474 ECOLOGY AND WILD LIFE CONSERVATION 



squirrels and other den-loving species. After these serai stages (or 

 sere), the forest finally became relatively static again and remained that 

 way until our ancestors destroyed it once more with the ax and saw. 



Another interesting succession occurs along the shores of a shallow 

 lake as it gradually fills up with sediments and aquatic vegetation. This 

 is illustrated by Reelfoot Lake in western Tennessee, a lake that was 

 formed when an earthquake in 1811 caused the land to settle. In the 

 century and a half since then, many parts of the shallow lake have filled 

 up with aquatic plants and debris. A large patch of open water at the 

 southern end of the lake contains many fish ; diving birds, such as ducks, 

 grebes and coots which swim on the surface, and a varied plankton 

 furnishes an abundance of food. Water plants, such as pondweeds and 

 water lilies, float on the surface of the shallower portions of the lake, 

 many of them with their roots in the mud bottom. Here feed the cat- 

 fish and turtles, herbivorous ducks dive for roots or tip-up for them, and 

 aquatic insects are common. Closer to the shore or in very shallow 

 places, plants with their roots in the muddy bottoms send their leaves 

 and flowering stalks into the air. These include saw grass, cattails, and 

 sweet flag. Here the bitterns and redwing blackbirds nest a few inches 

 above the water, the kingrail piles up its mound-like nest on the bottom, 

 the grebes construct their floating rafts, and the muskrats build their 

 dens. Wading birds, such as herons and egrets, feed here on tadpoles, 

 frogs, and water insects. Water snakes are most common in this zone. 

 Cypress trees grow to large size in one area and play host to a great 

 colony of nesting egrets and herons. A peregrine falcon also nests in 

 a similar location. On the shores of the lake, where they may be occa- 

 sionally flooded in wet seasons, grow many woody plants that need semi- 

 aquatic conditions, including swamp maples, black willows, and button 

 bush. Here may be found the raccoon and mink, and such nesting birds 

 as the yellowthroat, waterthrush and prothonotary warbler, the latter 

 particularly abundant in dead snags often standing in the water. Finally 

 on the dry land beyond the influence of the lake, there grows the typical 

 trees and shrubs of the region, inhabited by upland birds and mammals. 



In recent years the aquatic plants have encroached so rapidly upon 

 the open water of Reelfoot Lake that they threaten the very existence 

 of the lake. The U. S. Fish and Wildlife Service now face the dilemma 

 of either draining the lake and turning it back into farmlands which 

 would displease the sportsmen, or dredging the shallow places and rais- 

 ing the water level to prevent the plants from coming back and thus 

 displeasing the farmer, some of whose fields would occasionally be 

 flooded. 



