OYSTERCATCHER AND NATURAL ENVIRONMENT. 4G1 



the 9'5 kilometres of river this gives one pair per 190 metres. 

 On the Garry between Blair and Killiecrankie, the number of 

 pairs is more difficult to estimate, on account of the locally 

 abnormal habits already mentioned. It is believed to be about 

 ten in the 4 kilometres of river, and is equivalent to one pair 

 per 400 metres. The south side and east end of Loch Tummel 

 are occupied by eight to ten pairs (nine in 1912), equal to one 

 pair per 490 metres. The number of pairs found yearly in the 

 2 kilometres long, tree-stump area in Glen Fender is three — 

 that is, one pair per 670 metres. On the 3*2 kilometres of the 

 Eiver Orchy between Loch Tulla and the bridge, two pairs are 

 stationed (1909, 1910), being equal to one pair per 1600 metres. 



The Eiver Orchy is a fairly large river with large areas of 

 light grey shingle. The glen is open and is occupied by a very 

 small human population. The soil is inferior and suitable only 

 for sheep-pasture. There is little cultivation. The birds, there- 

 fore, have to depend on the river banks and the hillside for their 

 feeding-grounds. The supply of worms and larvae is not so 

 plentiful as it is on the Tummel. 



The hill-stream habitat comes next in an ascending order. 

 Its low grade value is probably due to elevation above sea-level 

 (230-305 metres), which certainly restricts the area under culti- 

 vation, and probably affects the supply of worms and larvae as 

 well. The local feeding-ground comes within the normal range 

 of the Curlew, and much of the area being marshy, there is also 

 a large number of Snipe. Both of these birds compete with the 

 Oystercatcher in the subterranean ground stratum of the local 

 feeding-ground. The hill-stream habitat is peculiar in the sense 

 that it owes its occupation by the Oystercatcher, not, it would 

 appear, to the presence of the Fender Burn and other common 

 elements of an occupied station, but to the large number of 

 bleached tree-stumps scattered over the local feeding-ground. 

 The young assimilate in colour to these stumps, which are 

 frequently associated with the crouching response. The stumps 

 also contribute to the food supply. The area has great breadth, 

 and the shingle-beds in the burn course are small. The young- 

 are led much greater distances away from the shingle than is 

 usual in other stations, and the reason which makes this possible 

 appears to be, the tree- stumps afford protection to the young, 



