Chiffchaff (Common Chiffchaff) - Blagdon Lake Birds

Common Chiffchaff Phylloscopus collybita (Vieillot, 1817)

Reservoir, Guernsey, Channel Islands © Nigel Milbourne 2007

Common Chiffchaff Phylloscopus collybita collybita (Vieillot, 1817)

Common, passage migrant, summer visitor. Breeds. Occurs mainly March to October, but some overwinter.

I have been conducting regular spring passerine counts around the perimeter of the lake using a similar methodology to that of the BTO Breeding Bird Survey (BBS). I count singing males heard from within the lakeside boundary as far as one field away. My survey walks are conducted by walking in a clockwise direction around the lake during the first week in April and May (or, as close as I can make them), early in the morning in good weather conditions (ideally sunny and still). The 2001 gap in the April counts was due to restricted access during a foot and mouth outbreak.

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The graph shows that birds are still arriving to set up territory when I count at the beginning of April, then during May it appears that the territories have been established with many of the April singers having moved on. Counts made during May have all been in the first week with the exception of 2000 (30th April), 2002 (26th May), 2004 (14th May) and 2007 (13th May). However, none of these counts appear to be out of line with expectations given the April trend. A low April count with a high May count as shown for 2013, reflects an exceptionally cold early spring during which migration was held up. It appears that there has been little change in the number of singing males from 1998 to 2013, despite slight annual fluctuations. The number of singing birds doesn’t necessarily reflect breeding success, which is something that I don’t measure. For example, it was generally reckoned that the awful wet summer of 2012 was not especially good for breeding birds in the UK but my data doesn’t show this.

The Breeding Birds of the Avon Region 2010 showed the Chiffchaff to have been present in 87% of the regions 1-km squares, and to have increased by 8% in the year from 2009-10. The report also shows the Blackcap to have increased by 15% between 2000-10. The authors commented “the good 2009 breeding season may have also contributed to the increases of… migrants such as Swift, Blackcap and Chiffchaff (which) may also have benefited for the same reason” and they suggested a total breeding population of 9 300 pairs.