NO. 1220. OX yoirni AMERICAN WIIEATEAR8—STEJNEGER. 477 



(pied du Koi), l)ut the reason why I liave ventured to ignore tlu-ni in 

 the face of the above series of 45 hiixls is that Dr. Finseh himself .says 

 that the wing' feather.-? of some of the specimens were very worn.' 



A look at the table of measurement also shows that the Alaskan 

 specimens belong to the smaller, typical bird. We have, consetiuently, 

 in America both forms. Saxicohi (vnantJir in Alaska and Saxicola 

 leucorhoa in Greenland and adjacent parts of northeastern North 

 America. As all the birds found in the latter part of the continent 

 belong to the large race, it is settled ])eyond the shadow of a doubt that 

 the Wheatears which breed in Alaska do not migrate by way of (li-een- 

 land or Lal)rador, ])ut that they retrace their steps into the Tchuktchi 

 Peninsula and farther south into Asia, as indicated by me fifteen 

 jears ago. 



The Wheatear, the most widely distributed species of the genus 

 Saxicola., thus extends its range across the entire pala?arctic continent 

 from the Atlantic to the Pacilic Ocean. At both extremities of its 

 home continent, however, it has expanded its range into the New 

 World, and no one who follows on the map the route of the retreating- 

 winter migrants can for a moment be in doubt that these routes realh' 

 represent the way by which the species originally invaded America. 

 It would be dithcult to find a more beautiful example to illustrate that 

 now well-known law which was tirst formulated b}" Prof. Johan Axel 

 Palmen, of Helsingfors. Moreover, no better example could be found 

 for demonstrating the necessity of minute discrimination in ascertain- 

 ing the characters b}^ which these ''migration route races,'' as Palmen 

 calls them, are characterized. 



It seems that one more lesson can fairly be drawn from the difl'er- 

 entiation of the Greenland race, viz, that the Greenland-Iceland-Eng- 

 land route must be considerably older than the Alaska-Tchuktchi- 

 Udski route, since it has resulted in the establishment of a separable 

 race. A consideration of the further fact that no regular migration 

 route could have been effected between Greenland. Iceland, and Great 

 Britain during the present distribution of land and water in that part 

 of the world also leads us back to a period when the stretches of ocean 

 now separating those islands were more or less bridged over by land. 

 For such a condition of affairs we shall have to look toward the ))egin- 

 ning of the glacial period. At that time it must, therefore, be assumed 

 that the Wheatear extended its range into Greenland. The advent of 

 the typical form into Alaska, on the other hand, is probably one of 

 very recent time, an assumption corroborated by the somewhat uncer- 

 tain and erratic distribution of the species in that northw^estern corner 

 of our continent. 



' ' ' Narnentlich sind die Spitzen und Aussensiiume der Schwingen und Schwanzfedern 



8ehr abgenutzt." 



