4 ROCHESTER ACADEMY OF SCIENCE. 



Many species are difficult to classify under any one of the heads 

 just given, as, for example, the robin, which is a summer resident 

 and at the same time is often found throughout the winter, and hence 

 might be classed as a resident; or the mallard, which is chiefly a 

 transient visitant, but has been known to breed in this region, and 

 also occurs throughout the winter in favored localities. In cases 

 such as these, the bird is ranked according to the general, rather 

 than the exceptional mode of occurrence, and the exceptions noted. 



RELATIVE ABUNDANCE. 



It is practically impossible to take a census of the bird life of 

 any region ; nevertheless an attempt has been made to give a general 

 idea of the comparative abundance of birds by adopting terms in 

 ordinary use. The commonest birds, such as the robin, cat bird, song 

 sparrow, etc. , are called abundant species ; next in order come birds of 

 common occurrence, such as the meadowlark, savanna sparrow and 

 bobolink. 



Fairly common birds are such as may be found in limited 

 numbers at the proper place and season : for example, the loggerhead 

 shrike, rose-breasted grosbeak and scarlet tanager. 



The expression uncommon has been applied to birds, which, 

 though by no means rare, are met so seldom that they can not be 

 called fairly common ; they visit the region regularly, but in very 

 limited numbers. Birds of occasional occurrence are those which 

 are not found here regularly each season, but may be expected in 

 each locality at intervals of a few years at most; the whistling swan, 

 redpoll and snowy owl are examples. 



The term rare is reserved for birds which have been recorded 

 but a very few times in this region, but yet cannot be regarded as 

 stragglers from their regular range or migration routes; to this class 

 belong the Eskimo curlew, kittiwake and blue-gray gnatcatcher. 



Accidental birds are those which are wanderers from their proper 

 home, usually driven here by storms or unknown causes; here belong 

 the petrels, tropic bird, black skimmer, Bullock's oriole and cinnamon 

 teal. 



In the residence and migration chart a closer approximation to 

 the correct statement of relative abundance may be found graphically 

 represented. 



