Wet and windy weather cause of swallow die-off

October 2, 2013

SALEM, Ore.―The recent wet and windy weather has taken a toll on Oregon’s Barn and Violet-green Swallows. On Monday, veterinarians for the Oregon Department of Fish and Wildlife received multiple calls from Oregon residents about dead and dying swallows. Reports have come from the Port of Saint Helens to as far south as Junction City.
Groups of from 10 to 200 swallows were reported dead or near death in barns and other structures where they perch. Mortality appears to be greater closer to rivers and standing water where the birds concentrate.

Colin Gillin, ODFW State Wildlife Veterinarian, estimates that thousands of birds have died. “This type of mortality event is unprecedented and considered a rare and unusual event,” said Gillin. “The effect on bird populations is unknown.”

A number of birds were examined at the Oregon State University Veterinary Diagnostic Laboratory and pathologists determined the swallows were thin and had not eaten recently with their cause of death most likely being weather-related starvation. Veterinarians believe that the four consecutive days of rain and wind prevented the swallows from feeding at a time when they would normally be preparing for winter migration. September was the wettest on record for the Willamette Valley.

Swallows feed on insects during flight and inclement weather events can have an effect on young and weaker birds that cannot take in enough food to meet their energy requirements. Swallows are seasonal migrants to Oregon and migrate to Central and South America during winter.