MIGBATIONS OF BIRDS AT TUSKAB BOCK. 187 



rough, windy days, more birds seemed to halt than when the 

 weather was intermediate, and especially when it was uncertain 

 in character. 



In the first case, the birds, possessed perhaps of an in- 

 stinctive knowledge that the weather appeared settled, took 

 things relatively leisurely, and so were probably tempted to 

 come down and endeavour to relieve their hunger, small flies, 

 their natural food, being plentifully distributed in warm weather 

 over the drift seaweed and other material. In the second 

 case, the high wind no doubt acted as a deterrent factor in their 

 flight. But I should point out that in reality very few birds 

 appeared under such weather conditions, especially when per- 

 sistent. Indeed, on several windy mornings no birds crossed 

 the Kock at all. Having alighted, the behaviour of Wagtails 

 and Pipits was fairly characteristic. Both were active and wary, 

 the Wagtails, however, more so, and if I suddenly appeared 

 from ambush the birds would immediately ascend and fly off. 

 When, however, the wind was fresh they laid low, and could 

 generally be approached quite closely. Only exceptionally, 

 however, did I observe exhausted or listless Meadow-Pipits, and 

 no Wagtails in this state. I cannot give at the present moment 

 an estimate of the proportion of White and Pied Wagtails,* but, 

 excluding the small number of Kay's Wagtails which I noted, 

 I would say that these two species, taken together, formed two- 

 thirds, and Grey Wagtails one-third, of the whole number 

 observed. I first was under the impression that the Meadow- 

 Pipit was the only species of its kind which affected these 

 diurnal passages, but at the termination of my visit I collected a 

 Kock-Pipit, which, with several others as well as with Meadow- 

 Pipits, I actually saw descending and alighting as their com- 

 panions winged their way onwards. The familiar note of the 

 Meadow-Pipit largely predominated, but now and again I de- 

 tected cries somewhat similar in character, but differing in 

 pitch and accentuation. The similarity of the voice of Pipits 



* While this paper has been passing through the Editor's hands, I have 

 carefully examined thirteen Wagtails obtained on the Rock last autumn 

 (1912). I find that eleven are white and two pied. My best thanks are due 

 to Mr. Eagle Clarke for aiding me in the identification of the species, which 

 in immature garb closely resemble one another. 



