558 MIGRATION 
of the weather.!. This is not very wonderful, for the movements of 
the migrants, if governed at all by meteorological forces, must be 
influenced by their action in the places whence the travellers have 
come, and therefore to establish any direct relation of cause and 
effect corresponding observations ought equally to be made in such 
places, which has seldom been done.? As a rule it would seem as 
though Birds were not dependent on the weather to any great 
degree. Occasionally the return of the Swallow or the Nightingale 
may be somewhat delayed, but most Sea-fowls may be trusted, it is 
said, as the almanack itself. Were they satellites revolving around 
this earth, their arrival could hardly be more surely calculated by 
an astronomer. Foul weather or fair, heat or cold, the PUFFINS 
(Fratercula arctica) repair to some of their stations punctually on a 
given day as if their movements were regulated by clock-work. 
Whether they have come from far or from near we know not, but 
other Birds certainly come from a great distance, and yet make their 
appearance with scarcely less exactness. Nor is the regularity with 
which certain species disappear much inferior; every observer 
knows how abundant the Swirr (Cypselus apus) is up to the 
time of its leaving its summer-home—in most parts of England, 
the first days of August—and how rarely it is seen after that time 
is past. 
It must be allowed, however, that, with few exceptions, the 
mass of statistics above spoken of has never been worked up and 
digested so as to allow proper inferences to be made from them, 
and therefore it would be premature to say that little would come 
of it, but the result of those few exceptions is not very encouraging. 
The most important is due to Dr. von Middendorff who carefully 
1 Herr Gitke in the valuable work presently to be particularly noticed, 
attaches much more importance to the effects of weather than I am inclined to 
do, though I am far from saying that his opinion may not be borne out by his 
experience on Heligoland, where his observations were made. That is a spot so 
small that, though exceptionally favoured as a resort for Birds-of-passage, it 
might easily be missed (as indeed it frequently is) owing to the wind lying in 
such a quarter as would turn them from their usual course. He certainly gives 
(p. 85) a remarkable instance of a temporarily reversed movement in March 1879, 
doubtless caused by the setting in of bad weather ; but in nearly all cases Birds on 
their northward Migration do not retrace their flight but persevere in the efforts 
to get forward, even though when they reach their goal they may succumb and 
perish for want of food through the severity of the season. 
2 To a limited extent it must be admitted that the popular belief as to certain 
Birds being the harbingers of severe weather is justifiable. Cold comes out of 
the north, and when it is accompanied, as is most generally the case, by heavy 
falls of snow, such Birds are of course driven southwards to seek their living. 
But as often as not the Birds arrive with the kind of weather they are com- 
monly held to prognosticate, while sometimes this does not follow their 
appearance. 
