192 SEA-BIRDS 



adults may visit the colony without feeding it (Ainslie and Atkinson). 

 This supposition was intended to explain the excessively large number 

 of adults present in relation to the number of young birds which were 

 fed; but we believe that this increase is explained more satisfactorily 

 by inferring that at that time (July-August) on North Rona there was, 

 as in other petrel colonies in midsummer, the usual influx of yearling 

 or "sweethearting" birds. Irregular feeding begins quite early in the 

 frigate-petrel (Richdale) and also the little shearwater (Glauert says 

 "normally the chick is fed every second night for the first fortnight"). 

 Intervals of two to three days between feeding is recorded of the storm- 

 petrel (Lockley, 1932). 



The nestling is eventually abandoned before fledging. This at least 

 happens to the young of the Manx, little and great shearwaters; 

 and there is very strong evidence that those of the storm- and Leach's 

 petrels and fulmar are forsaken in like manner. The '^''starvation 

 theory", of abandoned fasting nestlings^ has also for long been widely 

 stated to apply to the largest of the tubenoses, the albatrosses; but 

 recently Richdale (1952) has shown that the royal albatross Diomedea 

 epomophora has no starvation period^ and he summarises evidence to show 

 that other species, including the wandering albatross D. exulans, have 

 little, if any. The same may apply to at least one of the smaller petrels^ 

 for Roberts (1940) suggests that the Wilson's petrel is not abandoned 

 and may be fed even after it is fully fledged. However, it does seem 

 to be a fact that among all tubenoses intensively studied, apart from 

 albatrosses and Wilson's petrel, the young is positively deserted at the 

 end of the fledging period and stays on its nest for a time much longer 

 than the normal interval of parental inattention, being then fat and 

 as heavy as or slightly heavier than an adult. For the great shearwater 

 the period between the last feed and the flight to the sea is about 

 a month. For the Manx shearwater it is ten to twelve days and for 

 the little shearwater eight to thirteen days. At the end of this period 

 of starvation the subcutaneous and body-cavity fat is greatly reduced 

 by absorption into the blood stream and apparently is partly used up 

 in hardening and setting the feathers. 



When there is room to do so the abandoned chick exercises its 

 wings much during this period. Thus young fulmars are seen to flap 

 their wings as they sit on ledges in September, and even flutter from 

 one ledge to another; while the few remaining adult fulmars, taking 

 no interest in them, visit and gape and enjoy themselves elsewhere on 

 the ledges. Abandoned Manx shearwater fledgelings come out from 



