452 RAMBLES ABOUT HOME. 



in liis preface : " From the geographical position of the 

 district it is particularly favorable for observation, being 

 the resort, at some period of the year, of a large proportion 

 of the birds of this continent; and, from the fact of its 

 being the temporary resting-place of most of the migratory 

 birds, there is probably no district of the same extent in 

 this country that is frequented by such a number of species. 

 A considerable number of our summer visitants from the 

 Gulf States and Mexico appear to make it their northern 

 limit, while other flocks remain only a short period in spring, 

 and migrate still further north, penetrating as far as British 

 America to breed ; and these again arrive in autumn on 

 their return journey to their winter retreats. It may like- 

 wise be noted that the district is the southern limit of many 

 species which breed at Hudson's Bay and the fur countries, 

 and pass the winter on the Delaware and Chesapeake, thus 

 forming a line of separation, so to speak, for the migratory 

 flights of many interesting birds coming from opposite di- 

 rections. 



" On consulting the list, however, it will be remarked 

 that the proportion of what may be considered resident 

 birds is small. This fact seems to have attracted observa- 

 tion as far back as the time of Dr. Benjamin S. Barton, 

 who published a work, entitled ' Fragments of Natural 

 History,' about seventy years ago, in which it is stated 

 that, in the district now spoken of, very few species remain 

 all the year, and that even of these there appeared to have 

 been a partial migration in severe winters ; such birds, 

 especially, as lived on insects and small fruits being com- 

 pelled to retire southward a fact still noticeable at the pres- 

 ent day many species that usually migrate remaining in 

 mild and open winters. Closer observation of late years, 

 however, has enabled ornithologists to affirm with certainty 

 that, of so-called migratory birds, a greater number pass 

 the winter with us than has been hitherto supposed." 



Elsewhere in his preface the author further remarks : 



