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Status of the Socotra cormorant in the Arabian Gulf after the 1991 Gulf War oil spill, with an outline of a standardised census technique

A b s t r a c t: Since the 1991 Gulf War oil spill, numbers of breeding pairs of the endemic Socotra cormorant Phalacrocoraxnigrogularison the three extant colonies in Saudi Arabia have tripled from 10,000 breeding pairs in 1991-1992 to 30,000 pairs in 1994-1995. The present numbers still represent a decline of 40 % compared to a previous population estimate in 1981. Although the Gulf War oil spill killed an estimated 8,000-10,000 birds of the Saudi Arabian population, this clearly could not have been the only reason for such a large decrease in numbers between 1981 and 1991. Similarly, the tripling of the breeding population since the Gulf War cannot be attributed solely to a dramatic recovery since the oil slick. The present population for the entire Arabian Gulf is estimated to be 225,000-235,000 breeding pairs in 11 colonies, of which several are threatened by increasing disturbance and development. More than 95 % of the Gulf population is restricted to three colonies. Urgent action must be taken to protect the few surviving colonies of this globally near-threatened and vulnerable species. In order to understand present population trends, regular and regionally coordinated counts of all extant breeding colonies, using standardised methods, remain a priority. Yearly fluctuations in numbers in and between colonies and an extended breeding season complicate the assessment of exact population sizes. Hence a general outline for a standardised methodology, based on the experiences gained at the colony of Judhaim Island in Saudi Arabia, is proposed and discussed.


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