OYSTERCATCHER AND NATURAL ENVIRONMENT. 377 



in this locality. At Moulinearn and Ballinluig the young are 

 led to the shingle soon after they leave the nest, and thenceforth 

 the shingle forms both their refuge and resting place. The eggs 

 laid on mud or turf are not better protected by their surround- 

 ings than they would be on shingle, but in disturbed areas they 

 have a better chance of escaping human observation which, by 

 tradition or personal experience, tends to be concentrated on the 

 shingle. The young get the benefit of the shingle even in dis- 

 turbed areas, because, unlike the eggs, they can occupy positions 

 likely to evade detection on the approach of danger. And in all 

 the stations examined, with the exception of those in the hill- 

 stream habitat and in the aberrant area of the Garry, 

 the shingle forms the headquarters of the young. In wet 

 weather, however, the shingle looks almost black. The eggs 

 and young then show up more distinctly. But the deficiency 

 has less importance than it seems to have. The adults, which 

 stand out conspicuously from the dry light grey shingle, assimi- 

 late more or less completely to the shade of the wet stones, and 

 during wet weather the parents are covering either the eggs or 

 the young. After a short exposure to rain the wetting of the 

 outer down changes its hue from light greyish to drab. The 

 young then approach in shade that of the wet stones. 



Evidently the essential requirement of a breeding territory 

 is an open area of sufficient extent, and approximating in colour 

 appearance to that of the eggs and young. These conditions 

 are best fulfilled by shingle devoid of vegetation. The bareness 

 of the normal breeding territory has, however, a wider signifi- 

 cance. After the young are hatched, and for several weeks to 

 come, they are prevented by the parents from going among wet 

 grass when the temperature is low. The combination of moisture 

 and low temperature occurs regularly in the early morning, and 

 occasionally through the daytime as well. The chicks are 

 compelled to remain on the shingle where, though the stones 

 may be wet, the chicks at least remain dry. The proceeding 

 must have attached to it a pronounced biological advantage, for 

 I have repeatedly seen hungry chicks which have already learnt 

 the association of the position of the feeding-ground with the act 

 of being fed, trying to entice the adults to follow or lead them 

 on to the wet grass to be fed. A second result of the bareness 

 Zool. 4th ser. vol. XIX., October, 1915. 2 g 



