x INTRODUCTION. 



varied markings, and the nest which contains it with its infinite diversity 

 of structure and position. 



Until very recently the great variety of colour in the plumage of birds 

 was looked upon as so much ornament of no particular use to the species, 

 but for the sole purpose of gratifying the eye and adding to the general 

 harmony of animated nature. Within the last thirty years scientific 

 research has shown that many of the beautiful colours on the plumage of 

 birds materially affect not only their welfare, but, as will shortly be seen, 

 that of their young, and consequently the very existence of their species. 

 This beauty is not given aimlessly, it has a fixed and definite object the 

 benefit of the species acquiring and possessing it. The student of birds 

 must therefore view each varied tint on their plumage not as so much mere 

 ornament, but as a factor which is or has been essential to the safety or 

 well-being of the species possessing it, which has had its origin in the 

 struggle for existence to which each bird is subject, either through natural 

 or sexual selection. In like manner the infinite variation of colour, and 

 to some extent of form, in the eggs of birds and the endless diversity of 

 their nests have had their origin in the subtle laws of variation and 

 inheritance, aided by natural selection and the survival of the fittest. 



No writer has investigated this interesting subject so closely as 

 Mr. Wallace ; and the views he has taken, together with the conclusions at 

 which he has arrived, are probably well known to most of our readers. 

 Mr. Wallace's theory of birds' nests is said to be far too sweeping and 

 arbitrary ; and certainly it does not explain all the facts. He divides birds 

 into two great classes one in which the sexes are alike and of conspicuous 

 or showy colours, and which nidificate in a covered site ; and the other in 

 which there is a marked difference between the colour of the sexes, the 

 male being showy and the female sombre, and which nidificate in an open 

 site. Nearly all known birds are supposed to come into one or the other 

 of these two groups. In each of these great divisions, however, there are 

 almost as many exceptions as there are cases that conform to the rule ; 

 and this has been taken advantage of by Mr. J. A. Allen, the well-known 

 American ornithologist, Avho endeavours, by a critical study of the nidifi- 

 cation of North-American birds, to overthrow the whole theory (Bull. 

 Nutt. Orn. Club, 1878, p. 23). In treating the subject so far as birds and 

 their nests are concerned, I propose to divide birds into the same two 

 great groups as Mr. Wallace ; but I shall subdivide them into several minor 

 groups, which will include all the " exceptions" to either great rule. I 

 purpose specially to take examples of each, as far as possible, from birds 

 inhabiting our own islands, as being most interesting to the student of 

 British oology. In the birds belonging to the class which build open nests 

 we will notice as the first group 



Birds in which the plumage of the male is bright and conspicuous 



