OYSTEROATCHER AND NATURAL ENVIRONMENT. 427 



marks visible in the end of May. The subsequent rise was 

 anticipated by marking the posts from the observed lowest 

 water-level. 



Table 2, Showing Positions of First and Second Nests of each Pair 

 Relative to Water-Level : Loch Tummel, 1912. 



Nest A 1 (unknown) A 2 Below winter H.W.M. 0'9 m. 



Above water-level,time 

 of laying ... ... 6'4m. 



NestB 1 Above winter H.W.M. 1-2 m. B 2 Below winter H.W.M. 2-1 m. 

 Above water-level, time Above water-level, time 

 of laying 6'7m. of laying 6'lm. 



Nest C 1 Above winter H.W.M. ? C 2 Above winter H.W.M. ? 



Above water-level, time Above water-level,time 



of laying ... ... 6*4 m. of laying ... ... 6"4 m. 



Nest D 1 On winter H.W.M. D 2 On winter H.W.M. 



Above water-level, time . Above water-level, time 



of laying 6*85 m. of laying 10 m. 



Remarks. — At A 2 the winter high water-mark passed along 

 the grass bank slightly above the shingle. On June 15th, 1912, 

 the bird was flushed from the nest, which contained a pool of 

 water. The margin of the loch was not far from the rim of the 

 nest, the height of which was subsequently fixed at 0'74 m. above 

 water-level at the time of laying. This bird converted the nest 

 hollow into a platform 0*03 m. higher than its surroundings, 

 and continued to incubate. The danger was past after the 

 17th, and the bird continued to sit. At B 1 and B 2 the position 

 of the winter high water-mark was fixed with difficulty, there 

 being no drift. The second nest was 3'35 m. further down the 

 shore than the first, but the two nests were both situated at 

 similar distances from the water-levels at the respective times 

 of laying. The height of B 2 was later fixed at 0*66 m. ; that of 

 B 1 was +0 - 9 m. above bottom level. On June 17th, 1912, 

 B 2 was drowned out and deserted, being 0'05 m. under water. 

 At C 1 and C 2 the position of the winter high water-mark could 

 not be determined, but judging from collateral evidence both 

 nests were considered to be much above that level. Both 

 nests were equidistant from the water-levels at the time of 

 laying. C 2 escaped the highest flood-level of June 17th 

 with a good margin, the calculated height above bottom level 



