428 K. C. PARKES 



At any rate, members of the family Corvidae other than the jays 

 have continued to enter the New World, some so recently that the 

 American populations are barely separable subspecifically from 

 their Old World relatives (the family thus paralleling the owls in 

 this respect). The Magpie {Pica pica) now exists in North America 

 in two well-marked forms: the Black-billed [P. p. hudsonia), very 

 similar to Old World races, and the Yellow-billed, usually considered 

 a full species (P. nuttalli). Only the latter is known from fossil 

 (late Pleistocene) remains in North America, from within or close 

 to its present range in California. The magpies of North America 

 may well represent a double invasion by the same Old World 

 species (see Lanius, beyond). Again, within this family, the genus 

 Corvus has entered the New World at least twice, and probably 

 more often. A cluster of closely related species of this genus in the 

 southern United States, West Indies, and Mexico probably represents 

 a rather early invasion, since these species at present have no clear 

 affinities with any Old World crows. On the other hand, the southern- 

 most penetration of this genus in the Americas is that of the Raven 

 (C. cor ax), which has reached Nicaragua. Pleistocene fossils of the 

 Raven are known from as far south as Nuevo Leon, Mexico, yet 

 all New World Ravens are only subspecifically different from those 

 of the Old World, and the northernmost populations are barely 

 separable. 



The weakness of the fossil record is nowhere better demon- 

 strated than in the large order Passeriformes, the perching birds, 

 to which half our living species belong. Wetmore (1956) listed from 

 North America (including the West Indies) only 51 species of 

 passeriform birds known from fossil (for one species Recent cave) 

 remains. Of these 51, no fewer than 44, or 86%, are Pleistocene 

 fossils of living species. A single species, for which the family 

 Palaeospizidae has been erected, is known from the Upper Miocene 

 or Oligocene; one extinct genus of finch is known from the Middle 

 Pliocene ; two extinct genera of blackbirds are known from the late 

 Pleistocene, and one of these may prove to be of Recent origin; 

 and two extinct species of living genera are known from the late 

 Pleistocene. All the extinct species of living passeriform families 

 belong to families of New World origin. Thus we have none of the 

 sort of evidence quoted earlier for the cranes to show that deductions 

 on the basis of the living forms only may be highly misleading. 



