One of the sure signs that the seasons have turned is hearing the song of the chiffchaff - the first of the incoming summer migrant warblers to arrive at the University. Walking through Great High Wood at lunchtime today I heard my first one this year, chiff-chaffing away in the shrub layer beneath the bursting horsechestnuts and the yet dormant beeches. Its about a week or two later than the first one I heard last year.
Not that long ago you could be sure that you were listening to a tiny brown bird that had just flapped its way to Durham from southern Europe or even Africa but these days you can't be too sure because the number of over-wintering chiffchaffs in the UK has been steadily increasing for some years now. There is a map here on the RSPB web site which shows the north/south divide for over-wintering and I am sure that its a fair bet that the line is moving northwards. In fact I heard one singing in the hedgerow on the east side of the Science site as late as September 29th last year.
By contrast, the willow warbler, which to look at is a dead ringer for the chiffchaff, seems to be a total migrant with no over-wintering recorded at all (map here). It will be a week or two before the first of these little birds arrives in our grounds.
Although the chiffchaff and the willow warbler look so alike, their songs are totally different. You can compare recordings of each on the two web site links.
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