128 BIRD LIFE ON ISLAND AND SHORE 
wheeling and circling overhead, collision must have 
been otherwise almost inevitable. 
As on islets visited in 1910 and 1911, the quantity 
of Petrel attracted landwards varied every night. 
Their numbers were greatest on perfectly cloud- 
less evenings. With a sky overcast or even cloudy 
fewer birds appeared. Though darkness was always 
shrouding the sea before they came, the time of 
arrival, too, differed slightly from day to day. 
With waning light parties began to reach the 
land, to draw inwards to their island. From head- 
lands we could watch them drifting restlessly to 
and fro in bands and companies low on the water ; 
then as twilight deepened into dusk they would 
rise higher and higher from the ocean levels, until 
at last the forerunners of the flight were hawking 
and wheeling over and around the island. Mean- 
time, even before a single bird had pitched, the 
island had begun faintly to wail and murmur. 
From a burrow here and a burrow there, already 
there had arisen intermittent snatches of strange 
tuneless chants. Now with the faster fall of 
Petrels from the sky—much as the congregation 
of an old-fashioned kirk follows the precentor’s 
lead—bird after bird, pew after pew chimed in, 
louder and louder the commotion grew. From 
twos and threes, from dozens, from scores, from 
hundreds, from thousands, from tens of thousands 
of burrows, rose an intensifying babel of. sound. 
