32 MIGRATION OF BIRDS 
ical Survey, pp. 1-79, one map.—1904. Russexu, I. C., North America, 
Chap. III, Climate, pp. 184-203 (Appleton). 
Nots.—Discussion of the faunal affinities of the region in question 
will frequently be found as introductory matter in ‘local’ or state bird 
lists; see especially (in the Bibliographical Appendix) under Georgia, 1909, 
Howell; Illinois, 1890, Ridgway; Iowa, 1907, Anderson; Kentucky, 1910, 
Howell: Maine, 1908, Knight; Maryland, 1900, Merriam and Preble; 
Massachusetts, 1901, Howe and Allen; Nebraska, 1909, Wolcott; New 
Hampshire, 1904, Allen; New Jersey, 1894, 1909, Stone; New York, 1910, 
Eaton; North Carolina, 1886, Brewster; Ohio, 1903, Jones; Pennsylvania, 
Stone, 1891, 1894; Dwight, 1892; Todd, 1893, 1904. South Carolina, 
1890, 1891, Loomis; Tennessee, 1910, Howell; Virginia, 1890, Rives; West 
Virginia, 1890, 1898, Rives. 
Tue Micration or Brirps 
Times of Migration 
Extent of Migration 
Routes of Migration 
How Birds Migrate 
Why Do Birds Migrate? 
Migration is the most distinctive phase of bird-life. Certain mam- 
mals, fishes, and even insects migrate, but no animals approach birds 
in the extent of their migrations. Wholly aside from the interest which 
is attached to a study of bird migration in the broader aspects, as we 
attempt to,determine its origin and extent and the various factors 
which govern the times and manner of a bird’s journeys, there is a 
fascination and excitement for the student in observing the arrival and 
passage of the great army of feathered travelers which ever renews 
itself when birds 
“Part loosely wing the region; part more wise, 
In common, ranged in figure, wedge their way 
Intelligent of seasons, and set forth 
Their aéry caravan, high over seas.” 
To the nature lover birds are a living calendar. ‘What was that. 
sound that came on the softened air? It was the warble of the Blue- 
bird from the scraggy orchard yonder. When this is heard, then has 
spring arrived.” 
Times of Migration According to the nature of their occurrence 
the birds of temperate regions may be grouped seasonally as follows: 
1. Permanent Residents—Includes species that are represented 
in the same locality throughout the year. In temperate and boreal 
Eastern North America few species are permanently resident as indi- 
viduals. Possibly Ruffed Grouse and Bob-whites pass their lives in a 
comparatively restricted area. But the winter Crows, Jays, and Nut- 
hatches of a certain locality are probably not the ones that nested there. 
2. Summer Residenits.—Includes species that come to us from 
farther south in the spring, rear their young, and return to the south 
in the fall. As a rule, the first species to come in the spring are the last 
