go Our Bird Friends. 



sat upon by an Eider Duck. The two Ijirds had 

 nested within a i^w ieet of each other : and as 

 the Lesser Black Back or some of its neighbours 

 had sucked the Eider Duck's eg^o:s — the shells 

 of which were lying scattered round — she had 

 promptly retaliated l)y usurping the Gull's nest 

 and eofors. 



Of course, everybody knows of the Cuckoo's 

 strange habit of making other birds do its work at 

 the expense of their own ofispring. ('uckoo's eggs are 

 only about one quarter the size they ought to be 

 in proportion to the bird that lays them : they vary 

 in colour more than those of almost any other 

 l)ii-(l, and have been found in the nests of upwards 

 of a hundred different species. Some naturahsts 

 think that the bird has the power of adapting the 

 colour of its ^g^ to that of the foster-parent, into 

 the nest of which it drops it. Two Cuckoos' eggs 

 have frecpiently been found in one nest, and on 

 rare occasions even three. There can be no doubt 

 that the ^^^ is first laid and then taken in 

 the bill and safely deposited in the nest of the 

 bird selected t(^ become the foster- parent, for it 

 has been found in covered nests, and Cuckoos have 

 been shot with their eggs in their bills. 



The period of incubation varies considerably. 

 Some birds, such as Tits, Thrushes, and Blackbirds, 

 sit about a fortnight, whilst others, such as W'ikl 

 Ducks and Seagulls, brood double that time. 'i1ie 

 rufiin is S.I id to sit on her siniile esfi.j' for five wearv 



