THE EAZOKBILL. 



793 



Primaries 

 ' of i st ~ Winter 

 plumage 

 c/ro wing 



Secondaries 



orisi-winier 



plumage 



growing 



First winter. — Like adult winter but white tips to secondaries 

 rather narrower. The juvenile body-plumage and wing-coverts are 

 moulted July-Oct., and at same time tail-feathers and primaries 

 and secondaries grow. First summer. — Sometimes like adult except 

 for narrower white tips 

 to secondaries, some- 

 times throat mixed with 

 white ; wings and tail 

 especially becoming very 

 worn and pale brown by 

 May and June.* 



Measurements and 

 structure. — $ wing 185- 

 202 mm., tail 71-84, 

 tarsus 30-34, bill from 

 feathers 30-35, greatest 

 depth 21-23 (12 British 

 measured) . $ wing 1 85- 

 200, bill length 29-34. 

 First winter $ and $ 

 wing 177-193, tail 60- 

 75, bill length 26-31, 

 depth 14-18. Prima- 

 ries : 1st longest, 2nd 

 3-5 mm. shorter, 3rd 

 7-15 shorter, 4th 18-25 

 shorter, 5th 28 - 37 

 shorter ; narrow and 

 pointed. Outer second- 

 aries shorter than 10th 

 primary, inner ones 

 about equal to 8th or 



9th, tips rounded. Tail wedge-shaped, 12 feathers, pointed and 

 narrow, central pair longest. Tibia feathered almost to joint 

 and inserted far back ; tarsus compressed ; three toes (hind toe 

 absent) fully webbed ; claws curved and rather short, middle one 

 dilated. Bill in adult much compressed, sides nearly flat with three 

 well defined curved grooves on upper and two on lower mandible, 

 ridge of upper mandible decurved in an arc to blunt pointed tip, 

 under mandible sloped up from prominent angle but somewhat 

 recurved at tip, proximal portion of bill covered with feathers 

 except along gape where on each mandible is a prominent horny 

 ridge. In first winter birds bill is very much smaller, much less 

 arched, sides not grooved, and rictal ridge not prominent. In 

 second winter bill is much more like adult but smaller, not so 



Gresfer coverts 

 uvenile 



Primary coverts 

 \/eni/e 



Underside of wing of juvenile Razorbill (A. torda) showing- 

 primaries and secondaries commencing to grow under 

 juvenile coverts, which from above have appearance of 

 remiges. 



* It would appear that some individuals do not attain the brown throat 

 in first summer, but no skins of such birds are available for examination. — 

 H. F. W. 



