In other instances it is quite unlike in size and colour, as in the 

 other examples shown, where the foster parents are the Wren 

 (Troglodytes parvulus) and Hedge sparrow (Accentor modularis). 



SIZE OF EGGS IN COMPARISON WITH THAT OF 



THE BIRDS. 



The size of eggs is generally, but not at all constantly, in 

 proportion to that of the parent. Eggs from which the young are 

 hatched in a relatively fully developed state are large, as in the 

 case of Game birds. The number of eggs to be covered by the bird 

 must also be considered. 



The Partridge (Perdix cinerea) lays twelve to twenty eggs in a 

 nest, whilst the Common Snipe (GoMinago cmlestis), although a 

 much smaller bird, lays eggs of equal size to those of the Partridge ; 

 but there are never more than four in a nest. The young of both of 

 these birds are able to run as soon as hatched. 



The Snipe (Gallinago codestis) and the Blackbird (Turdus merula) 

 differ but slightly in weight, but the eggs of the former are far 

 larger than those of the latter. The young Blackbirds are helpless 

 when hatched. 



The Cuckoo (Guculus canorus) and Missel thrush (Turdus 

 viscivorous) are of about equal size, but the egg of the former is 

 many times smaller than that of the latter, which is but little 

 larger than that of the Sparrow {Passer domesticus). The young of 

 all these birds are helpless when hatched. Although the egg of the 

 Cuckoo is so comparatively small, yet it is not small enough to be 

 inconspicuous amongst the eggs of the foster bird. 



The Guillemot ( Uria troile) and the Raven (Gorvus cor ax) are of 

 about equal size but the egg of the former is considerably larger 

 than that of the latter. The Guillemot lays only one egg and the 

 Raven from four to six. The young of both are helpless when 

 hatched. 



The White-tailed eagle (Haliaetus alhkilla) is five or six times 

 larger than the Guillemot ( Uria troile), but their eggs are of about 

 equal size. 



FORM OF EGGS. 



Eggs of the same species, and even of the same parent, often show 

 much variation in shape, but usually a certain amount of uniformity 

 is maintained in each group of birds. 



