i8q4 1 Loomis on Birds of Chester Comity, South Carolina. IOI 



well as at the North in a species that is resident in both sections. 

 The Blue Jay and Cardinal are examples. This obviously pre- 

 vents over-crowding. Southern Florida, the Bahamas, West 

 Indies, Mexico, Central and South America receive the surplus 

 population from the northward. As the continental land area 

 north of the Tropic of Cancer is so great, being about three 

 times larger than that south of the Tropic of Capricorn, and as 

 Central America and about half of Mexico are the only parts of 

 the continent within the tropics, it is not surprising that the 

 periodic flight from northern winter should extend far into South 

 America. 



In short, the population is lessened where the necessities are 

 greatest, and changed in character where food is plentiful, 

 apparently because the food is not suitable and because room 

 is needed for those coming from above. 1 Whether it be the 

 migration of the Plumed Partridge from the eastern slope of 

 the Sierra Nevadas across the summit to the western slope, 

 or whether it be the migration of the Brown-headed Nuthatch 

 from the mountains of the Carolinas to the lower country, or 

 of the adults of the Louisiana Water-Thrush before the close 

 of June, or whether it be the migration of the American Pipit 

 with the advent of snow, or of the Snowflake from hyperborean 

 regions to the more northern portions of our country, or of 



1 The breeding land birds of temperate South America seem to find ready means 

 of subsistence after summer without partial migration into North America, ample 

 accommodation apparently being found by indigenous migrants, for there are indeed 

 refugees from southern winter, numerous species migrating northward. See Sclater 

 and Hudson's Argentine Ornithology.' The distribution of land probably accounts 

 for the absence of such transmigration, for over two-thirds of the southern continent 

 lie within the tropics. Among oceanic birds, Mr. Brewster has shown the high proba- 

 bility of a migration northward from an antipodean breeding habitat in at least one 

 species of the family Procellariidae ; viz., Wilson's Petrel. See Proc. Bost. Soc. Nat. 

 Hist., XXII, Oct., 1883, pp. 403, 404. Rev. A. E. Eaton's discovery of the breeding 

 of this species during January and February on Kerguelen Island (Saunders's An 

 Illustrated Manual of British Birds,' p. 730) bears out Mr. Brewster's conclusions. 



There is some migration, at least, in breeding birds in tropical regions, but how far 

 the presence of winter birds is compensated for has not been determined. Mr. Chap- 

 man mentions three species that are found in Cuba only during summer (Bull. Am. 

 Mus. Nat. Hist., IV, p. 284), and Mr. Ridgway in writing of the migration of Hum- 

 mingbirds (Rep. U. S. Nat. Mus. for 1890, p. 267) speaks of "slight migrations when 

 the food supply of a given locality fails them, or when, on high mountains, the in- 

 creasing cold forces them to descend to the warmer slopes and valleys." 



