THE OR LET ON SWIFTS. 
29 
but did not again feed them. I watched for another ten 
minutes, and then, wishing to examine the bird, put out my 
hand to take it, but it slipped through my fingers and was gone. 
1 was not able to look at this nest again for a week or more, 
and then found the young ones dead. This may have been the 
result of my interference, but if so, it was an unusual one, for I 
have handled many Swifts on the nest and never known them 
desert ; but I have found other young Swifts dead in the nest 
without apparent cause, and certainly without being at all dis- 
turbed by me or anyone else. Gilbert White also mentions 
finding two young ones dead in a nest. :;: I have watched young 
ones being fed since, but the help of a hand-mirror has been 
necessary to enable me to see round a corner. 
The young are a long time coming to maturity. I weighed 
one that had been hatched for fifteen days and had died un- 
accountably. It was in good condition and weighed ij oz., 
only a quarter of an ounce under the weight of an old bird. Its 
back was covered with the bluish down, and the quill feathers 
were half an inch in length. The young Swift does not leave 
the nest until it is completely fledged and fully equipped for its 
aerial life, without needing further assistance from its parents. 
But it takes six weeks from leaving the shell to bring it to this 
state of perfection, and often more, especially if there are two 
young ones. The time varies a good deal. There were two 
nests here, each containing a single bird hatched on the same 
day, but one flew three days before the other. And in another 
nest the stronger of the two birds took more than its share of the 
food, and so fledged faster and flew seven j days sooner than 
the other, and yet they were hatched on the same day, or, to be 
more exact, there was less than twenty-four hours between 
them. 
If we count the period of incubation (three weeks including 
the day the egg is laid), the total time required for the develop- 
ment and growth of a Swift is more than two months. The 
Swallows and Martins have a second brood, but the Swifts are 
contented with one, which is not to be wondered at. 
They leave Orleton on or about the nth of August. The 
climate has nothing to do with their departure at this date, nor 
has the question of food. They go as soon as the young take 
to the wing, and they do not even wait for one another. But 
the young come out so much about the same time that most of 
them leave together. The Swifts come to Europe to breed and 
for that purpose alone, and as soon as the business is over they 
hurry back to Africa. This explains the mystery of their 
leaving suddenly when everything seems conducive to their 
* Letter 52, page 264, original edition. 
f I stated in a letter to the Times, Sept. 10, and elsewhere, that it was nine 
days, but I find that owing to the way in which the entries were made in my 
notebook I mistook the time. It was seven full days. 
