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RE: Vocalization intensity and species density

Subject: RE: Vocalization intensity and species density
From: "Kevin J. Colver" <>
Date: Sat, 20 Apr 2002 17:36:08 -0600
I'm just back from a trip to Organ Pipe National Monument where the
birds are singing very little this year.  The park biologist tells me
that his bird counts this year are down 80% over previous years, due to
the severe drought conditions.  The only place I noted much singing was
near park headquarters and campgrounds where birds had access to human
introduced resources such as water and picnic leftovers.

Yes, it was my impression that the birds remaining sang much less than
expected.  The dawn chorus was abbreviated.  Survival mandates a balance
between dangerous public display needed for breeding purposes and
keeping a low profile when possible.  Birds will only get up on the
cactus and sing if they feel the compelling drive to do so.

On the other hand, a lost wanderer may sing quite a bit.  We had an
Ovenbird singing persistently in our canyon a few years ago, never could
attract a mate because he was a thousand miles from the ladies.

Kevin J. Colver
114 North Clark Lane
Elk Ridge, UT  84651

-----Original Message-----
From: Mark Oberle  
Sent: Thursday, April 18, 2002 9:05 PM
Subject: [Nature Recordists] Vocalization intensity and species density

A few years ago I documented evidence of breeding Red-breasted Nuthatch
(Sitta canadensis) and Golden-crowned Kinglet (Regulus satrapa) in the
southern Appalachians of Georgia. This population had been previously
undetected because they did not vocalize much  and perhaps because few
birders had been in that area of mature white pine and hemlock after
migration. Now that I have been back in Seattle for a few years, I have
unquantitated impression that these two species do  in fact vocalize a
more in the NW USA than at the edge of their range in north Georgia.
Although it might make sense, I could only find a few papers arguing
at low densities, such as at the edge  of their range, species might
to vocalize less than at higher population densities, with a lot of
rivals nearby. Does anyone have any similar or counter impressions?

Oberle, M.W. and J.C. Haney. Possible breeding range extensions of
forest birds in northeast Georgia. The Oriole. 1997. 62(3-4):35-44.

Rappole, J.H., W. J. McShea, and J. Vega-Rivera. 1993. Evaluation of two
survey methods in upland avian breeding communities. J Field Ornith.

Mark Oberle
2006 23 Ave. East
Seattle, WA 98112-2936
Tel: 206-324-3844

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