From edges, predators and cowbirds routinely wander several hundred yards into forested areas. So to be safe, forest-nesting birds must stay at least 300 yards inside the edge. From the air, an observer can see that tracts of forest large enough to provide this buffer zone are uncommon.
Clearly, forest fragmentation is bad for forest-dwelling birds and other plants and animals that do best deep inside extensive tracts of trees.
On the other hand, many species of birds thrive in edge habitat. Robins, cardinals, song sparrows, downy woodpeckers, and many common backyard species routinely venture in and out of edges in both directions. The difference is these species thrive in edge habitat. Edges benefit common species, while forest-dwelling species decrease as edge habit increases.
The latest threat to large tracts of unbroken forest is the natural gas fracking industry that is proliferating in parts of Pennsylvania, West Virginia, Ohio, and soon New York. Drilling pads and access roads require clearing blocks of land. But the greater threat comes from the pipeline rights of way required to transport the natural gas. They crisscross the countryside like giant spider webs that snare deep forest dwelling wildlife.
I know the gas industry provides good jobs, and it warms my heart to see workers' license plates almost exclusively from Texas, Oklahoma, and Utah. A few weeks ago, a pickup from Alaska drove past my house to a nearby pipeline. But I can't help wondering if 50 years from now, when the gas boom is over, it will have been worth the ecological toll.
Send questions and comments to Dr. Scott Shalaway, 2222 Fish Ridge Road, Cameron, WV 26033 or email sshala...@aol.com.