xviii. 7 ORDERS OF BIRDS 517 



Order 3. Procellariiformes. Petrels 



The petrels (Fulmarus), shearwaters (Puffinus), and albatrosses 

 (Diomedea) are birds highly modified for oceanic pelagic life, some of 

 them very large. They lay one white egg, often in burrows. Their 

 long narrow wings are specialized for soaring flight (Fig. 273). 



Order 4. Pelecaniformes. Cormorants, Pelicans, and Gannets 



This is another order of aquatic birds, much modified for diving 

 and fishing and including the cormorants (Phalacrocorax), pelicans 

 (Pelecanus), and gannets (Sida). They nest in colonies on rocks or 

 trees; the eggs are usually unspotted and covered with a rough chalky 

 substance. These birds make spectacular dives when fishing; gannets 

 may plunge from more than 50 feet. 



Order 5 . Ctconiiformes. Storks and Herons 



The storks (Ciconia), herons (Ardea) (Fig. 274), and flamingoes 

 (Phoenicopterus) are large, long-legged birds, living mostly in marshes 

 and feeding mainly on fish. They are strong flyers and some of them 

 perform extensive migrations. Nests are usually in colonies and may 

 be used year after year; there are elaborate display ceremonies. Eggs 

 are few and unspotted. 



Order 6. Anseriformes. Ducks 



The ducks (A?ias) and swans (Cygnns) represent yet another group 

 of birds specialized for aquatic life. The characteristic flattened bill 

 is used to feed on various diets. Some are vegetarians, a few filter- 

 feeders; some eat molluscs, others fish. The numerous eggs are usually 

 white or pale and the nest is built on the ground. 



Order 7. Falconiformes. Hawks 



This order includes the birds of prey that hunt by day, having 

 sharp, strong, curved bills and powerful feet and claws. The retina 

 contains mainly cones. Many different types are found throughout 

 the world. Most feed on birds or mammals, some on carrion, and a 

 few on fish or reptiles. Typical examples are the kestrel (Falco), eagle 

 (Aquila), buzzard (Buteo), and vulture (Neophron). The eggs, few in 

 number, are usually spotted and the nests are generally made on cliffs, 

 tree-tops, or other inaccessible places; some, however, are on the 

 ground. 



