OYSTERCATCHER AND NATURAL ENVIRONMENT. 341 



cultivation, and maintain a larger number of persons. Between 

 Blair and Killiecrankie the drifts are a mixture of moraines and 

 boulder clay. This area is occupied by numerous farms. On 

 the north side of Loch Tummel there is an important deposit of 

 boulder clay, which is largely farmed. The left bank of the 

 Tummel below Faskally has large deposits of boulder clay, and 

 is the chief area of arable cultivation in the valley. The alluvial 

 plains of the Tummel lie more as pasture than under cultivation. 

 Elsewhere there is a cold inferior soil suitable only for sheep 

 pasture. 



The meteorological data available come from Ochtertyre, 

 Central Perthshire (90 metres above M. S. L.). The mean 

 annual temperature is 8*16° ± 4-06° C. ; the average rainfall for 

 the year being 1*05 metres on 192 days (1871-1905). The 

 mean monthly temperature and rainfall for April, May, and 

 June are here given in the form of a table for Leith (sea-beach 

 habitat) and Ochtertyre (quasi river valley habitat), for the sake 

 of comparison. 



Table 1, showing Average Monthly Temperature and Rainfall for 

 April, May, and June at Leith and Ochtertyre (1871-1905). 



Temperature. April. May. June. 



Ochtertyre... 7*13° + 4*56° 10-05° + 5-11° 13*44° + 5*11° 

 Leith 7'31° ±4-16° 10-05° ± 4-28° 13-28° ± 4-34° 



Rainfall. 

 Ochtertyre... 0*058 m. 0*060 m. 0*076 m. 



Leith 0-036 m. 0*042 m. 0*049 m. 



The breeding stations within the area examined fall into 

 three distinct habitats— a hill-stream, a river valley, and a lake 

 beach habitat. The Fender Burn is representative of the first, 

 the Eivers Garry and Tummel of the second, and Loch Tummel 

 of the third. A strong similarity exists among all the stations 

 of each habitat, variability of the factors being much less 

 pronounced than in the winter environment. 



2. Hill-stream Habitat. — A general survey of the whole area 

 made in 1909 showed that Oystercatchers do not nest along the 



