CHAPTER II. 



GLACIAL EPOCHS AND WARM POLAR CLIMATES. 



The Origin of Birds — Fossilized Remains — Remote Terrestrial 

 Changes — The Post-Pliocene Glacial Epoch — Warm and 

 Cold Glacial Periods — Origin of Migration — Changes through 

 Tertiary Time — Local Glaciation and Vertical Migration — 

 Probable Future of Migration— Initiation of Migration in the 

 CHARADRiiDiE — Effccts of Polar Darkness on Birds — Birds 

 feeding at Dusk — Ancient Migrations — Migrations of Polar 

 Birds — Ancient Species of Charadriid/e — Inter-Polar 

 Migration — Mr. Seebohm's Glacial Theory of Dispersal — 

 Isolated Species of Charadriid^ in the Southern Hemi- 

 sphere — Shortness of Migration Flight in Southern Hemi- 

 sphere — Gradations of Migration — Incipient Migration — 

 Short Migration Flight — Long Migration Flight — Extended 

 Migration Flight — Table of Migrants — Migration demon- 

 strated — Return of Birds to Old Areas. 



If we accept the footprints upon the Bunter Sand- 

 stein of the Triassic System as evidence of the 

 presence of Birds, then these creatures may pro- 

 bably date their origin from ages so remote as the 

 beginning of the Mesozoic Period. Dr. Hitchcock 

 enumerates the footprints of as many as twenty- 

 three species of " birds " in the Triassic formations 

 in New England. Some of these are of enormous 

 dimensions (twenty-two inches in length), and in- 



