Foraging Behavior of the Hawaiian Stilt (Himantopus mexicanus knudseni) at Hāmākua Marsh, O'ahu, Hawai'i

Abstract

Understanding habitat use on a fine scale is essential for the development of management plans for threatened and endangered species. Several heavily managed State Wildlife Sanctuaries and National Wildlife Refuges provide critical foraging habitat for the endangered Hawaiian Stilt, or Ae'o (Himantopus mexicanus knudseni). The foraging behavior and habitat use of Hawaiian Stilts at Hāmākua Marsh State Wildlife Sanctuary, O'ahu, Hawai'i was investigated. Foraging tactics, success, and microhabitat were recorded for 227 birds over 24 2-hr periods from September to December 2021. Hawaiian Stilts made the most foraging attempts in shallow (< 8 cm deep) water, and had the most success in intermediate (8–15 cm deep) water. The most commonly recorded foraging tactic was pecking, while the most successful was plunging. Visual tactics were both more common and more successful than tactile. The overall foraging success rate for Hawaiian Stilts in this study was 0.16, markedly less than success rates observed by other researchers in related species. It is possible that prey in Hāmākua Marsh is either less abundant or less vulnerable to capture than in other similar habitats. Our results suggest that future habitat management for Hawaiian Stilts should prioritize areas of shallow water and further investigate food availability.