2026 Volume 75 Issue 1 Pages 85-101
The alpine zone, a global biodiversity hotspot, is one of the ecosystems most vulnerable to the effects of rising temperatures due to global warming. If global warming accelerates further, strong impacts on seed dispersal through mutualistic relationships with birds are predicted. Although Japan has many isolated areas of alpine zone above 3,000 m a.s.l., little is known about the avifauna of alpine zones. So far, there have been a few reports of fruit use by Rock Ptarmigan Lagopus muta, with little information on other fruit-eating birds and seed dispersers in alpine zones. In the alpine zone on Mt. Asama (2,568 m), where there are no ptarmigan, we used camera traps to study the avifauna and determined which species used the fruits of four ericaceous dwarf shrub species (Crowberry Empetrum nigrum var. japonicum, Bog Bilberry Vaccinium uliginosum var. japonicum, Japanese Wintergreen Gaultheria pyroloides, and Lingonberry V. vitis-idaea), and estimated which species were potential seed dispersers. During three years, 265 individuals birds of 27 species in 15 families were photographed. The dominant fruit-eating species was Large-billed Crow Corvus macrorhynchos, the dominant seed-eating species was Copper Pheasant Syrmaticus soemmerringii, and the dominant raptor species was Common Kestrel Falco tinnunculus, and an additional dominant insectivore was Barn Swallow Hirundo rustica. Of these, we observed Large-billed Crow, Dusky Thrush Turdus naumanni, and Oriental Turtle Dove Streptopelia orientalis eating Crowberry fruits, and Dusky Thrush and Copper Pheasant eating Bog Bilberry fruits. In particular, the crows frequently ate Crowberry fruits. Our findings suggest that Large-billed Crow is a major fruit consumer and a potential seed disperser of Crowberry in alpine zones where there are no Rock Ptarmigan.
