Editor's note: The Grapevine 'commissioned' this article due to concern expressed by one of our Dunnington readers, which you can read below the article. Our grateful thanks to Mike for finding and sharing some facts and figures on this topic.
Cats!
A “Marmite” topic if ever there was one.
Love them or hate them, they are undoubtedly garden birds’ number one predator, but what is their true effect, are they really responsible for the ongoing decline in bird numbers?
It’s difficult to get a handle on the true situation, but according to both the RSPB and the Mammal Society there is no scientific evidence that cats are responsible for the general decline in many gardenbird numbers. Looking through academic (and quasi-academic) papers, the most salient fact is that most trials run are local and lacking in rigour.
Domestic cats are rarely underfed, but most still hunt. There are also many feral and semi-feral cats around – but how many? Most trials count prey brought back to the cats’ home territories, but what percentage is that of what they catch?
The most recent figures of how much wildlife is killed by cats are from the Mammal Society. They estimate that cats in the UK catch up to 275 million prey items a year, of which 27 million are birds. This is only the number which were caught and brought home, though. We don't know how many more birds cats caught, but didn't bring back, or how many escaped but subsequently died.
The most frequently caught birds, according to the Mammal Society, are House Sparrows, Blue Tits, Blackbirds and Starlings whilst the most common garden birds are Wrens, Robins, House Sparrows, Woodpigeons (a bit big for most cats!), Chaffinches and Blackbirds. Make what you will of the disparity! Bird behaviour has lot to do with which are caught, and I suspect that birds in an area with large numbers of cats will change their behaviour accordingly.
The RSPB say “We also know that of the millions of baby birds hatched each year, most will die before they reach breeding age. This is natural, and each pair needs only to rear two young that survive to breeding age to replace themselves and maintain the population. It is likely that most of the birds killed by cats would have died anyway from other causes before the next breeding season, so cats are unlikely to have a major impact on populations.
Those bird species which have undergone the most serious population declines in the UK (such as Skylarks, Tree Sparrows and Corn Buntings) rarely encounter cats. Research shows that these declines are usually caused by habitat change or loss, particularly on farmland.”
What can cat “owners” do to reduce predation levels?
Number one must be to keep them in at night: it helps; we did so with our cats all their lives. This is particularly important during the breeding season when there are fledglings around. Inexperienced and hungry young birds, desperate for their first feed of the day are easy prey, and parent birds are all too willing to risk their own lives when feeding offspring. Lights out and cats out at bedtime is not a good idea!
Collars fitted with bells or sonic devices have also been shown to reduce predation rates. It make take a cat a few days to get used to one though…..
If you’d like to read further, try Floyd, L., Underhill-Day, J. C. (2013). Literature Review on the effects of cats on nearby protected wildlife sites. Unpublished report by Footprint Ecology for Breckland Council.
Mike Gray
A letter from a concerned Dunnington resident.
I am writing to inform you that I have been a member of the RSPB for twenty two years and that I find myself compelled to write to you with the situation in Dunnington and our bird population.
It is a known fact that our wild life and birds in this country are in serious decline and therefore we should be doing something to try and elevate this situation. I am a keen bird watcher and I and my wife try to encourage and help the wild life in and around the area where we live but there is a major problem and this problem seems to be the abundance of cats and lack of understanding from cat owners, currently we have four different cats that visit our garden and its disturbing to watch them on our wildlife camera come and go into our garden at all hours. We feed the bird’s everyday and make sure there is water for them to drink and bathe in if they require this and it’s very nice to observe them from our windows.
I can understand why there are a lot cats in Dunnington as people get older they may have lost a partner and they are lonely so they buy or get a dog or a cat for company if they are quite fit they may get a dog and they can then exercise the dog, but if they are less fit they may prefer a cat and the cat will be good company for that person which is nice. But the problem is that these people leave the cat flap open overnight and therefore the cats can come and go as they please. The problem then is these cats are out all day and night and this is causing a problem for our wildlife, there is never a week that goes by where I don’t find feathers or a dead or injured bird in or around our house albeit I have tried to make our garden as bird friendly as I can. We have had a six foot high fence erected to try and keep the cats out of our garden but to no avail despite several attempts of trying different deterrents to elevate this problem.
We have several trees in our garden where birds roost and build their nests but the cats in our area are decimating this situation by climbing the trees and catching the birds. It is now at this time of year when the birds start breeding and building their nest, and this is when the problems will start again the cats will get into our garden and kill the fledglings and the parents but sometimes they don’t eat them they play with them until they are dead or just leave a mutilated body on the lawn or in the garden. This then leaves me the task of disposing these dead or injured birds?
These irresponsible cat owners leave their cat flaps open all day and all night which allows their cats to wander around freely at their leisure and they travel from one garden to another looking for birds to catch and play with or eat. If these cat owners were to put a collar with a bell around the cats neck this might improve the situation a bit, the birds would hear the bell and either fly off or take cover somewhere else which might help this situation, also if they could close the cat flap on night.
Keith Rowling