Let's Talk About Birds: Northern saw-whet owls


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This is one of a series presented by the National Aviary, which works to inspire respect for nature through an appreciation of birds.

Crisp, starry nights and blue-sky days with pumpkin-orange colored trees can only mean one thing ... owls a-wing!

For a few weeks each fall, untold numbers of northern saw-whet owls fly over Pennsylvania in the dark -- dropping down occasionally on an unsuspecting mouse or shrew -- leaving no trace of their passage. They are winging their way silently southward, night after night, leaving behind the coniferous comfort of northern breeding grounds for hunting grounds farther south, mostly in the Virginias and Carolinas.

But, we didn't always know this.

The unseen migration of the northern saw-whet owl was a complete mystery to scientists until the mid-1980s. To determine whether the owls were present, researchers used a loud audio lure of the saw-whet's distinctively monotonous "toot-toot-toot-toot" calls to see if they could catch the owls after dark in bird-banding mist nets. Surprisingly, they attracted a much greater number than expected.

In the early 1990s, one of those enterprising researchers, David Brinker, conceived the idea of a network of owl banders throughout the Eastern United States, working together to unravel the mystery of saw-whet owl migration. "Project Owlnet" was born. Using the proven effective audio lure method, a growing number of cooperating owl-banding stations began documenting what proved to be a cyclical migration of saw-whet owls, with big movements one year and almost none the next. They even began catching one another's banded owls. When one bird bander catches a bird previously banded by another, it is called a "foreign retrap." This owl-banding network now generates dozens of foreign retraps every season, "connecting the dots" of the once-mysterious northern saw-whet owl migration.

The National Aviary is establishing a new Project Owl net-banding station near Pittsburgh with help from April Claus, the naturalist for Sewickley Heights Borough Park and Fern Hollow Nature Center. Visitors are welcome to stop by on designated nights this fall to discover if Pittsburgh is on the migration pathway of the saw-whet owl. If you're something of a night owl yourself and would like to join in this adventure, check the National Aviary website or Facebook page for details or contact me directly for more information about the next owl-banding session (Robert.mulvihill@aviary.org; 412-258-1148).

And, don't forget, the National Aviary will celebrate its annual "Owl-o-Ween" Saturday and Oct. 26 from 11 a.m. to 3 p.m., complete with a Halloween party, trick-or-treating, crafts and close encounters with raptors, owls and other creatures of the night.

science

First Published October 15, 2013 8:00 PM


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