GENERAL CHARACTERS OF THE AVIFAUNA. 29 



are quite a number, however, which are extremely rare, and by no 

 means entitled to be considered as inhabitants of the District. Such 

 may be divided into three classes: First, those which visit us in severe 

 winters, being driven beyond their usual range by inclemency of the 

 weather or scarcity of food; such as Nyctea nivea, Astur atricapillus, 

 Falco peregrines, Lanius borealis, Pinicola enucleator, Loxia americana, 

 L. leucoptera, uEgiothus linarias, Plecfrophanes nivalis. Second, those 

 which visit us in the latter part of summer, mostly the wandering young 

 of species breeding farther south, as Rhynclwps nigra, several species of 

 Ardcida', and probably Chamcepelia passerina. In the third and more 

 extensive class are to be ranged the stragglers proper ; species observed 

 for the most part but once, whose appearance is wholly fortuitous, 

 depending upon no fixed habit of the bird. Thus, several species of Sea- 

 Ducks (Fuligulince): three species of the pelagic family Procellariidce, 

 Graculus dilophus, Tyrannus verticalis, Milvulus forficatus ?, Chondestes 

 grammicus, the European Mareca penelope, have all been observed in 

 the District or immediate vicinity. Such occurrences are always inter- 

 esting, and should properly be enumerated in making up a list; but 

 they take no part in the regular order of things. 



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 

 Alleghanian or Canadian fauna in regions north and east of us, in the 

 latitude of New England and New York, or the same fauna farther 

 south at higher elevations north and west of us in the Appalachian chain. 

 Probably the majority go still farther north, to Labrador, the Hudson's 

 Bay regions, and even Arctic America. Our regular winter visitants, 

 as well as those which straggle at times from the north, do not, as a rule, 

 breed anywhere in the United States. Some, however, like Dendrceca 

 CBstiva, breed anywhere, apparently independent of latitude. Our reg- 

 ular fall migrants for the most part pass on through the United States 

 to winter in the West Indies and Central or even South America, though 

 some linger through that season along the Gulf coast. The manner in 

 which these extensive migrations are performed varies, doubtless, in 

 different cases, and it is very difficult to understand how some of the 

 weak, short-winged birds accomplish such immense distances. The 

 manner is almost as much of a mystery as are the impelling, control- 

 ing, and guiding causes, none of which have ever been satisfactorily 

 explained. Some birds appear to perform the long journey by contin- 

 ually flying from forest to forest, or from hedge to hedge; but, as a rule, 

 birds mount directly high into the air, and continue an uninterrupted 

 flight until hunger or weariness compels them to desist. This contin- 

 uous kind of migration is performed by some species at night. Some 

 of the small insectivorous birds have been observed just at daybreak 

 to descend from a great height, and after remaining motionless for a 

 while, as if to recuperate their energies, search diligently for food, and 

 resume their flight toward evening. Any one who has lived in the woods 



