SIDE LIGHTS ON BIRDS 



greater firmness. The house-martin, which btiilds 

 in situations where strength is more needed, curiously 

 does not appear to avail itself of this simple yet 

 effective device. 



It is noteworthy that, needing security and 

 shelter as they do, and often toiling so laboriously 

 to attain these advantages, so few birds com- 

 paratively avail themselves of natural recesses where 

 the greater part of the work is done for them. The 

 sensible hole-builders include the wryneck, nut- 

 hatch, puffin, kingfisher, and many others ; and it 

 may be noted here that most birds nesting in 

 darkened recesses lay eggs of the purest white. 

 Whether the phenomenon of protective coloration 

 has any bearing on this point remains to be de- 

 cided. It is dear, however, that if birds which 

 nest in open places, the curlew, ringed plover, or 

 the lapwing, for instance, laid white eggs they would 

 readily be detected. 



One of the most remarkable examples of pro- 

 tective colouring in eggs is to be found in those of 

 the Sandwich tern. This bird makes no nest 

 whatever. The eggs are simply dropped upon the 

 bare shingle, without even a depression to keep 

 them together. From a distance the birds are 

 seen clearly sitting, and as we approach the spot 

 they rise quietly. But where are the eggs ? Al- 

 though we search every inch of ground no sign of 

 an egg can be made out. After a prolonged 



scrutiny a man might be forgiven for leaving the 

 spot quite convinced that the bird had not laid. 

 But we happen to know that the eggs are here, 

 and we remain with our eyes fixed upon the ground. 

 The shingle is perfectly smooth. It is composed 

 of rounded pebbles, mostly white, but variegated 

 with many which are black or of a reddish hue. 

 As we are analysing a given inch we suddenly dis- 



28 



