xxviii INTRODUCTION. 



uniform and protective tint were their conditions of life to demand it; 

 birds laying eggs unadapted in colour to their changed conditions of life 

 would have small chance of transmitting those injurious colours to pos- 

 terity, would soon die out completely; and the birds that laid eggs most 

 suitable to the changed conditions and in harmony with them would in- 

 crease and multiply, and the colours on their eggs be preserved. This, I 

 believe, is how all eggs have got their beautiful tints, and how they are 

 preserved or changed as circumstances arise. 



Again, the young birds of many species absolutely depend for safety on 

 the colour of their down. The Lapwing is arrayed in tints that put us in 

 mind of the tropics ; the sexes are alike ; yet they build an open nest on 

 the bleak common, moor, or pasture, where sometimes not a shrub or 

 heath-tuft affords a haven of safety. Both birds lack weapons of defence ; 

 but note how the safety of their young is insured : their sombre plumage 

 of brown effectually conceals them from view. Upon the least alarm the 

 brightly-coloured parents leave their helpless young, who instantly crouch 

 to the ground and remain motionless ; their colour so closely harmonizes 

 with surrounding tints as to hide them efEectually from the enemy that 

 menaces them. The young of the Game Birds, all the Sandpipers, and 

 many sea-birds might also be given as instances, all of which (where the 

 parents' plumage is conspicuous and dangerous to the welfare of their 

 eggs or young, and which nest in an open site) have young of protective 

 tints. As our last group we notice 



Spotted eggs laid in covered nests. — As we found the anomaly of white 

 eggs in open nests, so we also find that of spotted and highly- coloured 

 eggs in covered nests. We will first notice a few instances amongst 

 British birds. We take as our first example the Jackdaw, whose eggs 

 are spotted and coloured in a remarkable manner, considering they are 

 laid in a covered nest. The Chough is another instance, and the Magpie 

 a third. I am inclined to believe that these three birds have changed 

 the form or position of their nest from an open to a covered one, and the 

 eggs are consequently gradually losing their colours. The eggs of the 

 birds just noticed are generally much paler than the eggs of the Crows 

 laying in open nests, and they seem slowly reverting to a colourless type. 

 When once any particular development ceases to be of any service its 

 tendency is gradually to die out ; and this, I think, is the reason that so 

 many birds nesting in covered sites lay eggs only slightly spotted, or, as in 

 many cases, when compared with the eggs of the family of birds to which 

 they belong, show a marked decrease of coloration. The Robin's eggs, as 

 compared with those of its ally the Bluethroat [Erithacus cmrulecula) , 

 furnish another instance. The Robin's nest is well concealed and often- 

 built in holes, and its eggs are often white or only faintly spotted ; the Blue- 



