194 REPTILES AND BIRDS. 



feed on vegetables, insects, molluscs, and fishes. They seek the 

 coast in the breeding season, where they build their nests on the 

 sand, in nooks and crannies of the rocks, or on the margin of lakes 

 and rivers. 



In the spring the sea-birds assemble in large flocks, pair, and 

 proceed to lay; their nests are - constructed generally without skill, 

 but always lined or carpeted with down, which forms a soft warm 

 bed for the embryo progeny. Certain localities are frequented by 

 preference, these' are occupied by innumerable flocks in the breeding 

 season, all of which seem to live together in perfect harmony. Some 

 of the families of the Natatores are valuable additions to the poultry- 

 yard. Ducks and Geese furnish delicate and nourishing food for 

 man j the Swan is gracefully ornamental on our lakes and ponds. 

 The down of all the aquatic birds as an article of commerce is of 

 immense value in northern countries. Their eggs constitute good 

 food, and in many countries the inhabitants consume them in great 

 quantities. Nor does their usefulness end here. Guano, so eagerly 

 sought for by the farmer, is the excrement of aquatic fowls — this 

 has accumulated for ages, until, in the South Pacific Ocean, it has 

 formed whole islands, some of them being covered with this valuable 

 agricultural assistant to the depth of ninety or a hundred yards. Nor 

 is this so marvellous, if it is considered that 25,000 or 30,000 sea- 

 birds sleep on these islets night after night, and that each of them 

 will yield half a pound of guano daily, which owes its unrivalled 

 fertilising power to the ammoniacal salts, phosphate of lime, and 

 fragments of feathers of which it is composed. 



The order of Natatores or Palmipedes we will form into four 

 families : — 1. Brevipennes. 2. Lamellirostres. 3. Totipalmates. 

 4. Longipennes. 



The Divers (Brevipennes). 



Divers, Colymbus ; Penguins, Aptenodytes ; Auks, Alca; Grebes, 

 Podiceps ; and Guillemots, Uria. 



The Birds which constitute this family of the Natatores are 

 characterised by wings so thin and short as to be almost useless for , 

 the purposes of aerial locomotion. They are also called Braehypteres, 

 from the Greek compound Ppuxvs, short, and icripa, winged. These 

 are all habitual divers and indefatigable swimmers, using their wings 

 as fish do their fins. To raise these after making the down-stroke 

 requires a considerably greater effort than a bird of flight makes in 

 raising its wings in the air, for which reason the second pectoral 



