BLUE HAWK, OR HEN-HARRIER. 293 
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America, of which he supposed the Hudson’s Bay ring-tail to 
be the young. The differences which he detected on compar- 
ing it with the European ring-tail must have been owing 
to a different state of plumage of his specimen of this ultra- 
changeable species. If, however, he had not mentioned the 
colours merely, as bringing it nearer to the ash-coloured 
falcon of Montagu, we might be inclined to believe that 
the specimen he examined was indeed a young bird of that 
species, which, though as yet unobserved, may, after all, 
possibly be found in North America. At all events, Wilson’s, 
and the numerous American specimens that have passed 
under our examination, were all young hen-harriers. 
After having stated that the error of considering the hen- 
harrier and ring-tail as different species had prevailed for 
years in Europe, it is but just to mention, that Aldrovandi, 
Brisson, Ray, and others of the older authors, were perfectly 
in accordance with Nature on this point. It was perhaps with 
Linné, or at least with Buffon, Gmelin, Pennant, and Latham 
himself, who afterwards corrected it, that the error originated. 
Latham, confident of his own observations and those of Pen- 
nant, who had found males of the species said to be the female 
of the Falco cyaneus (hen-harrier), and not reflecting that 
these males might be the young, exclaims, “ Authors have 
never blundered more than in making this bird (the ring-tail) 
the same species with the last mentioned (hen-harrier) ;” an 
opinion that he was afterwards obliged to recant. In physical 
science we cannot be too cautious in rejecting facts, nor too 
careful in distinguishing, in an author’s statement, what has 
passed under his own eyes, however extraordinary it may 
seem, from the inference he draws from it. Thus, to apply 
the principle in this instance, Latham might have reconciled 
the fact of males and females being found in the plumage of 
the ring-tail, with the others, that no females were ever found 
under the dress of the hen-harrier, and that some ring-tails 
would gradually change into hen-harriers. 
Whether or not the marsh-hawk of America was the same 
