MIGRATION 49 



Now, this resorting towards that element, at that season of 

 the year, seems to give some countenance to the northern 

 opinion (strange as it is) of their retiring under water. A 

 Swedish naturalist is so much persuaded of that fact, that 

 he talks, in his Calendar of Flora, as familiarly of the 

 swallow's going under water in the beginning of September, 

 as he would of his poultry going to roost a little before 

 sunset. 



An observing gentleman in London writes me word, that 

 he saw a house-martin,* on the 23rd of last October, flying in 

 and out of its nest in the Borough ; and I myself, on the 

 29th of last October, as I was travelling through Oxford, 

 saw four or five swallows hovering round and settling on the 

 roof of the County Hospital. t 



willows growing on the aits of the river Thames. I have not only witnessed 

 their departure, but also their arrival in this country. On the latter occasion 

 they alighted on the ground and appeared much exhausted. ED. 



* In a mild winter I have seen solitary swallows as late as the beginning 

 of December. ED. 



f* In Mr. Bennett's edition of White's Selborne, there is a very interesting 

 note of the late Dean of Manchester's (Mr. Herbert) on the instinct of birds. 

 He says that young swifts, the moment they leave the nest, have often 

 occasion to make the great migration, and that the various species of 

 hirundines remain in their nests till they are more completely feathered 

 than other birds. Thus when they come forth, they are matured for flight. 

 He thinks that the troublesome insects which infest their nests (hippobosca 

 hirundinis), are a resource in the scheme of Providence to force the young 

 birds to venture upon the wing from the perilous height at which their nest 

 is placed, by making the abode insupportable. 



Each bird, Mr. Herbert says, builds its nest in the same form and of the 

 same materials as its parent, and for the most part in a similar situation ; 

 but he thinks that, if the eggs were transposed into the nest of some nearly 

 related species, and the produce kept separate from all others of their own 

 kind, they would doubtless make their nests like those of the birds which had 

 reared them, and would also adopt their notes. I have observed, he adds, 

 young blackcaps raised from the nest in a large cage in which the perches 

 were very low, as soon as they fed themselves show a sudden anxiety at 

 roosting-time to find a higher perch, and flutter about so intent upon this as 

 to notice nothing else, and at last settle to roost clinging to the wires near 

 the top of the cage. This appears like a marvellous instinctive impulse ; but 

 I apprehend that, while in their native bush, they had noticed the parents 

 every evening, at roosting-time, fly upwards to a loftier situation in which to 

 pass the night. I therefore refer this to observation. 



Amongst other notices of peculiar instincts, Mr. Herbert refers to that of 

 young birds brought up in cages, selecting their proper food from amongst a 

 variety placed before them, and also that of migratory birds washing, and 



