108 



number of growing feathers is to be found all over the back and 

 a moderate number in the flanks. 



Moul ting-period of these birds (then about 21 months old): March 

 and April, possibly till half May. 



Bird in its first spring. — The bird shows, until its spring- 

 moult, no furrow in the bill and the latter itself is low. The first 

 furrow (the white one) arises during the moult into the first 

 breedingplumage. Whether the second furrow may arise shortly 

 after the first, can be taught by more material, a young female ot 

 April 28th (1922), in nearly complete breedingdress, has the second 

 one indicated indistinctly. 



A male of March 29th (1921) still is in winterplumage but the 

 inside of the skin shows a beginning of moult; another male 

 from the same days (April 1st, 1921) is in transition and already 

 has got the white furrow; two birds of April 17th and 23rd (1912) 

 are for the greater part in breedingdress and have got the 

 first (white) furrow; the cf of April 28th 1922 has already been 

 mentioned. Moulting-period of these birds (being in their first spring): 

 second half of March, most likely till the middle 

 of May and later, 



N.B. So the springmoult of Guillemots and Razorbills renews the 

 feathers of the head and those of the neck where the latter 

 will change its colour. And further a varying number of 

 bodyfeathers, mostly at least a number of the feathers of the 

 flanks. Wings and tail remain unmoulted. 



11. Measurements. 



On account of the later moult of younger birds, as it is shown 

 to take place by the preceding notes, we may be inclined to expect 

 that birds, one to two years old, may not yet have reached their 

 full development, even if this seems to be the case. In the Razor- 

 bill we can see the difference distinctly enough from the billfurrows. 

 But an eighteen months old Guillemot seems to be exactly similar 

 to an old one and still, it too, shows differences which are ]-ather 

 obvious when accurately looked at. They are the following: the so 

 called tarsus and the feet of a bird in its first winter are gray and 

 pale coloured, besides the tarsus is narrow ') and the bird itself is 



1) This narrow tarsus seems strange, young birds generally are supposed 

 to have a broader tarsus than old ones. 



