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News emerged this week that trial culls of magpies and crows are to go ahead at several sites in an effort to arrest the decline in UK songbirds [1]. Whether this action is justified or not is being hotly disputed, with the RSPB in the ‘anti-cull’ corner and Songbird Survival proclaiming its support. While this announcement largely appeared as if out of the blue, this particular issue has raised its head repeatedly over the years [2, 3, 4, 5, 6]

Do most UK corvids (birds of the crow family, Corvidae) take the eggs and/or nestlings of other birds? Undoubtedly. They are extremely adaptable and intelligent opportunistic omnivores. Are songbirds in decline? Generally speaking, yes.  And they have been in decline for the past 25 years or so.Data published a in January by DEFRA described the following [breeding] bird population fluctuations (note woodland and farmland bird population trends) [7]:

  • Farmland birds: Down 8% between 2003 and 2008.
  • Woodland birds: Little change between 2003 and 2008.
  • Water and wetland birds: Down 5% between 2003 and 2008.
  • Seabirds: Up 10% between 1999 and 2009.
  • Wintering waterbirds: 9% between 2002-03 and 2007-8.

But are corvids responsible for these declines? No. At least, not solely. As common predators, they unquestionably impact the populations of prey species. And in certain situations, it may be necessary to control their numbers. However, if the current trial is to be the precursor to a general cull, I’d be intrigued to know whether the science supports such action (and indeed, I’ll be doing some research on this topic). A recent study by the BTO found that there is no evidence to support the hypothesis that common avian predator (and corvids surely count as such) abundance is correlated with large declines in songbird populations [8].

“Although it is widely accepted that, in some situations, predators of nests, chicks and full grown birds do affect the abundance of avian prey species, until now the evidence that such effects are widespread amongst songbirds has been weak, having been based on a relatively small number of studies.”[8]

It seems that we must find a non-anthropogenic cause for the decline in songbird numbers, so we point our fingers at cats, raptors, corvids, squirrels; anything and everything but ourselves. As is so often the case, the decline in songbird numbers is likely to be largely attributable to human activities and then largely changes in land management. I’ll be interested to read the results of these trials though at the moment it appears to be little more than a case of throwing the sheep to the wolves, as it were.

[1] The Telegraph – Magpies and crows to be culled to protect songbirds
[2] Mail Online – The magpie menace slaughtering our songbirds
[3] The Telegraph – Magpies not to blame for songbird decline
[4] The Guardian – Magpie threat to songbirds
[5] Times Online – Charities in dispute over culling magpies
[6] Times Online – Songbirds and culling magpies
[7] DEFRA – Population of wild birds: 1970 – 2009
[8] BTO -Are predators to blame for songbird declines?

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