AQUATIC BIRDS. 105 



General observations. 



beats the water ; but as they gather them in 

 again, for a second blow, their front surface con- 

 tracts, and does not impede the bird's progres- 

 sive motion. 



As their toes are webbed in the most conve- 

 nient manner, so are their legs also made most 

 fitly for swift progression in the water. The legs 

 of all are short, except three, namely, the fla- 

 mingo, the avosetta, and the corrira. Except 

 these, all web-footed birds have very short legs ; 

 and these strike, while they swim, with great 

 facility. Were the leg long, it would act like a 

 lever whose prop is placed to a disadvantage ; 

 its motions would be slow, and the labour of 

 moving considerable. For this reason, the very 

 few birds whose webbed feet are long, never 

 make use of them in swimming ; the web at the 

 bottom seems only of service as a broad base, to 

 prevent them from sinking while they walk in 

 the mud ; but it otherwise rather retards than 

 advances their motion. 



The shortness of the legs in the web-footed 

 kind, renders them as unfit for walking on land, 

 as it qualifies them for swimming in their natural 

 element. Their stay, therefore, upon land, is 

 but short and transitory ; and they seldom ven- 

 ture to breed far from the sides of those waters 

 where they usually remain. In their breeding 

 seasons, their young are brought up by the 

 water-side ; and they are covered with a warm 

 down, to fit them for the coldness of their situa- 

 VOL. iv. NO. a/j. o 



