WASHINGTON—On a recent sunny spring day, cardinals, meadowlarks and bobolinks flit through the wooded patch between Kenilworth Marsh and the Anacostia River. A serpentine concrete bike and foot path winds through this pastoral stretch just blocks from a dense working-class neighborhood, but nobody is here.

Steps away, a dozen or so neighbors jog and power walk on a synthetic city track. Walkers and bikers say they are afraid of the path through the woods after a series of recent attacks. Cliff Robinson pauses to explain.

“Because of those turkeys!” says Mr. Robinson, 70, a retired court-services employee. “I was attacked there. Three weeks ago. I was trying to get away from him and he came after me. He wouldn’t let me pass.”