According to a new study from the UK, outdoor cats impact birds even if the cats don’t actually hunt. The research, published in the Journal of Applied Ecology, was led by Karl Evans at the University of Sheffield. The report concludes that even a brief appearance of a cat near a bird nest leads to behavioural changes in parent birds that lead to a roughly 1/3 reduction in the amount of food brought to nestlings.
Additionally, the natural response of parent birds to the appearance of predators — alarm-calling and nest-defense — dramatically increases bird nest predation by other animals who’ve been alerted to the nest.
Even more worrying is the fact that the study found no evidence that parental feeding rates returned to normal even after the cat model had been removed, even up to 90 minutes later. Further, there was no evidence that the parents at any time compensated for the reduced feeding rate, by bringing more food at a later time.