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Re: What happened to the Bewick's wren?

From:

"BUTCHER, Greg"

Reply-To:

BUTCHER, Greg

Date:

Tue, 23 Jan 2007 16:58:12 -0500

Interesting question. Because the population had invaded the east so soon before it started losing ground again, it may have had lower genetic variability than a more established, big population would have and thus less ability to adapt to changing conditions. But I think that would be a contributing factor rather than a leading factor. I'm wondering if forest dynamics in the East have been more dramatic than they have been out west. (There are lots of places out west where shrubs are the climax vegetation, whereas in the East they are almost always successional.)

Greg Butcher
Director of Bird Conservation
National Audubon Society
1150 Connecticut Avenue NW, Suite 600
Washington DC 20036
Tel.: 202-861-2242, ext. 3034
Fax: 202-861-4290


Protecting our Great Natural Heritage through the Important Bird Areas program,<http://www.audubon.org/bird/iba>, 
and the WatchList, <http://www.audubon.org/bird/watchlist>.



-----Original Message-----
From: Maryland Birds & Birding [mailto:[log in to unmask]]On
Behalf Of Paul O'Brien
Sent: Tuesday, January 23, 2007 4:10 PM
To: 
Subject: Re: [MDOSPREY] What happened to the Bewick's wren?


Curiously, of the ten recognized subspecies of Bewick's Wren, only the 
nominate bewickii of the east has declined.   The other subspecies are stable or 
increasing.   Could there be a genetic susceptibility factor?   Just curious.

Paul O'Brien
Rockville, Mont. Co., MD

In a message dated 1/23/07 3:55:13 PM,  writes:


> From what I understand, Bewick's Wren is essentially gone everywhere east 
> of the Mississippi River. It is one of the most dramatic range losses of our 
> lifetime, yet no one ever really had a handle on what was happening or what 
> could be done about it. Speculation has focused on competition with House Wren 
> and changing forests. According to Birds of North America (BNA), Bewick's 
> Wren prefers open brushy woodlands. Our woodlands tend to be more closed-canopy 
> than they used to be, and to have less underbrush (because of deer 
> overbrowse). House Wrens seem to like the forests and edges that we have now. The BNA 
> account suggests an initial colonization of the East by Bewick's Wren in the 
> late 1800s right after a major deforestation, then a replacement of Bewick's 
> Wren by House Wren from 1920 to 1980. House Wrens peck holes in the eggs of 
> species that nest nearby, plus they prefer a more mature forest than does 
> Bewick's Wren.
> 
> Retreat of Bewick's Wren may be similar to the retreat of Golden-winged 
> Warbler, which has retreated behind an expansion of Blue-winged Warblers.
> 
> There has been no cold weather worth mentioning since the late 1970s in the 
> United States east of the Mississippi and most songbirds that winter in the 
> Eastern USA that are sensitive to cold weather have been expanding their 
> ranges, not contracting (including Carolina Wren).
> 
> Bewick's Wrens have stable populations out west, according to the Breeding 
> Bird Survey, so the species as a whole is doing fine, although the chances 
> that it will ever re-colonize the East seem very low (although they did colonize 
> the East from the West in the second half of the 1800s). The Ozark Mountains 
> of Missouri seem to be the eastern-most stronghold for the species now.
> 
> Greg Butcher
> Director of Bird Conservation
> National Audubon Society
> 1150 Connecticut Avenue NW, Suite 600
> Washington DC 20036
> Tel.: 202-861-2242, ext. 3034
> Fax: 202-861-4290
> 
> 
> Protecting our Great Natural Heritage through the Important Bird Areas 
> program,<http://www.audubon.org/bird/iba>,
> and the WatchList, <http://www.audubon.org/bird/watchlist>.
>