302 
ALCAD^. 
shooting many undoubtedly old birds in grey plumage in the 
very depth of winter. In order to clear up these difficulties, 
1 liave paid unremitting attention to the species during a long 
series of years ; and simple though the result appears, it 
has cost no small amount of labour, and, I fear, a large sacrifice 
of bird life ; but as containing indisputable facts, the abstract 
of my notes may be relied upon, even should my conclusions 
appear erroneous. 
Both old and young are grey in ivinter. Upon this question 
there can be no doubt as regards the young, but the older 
Amters, who, with their flint guns, seldom wasted time in 
attempting to shoot these or any other quick divers upon the 
water — much less upon wing — asserted that the adults left 
the island as soon as the breeding season was over, Avithout 
undergoing any change. My OAvn notes shoAV that the com- 
mencement of the autumnal change — Avhich is noAv a settled 
fact — is observable as early as the first Aveek in August ; and 
I have AA’atched the various successive modifications until the 
acquisition of the perfect winter dress. It must be admitted, 
hoAvever, that those Avhich migrate do so suddenly, and Avhile 
still in summer plumage, and that those Avhich remain are 
exceedingly feAV in proportion. The young do not migrate until 
their second autumn. In Avinter an old bird may be dis- 
* I must here again acknowledge the persevering and judicious manner in 
which Eobert Mouat afforded me his aid, especially with regard to this parti- 
cular subject; — fully understanding the difficulties to be investigated, and 
avoiding much needless slaughter by procuring only such specimens as he 
knew would prove useful. Of his indomitable perseverance but one instance 
need be given. Shortly before my departure for the south, I sent him one cold 
spring morning to a distant bay to procure six specimens of the Black Guillemot 
— one of which was to be a black one if possible — in the most interesting states 
of plumage he could find, at the same time reminding him that it would pro- 
bably be the last chance. It was not until after dark that he presented him- 
self, in a sad state of cold, dampness, and hunger, carrying one perfectly black 
specimen, and five in various stages of grey. I then ascertained the cause of 
his long absence. Almost at the first shot the pivot of the hammer of his gun, 
which was only a single barrel, broke short off ; but he would not return, and, 
with a true Shetlander’s knack of getting out of a scrape, he resorted to the 
apparently hopeless expedient of holding the gun at the aim while his com- 
{tanion struck the cap with the flat of a chisel ! Of cour.se the misses during 
the day were numerous, but for all that he attained his object triumphantly. 
