[bcbirdclub] Fw: [Va-bird] CCB completes Golden-winged Warbler and Bewick's Wrenassessment
- From: "Roger Mayhorn" <mayhorn@xxxxxxxxxxxx>
- To: "Buchanan County Bird Club" <bcbirdclub@xxxxxxxxxxxxx>
- Date: Wed, 16 Jan 2008 13:02:10 -0500
For those interested this report about the decline of the Golden-winged Warbler
and the Bewick's Wren in Virginia appeared on VA-Birds.
Below is a photo of a male Golden-wing that I took here in my yard last
September.
Roger Mayhorn
Compton Mt
----- Original Message -----
From: Mike Wilson
To: va-bird@xxxxxxxxxxxxx
Sent: Tuesday, January 15, 2008 4:34 PM
Subject: [Va-bird] CCB completes Golden-winged Warbler and Bewick's
Wrenassessment
The Center for Conservation Biology recently finished a report that
assessed the status of Golden-winged Warblers and Bewick's Wrens in Virginia.
This study was made possible through funding by the State Wildlife Grants
program in cooperation with the Virginia Department of Game and Inland
Fisheries. To download report visit our Golden-winged Warbler webpage at
http://www.ccb-wm.org/Golden-winged_Warbler/GWWA.htm
Project Summary:
The Appalachian Mountains of Virginia have long been considered population
strongholds for Golden-winged Warblers (Vermivora chrysoptera) and Appalachian
Bewick's Wrens (Thryomanes bewickii altus). However, both of these species
have undergone dramatic population declines in Virginia and throughout the
greater Appalachian region including the general belief that Bewick's Wrens are
extirpated from this state. Reasons for the decline of these species may be
many, but the most common explanations point to the loss and degradation of
early successional breeding habitat. Golden-winged Warblers and Bewick's Wrens
use shrubby, early successional habitats for breeding such as idle vegetated
areas, forest clear-cuts, alder swamps, utility right-of-ways (ROWs), and
others. Several forces have worked together to cause the recent decline in
early successional shrublands including direct losses caused by human
development, re-forestation of farmland, fire suppression, and changes in
agricultural and forestry practices. In addition, Golden-winged Warblers may
be declining because of competition for breeding habitat and hybridization with
Blue-winged Warblers. Blue-winged Warblers have been expanding their range
eastward and into higher elevations that were once occupied exclusively by
Golden-winged Warblers.
We systematically surveyed for the presence of these three species across
40 counties in Virginia's Appalachian Plateau, Ridge and Valley, and Blue Ridge
physiographic provinces. Surveys consisted of 11-minute point counts aided by
the use of recorded species playback. This effort resulted in the survey of
932 points at 863 different shrub patches. We detected 56 Golden-winged
Warblers within 34 patches across only 12 counties. Highland county supported
the overwhelmingly greatest number of Golden-winged Warblers with 28 birds
observed in 18 patches. A total of 91 Blue-winged Warblers were detected in 62
different habitat patches across 18 counties. Blue-winged Warblers were
detected in all but one county where Golden-winged Warblers occurred. The two
species distributions overlapped in elevation but differed somewhat in habitat
use. Golden-winged Warbler used idle farm/pastureland and forest clear-cuts at
a greater rate than expected by chance and used utility ROWs, shrubby wetlands,
and other shrub patches less frequently than expected. Blue-winged Warblers
showed the opposite pattern for most of these habitat types. Hybrid warblers
were detected infrequently but found within 7 counties. We did not detect any
Bewick's Wrens during surveys.
Comparing our data with historical records indicate that Golden-winged
Warblers are continuing to decline in Virginia and are being replaced by
Blue-winged Warblers in order of abundance. The overall low number of
Golden-winged Warbler detections may provide justification for regulatory
protection and highlights the importance for their conservation. Geographical
and habitat use patterns of Golden-winged Warblers from this study provide
guidance for management.
Mike Wilson
Center for Conservation Biology
College of William and Mary
PO Box 8795
Williamsburg, VA 23187-8795
phone: 757-221-1649
fax: 757-221-1650
email:mdwils@xxxxxx
www.ccb-wm.org
--------------------------------------------------------------------------------
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