APPENDIX N. 163 



I think it possible that this may have had a wrong locality 

 accidentally attached to it^ and may in reality be Icelandic 

 and not Scandinavian. In the white colour of these bars 

 this Yukon Falcon resembles the adults of both H. islandus 

 and of H. holbmlli ; but in their depth^ measured from their 

 upper to their lower edge, it agrees with H. holboelli rather 

 than with H. islandus. The Yukon bird resembles the 

 adults, both of H. islandus and of H. holboelli, in the almost 

 spotless white of the upper breast; but it differs from 

 H. islandus and from the paler adults of H. holboelli in the 

 greater size of the dark spots on the abdomen, and in the 

 cross bars on the tibial feathers, in which it resembles H. gyr- 

 falco and the darker adults of H. holboelli. 



On the whole this Yukon Falcon seems to me to be a 

 specimen of an intermediate character ; and I suspect that it 

 is one in which the peculiarities of H. gyrfalco have been 

 modified by hybridism with H. holbce.Ui. 



No. 1524. Alaska. — This is evidently a bird in the first 

 year's plumage ; but from the appearance of the lower back 

 and tail, and also from the spots on the lower scapulars, I 

 should suppose it to be nearly, or perhaps quite, twelve 

 months old ; it resembles the ordinary dress of the Scandi- 

 navian examples of H. gyrfalco at a corresponding age. 



No. 1486. Alaska. — This bird seems to me to be of similar 

 age to the last, but to resemble the ordinary immature dress 

 of H. holboelli rather than that of H. gyrfalco, notably in the 

 broad white borders to the feathers of the upper part of the 

 head, in the whity-brown edges to all the feathers of the 

 mantle, and also in the decidedly white hue of the pale cross 

 bars on the tail. 



The result of the comparisons which I have here recorded 

 leads me to agree with the conclusion previously arrived at 

 by Mr. Sharpe and by Mr. Dresser that H. gyrfalco is found 

 in the northern parts, not only of Europe and of Asia, but 

 also of North America. The North-American range of this 

 species, however, has not at present been very clearly ascer- 

 tained, especially to the eastward ; and a similar uncertainty 

 exists as to the western limits of H. holboelli, as also to the 



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