Eurasian Blackcap

Eurasian Blackcap Sylvia atricapilla (Linnaeus, 1758)

Blackcap Sylvia atricapilla atricapilla (Linnaeus, 1758)

(Fairly common PM, SV & WV. B.)

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 ♂♂, and include any other ♂♂ that I see that aren't singing, within the lakeside boundary. 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.

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. 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. If I were to fit a trendline to the May counts, one would see that there has been a steady increase from the 15 singing ♂♂ in the base year of 1998 to the 31 in 2013, despite annual fluctuations, with the last three breeding seasons all appearing to be above average. Note that 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 2013 showed the Blackcap to have been present in 85% of the regions 1-km squares, and to have decreased by 18% in the year from 2012-13. The report also shows the Blackcap to have increased by 45% between 2003-13. Bland & Tully (2010) 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 10 400 pairs.

Bibliography (sources of information)

  1. Bland, R & Tully, J. The Breeding Birds of the Avon Region 2010. Avon BTO.
  2. Stoddard, D.R. The Breeding Birds of the Avon Region 2013. Avon BTO.

Updated 3 January, 2018