ORNITHOLOGICAL CLUB. 95 



In view of this fact, the announcement of a third specimen for Massa- 

 chusetts may he of interest. On Octoher 2, 1876, while collecting at 

 Concord, Mass., I shot a female of this species in fine autumnal plumage. 

 "When first observed it was gleaning industriously among some low, scat- 

 tered birches, in company with several Black-throated Green Warblers 

 {Dendrceca virens), a few Black-polls (D. striata), and one or two Nash- 

 ville Warblers (Helminihophaga ruficapilla). Its small size and dark colors 

 first drew my attention to it, and led me to suspect its identity. It proved 

 upon dissection to be a bird of the year. — William Brewster. 



Variable Abundance of Birds at the same Localities in dif- 

 ferent Years. — It has probably been observed by most of our field 

 ornithologists, that many of our rarer birds are to be found in larger num- 

 bers during some'of their annual or semiannual visits than -.during others. 

 This is an interesting fact ; but it is a fact of much greater interest that 

 our commonest summer residents are similarly variable, and that, as a 

 general rule, where one species varies in this respect, the deviation extends 

 to all in the same degree. A small increase or decrease in the multitude of 

 universally common species is, of course, less noticeable than a proportion- 

 ate variation in the numbers of those which are less abundantly distrib- 

 uted ; but that the former are as regularly subject to such variation as 

 the latter is beyond all doubt. So absolute and unchanging is this law, 

 that its effects may be detected from the appearance of the earliest spring 

 arrivals to the coming of the last of the vernal migrants. Should the 

 army of Thrushes and Finches that arrive from the south about the last 

 of March be unusually large and continuous, you may prophesy with al- 

 most entire confidence a good year for birds. In the vicinity of Portland 

 the seasons of 1875 and 1876 have been remarkable in examples of ex- 

 treme numerical variation ; the one for the paucity of rare species, the 

 other for their abundance. During the past season (1876) White-crowned 

 Sparrows occurred in almost unprecedented numbers, often appearing in 

 flocks of six or eight ; the previous season but one was taken, to my 

 knowledge. In 1876 specimens of the Mourning and Bay -breasted War- 

 blers were taken ; the one new to the locality, the other not having occurred 

 for six years. The Great-crested Flycatcher was common in 1876, rare in 

 1875. With a few exceptions, the same difference has been perceptible in 

 the case of every species. 



i But what is it that exerts so potent an influence over our birds ? Not 

 the weather, it would seem ; for heat or cold, storm or calm, causes 

 but a slight difference in the time of the arrival of a species, much 

 less in its numbers. An apparent auxiliary cause is the weather of the 

 winter preceding the spring. If the winter be mild and rather free from 

 snow, there is an evident increase in the numbers of the earliest arrivals 

 in March ; but it can hardly be supposed that a bird which does not make 

 its appearance till the last of May feels the effects of mild weather several 



