is just that bit more mellow and gentle, but even many experienced birdwatchers can struggle to tell them apart.

But there's one very major difference between the two species. Garden Warblers spend the winter in Africa, and arrive back in the UK in April. Blackcaps, on the other hand, often only migrate as far as Spain and Portugal during the winter months (birds ringed near Corby have been recovered in both countries), then return in March and April.

But more and more people are seeing Blackcaps during the winter, often visiting garden feeders. So, are these birds that have given up on migration?

Well, no. In fact, the evidence is that our breeding Blackcaps still head south for the winter, but are replaced in some areas by birds from Central Europe, especially Germany, who find our mild winters preferable to the much colder climate there. When spring arrives, they return to the Continent.

It's another example of how complicated migration is. Birds are always on the move, even around us is the woods and parks of Corby, without us necessarily noticing.

And if you want to see a Blackcap, look for a small, slightly plump, grey-brown bird with a black cap (male) or rufous brown cap (female). The song starts with a lot of chattering, before opening out into a pleasant, fluting warble.

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