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, braining; 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. 



