202 ZOOLOGY. 



penguin also is endowed with this apparatus, which enables 

 it to adjust its eye to see above and under the water. 



Though birds (except the night-birds, especially the 

 owls) have no external ear, they can hear well; otherwise 

 what would be the use of theL powers of song? 



The eggs of birds are, with the exception of those of liz- 

 ards, enormous in proportion to those of other vertebrate 

 animals. The largest egg known is that of the ^Epyomis, 

 an extinct bird of Madagascar, which is about a third of a 

 metre (13£ inches) in length. Birds lay but few eggs, and 

 the young of those which build nests when hatched are 

 blind, naked, unable to walk, and are fed by the parent 

 birds. In the fowls, such as the hen and partridge, in the 

 wading birds as well as the ducks and other swimming 

 birds, the young, on breaking from the shell, walk or swim 

 and pick up their own food. 



At the close of the breeding season birds moult their 

 feathers; but some birds moult twice and thrice. The 

 quill-feathers are usually shed in pairs, but in the ducks 

 they are shed at once, so that these birds do not at this time 

 go on the wing, while the males put off the highly colored 

 plumage of the days of their courtship, and assume for sev- 

 eral weeks a dull attire. In the ptarmigan both sexes not 

 only moult after the breeding season is over into a gray 

 suit, and then don a white winter suit, but also wear a third 

 dress in the spring. In the northern hemisphere the males 

 of many birds put on in spring bright, gay colors. Other 

 parts are also shed; for example, the thin, horny crests on 

 the beak of a western pelican (Pelicanus erythrorhynchus), 

 after the breeding season, are shed like the horns from the 

 head of deer. Even the whole covering of the beak and 

 other horny parts, like those about the eyes of the puffin, 

 may also be regularly shed. 



As a rule, male birds are larger and have brighter colors, 

 with larger and more showy combs and wattles, than the 

 females, as seen in the domestic cock and hen; and the or- 

 namentation is largely confined to the head and the tail, as 



