Mr Black wall on the Instincts of' Birds'. 251 



Mr White observes, too*, that in the neighbourhood of Selborne, 

 martins build year by year in the corners of the windows of a 

 house without eaves, situated in an exposed district ; and as the 

 corners of these windows are too shallow to protect the nests 

 from injury, they are washed down every hard rain ; yet the 

 birds drudge on to no purpose from summer to summer, with- 

 out changing their aspect or house. 



These actions, it cannot be denied, seem to indicate a more 

 limited degree of sagacity in birds, than might be inferred from 

 those immediately preceding them. This apparent contradic- 

 tion, however, may be easily reconciled, by admitting, what in 

 all probability will be thought sufficiently obvious, that the dic- 

 tates of the understanding are frequently too feeble to resist the 

 powerful influence of instinctive impulse. Several examples il- 

 lustrative of this view of the subject, will be found interspersed 

 through the remainder of the essay. There is not any neces- 

 sity, therefore, for entering into a more detailed consideration of 

 it here. 



'-'After the business of nidification is completed, parturition 

 commences, which is succeeded by incubation, and as the birds 

 will frequently continue to deposit their eggs in the same nest, 

 though all except one or two should be removed as fast as they 

 are laid, or exchanged for others of a different size and colour ; 

 and as they will sometimes, after having produced their appoint- 

 ed number, sit upon a single egg, or the eggs of other birds in- 

 troduced for the purpose of experiment, on artificial ones of 

 chalk, or even upon stones of any irregular figure; it is plain 

 that the act of depositing and incubating their eggs can be as- 

 cribed to instinct only. 



The parental offices of birds to their young, are also regulated 

 by instinctive feeling, as is evinced by their bestowing the same 

 attention on the offspring of other species, when committed to 

 their care, as they do upon their own. Thus the titlark and 

 hedge-warbler manifest the warmest attachment to the young 

 cuckoos, their foster nurslings, though they suffer their own pro- 

 geny, ejected by the iritruders, to perish from neglect within a 

 short distance of the nest ; and this affection continues with lit- 

 tle diminution, till their sup|)osititious offspring have nearly at- 



• Natural History of Selborne, p. ICO. 



