110 



HARDWICKE'S SCIEN CE - GO SSIP. 



[May 1, 1870. 



improbability of her being subject to thus much 

 regularity of habit, and indeed such has been as- 

 serted as an observed fact. If, then, this be so, 

 there is every probability of her offspring inheriting 

 the same habit, and the daughter of a Cuckoo 

 which always placed her egg in a Reed Wren's or 

 a Titlark's nest doing the like." In other words, 

 the habit of depositing an egg in the nest of a 

 particular species of bird is likely to become 

 Hereditary. 



This would be an excellent argument in sup- 

 port of the theory, were it not for one expression, 

 upon which the whole value of the argument seems 

 to us to depend. What is meant by the expression 

 " once successfully deposited" ? Does the Cuckoo 

 ever revisit a nest in which she has placed an egg, 

 and satisfy herself that her offspring is hatched and 

 cared for ? If not (and we believe such an event 

 is not usual, if indeed it has ever been known to 

 occur), then nothing has been gained by the selec- 

 tion of a Reed Wren's or Titlark's nest (as the 

 case may be), and the Cuckoo can have no reason 

 for continuing the practice of using the same kind 

 of nest from one season to another. 



While admitting, therefore, the tendency which 

 certain habits have to become hereditary in certain 

 animals, we feel compelled to reject the application 

 of this principle in the case of the Cuckoo, on the 

 ground that it can only hold good where the habit 

 results in an advantage to the species, and in the 

 present instance we have no proof either that there 

 is an advantage, or, if there is, that the Cuckoo is 

 sensible of it. 



Touching the question of similarity between eggs 

 laid by the same bird, Professor Newton says : — 

 c; I am in a position to maintain positively that 

 tbere is a family likeness between the eggs laid by 

 the same bird " (not a Cuckoo) "even at an interval 

 of many years," and he instances cases of certain 

 Golden Eagles which came under his own observa- 

 tion. But do we not as frequently meet with in- 

 stances in which eggs laid by the same bird are 

 totally different in appearance ? Take the case of a 

 bird which lays four or five eggs in its own nest 

 before it commences to sit upon them — for example, 

 the Sparrow-hawk, Blackbird, Missel-Thrush, Car- 

 rion Crow, Stone Curlew, or Black-headed Gull. 

 Who has not found nests of any or all of these in 

 which one egg, and sometimes more, differed entirely 

 from the rest ? And yet in each instance 

 1 hese were laid, as we may presume, not only by the 

 same hen, but by the same hen under the same con- 

 ditions, which can be seldom, if ever, the case with 

 a Cuckoo. 



Looking to the many instances in which eggs laid 

 by the same bird, in the same nest, and under the 

 same circumstances, vary inter se, it is not reason- 

 able to suppose that eggs of the same Cuckoo de- 

 posited in different nests, under different circum- 



stances, and, presumably, different conditions of the 

 ovary, would resemble each other. On the contrary, 

 there is reason to expect they would be dissimilar. 

 Further, we can confirm the statement of Mr. 

 Dawson Rowley, who says, "I have found two 

 types of Cuckoo's eggs, laid, as I am nearly sure, 

 by the same bird." {Ibis, 1865, p. 183.) 



It is undeniable that strong impressions upon the 

 sense of sight, affecting the parent during conception 

 or an early stage of pregnancy, may and do influence 

 the formation of the embryo, and it has conse- 

 quently been asserted that the sight of the eggs lying 

 in the nest has such an influence on the hen Cuckoo, 

 that her egg, which is ready to be laid, assumes the 

 colour and markings of those before her. This is 

 not, however, supported by facts. For the egg of 

 a Cuckoo is frequently found with eggs which 

 do not in the least resemble it {e.g., those of the 

 Hedge-sparrow) ; or with eggs which from the nature 

 of the nest could not have been seen by the Cuckoo 

 (as in the case of the Redstart, Wren, or Willow 

 Wren) ; or deposited in a nest before a single egg 

 had been laid therein by the rightful owner. 

 Again, two Cuckoo's eggs of a different colour 

 have been found in the same nest. If both were 

 laid by one bird, we have a proof that the same 

 Cuckoo does not always lay eggs of the same colour; 

 if laid by different birds, then the Cuckoo is not so 

 impressionable as has been supposed. 



What really takes place, we believe, is this:— The 

 Cuckoo lays her egg upon the ground; the colour oi 

 the egg is variable according to the condition of the 

 ovary, which depends upon the age of the bird, the 

 nature of its food, and state of health at the time of 

 oviposition. With her egg in her bill, the bird then 

 seeks a nest wherein to place it. We are not un- 

 willing to accept the suggestion that, being cogni- 

 zant of colour, she prefers a nest which contains 

 eggs similar to her own, in order that the latter may 

 be less easily discovered by the foster parents. At 

 the same time, we so frequently find the egg in 

 question amongst others which differ totally from 

 it in colour, that we cannot think that the Cuckoo is 

 so particular in her choice as Dr. Baldamus would 

 have us believe. 



J. E. Darting. 



Mergansers.— The capture near Guildford of 

 two species of Merganser is reported by Dr. Capron 

 in last month's Gossir (p.95).— On the breaking up 

 of the winter of 1866-7, several specimens, both of 

 Mergtis ■merganser and M. albelhis, were shot in 

 Sussex, and the Merganser family seem most plen- 

 tiful in the south of England about February. Will 

 any one inform me if this is the case, and also if it 

 is true that the majority of smews that visit our 

 southern shores arc females ?— J. R. 



