Two years’ research by the Game & Wildlife Conservation Trust indicates that grey squirrels have a significant effect on certain woodland birds’ fledging success. In a pioneering project, which tested the effects of removing grey squirrels from groups of woods, some birds experienced a better success in rearing fledged young than in a comparable group of woods where no squirrel control was undertaken.
“The results from this research work indicated that grey squirrels at particular densities have a noticeable effect on some birds, particularly those which have open nests, rather than nesting in holes or hollow trees,” said George Farr Chairman of the European Squirrel Initiative who commissioned the research.The project used a method, known as a ‘randomised removal experiment’ never attempted before, rather than only looking at possible correlations between the presence of grey squirrels and birds in woods [footnote 4].
“The aim of the work was to test the idea that removing grey squirrels from woods might lead to a consequent increase in fledging success of woodland songbirds”, continued Mr Farr. “We also wanted to see if there were any differences between the effects on birds which build open nests, and those which are hole nesters”. Hole nesting species included great tit and nuthatch, while open nesting species included chaffinch and blackbird. An improvement in productivity was 20% or more in some open-nesting species in woods where squirrels were removed.
“The study indicated when grey squirrels were at a relatively high density and were then removed there was a measurable positive effect on the post nesting fledging of the woodland bird community,” said Prof Nick Sotherton of the Game & Wildlife Conservation Trust. “The outcome would, then suggest that the grey squirrel has a case to answer. However more work needs to be done in order to build up a definitive picture of the full
impact grey squirrels have”, he added.
Notes to Editor:
Issued on behalf of the European Squirrel Initiative by Kendalls.
For more information, please contact Andrew Kendall, telephone 01394 610022.