PALAEARCTIC ELEMENT IN NEW WORLD AVIFAUNA 427 



Cuculidae is represented in the Americas by thirty species, which 

 are arranged in ten genera, not a single one of which occurs in the 

 Old World. In the pigeon family, Columbidae, there are nineteen 

 endemic New World genera, some highly distinctive. The twentieth 

 genus, which is shared with the Old World, is the eminently success- 

 ful genus Coliimba, to which the domestic pigeon belongs. There are 

 no fewer than eighteen New World species of Columba, of which 

 seventeen are confined to the warm latitudes between the Rio 

 Grande and south Florida to the north and approximately Buenos 

 Aires to the south. Darlington (1957, p. 273) argued for a tropical 

 New World origin of the genus Columba, with dispersal to the Old 

 World through the north. To me, the facts suggest, rather, (1) an 

 origin in the Old World, (2) a secondary radiation in the New World 

 tropics, and (3) a quite recent northward movement by a single 

 species, the Band-tailed Pigeon (C. fasciata), which now ranges 

 from Central America to southwestern British Columbia. That 

 Columba was originally a tropical genus is suggested not only by 

 the somewhat greater number of tropical than of temperate species 

 in the Old World, but by the fact that the genera currently placed 

 closest to Columba (Peters, 1937) are also confined to the Old World 

 topics. This would give strength to the idea that Columba is older 

 in the Old World than in the New, as would the fact that a larger 

 number of species has been able to become adapted to temperate 

 conditions in the former area than in the latter. 



Turning now to the family Corvidae, we may note that the 

 greater diversity of the jays in the New World is evidence for an 

 early secondary radiation from corvid stock. It is, in fact, quite con- 

 ceivable that the few jays of the Old World may represent a re- 

 invasion of the Old World. One genus of jays, Perisoreus, now 

 inhabits northern coniferous forests of both hemispheres, with a 

 distinct but related species {"Boanerges'' internigrans) in the moun- 

 tains of western China. Amadon (1944, p. 5) believed that the 

 distribution of Perisoreus leaves "little doubt that it is an Old World 

 genus which reached America recently, later than the other American 

 jays." If the jays, as postulated above, represent a reinvasion of the 

 Old World by corvid stock which had differentiated in the New 

 World, then Amadon 's interpretation would require Perisoreus to 

 have returned, so to speak, to the New World. This is possible, 

 but a New World origin for Perisoreus itself must be considered. 



