Bird predation by domestic cats on Hahajima Island, Bonin Islands, Japan ornithological science

Abstract

The Bonin Islands are oceanic islands situated in the northwest Pacific Ocean 1,000 km south of the Japanese main island of Honshu. These islands lacked terrestrial mammalian carnivores until human colonization in 1830. Early immigrants introduced domestic cats Felis earns to the islands, some of which escaped from the island's residential area. Even by 1877 there were already reports of there being many feral cats on the island (Obana 1877). Cat predation is known to impact native bird populations on various islands around the world, such as the offshore islands of New Zealand and the Canary Islands in the eastern Atlantic Ocean (Fitzgerald & Veitch 1985, Nogales et al. 1992, Powlesland et al. 1995). In the Bonin Islands also, many studies have highlighted the impact of cat predation on native birds (e.g. Tokyo Regional Forest Office 1994, Tokyo Regional Forest Office 1996, Kawakami 2000). Ya-mashita (1934) supposed that the extinction of endemic birds (such as the Ogasawara Islands Thrush Tardus rerresrris and the Ogasawara Islands Grosbeak Chaunoprocrus ferreorostris) in the Bonin Islands was partly caused by predation of increased feral cats. But, no detailed study has been conducted on the diet of feral cats. Cat predation on small birds is considered to be underestimated, because such prey are eaten whole by cats and few visible remains are left after predation (Kawakami 2000). Reprinted from Kawakami K, Higuchi H (2002) Ornithological Science 1:143-144, with permission of The Ornithological Society of Japan.