. Key to North American birds [microform] : containing a concise account of every species of living and fossil bird at present known from the continent north of the Mexican and United States boundary, inclusive of Greenland. Birds; Ornithology; Oiseaux; Ornithologie. JJIUKCTJONS FOR VSISO TIIK KKYS. 2'29 nancy if not boyoiul wrtnin bounds. A variation of, say, five jxt cent, may l>e safely allowed (III birds not largi'r than a robin : from tliis size up to that of a crow or hawk, ten |M-r cent.; fill- larger birds even more. Some birds vary up to twenty or twenty-five jH-r cent., in their t
. Key to North American birds [microform] : containing a concise account of every species of living and fossil bird at present known from the continent north of the Mexican and United States boundary, inclusive of Greenland. Birds; Ornithology; Oiseaux; Ornithologie. JJIUKCTJONS FOR VSISO TIIK KKYS. 2'29 nancy if not boyoiul wrtnin bounds. A variation of, say, five jxt cent, may l>e safely allowed (III birds not largi'r than a robin : from tliis size up to that of a crow or hawk, ten |M-r cent.; fill- larger birds even more. Some birds vary up to twenty or twenty-five jH-r cent., in their tiital length at least. Ho if I say of a sparrow for instance, "length ."ix inches," and the !i|icciiiien is found to be anywhere between live and thrw-fourths and six and tine-fourth, it will be ([uitc near enough. But the relative jiroinirtions of the different iwrts of a bird are iiiiicli more constant, and here less discrepancy is allowable. Thus " tarsus lougiT than the iiiidtlle tiM'," or the reverse, is often a matter of much less than a (piarter of an inch ; and as it is upon just such nice points as this that a great many of the geuj-ric analyses rest, the neces- sity nf the utmost accuracy in measuring, for the uscomes obvious. When I tiiid it necessary to use tli(M|ualification "about" (us, "bill rtfcon/^= tarsus'') I jirobably never mean to indicate a difference of more than five per cent, of the length of the |»art in (jMestioii. It may be well to call attention to the fact, that most |)enions unuccustouie. This seems to be au optical effect con- nected with the solidarity of the object, as is well ilhistrateil in dniwing plates of birds, which, when mad(! exactly of life-size, always look larger than the original, on account of the tlatuess of the paper. The ruler or tape-line, therefore, should always Im- usitl, and particularly in those cases where analyses in the key rest upon dimensions. It is hanlly necessary to add, ti
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectbirds, bookyear1884
