246 NATURE IN DOWNLAND 



ducted incline one to think that sight and hearinor 

 in some gregarious species of aerial habits are supple- 

 mented by another faculty — a very delicate sense 

 of touch, as in the bat ; that it is a sensation of re- 

 pulsion informing each member of the flock of the 

 nearness to it of others, and prevents them from 

 touching or striking against and impeding one another. 

 When the flock turns or changes its formation, it may 

 be observed that while numbers of birds are stream- 

 ing away to this or that side with accelerated speed, 

 others, at points where confusion would seem inevit- 

 able, suspend their flight, and remain almost motion- 

 less at equal distances apart until the moment comes 

 for them to join in the swift movement. 



Black-headed gulls are as abundant as rooks on 

 the flat country and on the neighbouring downs where 

 there is tillage, and may often be seen in screaming 

 crowds following close at the heels of the ploughman. 

 When not feeding they are seen at rest on- a green field, 

 and at a distance may be taken for a great patch of 

 unmelted snow. That beautiful order which so many 

 gregarious birds observe when on the wing in flocks 

 is adhered to by the gulls even when resting on the 

 earth. They invariably sit or stand on the grass with 

 beaks all pointing one way, to the wind, all at equal 

 distances apart. These white flocks resting on the 

 green fields are a familiar feature of the winter land- 

 scape in this district. 



Altogether, this is a spot in which an observer of 



