392 BIRDS OF THE WEST OF SCOTLAND. 



Ducks I have skinned, indeed, contained nearly the same species 

 Lacuna vincta and Patella pelludda. These, with young speci- 

 mens of Mytilus edulis, mixed with some fragments of pebbles, 

 seem to constitute their chief food in this particular locality. 

 The birds must search deliberately (as indeed I have seen them 

 doing when the surface of the water was unruffled) at the bottom 

 for these shells, and go from one mass of seaweed to another, 

 picking them off the fronds to which they adhere. From the 

 stomach of one specimen I took upwards of 100 shells, all in the 

 most perfect state, being clean and free from sand. Of six 

 beautiful specimens now on the table as I write four males and 

 two females only one was found to have been feeding on small 

 Crustacea, its stomach being filled with entire as well as mutilated 

 specimens of Idotea tricuspidata. In clear frosty weather, these 

 birds often collect into very large flocks, and remain far out from 

 the land over some well known sandbank, where they appear to 

 find their favourite food in abundance. On exceptionally quiet 

 evenings their singular cries are heard by persons on shore, though 

 the birds themselves are not in sight. This strange music is heard 

 at all hours of the day, and reaches the shore from very great 

 distances, especially when a flock is acting in concert. The cry is 

 not uttered on one key, but is modulated, and though not so loud, 

 it in some measure resembles the note of the swan. I believe the 

 male to be the chief performer, although it has been said on 

 apparently good authority that both sexes are alike in that respect. 

 The trachea of the male, as is well known, presents a peculiar 

 conformation the end near the kidney-shaped protuberance being 

 flattened and divided into five oblong spaces, covered with a 

 membrane resembling the panes of a window. Some authors 

 think that this curious mechanism is in some way connected with 

 the extraordinary sounds emitted by the bird, but others say that 

 the female utters the same note, while her windpipe has no such 

 peculiarity of construction. My impression, from what I have 

 repeatedly observed, is that the female utters but one note, or 

 syllable, while the male runs over five. When a flock consists of 

 males only, as is often the case, the cries are always clear, distinct, 

 and unbroken : on the other hand, where a proportion of females 

 is seen, the notes are ogh, agh, or ugh, breaking upon the more 

 intelligible voice of the male, and destroying in some measure its 

 full effect. It is a difficult matter to decide; one thing, however, 



