Grey squirrels (Sciurus carolinensis) were introduced into Britain and Ireland in the late 1800s and early 1900s from North America. The species is classed as invasive, and it has spread across many parts of Britain and Ireland, much to the detriment of the Eurasian red squirrel (Sciurus vulgaris), whose numbers generally decline in the presence of the larger competitor. However, a new study by Colin Bonnington, Kevin Gaston and Karl Ewans, and published in Ibis has shown that urban bird populations, especially those depending on supplementary feeding, may also be negatively impacted by the presence of the grey squirrel.
Grey squirrels will frequent garden bird feeders in urban areas, and in doing so may deter garden birds from using the feeders. Until now, little quantitative evidence was available to support this observation. Bonnington and colleagues sought to investigate what effects (if any) the grey squirrel may be having on the feeding birds, by observing bird feeders throughout urban Sheffield.
The results showed that all bird feeding activates were negatively impacted by the presence of a feeding grey squirrel. During direct observations, the robin was the only bird species to use the feeder while in the presence of the grey squirrel. Other species that were negatively impacted included the coal tit, bullfinch, chaffinch, goldfinch, long-tailed tit, blue tit, and nuthatch. Larger species including the wood pigeon and blackbird continued to feed under the feeders, even in the presence of a grey squirrel. The authors also suggested that if other bird species had been present, that these too would suffer similar impacts from the presence of a grey squirrel at a feeder.
Bonnington goes on to say that the impacts of grey squirrels may be at their highest during winter months, when birds have low energy and are in greater need of supplementary food resources. While more research is needed to understand how long it takes a displaced bird to return to a feeder, it remains clear that grey squirrels do impact feeding birds at feeders. Furthermore, supplementary feeding appears to benefit the grey squirrel, and may in the long run facilitate their continued survival and population expansion. One of the ways to reduce competition between feeding birds and grey squirrels in your garden may be to use a squirrel poof feeder, such as a spinner. For sheer entertainment purposes, I recommend something like this…http://www.youtube.com/watch?v=dEW9TG6Dcgg
About the photographer: Brian Power runs the Wild Carlow Facebook page, where he posts some of his own wildlife photos and observations, and encourages members of the public to also participate.