MARCH 25, 2016
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. They've become the centre of one of
greatest biological mysteries, and scientists are scrambling to discover why. Canada
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
, according to a 2012 report
by the North American Bird Conservation Initiative. Many birds in this category
are now listed as threatened in Canada . Canada