Ix YOUTH, MATURITY, AND AGE 201 
the young birds resemble. If the two sexes are alike 
when mature, the young birds may, as with the Robins, 
have a distinct plumage of their own ; or, as with the 
Kingfisher and Jay and many sober-hued birds, young 
and old may be alike. Still the resemblance is often 
not exact. When, as in the case of the Dunlin, both 
sexes put on a distinct and richer dress in spring, it is 
the old birds in their winter garb that the young 
resemble. 
The age at which maturity is attained varies much 
in different species. Our small birds are ready to nest 
the first spring after their birth. In some cases there 
is no difference of plumage; the young swallows 
arrive later than the old ones, but when they have 
arrived they are indistinguishable. Gulls, however, do 
not appear in quite mature plumage till their third or 
fourth year, or even their fifth—z.e., till the moult at the 
end of their fifth summer. The young Lesser Black- 
backed Gull keeps his first plumage till the summer 
following. Then comes a moult, after which we find 
him still brown but paler than in his first year. At the 
end of his third summer his colour becomes an ashen 
gray, and the tail is in some specimens white, in others 
mottled. None of the primary wing-feathers, or, at 
any rate, only one of them, has a white spot or 
“mirror.” The moult after his fourth summer brings 
him to the plumage of his maturity—back and wings 
black, breast white, head white with dusky streaks 
that will pass away and leave pure white in spring. A 
Gannet, which may be described as grown up, has nota 
single black feather except the primaries ; all the rest 
of him is white except the fine cream-coloured head 
- U2 
