E. LÖNNBERG, BIRDS FROM TRANSBAICALIA AND MONGOLIA. 25 



t han in Swedish specimens which ha ve the stumpy shape 

 of tlie bill as figured by Hartert in No vitates Zool. VoL 

 7, 1900, p. 527. This difference is not only due to the wearing 

 of the bill through härd work in the single generations, but 

 it represents adaptations to different habits of life. The bill 

 of the Mongolian Woodpecker is much more slender with 

 somewhat concave lateral contours so that, for instance, 

 15 mm from the base of the culmen the bill of a Swedish 

 Woodpecker is fully 1 mm broader than that of the Mongolian 

 at the same place. In correspondence with this the cul- 

 minar ridge is sharper and higher in the latter than in the 

 former the bill of which looks much flatter. The same is 

 the case with the lower mandible and the ridge of the same. 

 The length of the bill in itself is of less importance but 



. Må 



Fig. 9. Billes of Swedish a., and Mongolian b. Wood- 

 peckers from the side and from above. 



in most cases it affords a very good characteristic, as well 

 The average length of the bill in Swedish specimens may 

 be estimated to 27 mm: — and the variation is as a rule 

 confined between the limits of 25,5 and 28,5 mm. Exceptio- 

 nally a Swedish specimen may be f ound — I have seen one — 

 in which the bill is not worn at all and therefore has attained 

 a length of fully 30 mm. But in this case the difference 

 in breadth and shape is quite as striking as in normal cases 

 and the lateral contour of the bill of such a specimen is plainly 

 convex. 



The length of the culmen of the Mongolian Woodpeckers 

 of this collection is from 30 to 31,5 mm. The difference in 

 size and shape of the bill of this Woodpecker and the typical 

 birds from Sweden is more iully elucidated by the accom- 

 panying figures. On these may also be seen that the Swedish 



