Like The Atlas of Breeding Birds in Britain and Ireland (1976) that inspired it, Ontario’s atlas survey of breeding birds is a monumental exercise in citizen science, in which thousands of eager amateur (and professional) naturalists across the province report on the whereabouts of breeding birds, collecting vast amounts of data that simply would not be available otherwise.
“It’s incredibly valuable,” says Wendy Francis, Ontario Nature’s former director of conservation and science. Ontario Nature helped get the province’s first breeding bird atlas off the ground and is a founding sponsor of the second. “Nonprofit organizations can rarely do their own original scientific research. To have the capacity to do this kind of comprehensive study across the province, and to repeat it every 20 years and look at trends, is not something that’s available to most environmental organizations … We simply couldn’t afford to do it without the volunters.”
The granddaddy of the modern bird atlas movement, the first British atlas, was based on a survey conducted between 1968 and 1972 by about 10,000 contributing “twitchers,” or birdwatchers. Its system of grid-based atlassing quickly became the model used elsewhere. Denmark and France published their atlases around the same time, and much of the rest of Europe, New Zealand and some African countries quickly followed suit.
In the late 1970s, the notion literally winged its way to Ontario when George Francis, now a professor emeritus of environment and resource studies at the University of Waterloo, flew home after seeing Britain’s atlas in a British bookstore and tried to convince people the same could be done here. Eventually, says Cadman, the idea caught on. Now, most Canadian provinces and U.S. states have breeding bird atlases, and many researchers are compiling similar atlases for other animals and even plants.
“I’m all for citizens’ science,” says York University biology professor Bridget Stutchbury. “I think the volunteers on these projects have proven for decades how good they are at it and how passionate [they are] about it. There is no way in the world you could raise enough money to pay people to do what people are doing out of their own interest and concern for nature.”
Stutchbury is the author of the recently published Silence of the Songbirds, which describes declining songbird populations in North America and around the world. Stutchbury argues that globally dwindling bird numbers signal a dangerously unhealthy environment.
The new Ontario breeding bird atlas, however, tells a different story. It suggests that many of the same bird populations that the United States-based Breeding Bird Survey shows are in decline – such as wood thrushes and rose-breasted grosbeaks – appear unchanged here (at least as reflected in the changes in bird prevalence). The populations of other birds shown to be faltering across the continent, such as Wilson’s warblers, appear to have increased in Ontario.
Stutchbury is sceptical of these results. She points out that the changes in distribution that show up as changes in the number of atlas squares in which birds are found provides a crude measure of shifts in actual populations. “It’s not really a criticism,” she says, “it’s just that there are limitations on the kinds of questions you can answer.”
Peter Blancher, a land bird scientist with CWS who analyzed breeding bird records collected for the atlas, agrees that comparing the results of the two atlases has not been easy. For starters, as many as 700 more volunteers clocked almost 25 percent more field hours in the new atlas compared to the first. Furthermore, birders spent different amounts of time within the same individual atlas squares between the two atlases. Blancher calculated the prevalence (the likelihood-of-being-found-in-a-square) figure for each species to overcome these pitfalls.
A change in the prevalence of birds between the first atlas and the second offers a glimpse of the direction in which bird populations might be moving, but it says nothing about the actual size of these populations. The new atlas attempts to address this by also including results from “point-count” bird censuses used to estimate how many birds of each species are living in Ontario.
Future point-count surveys will reveal increasingly accurate population shifts. But, for now, the atlas uses bird prevalence based on the atlas square data to reflect population changes – including the precipitous declines of three of Ontario’s endangered bird species. The likelihood of finding loggerhead shrikes, Henslow’s sparrows and northern bobwhites in an atlas square plummeted by 60 to 80 percent since the first atlas. Moreover, declines were detected for many neotropical migrants in the Carolinian region – the veery declined by 27 percent and the ovenbird by 22 percent. The prevalence of many waterbirds in the same region are also declining, including the American bittern (down 37 percent), common moorhen (down 38 percent) and spotted sandpiper (down 18 percent).
“The results would suggest that of all the regions in the province, the Carolinian is the one in which there should be greatest concern for bird populations,” says Cadman.
Conversely, the bird populations of the north seem to be thriving. Canada’s boreal forest is the breeding ground for about a third of all North American birds, and in Ontario, it makes up more than half of the province’s forested area.