240 



Aquatic Organisms 



wild ducks and geese eat great quantities of duckmeat 

 (Lemna) and succulent submerged aquatics. Canvas- 

 backs fatten on the wild celery (Vallisneriaj. In 

 Cayuga Lake in winter they gorge themselves with the 

 starch-filled winter buds of the pondweed, Potamogeton 



FtG. 147. Floating nest of pieil-billed grebe (Podilymhus pndiceps) in 

 a cat-tail marsh, surrounded by water. 



ptisillus. They also dive and pluck up from the bottom 

 mud the reproductive tubers of the pondweed, Potamoge- 

 ton pectinatus ('see fig. 22S on p. 381). 



AVater birds, having attained the freedom of the air, 

 are wide ranging beyond all other animals. They come 

 and go in annual migrations. They settle here and 



