34 BIRD GALLEKY. 



(186) and Black Grouse aud Willow-Grouse (182) are exhibited, these 

 being much rarer than the hybrid with the Capercailzie. 



[Case 18.] In the circumpolar Willow-Grouse {L. lagopus) (188) and Ptarmigan 

 (L. mutus etc.) (181-183) there are three distinct changes of plumage 

 in summer, autumn, and winter in both male and female alike, the 

 winter plumage being white in all. 



The great peculiarity of the Ked Grouse (L. scoticus) (185), and one 

 without parallel among birds even of this genus, lies in the fact that 

 the changes of plumage in the male and female occur at different 

 seasons. 



The male has no distinct summer (nesting) plumage, but has distinct 

 autumn and winter plumages, retaining the latter throughout the 

 breeding season. 



The female has a distinct summer (nesting) plumage, also a distinct 

 autumn plumage which is retained till the following spring. 



To put it more concisely, both male and female have two distinct moults 

 during the year, but in the male they occur in autumn and winter, and 

 in the female in summer and autumn, the former having no distinct 

 summer and the latter no distinct winter plumage. 



The Red Grouse is generally regarded as merely an insular form of 

 the Willow-Grouse, and it might naturally be supposed that as the 

 British species does not turn white in winter, such protective plumage 

 being unnecessary in the localities it inhabits, the winter moult had been 

 gradually dropped. But as already shown, this is the case with the 

 female only, and the male, for some unknown reason, changes the newly 

 acquired buff and black autumn plumage for a winter garb of chestnut 

 and black, which is retained till the following autumn. 



Order II. PTEROCLETIFOKMES. 



Family PTEROCLID^E. SAND-GROUSE. 



[Table- This small order includes only sixteen species, intermediate in their 

 case ' J affinities between the Pigeons and Game-Birds. The skeleton resembles 

 that of the Pigeons in many important points, but the digestive organs 

 are like those of the Game-Birds. The bill is very similar in shape to 

 the latter, but not so strongly developed, while in the outward ex- 

 pression, general shape of the body, the soft and easily detached 

 plumage, and the long pointed wings, we find a marked resemblance to 

 the Pigeons. The feathers of the body are provided with a well- 

 developed aftershaft. As might be expected from the shape of the 

 wings and the great development of the pectoral muscles which work 

 them, all the Sand- Grouse are birds with immense powers of flight, able 



