Canada's national environmental agency has assessed the various ways in which birds meet their untimely end owing to human activity. The main culprit? Cats, who are responsible for a whopping 196 million bird deaths each year.
Owing to human activity, birds can get killed any number of ways.
Outside of cats, the leading causes of bird deaths in Canada each year include power transmission lines (25.6 million), flying into houses (22.4 million) and vehicles (13.8 million), hunting (4.7 million), agricultural pesticides (2.7 million), and flying into low/midrise/tall buildings (2.5 million). The researchers considered more than 25 human-caused sources of bird mortality.
But nothing compares to cats, which can be divided into two categories: death by feral cats (116 million) and death by domesticated cats (80 million).
These numbers are comparable to those of the United States, with recent estimates of bird deaths by cats between 1.4 billion to 3.7 billion each year. It's a North American problem, one with implications to conservation efforts and the spread of diseases (like T. gondii and rabies).
The Ottawa Citizen reports:
The numbers don’t surprise veteran Ottawa birder Bruce Di Labio.
“Cats are the biggest killer of our bird life in North America.
“People let them out. They’re responsible, and indirectly they are leading to the killing of these birds by letting the cats out,” he said.
“A lot of people who own cats probably don’t even realize,” he said. “Those animals are decimating our bird population ... They’re hunters. They’re natural hunters. That’s what they do.”
According to Environment Canada, several billion birds from over 400 species breed each year in Canada in a wide variety of habitats. But shorebirds, grassland birds, and aerial insectivores in particular have experienced rapid declines, many of which can be attributed to human-driven habitat change and mortality across North America over the past 40 years.