Colonel Lee's Birdhouse
Driving north across the Francis Scott Key Bridge, looking south, it's the hexagonal chunk of brown granite poking its head above the dancing chop of the Patapsco River- - a landmark that many-a-time has inspired the question, "What is that?"

It's Fort Carroll, the built-like-a-tank outpost begun in 1847 to stop dead-in-its-tracks any attempt to invade the thriving 19th century port city of Baltimore. U.S. Army Brevet Colonel Robert E. Lee (yes, that Robert E. Lee) had high hopes for the fort when he oversaw much of its construction. But Fort Carroll never saw action and was never even completed, thanks to several twists of fate. Now, the Fort seems to have found a noble, albeit unusual occupation: it's become home to a world-class colonial nesting bird rookery, the most diverse colony of species within 100 miles. There is a problem, though: the trees that make up the rookery's nesting cradles may be threatening Fort Carroll's structural integrity. But, the offending trees can't be cut because state law protects the rookery.

The quandary: save the Fort, or keep the birds? DNR Ecologists Dave Brinker and Jim McKann visit the fort to learn more.