Prey resource and diet of Amami jay nestlings during the breeding season

Abstract

The Amami jay Garrulus lidthi, a species of forest bird endemic to the Amami Islands, Japan, breeds between February and early June. The early start of breeding may give the species some advantages, such as the possibility of increased reproductive success due to breeding in a season when potential predators are inactive. However, to benefit from this potential seasonal advantage, adults must obtain enough food to successfully raise chicks throughout the breeding period. We investigated the availability food resources and the diet for Amami jay during the early breeding season. We conducted the study by observing and collecting available prey items between February and May 2012, including arthropods, with methods such as visual encounter along line transects, beating and netting from the vegetation, and pit-fall traps. We also recorded the food provisioned to chicks by identifying prey from video recordings at nest sites, and by fecal analyses of chicks. We found that the most frequent food item provisioned to chicks were arthropods such as Blattodea, Orthoptera, Coleoptera, Mecoptera, Lepidoptera, Hymenoptera, Araneae, and Opiliones. Those results suggest that the Amami jay captures ground cursorial species during the early spring (February and March) breeding period. The availability of these arthropods varied during the season, but those arthropods were the most available prey species in terms of both population and biomass throughout the breeding season. These findings suggest that the Amami jay has a broad prey base of ground-dwelling arthropods that it utilizes, and that according to changing prey availability during the breeding season, it can vary the food items that it provisions to its young.