N ATA TORES. 417 



The foot of the Grebes is not webbed, but has each toe sepa- 

 rate and flattened, (Plate IX. fig. 26,) somewhat like that of the 

 Coot in the last order, with this exception, the Swimmers are all 

 marked by having the toes united by a membrane, giving to the 

 foot the form of a powerful oar, as in the common Duck or 

 Goose, (Plate IX. fig. 24.) In those species which are eminently 

 aquatic, the feet are placed far back on the body, (see Auk on 

 the Chart,) which renders their gait clumsy and shuffling on land, 

 but gives to the backward stroke of the foot in the water an im- 

 petus that helps them in swimming ; the tarsus is also flattened 

 sidewise, diminishing the resistance to progression in the water. 



The form of the body is flattened horizontally, (not laterally, 

 as in the Waders.) the better to float on the surface. The plu- 

 mage is remarkably thick and close, particularly on the under 

 parts of the most aquatic kinds ; besides which the skin is cov- 

 ered with a dense coat of soft down. The outer surface is usu- 

 ally polished and satin-like, probably from the oily secretion 

 which the bird frequently applies to it. The larger part of the 

 Swimmers have a copious and peculiarly oily secretion of fat. 



As Cuvier remarks, these are the only birds in which the neck 

 is longer than the legs, which is sometimes the case to a consid- 

 erable extent, for the purpose of enabling them to search for 

 food in the depths below, while, they swim on the surface. The 

 tail is generally short, and so are the wings; hence, flight is in 

 most feeble, and in some altogether denied : and yet it must be 

 noted, that in the order Natatores are found examples of the long- 

 est wings, and the highest powers of flight of the entire class of 

 Birds, as, for example, in the Frigate Pelican. The Petrels and 

 Terns have also great length of wing. 



The web-footed fowl resort to fens, morasses, broad rivers, 

 inland lakes, rocky coves, &c., and they are found also on the 

 ocean's wide expanse. The marine kinds are more numerous in 

 the colder seas of the North, than in those of tropical regions. 



This order includes the following families: (1) Anatida, 

 Ducks; (2) Colymbida, Divers ; (3) Akida, Auks; (4) Procel- 

 larida, Petrels ; (5) Larida, Gulls 5 (6) Pelecanida, Pelicans. 



FIRST FAMILY. DUCKS. 

 Anatida, (Lat, anas, a duck.) 



This numerous family have the beak thick and broad ; high 

 at the base, and covered throughout almost its whole extent with 

 a soft skin, the tip alone being horny; the edges are cut into thin 

 parallel ridges, or small teeth ; the tongue is large and fleshy, 



