昆虫学、鳥類学、爬虫類学: 現在の研究
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概要

The Caspian Tern Hydropogne caspia in Tanzania

Neil Edward Baker

Prior to the late 1980s the Caspian Tern was considered a vagrant to coastal Tanzania. Since the early 1990s numbers wintering along the coast have continued to increase to the extent that there are now approximately 700 birds spending their non-breeding season north of 8 degrees south. Data from regular counts at key sites suggests that four roost sites hold more than 100 birds each. It is suggested that these birds are from the poorly known Malagasy population estimated at 1,000 to 2,000 birds with a 1% level of just 15 (Wetlands International 2012). If this is the case these counts represent either a major shift in the behavior of these birds or an undocumented increase in the size of the population. If the former then Tanzania now seasonally hosts approximately 50% of the population with four sites holding more than 6% and as such they qualify as shadow Ramsar sites.