no BIRDS OF THE PLAINS 



young are able to fend for themselves, the parents some- 

 times behave in what seems to human beings a most 

 unnatural way : they drive off their offspring by force. 

 As a matter of fact, this behaviour is quite natural ; it 

 is dictated by Nature for the benefit of the species. 

 Strong as the maternal instinct is, it is liable to be over- 

 ridden by stronger instincts, such as that of migration. 

 When the time for the migratory journey comes round, 

 the parent birds will desert, without apparently a pang 

 of remorse, or even a thought, the broods for whose 

 welfare they have been slaving day and night. This 

 desertion of later broods by migratory birds is far 

 commoner than is generally supposed. In 1826 Mr. 

 Blackwell inspected the house-martins' nests under the 

 eaves of a barn at Blakely after the autumnal migration 

 of these birds. Of the twenty-two nests under the eaves 

 inspected on nth November, no fewer than thirteen 

 were found to contain eggs and dead nestlings. 



