BULLETIN OF THE NUTTALL 



ON GEOGRAPHICAL VARIATION IN TURDUS 

 MIGRATORIUS. 



BY ROBERT RIDf;wAV. 



Certaik differences between Eastern specimens of the common 

 Robin and those from the Rocky Moimtaius were first pointed out 

 by Professor Baird, in- his "Review of American Birds" (18G4, 

 pp. 28, 29), in the following words. • " In highly phimaged speci- 

 mens from the East the feathers of the interscapular region are 

 frequently, even generally, tinged with blackish in their centres, 

 passing gradually into ash on the edges, and the black of the head 

 ccas:;s to be abruptly defined. There is. also usually a well-defined 

 whitish tip, half an inch long, to the outer tail-feathers. In Rocky 

 ilountain skins the tail is either black, except a very narrow 

 whitish edge, or the white tips of Eastern specimens are replaced 

 by a dull gray. The black of the head, too, is better defined, the 

 interscapidar feathers more unifoi-mly ash, and the upper parts 

 without the fain.t brownish wash so frequently seen in Eastern 

 specimens. There are, however, some exceptions to these features 

 in specimens from each locality. The colors generally of Western 

 birds appear to bo paler." Again, in the "History of North 

 American Birds" (Vol. T, p. 25), the same and additiotial difterou- 

 ccs are alluded to, as follows : " There arc some variations, both 

 of color and proportions, between Eastern and Western spcci- 

 r^ens of the Robin. In the latter there is a tendency to a 

 longer tail, thoiigh the difference is not marked , and, as a rule, 

 they slightly exceed Eastern specimens in size. The broad white 

 tip to the lateral tail-feather — so conspicuous a mark of Eastern 

 bii'ds — is scarcely to be found at all in any Western ones ; and in 

 the latter the black of the head is very sharply defined against the 

 lighter, clearer ash of the back, there hardly ever being a tendency 

 in it to continue bacKwaid in the form of central spots to the 

 feathers, as is almost constantly seen in Esistern examples; of 

 Western specimens, the rufous, too, is appreciably lighter than in 

 Eivstern." 



Very extensive material received at the National Museum since 

 the above was written tends to confirm the constancy of most of 

 these diCFerences between Eastern and Western Robins, while other 



