The haunting loon call that’s synonymous with Canadian wilderness may be under threat. According to a 40-year survey of the species conducted by Birds Canada, fewer common loon chicks are surviving to adulthood than in the past, a trend that comes as a surprise to scientists.
Since 1981, more than 4,000 volunteer birders have been recording observations of the species on 4,500 lakes. Researchers analyzed the cumulative data and found that during the past three decades, common loon productivity declined at a rate of 1.4 per cent per pair per year. In the 1990s, loons had an average of 0.7 young per pair per year, but in recent years, that number has fallen to 0.55. Scientists believe if productivity falls below 0.48, loon populations will likely start to decline.
“This result is monumentally important because these declines have been formally documented in only one other study focused on a single county in northern Wisconsin,” says Dr. Doug Tozer, director of waterbirds and wetlands for Birds Canada. “Without the dedication of the volunteers providing reliable, carefully collected data, the world would have no idea the common loon is in trouble.”
Scientists are unsure exactly what’s responsible for the decline. The study considered factors that have been known, or are thought, to influence loon productivity, including human disturbance, early spring temperatures, predation by bald eagles and food competition with double-breasted cormorants, but ultimately ruled each out.
Instead, the study’s authors theorize a complex interaction of damage caused by acid rain, mercury pollution and climate warming may be at least partly responsible. Further research, including continued observation by citizen scientists, will be critical in helping researchers solve the mystery of the decline — and ensure that the quintessential call of Canada’s wilderness is heard for many generations to come.
Dressing for feeding success