Prey selection in precocial chicks of the Endangered Hawaiian Stilt (ae‘o - Himantopus mexicanus knudseni)
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2020-09-30
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Recovery of endangered species is dependent upon maximizing reproductive success and 1 minimizing mortality, but management actions aimed at increasing recruitment are often 2 hindered by a lack of knowledge at critical life history stages. For example, the dietary 3 preferences of precocial chicks may differ from nesting adults; thus, the optimal foraging habitat 4 may also differ between these life stages. The Endangered Hawaiian Stilt (ae‘o - Himantopus 5 mexicanus knudseni), a subspecies of the Black-necked Stilt, is considered a generalist forager, 6 but little is known regarding prey selection in precocial chicks. In this study, stable isotope 7 mixing models were used to estimate the contribution of potential prey sources to stilt chick diets 8 in wetlands on O‘ahu Island, Hawai‘i. We found predicted contributions to be similar among 9 potential prey items at a site with high prey diversity and the oldest and largest chicks. At three 10 other sites, younger chicks appeared to select particular items from among available prey, 11 including species in the orders Hemiptera (true bugs) and Araneae (spiders). Species in these 12 orders were lower in biomass compared to other species available at each site, suggesting the 13 chicks were selecting for these items from among available prey items, similar to other related 14 species. Our results suggest that Hawaiian Stilt chicks may preferentially select certain prey 15 items which are easy to handle and high in nutrients important to development, and likely 16 diversify their diet as they gain dexterity and height. The results from this study may inform 17 decisions for optimal habitat and macroinvertebrate management in Hawaiian Stilt nesting sites 18 to maximize reproductive success and survival.
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Cole A, Harmon KC, Phipps C, Price MR. 2020. Prey selection in precocial chicks of the Endangered Hawaiian Stilt (ae‘o - Himantopus mexicanus knudseni). Report prepared for the Undergradiate Research Opportunities Program, University of Hawaiʻi at Mānoa, Honolulu, HI.
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