136 ANNALS OF SCOTTISH NATURAL HISTORY 



month of November, or even earlier, when many of the 

 flank feathers show traces of an irregular buff stripe or spot 

 next the terminal half of the shaft (Fig. 7). As the bird 

 only changes about half the flank feathers, these buff marks 

 are only to be observed on such as are destined to undergo 

 alteration of pattern, which, roughly speaking, means every 

 second or third feather. The buff gradually spreads along 

 the shaft, then becomes constricted and broken up into 

 patches, which gradually spread laterally towards the margins 

 of the webs, forming wide irregular buff bands (Fig. 8). 

 Meanwhile the interspaces become black, and the rufous of 

 autumn dies out. 



When the summer feathers are supplied by moult they 

 usually begin to make their appearance about the beginning 

 of March, and even when fully grown may generally be 

 recognised from the former by their more regular black and 

 buff barring (Plate VI. Fig. 9). The change of pattern 

 without a moult appears to take a long time to become 

 complete, for we find, as already shown, that feathers altered 

 in this way begin to show traces of the coming metamor- 

 phosis as early as the beginning of November, and are often 

 imperfectly rearranged by the end of April ; whereas, when 

 the summer feathers are supplied entirely by moult, no 

 change whatever is visible in the autumn plumage of the 

 flank feathers till at earliest the end of February, when the 

 first new feathers begin to appear. It must, however, be 

 noted that in one bird from Nairnshire obtained in the 

 middle of December, a single half-grown summer feather is 

 visible on the left flank, though no doubt this is quite 

 unusual. 



After making allowance for the different type to which 

 each individual belongs, irregular as the moults and changes 

 of these at first seem (no two individuals being exactly alike 

 at the same date), it will nevertheless be found that all the 

 changes are governed by fairly well-marked laws, though 

 they are to some extent subject to the external influence of 

 climate. For instance, some females shot in October 

 especially in cold years when winter sets in early have 

 entirely finished their autumn moult, no young feathers 

 being found even on the back of the neck and mantle ; 



