Thursday, December 13, 2007

And now to sleep...

We've wrapped up what can only be described as a remarkable season of saw-whet owl banding, and I suspect everyone on my crew is enjoying the chance to get caught up on their sleep. I know I am.

We’ve been banding migrant owls since 1997, and last year was one of the worst seasons on record – only 202 of the miniature owls, the product of two solid months of netting, every rainless night from dusk until midnight at three sites in central Pennsylvania.

This year was a stunning difference, though. As I've explained in earlier posts, this autumn marked the peak in a four-year cycle in saw-whet populations, and coincided with a crash in the number of small rodents in Canada. The result was an "irruption," a great wave of owls flooding south into the eastern U.S.

When we furled our nets for the last time a week ago, we'd netted 895 saw-whets – 393 of them at our Hidden Valley site in Schuylkill County, 284 at Small Valley in Dauphin County, and 218 at King's Gap in Cumberland County. Each owl was ringed with a lightweight, government-issued band stamped with a serial number, measured, and released.

Twenty-three of the owls we caught, though, were already banded, and these so-called foreign birds are always an exciting highlight. Thanks to a network of owl researchers called Project Owlnet, and the federal Banding Lab's online reporting system, we were able to quickly determine where most of these birds came from – and the results often surprised us.
Where our autumn 2007 owls came from.

Not surprisingly, many of the recoveries were of owls banded to our north, at places like Prince Edward Point Bird Observatory, on the north shore of Lake Ontario (seven owls) or Timiskaming and Hillardtown Marsh, near the Ontario/Quebec border (two owls). While many of the owls were banded earlier this fall, about half had been banded in previous years, including two banded in 2006 in the Shawangunk Mountains of southern New York, 2005 owls from Long Point, Ontario and Williamstown, Massachusetts, and a 2004 bird from Prince Edward Point.

The most remarkable foreign owl was the first of the season, netted Oct. 7 at Hidden Valley – a bird that had been banded at the end of July as a juvenile at Whitefish Point, on the upper peninsula of Michigan. It was one of more than 700 saw-whets the Whitefish Point Bird Observatory banded this summer, most of them in the "chocolate" juvenile plumage. Given that our site is almost 600 miles east/southeast of the UP of Michigan, it's an indication of how widely these birds wander.

Even though we've wrapped our nets for the season, the migration continues; Holiday Beach, Ontario, reports a few saw-whets still passing through, and I'll continue to net in the yard the rest of the month. And last week, my good friends and colleagues Bob and Martha Sargent netted a couple of saw-whets in north Alabama, where I suspect the big push has yet to arrive.

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