232 BULLETIN OF THE 



with a gradual transition from the one to the other, through specimens 

 from intermediate localities, is seen in Troglodytes aedon, Geotklypis 

 triclias, and Seiurus noveboracensis. In Pipilo erythrophthalmus, Orlyx 

 virginianus, Corvus americamts, and Cyunura cristata the bill is appre- 

 ciably larger in the Florida than in the northern form. In Corvus 

 americanus this difference was long since noticed by Professor Baird, 

 the larger bill of South Florida specimens having led him to recog- 

 nize a variety floridanus of this species, based chiefly on this difference.* 

 The same author has also referred to the larger size of the bill in 

 Florida specimens of Ortyx virginianus.^ 



In some species individual variation is so great that it is unsafe to 

 draw conclusions respecting geographical variation from the examina- 

 tion of a small number of specimens. This is notably the case in 

 Sturnella ludoviciana, in which the bill varies greatly in size and form, 

 as does the bird in general bulk, at all localities. In the average, how- 

 ever, Florida specimens of this species seem to have a relatively longer 

 and slenderer bill than those from the Northern States. 



As already noticed, variation in the bill is not equally marked in all 

 species, but it occurs in too many to admit of the supposition that the 

 numerous cases wherein it is clearly marked are exceptional, or that it 

 does not follow a general law of geographical variation. The observa- 

 tions above detailed are based on specimens collected on the Atlantic 

 coast, from New England southward to Florida, and refer exclusively 

 to species breeding within that range. But specimens of species which 

 breed entirely to the northward of this range, collected during their 

 semi-annual migrations, corroborate the law already staled, namely, 

 an increase in the size of the bill to the southward in specimens of the 

 same species from different breeding stations. In the Anatidce and 

 TringcE, which breed far to the northward and pass the winter in lower 

 latitudes, it is noticeable that, while those which arrive first in the fall, 

 and those which return north latest in the spring, are smaller than 

 those that arrive later and depart earlier, they have, nevertheless, 

 relatively larger bills. This has been especially noticed in species of 

 Fulix, Bernicla, Actodromas, and Macrorhamphus. Professor Baird 

 has also referred to the larger size of the bill of the southern repre- 

 sentatives of Lagopus ulbus as compared with those from further north, 



* Birds of North America, p. 568, 1858, 



t Am. Journ. Sci. and Arts, 2d Ser., Vol. XLI, p. 191, 1866. 



