How colourful collars can help reduce the number of birds killed by domestic cats

Rainbow coloured, high-visibility ruff collars for free-roaming house cats can reduce the number of birds the felines are able to kill, according to preliminary results from a study at the University of Northern British Columbia in Prince George, B.C.

"It looks like the high-viz collars work," said Professor Ken Otter, chairperson of UNBC's department of ecosystem science and management. 

Because birds have excellent colour vision, the flashy collars appear to provide the birds with an early warning system against stealth attacks by cats.

"To the bird, this rainbow colour stands out like a sore thumb," said Otter. "It's the opposite of a hunter's camo. "

Otter says an initial study with 14 house cats and their owners showed the cats brought home fewer dead birds when wearing the rainbow collars. But concerns that cats could be a vector for COVID-19 with the potential to infect researchers meant his work was put on hold during the pandemic.

Otter hopes to recruit about 40 more cats and owners in Prince George in the coming months to provide more "robust results." The owners will be asked to log any birds their cat kills during one week with the collar on and another with the collar off.

He says the research is important, because scientists estimate Canadian domestic cats kill between 150 million to 300 million birds a year, contributing to the overall decline in bird populations.

Collar bells not effective

Otter says hanging bells on cat collars isn't usually effective because cats learn to suppress the bell sound while they're hiding and standing still.  

"By the time the cats pounce, it's too late ... for the bell ... to alert the birds." 

He hopes high-visibility collars may give cat owners a new tool for protecting birds.

"You can decrease the impact that your free-roaming cat is actually having," he said. 

Collars don't hold back mousers

For people who rely on their cats to be mousers, Otter says his initial findings showed the multi-hued collars didn't affect the number of rodents, including house mice, the cats killed. 

There was also evidence that the majority of house cats kill just a few birds, and only a very small minority are "really prolific hunters."

Otter is collaborating with UNBC environmental and sustainability studies professor Annie Booth on a range of cat research projects.

Booth says these kind of studies are long overdue.

"One of the things that I think is really fascinating is just how little research there is on dogs and cats," Booth said.  

"We always studied wildlife. Now, we're finally starting to see a real rise in interest in domestic animals, our nearest and dearest. Cats are a very popular animal, but also very controversial, because people don't want to see their cats picking off birds at the bird feeder. "