AVES. 387 



hemispheres, where they remain until the lakes and rivers are entirely 

 covered with ice, when they return to more temperate regions. They sub- 

 sist almost entirely on fishes and other aquatic animals which they catch 

 by diving. The merganser or large sheldrake {Mergus merganser), the 

 red-breasted merganser {M. serrator), and the hooded merganser, M. 

 cucullatus (pi 92, fg. 10), are the species common to the shores of North 

 America and Europe. Another, which is occasionally observed, is the 

 white merganser {M. alhellus). 



Fam. 11. CoLYMBiD^. A small group containing the divers and grebes, 

 birds which live almost entirely in the water, rarely venturing on the land. 

 They have the legs inserted more posteriorly than any other swimmers, 

 which enables them to move on the water with great velocity. 



Sub-fam. 1. ColymhincB, or Divers. Bill long, straight, compressed, 

 very acute ; wings long, pointed ; tail short ; tarsi short, compressed ; toes 

 long, fully webbed before. Size large. 



Three birds only belong here. They breed within the arctic circle, but 

 migrate to more temperate climates during winter, and are usually observed 

 on the rivers and lakes swimming in search of aquatic animals which con- 

 stitute their food. They swim and dive with great facility and swiftness, 

 and are able to remain a long time under water, exposing only the bill or 

 part of the head when they return to the surface. The great northern 

 diver or loon, Colymhus glacialis {pi. 91, fig. 3), the black-throated diver 

 (C arcticus), and the red-throated diver (C septentrionalis) , are the 

 known species. 



Sub-fam. 2. Podicepince, or Grebes. Bill rather long, straight, com- 

 pressed, tip acute ; wings short ; tail very short or rudimental ; tarsi short, 

 compressed ; toes long and broadly lobed. Size smaller. 



There are about twenty-five species of grebes, which are scattered over 

 the world, and usually observed near the sea-coast. They are excellent 

 swimmers and divers, and are said to pursue fishes to a considerable depth 

 in the water. The crested grebe, Podiceps cristatus {pi. 91, fig. 1), the 

 horned grebe {P. cornutus), the little grebe, P. minor {pi. 91, fig. 2), and 

 several other species are found in both Europe and America. A very 

 curious bird of this group is the sun bird or sun grebe of South America, 

 Heliornis surinamensis {pi. 94, fig. 12). It is chiefly seen on the banks of 

 rivers and creeks, and possesses considerable beauty of plumage. 



Fam. 3. Ai.cidje. Contains the auks, guillemots, penguins, and some 

 other similar birds, the greater part of which inhabit the polar circles. 



Sub fam. 1. Alcince, or Auhs. Bill rather short, much compressed, tip 

 of upper mandible hooked and acute ; wings long and perfectly formed ; 

 tail short ; tarsi short, compressed; toes webbed. Size various. 



These birds are very abundant in northern latitudes, but appear only 

 occasionally in more temperate regions. They live chiefly in the water, 

 but are capable of flying (which is not the case with some birds of this 

 family). The great or king auk {Alca impennis) is the largest species, the 

 razor-billed auk, A. tarda {pi. 91, fig. 15), and the puffin, Fratercula arC' 

 tica {pi. 91, fig. 14), are other well known species. 



591 



