Owl banders at Assateague Island, Maryland, have recorded the highest number of northern saw-whet owls since 1999.
It seems that every four years, banding stations in Maryland get an increase in the number of saw-whets passing through and wintering over. The only glitch in that trend was in 2003, and Brinker believes West Nile virus may have had a big impact on the northern saw-whet population in Canada. Birds there, with little resistance to the virus, died.The banding station at Assateague is part of Project Owl-Net, which links banding stations across North America to increase our understanding of owl migration. The influx of saw-whet owls seems to be part of the same general movement of boreal birds that is bringing more winter finches than usual.
But this year, the birds are back and then some.
Brinker said it appears there is a food web link in the four-year cycles.
The coniferous forests in Canada produce lots of seeds some years, which attracts lots of mice and other small rodents. Saw-whets feed on these small rodents.
If a food supply is available, the saw-whet owls simply stay put. But when there is little seed and few mice, the saw-whets move south to find a food supply, like this year.
Through last week, the team at Assateague had captured, banded and released 152 saw-whet owls. Similar numbers are being found at other Maryland field stations, particularly two locations in western Maryland.
There, volunteers banded and released nearly 500 owls as of last week. A fourth study area, in Maryland west of Bridgeville, has had 106 owls pass through the banding station. The numbered leg bands include instructions on how to report an owl found dead or alive.