THE BIRDS OP THE PRIBILOF ISLANDS. 



417 



migration indicates a separation for the wliole of that vast period since the Glacial 

 period began. During and since that time these birds have differentiated in opposite 

 directions as wide as their winter habitats are apart. It seems certain that morinella 

 during the whole of Glacial time was a resident of North America, while probably 

 interpres was excluded therefrom, owing to the frigid conditions of Greenland and 

 Alaska. The presence now in these places of interpres indicates an extension of its 

 range due to the retreat of the ice. It would thus seem that morinella was cut off 

 from the parent stock by the Arctic ice accumulations and has continued isolated. 



Since the retreat of the ice to its present position the birds have reextended their 

 habitat to its present limits. Thus the distinctness and causation of the habitats of 

 the two birds, their varied migrating lines, the smallness and brighter coloration of 

 morinella are correlated factors bearing on the question of relationship. That mori- 

 nella has escaped its proper place till now is due to several causes. First, the 

 confusion by ornithologists of generic and specific characters in such a strongly 

 specialized genus; second, the absence of specimens in American museums showing 

 what the European, bird really is, and also a lack of home specimens, and, third, a 

 lack in European collections of a series of properly made fresh skins of the American 

 bird. For instance, Mr. Seebohm had but two unsexed specimens of morinella, yet 

 had positive views. The fact that individuals of morinella winter about the southern 

 borders of the United States will perhaps account for the differences observable in 

 the extent of the spring change, those that winter in southern South America 

 perhaps undergoing a less change on account of the greater length and severity of 

 their migration. To Drs. C. W. Eichmond and E. M. Hasbrouck, and especially to 

 Mr. E. J. Brown, I am indebted for the use of many specimens. I have examined in 

 all 167 specimens — 85 of interpres, 82 of morinella. 



Measurements of tMrty-one Virginia Spring specimens of A. morinella. 



May 23,1892 

 May 27,1892 

 May 16,1892 



do 



May 11,1892 

 May 13,1892 

 May 15,1894 

 Mav 23,1894 

 May 21,1894 

 May 15,1894 

 May 24,1894 

 May 25,1894 

 May 16,1894 

 May 15,1894 

 May 16,1892 

 May 15,1894 



do 



May 21,1894 

 May 15,1894 

 Sept. 1,1895 

 May 15,1894 



do 



do 



May 21,1894 

 May 16,1894 

 May 15,1894 

 May 16,1894 

 May 19,1894 

 May 21,1894 

 May 16,1892 

 Aug. 24, 189S 



Locality. 



Cobbs Island .. 



do 



do 



do 



do 



do 



Smiths Island . 



do......... 



do 



do i... 



do 



do 



do 



do 



Cobbs Island . . 

 Smiths Island . 



do 



do 



do 



do 



.....do 



.....do 



do 



do 



do 



do 



do 



do 



...do 



Cobbs Island .. 

 Smiths Island . 



Collector. 



E.J.Brown ... 



do 



do 



...do 



....do 



.?:.do , 



do 



do 



do..... 



do... 



...do 



C.W. Eichmond . 



do 



do 



E.J.Brown 



E. M. Hasbrouck. 



do 



do 



do 



W.Palmer 



E. M. Hasbrouck. 



do 



do 



do 



C. W. Sichmond . 



E.J.Brown 



do 



do 



do 



do 



W.Palmer 



Wing. 



5.50 

 5.65 

 5.85 

 5.45 

 5.60 

 5.78 

 5.95 

 5.67 

 5.73 

 5.74 

 5.77 

 5.72 

 5.90 

 5.70 

 5.73 

 5.80 

 5.50 

 5.74 

 5.70 

 5.80 

 5.87 

 5.72 

 5.82 

 6.08 

 5.75 

 6.00 

 5.75 

 6.80 

 6.00 

 5.80 

 5.92 



Tail. 



2.30 

 2.37 

 2.52 

 2.45 

 2.47 

 2.55 

 2.47 

 2.36 

 2.35 

 2.25 

 2.20 

 2.45 

 2.48 

 2.44 

 2.58 

 2.42 

 2.32 

 2.30 

 2.50 

 2.37 

 2.33 

 2.41 

 2.35 

 2.44 

 2.36 

 2.53 

 2.43 

 2.40 

 2.40 

 2.42 

 2.42 



Culmen. 



0.87 

 .89 



.86 

 .87 

 .95 

 .95 

 .90 

 .90 

 .90 

 .88 

 .93 

 .90 

 .90 



.94 

 .88 

 .99 

 .89 

 .88 

 .91 

 .91 

 .90 

 .97 

 .96 

 .96 

 .91 



Tarsus. 



1.00 

 1.02 

 1.05 



.96 

 1.00 



.96 

 1.05 

 1.02 

 1.00 



.89 

 1.03 



.96 

 1.04 

 1.05 

 1.03 

 1.07 

 1.04 

 1.06 



1.05 

 1.02 

 1.01 

 1.05 

 .99 

 1.00 

 1.00 

 1.01 

 1.01 

 1.02 

 1.07 



5947— PT 3 ^27 



