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Sunday, May 09, 2010

 

-- Forest Fragmentation and Nest Predation --

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Article here on increased nest predation by rat snakes accompanying forest fragmentation:

http://www.sciencedaily.com/releases/2010/05/100504124738.htm

From the article:

"Everywhere there have been camera studies, as long as it's in wooded or semi-wooded habitat, rat snakes emerge as the single most important predator. They're common throughout the range, and they're really good at finding bird nests."

and

"...rat snakes are very opportunistic," Weatherhead said. "I have a picture of a rat snake eating a full-grown squirrel. So that's a mouthful. They're generalists both in terms of the mammals they eat and in terms of the birds that they prey on. They'll take whatever birds they encounter, and because they're such good climbers, they can get to both low nests and high nests. They can climb just about any kind of tree. They eat bird eggs, fledglings and sometimes they'll even get the mom if she's sitting on the eggs..."
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Comments:
Ecologists and managers often focus on the condition of a given area of forest, but forest fragmentation may be as important if not more so, in ecosystem health and species diversity. Whether it's altered fire ecology, enhanced edge effects, or simply insufficient acreage to support a given species, the effects are profound.

People often focus on the loss of virgin forests before 1950, which was indeed tragic. But equally devastating if not more so was the loss of southern bottomland fores acreage after 1950:

http://www.lmvjv.org/historic_forest_cover.htm

In 1950 there was virtually a continuous swath of bottomland forest from the northeastern corner of La. to the coast. Most of this was not logged for timber, but merely obliterated to make room for agriculture.
 
In the last few decades I think ecologists have come to realize that forest fragmentation by work or recreational roads/paths (even if the remainder of forest remains intact) is harmful to a great many songbird species, especially migratory ones. It may be slightly less clear just how damaging fragmentation is to larger woodland species, but it's not likely to be a good thing.
The possibility of creating improved conditions for rat snake proliferation, in particular, doesn't bode well for cavity-dwelling species, let alone open nesters.
 
There is some good news, though, the creation and maintenance of forest corridors has long been a priority for conservationists, and the general trend in eastern North America is toward increasing forest maturity, increasing forest acreage, and decreasing fragmentation. Unfortunately the same cannot be said of many areas of the tropics.
 
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