Don't cats just play the role that predators used to play in our landscape?

While it is true that there are fewer native predators in the United Kingdom than would have once been the case, the problem is mainly one of numbers - domestic cats can reach densities of 100 times or more higher than native carnivores. In the UK there are many areas where there are estimates of hundreds or even thousands of cats within a single square kilometre, whereas the nearest competitor would be the red fox at about 37 per square kilometre. As a 2020 study puts it, the predation rate of cats "is similar or higher than the per-animal ecological impact of wild carnivores but the effect is amplified by the high density of cats in neighborhoods."

Sources:

• "Rural residents' free ranging domestic cats: a survey". Coleman, J. S. & Temple, S. A. (1993).
• "Differences in the capture rate of cage-trapped red foxes Vulpes vulpes and an evaluation of rabies control measures in Britain". Baker, P. J., Harris, S., Robertson, C. P. J., Saunders, G., & White, P. C. L. (2001).
• "The small home ranges and large local ecological impacts of pet cats". Kays et al (2020)
• "Cats per square kilometre". UK Animal and Plant Health Agency (2023)

Doesn't neutering cats stop them from hunting?

There is some evidence that neutered cats do less hunting than others - but the amount is still substantial. Almost all the cats in a 2006 study were neutered, but were still killing over 5 prey items each month.

Sources:

• Kayes, R. W., DeWan, A. A.. Ecological impact of inside/outside house cats around a suburban nature preserve(2006)

Does fitting a bell to a cat's collar solve the problem?

The evidence is inconsistent on how useful attaching a bell to a cat's collar is. One study suggested that attaching a bell cut predation rates by almost half, but another study found no benefit to birds (perhaps due to birds relying primarily on visual cues). There is also some indication that cats may learn to adapt to wearing the bell, meaning the reduction in predation seen in some studies may not be maintained over the longer term.

Regardless, no studies suggest that attaching a bell or other audio device to the cat entirely stops predation, so even if all cats were fitted with such devices, there would still be tens of millions of birds killed by these cats.

Sources:

• "Bells reduce predation of wildlife by domestic cats (Felis catus)" Ruxton et al (2002)
• "Predation of wildlife by domestic cats Felis catus in Great Britain". Woods, McDonald, Harris (2003)

What about better food/stimulation/etc?

Various measures are occasionally suggested to reduce the amount of predation - attaching bells to a cat's collar, feeding them more meat-dense food, engaging in daily play at home, etc. While these do seem to have an effect on prey brought home, the largest seen was 36% - nowhere close to being effective prevention.

Source:

• Provision of High Meat Content Food and Object Play Reduce Predation of Wild Animals by Domestic Cats Felis catus. Cecchetti, Martina et al. (2021)

Aren't cats only catching weaker birds that would have died anyway?

One study in 2008 suggested that the birds caught by cats tended to have worse physical condition than an average bird of that species. Indeed, some have selectively quoted this paper to say that these birds "would have been likely to die from other causes".

However, the same study goes on to add, "predation on birds may be highest at dawn, when fat reserves are lowest" meaning that the poor physical condition of the birds that were caught might mostly reflect a fact about when the hunting happens, rather than about the relative condition of the birds get hunted.

Indeed, it goes on to say that "cat predation was still frequently estimated to be equivalent to 20–40% of the total number of adults and juveniles combined." and that "Dunnocks, Robins and Wrens appear particularly susceptible to cat predation; in over half the sites studied, the estimated number killed exceeded the number of juveniles fledged". This goes well beyond cats only taking the weakest, and in fact suggests a situation where the population is not sustainable and is "heavily dependent on immigration from other areas."

Sources:

• "Cats about town: Is predation by free-ranging pet cats Felis catus likely to affect urban bird populations?" Baker, Molony, Stone, Cuthill, Harris (2008)