Extensive Migration in Birds. 



I. Species with protracts! but irregular migratic 



omedeidse. Phaethoniida (?) 



Kellariidse. Fregatidx (?) 



II. Species with a in ignition nnige of 30° lot. or 1 



Podicipidx. 



Urinatoridx (all ?) 



Stercorariidx. 



Laridse (most). 



Sulidx (most ?). 



Anatidx. 



Gruidx. 

 | Hal l»s i irginianus. 

 , Porzana. 

 L Ftdica americana. 



Phalaropodidx. 



Riciirrirostridse. 



Scolopacidx (most). 



Cliaratlriidx (most). 



Aphrizidse. 



Columbidx (most). 

 ^ Cathartidx (?). 

 [ Circus hudsonivs. 



Accipiter velox. 

 ^Falco (2 species). 



Ceryle alcyon. 



Sphyrapicns ravins. 



Micropodidx. 



■ ohibris. 



f Tyrwrmw (2 species). 

 | Mi/iarchns crinitns. 

 < Sayornia (2 species). 

 I Contopus (3 species). 

 I Em pi dona x (5 species). 

 ( Dnlidionys oryziroms. 

 I Icterus galbula. 

 f Calcarius. 



I Zonotrichia (2 species). 

 | Spizella (2 species). 

 ■[ Melospiza (2 species). 



Habia ludoviciana. 



Passerina cyanea. 



Pimnga (3 species). 

 Hirundinidx. 

 Vireo (4 species). 

 Mniotiltidse (most). 

 Motacillidx (most). 

 Qaleoscoptes. 

 Regulus (2 species). 

 Turdus (3 species). 



Now the species enumerated in Lists I and II migrate peri- 

 odically through an area of 30° lat., or more, that is, a migra- 

 tion range of considerable extent, and, with a few exceptions 

 to be considered later, all are sharply denned species, and 

 even though the breeding areas of most are very broad, none 

 of them have a tendency to split into geographical varieties. 

 Accordingly there must be be some relation existing between 



