Dietary characteristics of the Malayan Night Heron (Gorsachius melanolophus) in the Yaeyama Islands, southern Japan

The Malayan Night Heron (Gorsachius melanolophus) inhabits a range of tropical and subtropical zones in South, Southeast and East Asia. As this heron breeds singularly in dense forests, its detailed ecology is not well known and only piecemeal information on its diet is available. Thus, we quantitatively estimated its diet menu with an analysis of pellets and stomach contents in the subtropical Yaeyama Islands of southern Japan. The results showed that the heron frequently foraged on land snails, arachnids, freshwater crabs and insects; no fish were detected. Although the earthworm was believed to be a primary dietary source of this species, it was not detected in our results, as it does not remain in pellets due to its high digestibility. This indicated that this bird dominantly depends on soil animals that inhabit humid forest floors. While the heron does not directly utilize aquatic habitats, they likely prefer moist forests caused by watery environments such as streams and swamps. Wet forests should be conserved for maintaining populations of this heron species.