Forty years ago, swallows were a common sight in the summer, darting between the beams of old barns or swooping low over the waters of a creek. These swift aerial acrobats seemed to be everywhere -- perched on telephone lines by the dozen awaiting the fall migration, or whirling and diving around old wooden bridges in pursuit of airborne insects. Now, these birds have seemingly disappeared from midair, entirely abandoning large swathes of their former Canadian range. Some, like the bank swallow, have seen their numbers plummet by 98 per cent since 1970. The swallows' disappearance is part of a larger trend affecting birds known as aerial insectivores, which spend much of their lives on the wing in a constant search for airborne insects to dine on. This group, which includes chimney swifts, purple martins, and whippoorwills, has plunged by 70 per cent in population in Canada, according to a 2012 report by the North American Bird Conservation Initiative. Many birds in this category are now listed as threatened in Canada. "Algonquin Park used to have barn swallows nesting on every bridge," says Michael Runtz, a naturalist and instructor at Carleton University. "They were abundant, nesting everywhere...they're all gone now."
Myles Falconer is a biologist at Bird Studies Canada, a not-for-profit organization dedicated to the study of Canadian bird populations. He's studied bank swallows since 2010, and penned a 2014 report on the birds for the federal Committee on the Status of Endangered Wildlife in Canada. Forty years ago, these tenacious burrowing birds numbered over 70 million individuals. Now, a scant 1.4 million remain -- a survival rate of two per cent. Despite this decades-long decline, they were only designated as threatened in 2013, after COSEWIC researchers watched a third of the population disappear in under a decade.
Falconer says this is the case for many aerial insectivores, which have been neglected in most scientific studies because of how large their colonies appear.
"They're widespread and common still, and they're so widespread and common that nobody has done any really intensive work on them, he says.
"There's still thousands of bank swallows, so it's difficult to see a difference between thousands and hundreds of thousands."
Despite this apparent abundance, another 3.65 per cent of the population is lost each year. And although a federal bank swallow recovery strategy is in the works, Falconer says it will only attempt to halt the population decline. It's unlikely the bank swallows will ever be able to rebound to their 1970 numbers.
Source: Rabble blogs, March 25, 2016
http://rabble.ca/blogs/bloggers/jenhalsall/2016/03/hard-to-swallow-myst…
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