Subject: [Tweeters] owl competition
Date: Mar 9 14:34:56 2005
From: Charles Swift - charless at moscow.com


Interestingly, prior to 1980, Western Screech-Owl is virtually unrecorded on
WA CBCs. I presume this is due to owling effort more than anything else?
When considering birds/party hour with respect to owls**, I presume this
graph is using total party hours rather than owling party hours which would
probably be more accurate. If owling effort has increased proportional to
total effort than this is valid, however, if this is not the case the
results may be misleading.

In any case, I wasn't arguing that they are not decling. Any number of
things may be contributing to this such as habitat loss or change
(significant in the Puget Sound area in the past decade), poor productivity,
etc. Clearly competition/predation from Barred owls could be one factor. I
think it can be difficult to tweeze this stuff out.

thanks, Charles.

** some owl species are recorded during daylight on counts but I presume
screech-owls are recorded primarily nocturnally

>-----Original Message-----
>From: Jamie Acker [mailto:owler at sounddsl.com]
>Sent: Wednesday, March 09, 2005 12:09 PM
>To: charless at moscow.com
>Cc: Tweeters
>Subject: Re: [Tweeters] owl competition
>
>
>The Annual CBC data for Western Screech-owl from 1990 on shows a steady
>decrease in number of birds per party hour in Washington State. Many of
>our CBCs are in the Puget Sound, an area where the Barred Owl has made
>significant headway in recent years. While the CBC is not rigidly
>scientific, it does provide an indication of what is going on.
>
>For those interested, the website:
>
>http://audubon2.org/birds/cbc/hr/graph.html
>
>>From there, go to the graphing selection, and make selections. Kind of an
>interesting site. Might want to pull up the Barred Owl data too...
>
>-Jamie
>
>
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>