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Message: <blockquote data-quote="Nightranger" data-source="post: 2057709" data-attributes="member: 64473"><p>I don't know of any online links to studies but there have been a number of studies, including a recent one by the BTO funded by Songbird Survival. I know of a study in Norfolk from a few years back that found a temporary increase in prey species after predators were removed. However, the increase was slight and not sustained, providing the conclusion that most species are more or less at the level dictated by the environment rather than by predator populations. This is perhaps not such a surprise because there are mathematical models that show that predator populations are strictly linked to prey populations. This is equally true of magpies as it is for sparrowhawks because despite the difference in the predation behaviour it is still linked to prey availability. Indeed, magpies (or Corvids in general) only take eggs an nestlings as 10% of their food intake (see Tim Birkhead's excellent monograph published by Poyser).</p></blockquote><p></p>