Could we thank the shooting fraternity for the increase in the number of Common Buzzards

By Alwyn Jackson
I could never comprehend why, when so much energy and effort is put into ridding our countryside of alien species, a relatively small minority of people are allowed to flood our fields and woodlands with many millions of alien Pheasants and Red-legged Partridges at this time of year.
As far as I know, the impact of the release of these birds upon our ecosystem has never been studied but new BTO research has revealed that the release of Pheasants and Red-legged Partridges for commercial shoots may be boosting numbers of the avian predators and scavengers.
We don’t know for certain how many birds are released each year, but estimates based on the National Gamebag Census by the Game and Wildlife Conservation Trust put the figures at around 41-50 million. This equates to around 45,000 tonnes of biomass which is more than twice the combined weight of all our native breeding birds. Game management can have positive effects; measures to enhance agricultural habitat for gamebirds are likely to be advantageous to other species. The creation of woodland rides can also be of benefit to butterflies but what about the impacts of the gamebirds themselves? Their foraging habits could have effects. For example, they might alter hedgerow structure which is important for nesting birds or reduce the numbers of invertebrates available to other birds to eat. They may also increase disease or parasite transmission.
It has been established that the majority of birds released do not end up in game bags, but are predated, scavenged, hit by vehicles, or survive to become part of the breeding population. They are therefore potentially a large food resource available to predators and scavengers. Gamebird releases typically occur in late autumn, when other food may be scarce, so is it possible that predator populations are being sustained above levels they would otherwise reach without releases?
If it occurs, this inflation of predator numbers might alter predator-prey dynamics, increasing predation pressure on some vulnerable species, including declining breeding waders like Curlew.
This study used data from the BTO Breeding Bird Survey and Bird Atlas 2007-11 to identify associations between the occurrence patterns of gamebirds and the abundance and population growth rates of several generalist predators, including Buzzard, Jay, Raven, Magpie and crows (Carrion and Hooded combined). While many other factors influence predator abundance, such as fine-scale habitat variation, availability of other food sources, and game management activities, the results suggest that large-scale variation in avian predator populations is predominantly positively affected by gamebird releases. The potential implications of this finding need to be thoroughly tested. Such tests could include regulation of releases on a trial basis, to determine effects on ground nesting birds, for example the compulsory recording of releases and the number of predators controlled would also be valuable for a better understanding of the impacts, positive or negative, of gamebird releases on the wider environment.
I suppose it is a matter of “watch this space” but I for one will be interested in the outcome of such research should it ever materialise. A good reason for supporting the BTO!
Acknowledgements to BTO Researchers Henrietta Pringle, Mark Wilson, John Calladine, & Gavin Siriwardena, Head.

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