340 THE ZOOLOGIST. 



THE RELATION OP THE OYSTERCATCHER TO ITS 

 NATURAL ENVIRONMENT. 



By J, M. Dewar, M.D. 



(Continued from p. 291.) 



IV. — The Summer Environment. 



1. General Considerations. — The area which came under 

 observation as a nesting habitat consisted of Loch Tummel; 

 that portion of the valley of the River Tummel extending from 

 Faskally to the junction of Tummel and Tay at Ballinluig ; the 

 Vale of Atholl between the villages of Blair and Killiecrankie ; 

 and the lower part of Glen Fender. Only the south shore and 

 the foot of Loch Tummel were systematically observed. 



The rocks of the area belong to the metamorphic series, and 

 consist mainly of sedimentary limestones and schists, together 

 with numerous igneous sills scattered all through the various 

 schists. 



The area forms part of a " land of ridges and broad valleys," 

 the weather conditions being of the Atlantic type. From Loch 

 Tummel to the junction of the Tummel and the Garry, the 

 gradient is steep, and there are hardly any deposits of alluvium. 

 At the junction is a series of terraces, covered with gravel and 

 cut out of a thick deposit of boulder clay. Similar conditions 

 prevail as far as Pitlochry. From this point to Ballinluig the 

 gradient is slight, and the river has denuded the bottom of the 

 ancient glacial lake, forming a large plain of alluvium. Between 

 Blair and Killiecrankie the slope is considerable, but less than 

 in higher parts of the Garry. Here large alluvial terraces have 

 been formed. The hill-streams are mostly torrential in character, 

 and deposit little alluvium. The lower portion of Strath 

 Tummel is well wooded, while natural birch is general up to 

 about 300 metres. The distribution of the human population is 

 determined by the boulder clay deposits which favour arable 



