The presence of a blackcap feeding on fat balls in our garden today set me thinking about why there seem to be so many being recorded this winter. Along with chiffchaff rarely a day goes by without reports of these two warblers that in general you would expect to be in Africa by now.
When I first got interested in nature back in the 1970’s the issue of why most blackcap and chiffchaff migrated south for the winter while some chose to remain here was the subject of some speculation. I remember that one theory was that the rise in the popularity of feeding birds in gardens meant there was an increasingly adequate food supply for these species and there was no need for them to risk life and limb making the perilous journey south.
After a lot of research we seem to be far wiser now and have established that the birds we see here in winter are not the same ones that spend the summer here. Our summer birds do migrate south and are replaced by incoming birds from north-eastern Europe, especially Scandinavia. Indeed,we have established that some of the incoming chiffchaff are a different sub-species, the Siberian chiffchaff (Phylloscopus (collybita) tristis).
The question remains, though, as to why there are more being seen in winters now than back in the 1970’s and 1980’s? I don’t think you need to look too far for the answer of course; this must surely be an effect of the changing climate and warmer winters here now. This winter it seems the first frost we had was earlier this week and to get to mid-January without a frost is astonishing.
I suspect, and someone may be able to confirm this, that the numbers of blackap and chiffchaff passing through the country in winter are much the same as they have always been but that the need to move further south into Europe as the weather gets colder here is now much reduced. Perhaps the abundance of garden feeding stations does help to convince a few of them to stay but I am sure that is not the primary reason we are seeing them more often.
Whatever the reason they add a bit of variety and interest to garden bird watching and are always welcome here!
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