xii INTRODUCTION. 



RESIDENTS are species which are found in some district or 

 other of the county throughout the year, and therein breed 

 annually. 9 



SUMMER VISITANTS are species which appear annually in 

 the spring, remain through the summer for the purpose of rearing 

 their young, and afterwards depart in the autumn. 



WINTER VISITANTS are species which appear annually in the 

 autumn, and remain in more or less numbers throughout the 

 winter, departing in the spring for their breeding haunts. 



PERIODICAL VISITANTS are species which are observed in the 

 county only on their annual passage to and from their breeding 

 haunts in spring or autumn or both. 



CASUAL VISITANTS are species whose appearance in the 

 county is uncertain, but whose occurrence they being resident in, 

 or more or less regular visitants to, other parts of the British Isles 

 is not improbable, even though their visit may be very few 

 and far between. 



ACCIDENTAL VISITANTS are mere waifs and strays species 

 whose geographical range renders their occurrence in Britain quite 

 exceptional and more or less remarkable. 



These definitions have been carefully framed, and will, it is 

 believed, be found applicable to all cases. A few general remarks 

 upon them, illustrated by characteristic examples, desirable in 

 order to make their meaning perfectly unmistakable, will be given 

 in proceeding to analyse the Yorkshire fauna. 



