THE TUBE-NOSES l8l 



or searching for food that they hover, dropping their webbed feet to 

 the surface, and paddHng upon it Hghtly as if walking, and sometimes 

 diving for a moment. The word petrel (according to most dictionaries) 

 is derived from St. Peter who walked the waves. The frigate- and 

 Wilson's petrels use their long legs more often for this purpose and 

 have an even more erratic flight. But these dainty petrels also dive 

 well; we have seen storm-petrels at their best in wild weather off the 

 Rockall Bank feeding and diving in the heavy swell. They would 

 skim the marbled slopes of the sea, hesitate for a fraction of a second 

 as they sighted food, then plunge under the surface for perhaps one, 

 two or three seconds, scarcely folding their wings; and emerging 

 with the same ease, wings swiftly spread, and every feather perfectly 

 dry. Murphy (191 8) describes how Wilson's petrels dived to a depth 

 of several times their length, leaping forth dry and light- winged from 

 the water into the air. 



All tubenoses are good divers, but do not remain long under 

 water or dive deep. Their food is obtained near or on the surface. 



The little shearwaters, which are intermediate in size between the 

 storm-petrels and the Manx shearwater, have an intermediate flight 

 described by P. R. Lowe as consisting of 'Tour or five beats and then 

 a short glide and so on." 



There is no doubt but that the small sea-birds generally, and the 

 petrels in particular, are able to help themselves in storms by avoiding 

 those parts of the surface of the sea where the wind is most concentrated, 

 that is, the crest of the wave or swell. They follow the trough of the 

 wave, keeping closely to the windward slope where the water's surface 

 is much less disturbed and there is a good upward air current to sustain 

 them. B. Roberts (1940) repeatedly watched Wilson's petrel feeding 

 and gliding on these windward slopes, but if the birds rose more than 

 a few inches from the water they were instantly blown away downwind. 

 It is when the storm shifts suddenly through 90° and blows parallel 

 to the swell that small birds find no definite troughs in which to shelter, 

 and so become exhausted by constant wing-beating over the confused 

 water. As a result in changeable gales many are blown inland, or 

 drowned and washed ashore. 



Roberts refers to the problem which has confronted all observers 

 of pelagic birds — the inference that petrels in stormy latitudes have 

 few opportunites to sleep or rest during the six months of continuous 

 winter storms. But other birds apparently do without sleep for certain 

 periods (as on migration), while immature swifts which in summer are 



