Bird predation by cats—an alternative way to estimate the number of birds killed

Abstract

Many studies have tried to estimate the number of birds killed by cats, most of them based on the number of birds killed by a smaller number of cats in a local area and then scaled to larger areas, or a whole country. Such estimates can be confounded by several factors, and the results of one study may not always be applicable in another setting where climate, habitats, and societal structure differ. Here I used an alternative approach to estimate cat predation on birds using ring recoveries of birds reported to the Swedish national ringing scheme as killed by cats. With the assumption that ringed birds are taken by cats in an equal proportion as unringed birds, I estimate that about 0.03% of all passerine birds are killed by cats in Sweden annually. This amounts to about 100,000 birds per year, which is much lower than previous estimates.