Date: 11/6/17 10:53 am From: Tucker, Trileigh <TRI...> Subject: [Tweeters] Window strike species distribution - a puzzle
In the past 3 weeks or so, we’ve had three window strikes. This is unusual both in number (I don’t remember any previous window strikes in the 3 years we’ve lived here) and in the species: a Varied Thrush, a Pacific Wren, and just a couple of days ago, a Fox Sparrow—all fairly secretive forest species who don’t tend to hang around feeders.
The birds that flit around our deck at the feeders, not surprisingly, include none of these; they’re mostly the standard ravenous juncoes and chickadees and bushtits, with towhees and Song Sparrows foraging on the ground below, plus the occasional Downy Woodpecker, flicker, and Steller’s Jay on the suet.
The discrepancy makes me wonder which species are most likely in general to be victims of window strikes. I found a 1993 study<https://sora.unm.edu/sites/default/files/journals/jfo/v064n03/p0302-p0309.pdf> whose abstract affirms what I would have expected with feeders present: that “birds died from window strikes approximately in proportion to their abundance at feeders.” So I wonder what could be going on, both in species and in timing. I’d be interested in your ideas.
Our house is sided with stained vertically-oriented wood (photo here<2017-11-6_0511-Side%20of%20our%20house.JPG>), and I wonder whether the forest birds might tend to see the windows as small gaps between trees? This was the side of the house where we found the Fox Sparrow. The other two birds were found at the base of a very large living-room window at the back of our very deep (~15’ square) deck, under a flat deck roof maybe 8’ deep. I was surprised that the birds would fly that far under the roof to collide with the window. And that only the forest birds would do this, rather than the feeder birds as well.
I’m also wondering whether time of year is making a difference, not only somewhat in species abundance, but perhaps also, could the changing angle of light be making the windows and walls look more woods-like?
The studies I’ve read are suggesting that window decals don’t make much difference, but I’ll be putting some up just in case. I sure hate to see these gorgeous birds become the victims of window strikes.
Thanks for any insights. Of course, it’s entirely possible that there’s a completely obvious explanation that I’m just oblivious to.
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Trileigh Tucker, PhD
Professor Emerita of Environmental Studies