Monitoring of Populations of Breeding Terns and Crab Plovers on the Iranian Islands of the Persian Gulf

Despite the importance of the colonial breeding waterbirds in the Persian Gulf, few surveys have been carried out on populations of breeding waterbirds on the islands of northern Persian Gulf. This survey was conducted from late March to the end of August in 2011 and 2012. Data were compared with the previous study conducted in 2010. The results showed that of the ten breeding waterbird species on the northern Persian Gulf islands, three tern species and Crab Plover Droma ardeola are much the most numerous. The Bridled Tern Sterna anaethetus is the most abundant species (62,000–82,000 pairs), followed by Lesser Crested Tern Sterna bengalensis (27,000–28,000) and Crab Plover Dromas ardeola (13,000–19,000), while the Swift Tern Sterna bergii has a relatively small breeding population (2,800–3,200 pairs). There were significant differences in Bridled Tern nest densities between Sheedvar, Bani Farour and Nakhilu in 2011 (F2,142= 52.830, P<0.01) and 2012 (F2,151= 25.878, P<0.01). The highest nest density was recorded at Nakhilu Island, while the lowest was found on Sheedvar Island. Most of the breeding Lesser Crested Terns were found on Nakhilu Island. It seems that the breeding population of the Crab Plover on Dara Island in 2011 was the world’s largest colony of Crab Plovers ever found. The largest fluctuations took place in the breeding population of Bridled Terns on Bani Farour Island, but small fluctuations were recorded in the populations of other species during the 2011 and 2012 breeding seasons. It is concluded that drought, flooding and the presence of Golden Jackal Canis aureus were the three main natural phenomena affecting the population fluctuations of the terns. Further monitoring of populations, including investigation of reproduction and mortality rates during the breeding season, is necessary in order to recommend appropriate measures for the conservation management of the breeding waterbird populations.