318 INTRODUCTION TO NATURALISES CALENDAR. 



place by a loss of some parts of a feather, thereby bringing into view 

 some other portion, and so producing a different tint ; in others, the 

 colour of the feather entirely changes. These variations take place 

 more or less rapidly with the seasons ; but in some instances, the 

 change is effected in a day or two, as in many of the plovers and sand- 

 pipers, some 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 periodi- 

 cally 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 r 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. 



