58 Booth : Migration of the Common Swallow. 
Now let us assume that our local breeding Swallows have 
arrived and settled down — there may still be variation in the 
numbers present for two or three weeks, but this is caused by 
the coming and going of passing birds that have broken their 
journey for food or rest on their way to further northern breed- 
ing grounds. During the first or second week in May, according 
to circumstances, nest building will be commenced. From 
observations made, both in Norfolk and in Yorkshire, I have 
found that from the commencement of the first nest, until the 
fledged young are able to leave that same nest, takes quite 
seven weeks. By using this same calculation now, we may 
assume that nestlings of the earlier first broods would be on 
the wing by the end of June, or very early in July, and well 
able to look after themselves by the middle of July, when 
their parents would lose little time in commencing with the 
second nest. From now onwards, these youngsters, being 
left to their own devices, and without any household cares, 
would have much in common and would keep more together, 
than with the older birds, who would now be more concerned 
about their second brood. 
It is these young birds of the first broods, after flying about 
feeding for a few weeks, gaining strength of wing and power 
of endurance, that perform one of the many wonderful feats 
of bird migration. Unaided and without any leadership and 
while food is still very plentiful, they will embark on a journey 
of several thousand miles, over lands, seas, mountains and 
plains which they have never seen, and in varied climes where 
they have never been. Towards the end of August, assemblies 
of these young Swallows are much more noticable towards the 
evening as they cluster about some building, telegraph wires, 
or other similar position, all being very restless and excitable. 
Darkness comes on, and they are still there, and still restless ; 
but in the morning every, bird has gone. In these early gather- 
ings I have never detected any adult birds, and they are quite 
easy to tell ; but very often they are accompanied by young 
House Martins. Batch after batch leaves until well into 
September, when the young of the second brood are able to 
undertake the journey, and young and old birds then leave and 
travel together. It is often stated that there must be leader- 
ship by birds that have made the journey previously. If so, 
what about the young Cuckoo, left as a helpless, unfledged 
nestling in the care of foster parents, which as a rule, do not 
leave this country. Yet, two months or so later, and as soon as 
the bird gets strong enough, it wings its way to the land that 
its parents are already in, probably south of the Equator. If 
young Cuckoos can manage alone and unguided, why not 
young Swallows ? In the latter half of September vast numbers 
of Swallows (old and young together), congregate in various 
parts ; but particularly along the south coast of England. 
Doubtless they are made up of contingents from different 
Naturalist 
