512 THE BIRDS OF YORKSHIRE. 



were introduced with the idea that they would thrive, but 

 the experiment had proved to be a failure. 



It is doubtful if Grouse migrate far from their own ground 

 for any lengthened period ; the Rev. H. H. Slater informed 

 Mr. Eagle Clarke, on the authority of his uncle, Mr. T. Horrocks 

 of Eden Brows, Carlisle, that towards the end of October 

 every year there is a migration of packs of Grouse from the 

 Duke of Cleveland's moor* in Teesdale to Mr. Horrocks's 

 moors at Alston in Cumberland, a distance of twenty miles, 

 where they remain till the end of the season, and then return 

 to their own country. A large proportion of these emigrants 

 are hens, and are different in size and plumage, and readily 

 discriminated from the Alston birds, being only two-thirds 

 their size and weight, and the plumage more speckled and 

 yellow (cf. Zool. 1895, p. 107). Grouse have been seen 

 at Strensall, where a covey of eight or nine was flushed 

 on 1 3th August 1881. They also occasionally migrate 

 from their own ground to the neighbouring moors for food, 

 but this chiefly occurs during the afternoon, as they seldom 

 move about much during the day unless disturbed, and 

 feed only once a day, viz., towards evening. 



In severe winters, when there is a great depth of snow, 

 birds are driven down to the cultivated valleys literally by the 

 thousand, the moors being utterly deserted by them. So 

 long as the snow is soft at the top they are able to form tunnels 

 several feet in depth to get to their food ; when, however, 

 a thaw is followed by rain and succeeded by a frost, the 

 surface of the snow becomes glazed with ice, and they are 

 unable to make a way through owing to the formation of 

 their claws, which, admirably suited as they are for walking 

 on soft snow, are not adapted for burrowing through its 

 surface when frozen ; the result is that, forced by want of 

 food, they leave the moor in immense packs and travel down 

 to the low country where, as in 1886 and 1895, they feed on 

 corn and turnip leaves in the fields, on shoots of the black- 

 thorn, haws, and buds in the hedgerows, and wherever food 

 of any description is to be found. In weather like this they 

 may be seen perched in hundreds in the hedgerows and on 



