I tawt I saw a puddy tat
I did I taw a puddy tat!
(Livingston/May/Foster)
Although Elaine and I are “dog people” (but enjoy Garfield cartoons), we wondered what impact cats have on bird populations. We wanted to investigate whether cats are responsible for the decline in bird populations in North America.
Peter Marra, Head of the Smithsonian Migratory Bird Centre, loves cats. But he believes cats need to be removed from the landscape because they are the leading human-influenced cause of the death of birds.
Outdoor cats, Marra claims, have led to the extinction of 33 bird species. Of the 86 million cats Americans own, he estimates about 29 million each kill an average of two birds a week. Although pets are a problem, Marra sees feral or stray cats—up to 80 million in the United States—as the real issue, with each cat killing an average of 6 birds per week.
In 2012, using mathematical models for the previous 50 years of data, Marra estimated that annually, outdoor cats kill at least 2.3 billion birds and 12.3 billion mammals in the United States.
Since 1970, North American bird populations have declined by 3 billion, or one third of the 9 billion estimated 50 years ago. In Victoria, British Columbia, birders have been very worried about the rapid decline of birds in the area. Victoria is one of the deadliest places for songbirds in the country. In a 2013 Environment Canada study, Victoria ranked fourth after Toronto, Montreal and the lower mainland in cat-caused bird deaths.
On Vancouver Island, the streaked horned lark’s extinction was attributed to cats. The coastal vesper sparrow populations on the island have decreased by 85% in a decade according to the same study.
Every bird in southern Canada has a 1 in 14 chance of being killed by a cat. Across North America the species that suffer greatest predation from cats are house sparrows, robins, red-winged blackbirds, and ring-necked pheasants.
Environment Canada scientist Peter Blancher estimates that cats kill between 100 and 350 million birds annually. Thirty-eight per cent of those are by pets, the rest from feral cats. Of the 468 species of birds that appear regularly in Canada, 115 are vulnerable to cats due to their nesting or feeding behaviour. Forty of these species are common in urban or suburban areas. Twenty-three species are at risk in Canada, 10 of which have cats specifically identified as a factor in their decline.
Research presented by National Geographic combined bird death statistics for Canada and the United States. Researchers estimated that stray or feral cats killed 1.768 billion birds annually, and domestic cats 764 million. Included in the research were statistics for bird deaths caused by striking buildings, estimated to be 624 million, vehicle strikes at 213 million, 55 million from power lines, and 7 million from other incidents such as windmill collisions.
The challenge of course is a moral dilemma for society at large. Peter Marra notes that aside from bird killing, cats do have the potential to spread rabies and toxoplasmosis, a parasite found in cat feces. Wildlife ecologist Stanley Temple views cats as an invasive species that is causing major destruction to a part of complex ecosystems. To preserve dwindling bird populations, is the elimination of outdoor cats the answer?
We explore international solutions in our next column!
