468 AVES. 



Sub-fam. 2. Sterninae. Terns or sea-swallows. Beak long, straight, 

 tail usually forked. About 50 species, cosmopolitan. Sterna hirundo 

 L., terns ; St. fluviatilisf Naum., common tern, coasts and inland 

 waters of Europe, etc. Gygis Wagl. Arious Leach, noddies. 



Sub-fam. 3. Rhynchopinae. Rhynchops L., skimmers, Indian 

 Ocean and Atlantic side of Amer. 

 Fam. Alcidae. Auks. Pisci\orous, marine, periarctic birds, with short 

 wings (functionless in Alca impennis), heavy body, close plumage and fully 

 webbed anterior toes. Most species fly strongly. Their common breeding 

 places are on the coasts, where they lay their generally single egg on bare 

 ledges of rock, in crevices, or in holes in the earth. Alca impennis L., 

 great auk, flightless, extinct since 1844. A. torda L., razorbill. 

 Mormon arcticus (Fratercida Temm.) 111., puffin. Uria troile Lath., 

 guillemot; U. grylle Cuv. black guillemot, tysty. Mergalm alle 1.., the 

 little auk. 



Group 3> Pterocles. 



Desert birds with short, feathered n^etatarsus ; hallux small or absent ; 

 crop and caeca large. With nares imperviae, rudimentary vomer. The 

 short front toes are enclosed in a casing which is covered as far as the claws 

 with hairy plimiage. Eggs three in number. The yovmg are praecoces. 



Fam. Pteroclidae. Sand-grouse. Pterocles alchata Gray, Em-., 

 Africa, Asia. Syrrhaptes paradoxus Pall., Pallas' sand-grouse, Central 

 Asia, occasionally wanders into and breeds in Europe. 



Group 4. Columbae. 



The Columbae are most nearly allied to the Pteroclidae. They are of 

 medium size, with small head, short neck, and short legs. The beak is 

 longer than in the Galli, but weaker, and gently arched at the homy ex- 

 tremity. At the base of the beak the scaly cover of the nasal openings is 

 swollen, naked and membranous. The rather long, pointed wings enable 

 the bird to fly quickly and skilfully. The tail is weak and rounded, and 

 contains usually 12, rarely 14, 16 or 20 rectrices. The plimiage presents 

 hardly any difference in the two sexes. The short legs are unfitted for 

 rapid locomotion. The well-developed hind toe rests on the groimd. 



The vomer is small and often absent, and the nares impervious. The 

 crop is paired and large, and at the breeding season secretes, in both sexes, 

 a creamy fluid for the nourishment of the young. 



There are about 350 species, distributed over all parts of the world. 

 Tliey live in pairs, or in flocks in forests, and feed mainly on grain and 

 seeds. The species which live in the north are migratory ; others make 

 short migrations ; while others are residents. They live in a state of 

 monogamy, and lay two eggs (rarely one) in a rudely constructed nest. 

 Both sexes take part in hatching and in bringing up the young, which 

 are hatched almost naked ( "pipers" ), with closed eyelids, and, as 

 altrices, require the care of the parents for a considerable time. 



Fam. Columbidae. The beak with smooth edges, never dentated. 

 Columba livia L., rock-pigeon (Fig. 254) ; slate-blue, with white wing cov- 

 erts and two black bands on the wings and the tail ; is the ancestral form 

 of the numerous races of domestic pigeon ; nests on rocks and ruins, and 

 is distributed from the coast? oi the Mediterranean over a great part of 



