Monday, January 30, 2006

Rock Wren in a Shrike's Larder

This interesting message and incredible photograph came in to Bill of the Birds from my friend Bill Clark (that's the Nevada/Arizona Bill Clark, not the South Texas/hawk expert Bill Clark).

Nevada Bill Clark writes:
I was completing a Nevada Bird Count transect near Laughlin along the Colorado River. Around stop 9, I observed this hatch-year rock wren moving through a large creosote. Both of us were "ambushed" by a loggerhead shrike. The shrike whizzed by me, choosing the smaller prey. I did not witness the kill, but I knew something was going on. As I headed to my next point I flushed the shrike and it flew off with the wren. I made a note of the shrike's landing site and returned about 15 minutes later, having completed my survey, to discover this "hanging tree." From the wear and the amount of dried blood on the branches, it was apparent this site had been used previously.

A recent thread on a bird listserv I subscribe to was about the carrying capacity of raptors. A general consensus was that a raptor could carry about 1/2 its own weight. The wren was about 1/3 the shrike's weight. But what really impresses me is what you discover when you compare wing spread to body length. More wing= more lift, right? A golden eagle has a 2.5 to 1 wing-to-body ratio. A loggerhead shrike has about a 1.3 to 1 wing-to-body ratio. This loggerhead shrike is one strong dude! He's got to work lots harder to fly, carrying his prey item to the larder.
Thanks for sharing this experience, Bill!

It would have been even more amazing if the shrike had been able to subdue you (instead of the rock wren) and then flew to the larder tree, carrying you in its bill.

Now THAT'S a nature documentary I'd pay to see!

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