The Glaucous Gull is the only notable avian predator of the Little Auk. The Little Auk, though locally and periodically the most important, is nevertheless one of many different food sources available for Glaucous Gull. In 1983, the gulls killed ca. 3.0% of adults and subadults, 2.8% of fledglings and 4.5% of chicks. Their predation on Little Auk eggs was negligible. Strong winds favoured gull hunting. Higher predatory pressure was exerted on large Little Auk subcolonies than on small ones. Hedging in Little Auks was most intensive around midnight In 1983, 63.3% of young birds left the colony between 22.30 and 01.30. A lower proportion of young Little Auks died during the peak fledging than outside it. Gull predatory pressure contributes to strong synchronisation of the Little Auk breeding period. The intensive, concurrent fledging, limited to several days and a few "night" hours a day, considerably reduced young Little Auk mortality. During the Little Auk nestling period the gulls killed a relatively stable number of young birds regardless of the dramatic changes in their availability. At least 80% of young Little Auks (in relation to the number hatched) left the colony successfully. It is suggested that Little Auks nested originally in cliffs, laid two-egg clutches and young birds left the colony "precocially" owing to strong gull predation. The dramatic increase in Little Auk numbers caused by the take-over of a new nesting habitat (talus and rock debris) was not followed by a proportional increase in Glaucous Gull numbers, as these are limited by food shortage prior to Little Auk arrival and after their departure. This has resulted in a "disproportion" of the Little Auk (prey) and the Glaucous Gull (predator) numbers during the breeding season, thus improving the efficiency of the Little Auk's antipredatory behaviour and making deliverance from predatory pressure possible.
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