Mr.Aoki, chief advisor of the JICA Expert Team (JET), Mr.Watanabe, expert of wetland ecosystem conservation and the other members of JET went to Sorkhankol Wildlife Refuge by kayak to monitor a breeding condition of Whiskered Tern (Chlidonias hybrid) on 5th June, 2017. Whiskered Tern comes to the Anzali Wetland to breed from Africa or South Asia in spring.
As a result of monitoring, more than thousands (at least 1,000) breeding nests on the leaves of Water Caltrop (Trapa natans) were found in south area of Sorkhankol Wildlife Refuge. Water Caltrop is floating plant. Therefore the nests of Whiskered Tern are on the water surface. It is very safe place because terrestrial predator cannot approach there.
Almost half of nests had eggs and the remains were under building. However some nests already had chicks. It was the bingeing phase of Whiskered Tern breeding season.
According to HBW (http://www.hbw.com), the global population of Whiskered Tern has not been estimated precisely recently but is within the range of 300,000–1,500,000 individuals, and is thought to be fluctuating overall. Based on the result of our breeding bird survey in 2015 under the comprehensive ecosystem survey as a Joint Pilot Activities (JPA), 2,725 nests of Whiskered Tern were recorded in the west lagoon of Anzali Wetland. It means that at least 5,450 mature birds were breeding in Anzali wetland at that time. More than 1% of global population of Whiskered Tern depends on the Anzali Wetland as a breeding habitat. One of criterion of Ramsar wetland is “regularly supports 1% of the individuals in a population of one species or subspecies of waterbirds.”
Hence the Anzali Wetland obviously meets the criterion of Ramsar wetland. The Tern needs appropriate shallow water depth and dense aquatic plant community to make nest. In addition, Whiskered Tern changed its breeding site from west lagoon in 2015 to Sorkhankol. They could select a breeding site depends on the environmental factor such as water depth and situation of water plant community. It means some alternatives of habitat types exist in the Anzali Wetland. The Whiskered Tern is one of an important species as indicator. Based on the requirement of Whiskered Tern’s nest, a target of wetland water depth can be set for wetland ecosystem management.
We wish the many Whiskered Tern chicks growing well!!