If You Want Songbirds, Kill Magpies.
Mike Pennington said:
Another thread of deliberately obtuse cod-science. Having tried all the other debates we're now left with the old Magpie/songbird argument.
It has been proved time and time again that Magpie density does not affect the number of songbirds which survive to the the following year. Yes, they eat songbirds, but they are the birds that would have died anyway - if very Great Tit chick survived the winter we'd be swamped in the things by now.
Obtuse cod-science? That's rather dismissive and not a little patronising, isn't it? I freely admit that I'm only a foot-soldier when it comes to the scientific side of birding, so I'll leave others to pick the bones out of what follows. Please note, however, that these are NOT my words - they are extracts from an interesting article published in the April 2002 edition of
THE FIELD magazine under the title: 'If You Want Songbirds, Kill Magpies' based on the scientific paper referred to below and which was published in the
Journal Of Applied Ecology.
Quote ...'Biologists from the British Trust for Ornithology (BTO) and the University of East Anglia, who are the authors of
"Large-scale spatial variation in the breeding performance of song thrushes (Turdus philomelos) and blackbirds (T merula) in Britain", conclude: 'Nest failure rate during incubation increased significantly where corvids were more abundant, suggesting a role for avian nest predators in determining spatial variation in reproductive output." This might seem like common sense to anyone connected with game management but for many years it has been vigorously denied by bird protectionists.
'The Game Conservancy Trust comments that the result "comes as somewhat of a surprise, since the BTO and the RSPB have loudly proclaimed a 'not guilty' verdict for these corvids in relation to songbird declines. At Loddington we have seen a spectacular increase in song thrush breeding density which followed hard on the heels of improved nesting success brought about by crow and magpie control."
'The recent BTO study has the virtue of being extremely thorough and founded on a huge database: the nest records collected by thousands of amateur bird-watchers since the Thirties. A sample of this information, covering about 6,000 nests, was put alongside more than a dozen factors that might influence breeding success, from altitude and landscape to latitude and spring temperature.
'One of the most influential factors turned out to be the frequency occurrence of corvids. This study is serious science and it has produced an outcome that even the authors themselves may not have foreseen: predation is crucial.
'The biologists reached the conclusion after excluding carrion crows from their calculations; "Recent studies suggest that most predation is from smaller corvids, particularly magpies."
'The paper's authors are Emmanuel Paradis, Stephen R. Baillie, William J. Sutherland, Richard D. Gregory, Caroline Dudley and Humphrey Q. Crick and their study of large-scale ecological patterns is concentrated on the thrush and blackbird.'
Unquote
Anthony