86 REMARKS ON THE 
fifteen years’ observations ; but as these birds do not 
pair immediately on their arrival, and as they gene- 
rally produce two and sometimes even three broods 
in a season, it frequently happens that individuals 
have nestlings in October, the period at which the 
great body of their species withdraw from this 
country *. Many of these young birds, from imabi- 
lity to accompany their congeners in their 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 November, endeavouring to obtain a scanty sub- 
sistence. As the temperature of the atmosphere de- 
creases, however, the insects they prey upon gradually 
diminish, till at last their utmost exertions to procure 
a sufficient supply of food are unavailing; they then 
speedily become enfeebled, and concealing themselves, 
as is usual in such emergencies, numbers undoubtedly 
perish from exhaustion. A few accidental discoveries 
of birds thus situated, before the vital principle has 
been quite extinct, may very possibly have given rise 
to the opinion that European Swallows pass the winter 
season in a state of torpidity. 
It did not come to my knowledge that these late 
broods are sometimes deserted by the parent birds, 
before they are capable of providing for themselves, 
till the spring of 1821; when a pair of House-Mar- 
* At Tarvin in Cheshire, in 1819, I saw a pair of House-Mar- 
tins feeding their unfledged young on the 20th of October. 
