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 thei. 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 JEpyornis^ 
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 oft 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 [Pelicarms erythrorliynchus), 
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 Avattles, than tlie 
females, as seen in the domestic cock and hen; and the or- 
namentation is largely confined to the head and the tail, as 
