Earth Almanac: July/September 2003

No Stone Unturned

When other Arctic-breeding shorebirds squat on tropical shores, ruddy turnstones patrol beaches on both of our coasts. So leisurely is their migration to southern states and Central and South America that they sometimes hang around until after Christmas, or even later. Watch them as they dash on stumpy legs after retreating waves, flipping over pebbles and snatching the invertebrates that scurry away. The ruddy turnstone dislodges larger stones as if it were a colonial farmer—straining against them with its crowbar-like beak, rolling them over by pushing against them with its breast, and, when a stone is too firmly embedded, digging out the supporting sand or even enlisting the help of a neighbor. In pursuit of burrowing crustaceans it may dig a hole larger than itself. Perched or airborne, few shorebirds are more striking. Wings and back are splashed with white, brown, black, and chestnut red; lots of white shows in flight. The species can be tame to the point of brazenness. Approach slowly, and a bird may continue its investigations within a few feet of your boots.

Swirling to Sleep

A good month before bat renderings adorn school windows and shopping-mall aisles, real bats drift southward, swirling around the entrances of their winter hibernacula—usually caves or abandoned mine shafts. Some species, such as the mothlike eastern pipistrelle (so small it can fit through a hole the size of a dime), roost or hibernate in caves and mines year-round. Others, such as the little brown bat (above, right), found throughout most of the nation except the Southeast, roost in hollow trees and buildings during warm months, entering caves and mines only to escape the desiccation and freezing temperatures of winter. Male little brown bats arrive at the entrance first, attracting females with calls too high-pitched for human ears. After mating, females store sperm in their uteri through the winter. Ovulation and fertilization occur in early spring; birth, in early summer. Bats are in trouble worldwide. In temperate regions, one of the major reasons is human disruption of hibernacula. The expenditure of energy by wintering bats rousted by intruders can cause them to starve. The appearance of just one spelunker can destroy an entire colony.