More Proof That Housecats Are Birds' Biggest Enemy

Bird-safe glass is worthwhile, but keeping cats indoors would prevent far more songbird deaths.

Human-Related Causes of Bird Mortality

A new study finds an estimated 105–348 million birds in Canada each year are killed by domestic cats, making these pets and their feral compatriots the biggest human-related threat to wild birds—more lethal by far than large office buildings and wind turbines, which sometimes take the blame.

Researchers calculated that collisions with residential and low- to mid-rise buildings account for 24.8 million bird deaths, and tall buildings claim another 64,000—not an insignificant figure, especially when these deaths could be prevented with shading features or window film. Wind turbines were responsible for just 16,700 bird fatalities—about 13 birds a year per turbine in Canada—while the average feral cat there kills 24 to 64 birds annually. Although only about 25% of cats in Canada are feral, this group likely kills 59% of the birds that succumb to feline predation, suggesting a need to both keep cats indoors and to spay or neuter pets.

The study, published in Avian Conservation & Ecology provides firm figures that give more credence to similar findings by researchers in the United States. Although the most recent estimate of birds killed by cats in the U.S. is ten times higher than this estimate in Canada, researchers say this difference is in line with a higher human population and a larger number of feral cats.