It oftens happens, more particularly in birds that lay only two 

 or three eggs, that nearly all the colouring is deposited on one 

 or two eggs in a nest, the other eggs being nearly or quite 

 unmarked. The unmarked egg appears to be, indifferently, either 

 the first or the last one laid. 



An extreme instance is here shown in a clutch of the Osprey 

 {Pandion lialiaetus\ in which one egg is quite unmarked, and is 

 also smaller in size. 



The Eobin (Erithacus riibecula) is a striking example of a 

 bird laying several eggs of which one generally differs considerably 

 from the rest of the clutch, in this case in having a lighter ground 

 colour and more definite markings. 



The eggs of some species of birds exhibit endless varieties of 

 markings. This is strikingly the case in those of the Common 

 Guillemot {TJria troile), no two eggs being quite alike. A series 

 could be arranged from unmarked specimens to very richly 

 marked. The twelve specimens exhibited show also that the 

 markings may be either in blotches or streaks. A good example 

 of variability in the ground colour is also found in the eggs of the 

 same bird, which vary in this respect from white and stone colour 

 to green and blue. 



PROTECTIVE COLOURING OF EGGS. 



It is difiicult to account for the colouring of the eggs of many 

 birds, but in those instances in which the eggs are laid in open and 

 exposed situations the colouring is undoubtedly protective. The 

 eggs of many birds that lay in holes and dark places are white. 

 On the other hand, the eggs of pigeons, some of which build very 

 open and exposed nests, are also white, 



The Ptarmigan (Lagopus mutiis) and Grouse (Lagopus scoticus) 

 frequent heath-covered mountains and moors. The nest is a slight 

 hollow lined with a little grass, heather, and a few feathers. The 

 eggs are coloured in harmony with the surroundings. 



The Kentish plover {jEgialitis cantiana) and Ringed plover 

 (^Egialitis hiaticola) are examples of coast birds, which lay their 

 eggs in slight hollows in the sandy shingle. The colouring of the 

 eggs renders them most difficult to distinguish among the surround- 

 ing stones and pebbles. 



