30 THE GROUSE IN HEALTH AND IN DISEASE 



moult. In some districts undoubtedly the birds shift annually 

 in vast packs from the high ground to the lower moors, and 

 return again in the spring to breed. 



On rare occasions migration takes place upon a much more 

 serious scale, when the whole Grouse population of a district, 

 driven by hunger, rises in huge packs and works its way south- 

 ward in search of food ; this never happens unless a heavy 

 undrifted snowfall has been followed by a hard frost, whereby 

 a whole district is covered with an impenetrable sheet of frozen 

 snow, thus cutting off all access to the heather. Such whole- 

 sale migrations often result in a complete loss of the stock, 

 for the birds appear to lose their bearings, and though they 

 may sometimes find a haven on some distant moor, where 

 weather conditions are more propitious, several cases have been 

 recorded of the packs being seen on the low ground 20 or 30 

 miles from the nearest hill, or even flying out to sea, whence 

 presumably they never return. 



In the case of normal annual migrations many opportunities 

 have occurred for observing the power of flight of the Grouse. 

 The following passage may be quoted from Macpherson in the 

 Fur and Feather Series : 1 



" When snow and sleet have driven them down from the 

 hills they will then fly long distances. It is not at all unusual 

 for Red Grouse to cross the Solway Firth at a point where 

 the estuary measures two miles in breadth, and I have known 

 them fly longer distances. They often cross the valley of the 

 Tees, flying about a mile from one hillside to another." Millais 

 also writes : "I have twice seen Grouse on the wing when they 

 were crossing the ' Bring,' a wide channel which separates the 

 islands of Hoy and Pomona, Orkneys. The fishermen told 

 me this distance . . . was quite four miles across, and the birds 

 must have come at least another mile on the Pomona side 

 from the point where they left the moor." 2 In Millais' " Game 



1 Fur and Feather Series, "The Grouse," p. 36. 



a Millais, "Game Birds and Shooting Sketches," p. 53. London : Henry Sotheran 

 & Co., 1892. 



