400 
NATURAL HISTORY. 
their usual range, by scarcity of food or other causes ; such are the 
Nyctea nivea , Astur atricapillus, Collyrio borealis , Pinicola canadensis, 
and others. Second, those which visit us in July and August, which 
are mostly the young of species breeding further south. Examples 
of these are to be seen in the Rhynchops nigra, some species of Ardei - 
dee, &c. In the third class are to be ranged those whose appearance 
is totally accidental, dependent upon no fixed habit of the bird. 
Thus, species of T hallassidroma and Puffinus have been seen upon the 
Potomac, and a Milvulus (M .forjicatus, probably) and the Chamcepdia 
passerina have been detected. 
The great mass of the birds which pass through the district in their 
spring migrations do not stop to breed before reaching, at least, the 
New England States, and probably the majority go still further north, 
spreading through the Canadas and into British America to the region 
around Hudson’s bay. Our regular winter visitants, as the Junoo 
hyemalis , Spizella monticola, and the Anatidee generally, do not usually 
stop much short of Labrador and the regions of that latitude. Other 
species, however, breed with equal readiness in almost any latitude. 
Thus the Dendroica aestiva is very common through the summer in the 
district, and doubtless even further south; while it breeds also in very 
high latitudes in British America. During the winter these migra- 
tory species mostly retire to the Antilles, or into Central America, 
though many linger in the G-ulf States along our southern border. 
The manner in which these extensive migrations are performed varies, 
doubtless, with different groups of birds, but it is very difficult to 
conceive how some weak and short-winged species can perform the 
immense journey. Some accomplish the distance by continually flying 
from forest to forest, and from hedge to hedge; while others mount 
directly high into the air, and uninterruptedly continue their flight 
until hunger or weariness compels them to desist for awhile. This 
kind of migration is performed by some species wholly in the night 
time. Some of the small insectivorous birds have been noticed just 
at daybreak to descend from a great height, and after remaining 
motionless for sometime, as if to recuperate their energies, search 
diligently for food, and again resume their flight towards evening. 
The distance at which the notes of birds flying overhead can be 
heard is truly surprising. We have heard distinctly the mellow 
notes of the Bob-o’link while the bird itself was entirely beyond our 
range of vision. The loud “honking” of wild geese while migrating 
is well known. 
A circumstance which has considerable influenceon the appearance 
of birds in the immediate vicinity is the presence of a large city. 
This is most strikingly shown in the case of the ducks and other wa- 
ter fowl, to which the attention of the sportsman is especially di- 
rected. The peculiar character of Chesapeake bay and its tributa- 
ries render them the favorite winter resort of nearly all the species 
of Anatidee ; but the incessant persecutions to which these birds are 
subjected have effected a material diminution of their numbers, and 
caused a great part of them to retire to the bogs and inlets of more 
southern shores. The same is true, though less markedly, of various 
