The present status of the Cory's shearwater Calonectris diomedea on Filfla

Abstract

The presence of the Cory's Shearwater Calonectris diomedea on Filfla islet has been reported by several authors. The breeding colony on Filfla has been estimated as less than 30 pairs to about 200 pairs. Luxmoore-Duff (1947)was fairly certain that Shearwaters were not nesting on Filfla when he visited the islet on 11 May. He must have come to this assumption because at that time of the year the Cory's Shearwater would not have yet laid and the birds would be foraging out at sea during daylight. Two years later Trail (1949-50) visited Filfla in late July. Twenty-two occupied nests of shearwaters (species undetermined but presumably Cory's) were located among the boulder and rubble slopes. At night Trail estimated the number of arriving birds as over a thousand, possibly twice as many. This figure seems to be somewhat exaggerated. A hundred birds can make enough noise to mislead an inexperienced observer into overestimating their number. On the other hand, if Trail was correct, the sharp decline in numbers can be partly attributed to bombing (Sultana & Gauci 1970). Filfla was used for bombing practices until 1974.