MUSEUM OF COMPARATIVE ZOOLOGY. 425 



increase southwards in the number and even in the proportion of 

 species which are resident at the same locality the whole year. But 

 from the absence of exhaustive lists of the species occurring at numer- 

 ous localities, differing in latitude, it is difficult to make at present a 

 wholly satisfactory numerical comparison of the different ornithological 

 faunae.* 



occurrence ; three hundred and twenty-seven in ttie vicinity of New York City (Law- 

 rence), and three hundred and forty-three in New Jersey ( Turnbull). The number 

 given by Ross as observed by him in the " Mackenzie's River District" is one hundred 

 and ninety-two. Tne greatest number I have seen recorded from any restricted 1 icality 

 within the American tropical Realm is five hundred and forty, the number given from 

 Costa Rica by Messrs. Lawrence and Salvin. 



* Dr. Richardson in 1831, found that the number of species " known to rear their 

 young on the banks of the Saskatchewan " amounted to one hundred and forty-one. 

 At least twenty species more may now be safely added. Bonaparte, in 1S27, estimated 

 the number of species breeding at Philadelphia to be one hundred and four.' Messrs. 

 Coues and Prentiss in their list of the birds of the District of Columbia, published in 

 1861, mention forty-four species as being permanent residents, and fifty-nine others as 

 summering, making one hundred and three that probably breed in the District, — one 

 less than the number given by Bonaparte as breeding at Philadelphia. Messrs. S. F. 

 and W. M. Baird gave, in 1*44, one hundred and nine species as breeding at Carlisle, 

 Pennsylvania. The tfiree latter being inland localities, they may properly be compared 

 with the Saskatchewan district. The numerous lakes at the latter locality, however, 

 afford favorite breeding places for numerous water birds, while few such localities are 

 afforded by the other localities mentioned; but since few water birds breed so far south 

 as these localities, the difference in this respect is a fact of small importance. Dr. 

 Turnbull, in 1869, gave the number of permanently resident species in "East Penn- 

 sylvania and New Jersey" as fifty-two, and the number of summer visitors as one hun- 

 dred and fourteen, making a total of one hundred and sixty-six species that occur there 

 in summer; but the area included in this list is more extended, and embraces a greater 

 variety of surface than in the other cases, and includes several strictly- coast species. 

 Farther than this, an examination of his list shows that at least thirty of the one hun- 

 dred and sixty-six are either wholly of accidental or of very rare occurrence, and hence 

 do not regularly (many of them never) breed at the locality named. The number of 

 resident speeies in Massachusetts is not far from thirty, of summer visitors one hun- 

 dred and six. making one hundred and thirty-six that are more or less frequent in sum- 

 mer, — a number considerably less than undoubtedly -eccur in an equal area on the 

 Saskatchewan. Mr. ('. J. Maynard, in his careful analysis of the birds of Eastern 

 Massachusetts (Naturalist's Guide, Part II, pp. 162- 164, 1870), gives only one hundred 

 ami fifteen as being known with certainty to breed in the eastern half of that State, 

 one or two of which cannot be considered as breeding there regularly. While this 

 somewhat <-xr<-<-,\~ the number generally given as breeding at localities more to tin 

 ward, it is far less than the number given by Dr. Richardson as breeding on the Sas- 

 katchewan, and much less than the number now well known to be found there in 

 summer. Dr. Coues, in his " Synopsis of the Birds of South Carolina," indicates i , 1 1 1 y 

 nbout one hundred and thirty-five as being known to breed regularly in that State. 



