INTRODUCTION TO NATURALIST’S CALENDAR. 445 
ducks, and the head of the black-headed gull, &c.,so that exactness 
in the registration of these changes should be observed. Some of 
our summer visitants assume their breeding dress after arrival 
here, while others are partially changed, as if the operation had 
commenced, and was going on at the same time with the instinctive 
desire to migrate. And again, on the cessation of the duties of 
the male, does the brilliancy begin to fade, and the dark or rich 
contrasted tints to blend into a plumage broken and worn, and now 
commencing to be renovated by a new moult—all these mutations 
are worthy to be noted, and can be easily done at the same time 
that other facts are registered. 
It is during this same important period that a great change 
periodically takes place in the song and voice of birds. Many 
species sit and utter their call from some selected spot, which is 
frequented day after day; but others practise peculiar modes of 
flight, calling as they fly. The pleasing song of our warblers and 
thrushes, the call of the pigeons and cuckoo, are familiar examples 
of the first. The towering flight of the greenfinch, and the rise 
and fall of the pipits singing as they fly; the drone and flight of 
the snipe, and the shrill whistle of the curlew, are examples of the 
combined exercise ; but in every species there is a change more or 
less marked, which will be easily seen and noted by a practised or 
willing observer. 
There is yet another point worthy of attention, that is, the 
change in the general zoology of a district or locality which has 
taken place within a limited period, by an alteration of its physical 
character; by improvement, cultivation, draining; by planting, and 
the increase of wood ; by the rooting out and destruction of copse 
or natural wood ; by the introduction of some particular trees or 
brushwood. All these matters have a much greater influence on 
animal life than is at first imagined; and in the space of twenty 
or thirty years, we have seen the character of a locality almost 
changed, by the forsaking of some species, and the coming in of 
others. These changes go gradually on, but are at last complete, 
being naturally incidental to the artificial causes above-mentioned. 
