CONCERNING THE CUCKOO 105 



such as those of the wood-pigeon and house-sparrow. 

 But the instinct which leads the bird to choose 

 the right nest is well marked despite these occasional 

 lapses, and we shall have a word to say directly 

 as to the manner in which it probably originated, 

 in common with the cuckoo's other pecuUar instincts. 

 Nothing connected with the cuckoo has given 

 rise to so much discussion as the extraordinary 

 character of its egg and the manner in which it is 

 placed in the nest chosen to receive it. Every one 

 who has collected birds' eggs, or indulged in the 

 juvenile habit of birds'-nesting, or who has even 

 gone so far as to take an intelligent interest in the 

 dozen of new-laids ordered from the grocer's, must 

 have noticed one rudimentary fact respecting the 

 eggs of birds. The eggs of each species have certain 

 marked characteristics which distinguish them from 

 those of other birds : the common fowl's egg is 

 white, the duck's pale blue, the thrush's speckled 

 green, the skylark's dark brown. The eggs of each 

 kind of bird also vary but little in size. Now, strange 

 to say, the cuckoo's egg is a marked exception to 

 this almost invariable rule. The eggs of the cuckoo 

 have no particular colour. They have been found 

 green, grey blue, grey-mottled, green-mottled, and 

 pure white. Neither have they any particular 

 size. They vary in the most puzzling fashion, from 

 the size of a skylark's egg to almost that of a pigeon's. 

 Few of the authorities on the subject can agree 

 even as to what the average size should be. For 

 instance, two of the best known, to whom I refer 

 at random, state the size of the cuckoo's egg to be 

 respectively H inch by |f inch, and i inch to 

 I "8 inch by 75 inch to -61 inch — a sufficiently wide 



