HISTORY OF THE SWALLOW TRIBE. 37 



. Ble swallow appears in the neighbourhood of 

 Manchester on the 18th of April, and the house- 

 martin on the 23rd of the same month, at a 

 mf an of twelve yeais' observations, but as these 

 birds do not pair immediately on their arrival, and 

 4is they generally produce two, and often even 

 three broods in a season, it frequently happens 

 that individuals have nestlings in October, the 

 period at wliich the great body of their species 

 withdraws from this coimtry.* Many of these 

 young birds, from inability to accompany their 

 congeners in tlieir autumnal flight, are compelled 

 to remain behind, and some of the most vigorous 

 of them, may occasionally be seen, in favourable 

 situations, lingering about till the close of No- 

 vember, endeavouring to obtain a scanty sub- 

 sistence. As the temperature of the atmosphere 

 decreases, however, the insects they prey upon 

 gradually diminish, till, at last, their utmost 

 exertions to prociure a sufficient supply of food 

 are unavailing : they then speedily become en- 

 feebled, and concealing themselves, as is usual 

 in such emergencies, numbers undoubtedly perish 

 from exhaustion. A few accidental discoveries 

 of Inrds thus situated, before the vital principle 

 has been quite extmct, may, very possibly, have 



• At Tarvin, in Cheshire, in 1819, I saw a pair of martins 

 feeding their uoflcdgcd young on the 20th of October. 



