32 MIGRATION OF BIRDS 
ical Survey, pp. 1-79, one map. — 1904, Russell, I. C., North America, 
Chap. Ill, Climate, pp. 184-203 (Appleton). 
Note .—-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. 
< i - 1 
The Migration of Birds 
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 aery 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. Bummer Residents. — 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 
