The proverbial clock may well be ticking down on many common species of aerial insectivores in Canada

The guild of ‘aerial insectivores’ – birds that specialize on feeding on flying insects – includes Whip-poor-wills Caprimulgus vociferus, nighthawks, swifts, swallows, martins, and flycatchers. Early results from the second Ontario Breeding Bird Atlas indicated some startling declines and even range contractions for this guild. The magnitude of the declines, especially within the past 20 years or so, is alarming.

In the last two decades alone, populations have fallen by over 70% in the case of Bank Swallow Riparia riparia, Common Nighthawk Chordeiles minor, Chimney Swift Chaetura pelagica, and Barn Swallow Hirundo rustica, and by over 50% for Cliff Swallow Petrochelidon pyrrhonota, Olive-sided Flycatcher Contopus cooperi, Eastern Wood-Pewee Contopus virens, Northern Rough-winged Swallow Stelgidopteryx serripennis, Eastern Kingbird Tyrannus tyrannus, and Purple Martin Progne subis. Declines have been so severe that Chimney Swift, Common Nighthawk, and Olive-sided Flycatcher were recently designated as nationally Threatened species. Barn Swallow, Bank Swallow, and Eastern Wood-Pewee may not be far behind. For these and other aerial insectivores, the trend signals are getting stronger and more compelling. Of all the factors that could be affecting insect populations, perhaps the most obvious is the exceptionally widespread use of pesticides across the modern agricultural landscape. After all, these agents are specifically designed to control insect populations. It is reasonable to think that their application could have a cumulative population-level effect across broad geographic regions.

Source: Special Feature by Jon McCracken (attached)
BIRDWATCH CANADA, WINTER 2008, NUMBER 42, 4-7