164 



EGGS OF BIRDS. 



the egg- dropped into the nest of a bird on the point of sitting, it would 

 most certainly be hatched as long before the eggs of the bird whose 

 nest it was deposited in as it had been forwarded in the uterus. It has 

 frequently been observed, that where the egg of a cuckoo has been 

 found in the nest of a bird together with some of its own, that the 

 cuckoo's egg is hatched first. 1 This seems difficult to account for, 

 unless upon the principle we have suggested, as the egg of that bird is 

 rather superior in size to that of any bird whose nest it makes choice 

 of to deposit it in; amongst which the yellowhammer's is the largest, 

 weighing in general from thirty-six to forty-six grains ; whereas that 

 of the cuckoo weighs from forty-four to fifty-four grains. The other 

 birds which the cuckoo more generally chooses to incubate its egg, 

 seldom produce eggs above forty grains in weight, and mostly from 

 thirty to thirty-six ; if, therefore, the embryo of the cuckoo was not 

 sometimes enlarged before the egg was laid, is it reasonable to suppose 

 it would be first hatched ? 



In respect to the young cuckoo suffering the hedge-sparrow's eggs to 

 remain in the nest, as above-mentioned, which is contrary to the general 

 rule, we can only suppose some defect existed in the young cuckoo, or 

 that these eggs were so placed in some small cavity in the bottom of 

 the nest that its utmost efforts could not disengage them. These and 

 other accidental causes are much more likely, than that the hedge- 

 sparrow should lay these additional eggs at the time she was performing 

 the act of nutrition to her supposed offspring. 



From late observation we conclude the female cuckoo retires from 

 the male so soon as she feels an inclination to deposit an egg, and does 

 not admit him again while she is capable of laying, — all the eggs of the 

 first set being fecundated at the same time. This, indeed, is probable 

 with respect to all birds, though it is difficult to ascertain how the 

 prolific quality is regulated so as only to affect such a portion of eggs 

 in the ovarium; 2 and that every particular species should almost in- 

 variably lay the same quantity. 



The extraordinary growth of a young cuckoo is no more than what 

 happens with others produced from eggs of a disproportionate size ; for 

 instance, the egg of a raven is not half the size of that of the kite, and 

 yet the young of the former are not longer arriving at maturity than 

 the latter. Some birds are hatched blind, and entirely naked ; others 



1 Jenner, Nat. Hist, of the Cuckoo, p. 3. 

 2 Domestic fowls, separated from the male after the first impregnation, are known to 

 lay many prolific eggs. — Young on Turkeys, in Nat. Hist, of Norfolk. 



