Hawaiian duck behavioral patterns in seasonal wetlands and cultivated taro

Abstract

ABSTRACTAn important component for developing effective habitat management plans for the endangered, island‐endemic Hawaiian duck (koloa maoli; Anas wyvilliana) involves gaining a better understanding of how birds are using habitat and the habitat characteristics that may influence those behaviors. We conducted year‐round behavioral and habitat surveys to determine how Hawaiian ducks allocate their time to different activities throughout the annual cycle in managed natural wetlands and wetland taro (Colocasia esculenta) agriculture and to evaluate the relative roles provided by these wetland types. We used instantaneous focal sampling (n = 984 observation sessions; 328.8 hr) to estimate diurnal time activity budgets and quadrat sampling to characterize wetland habitat features from September 2010 to August 2011 at Hanalei National Wildlife Refuge, Kaua‘i, Hawaii, USA. The behavioral activities of birds differed between managed wetlands and taro. Hawaiian ducks spent a greater proportion of time resting (44% vs. 27%) and foraging (15% vs. 11%) when using taro compared to managed wetlands; whereas, birds allocated more time to maintenance (28% vs. 21%), locomotion (22% vs. 7%), and social interactions (1.3% vs. 0.5%) in managed wetlands than taro. Courtship activities accounted for <1% of male Hawaiian duck activity budgets but occurred over 5 times more frequently in managed wetlands (0.6%) than in taro (0.1%). In managed wetlands, birds foraged slightly more with increasing cover of flatsedges (Cyperus spp.) and lesser fimbristylis (Fimbristylis littoralis), decreasing cover of California grass (Urochloa mutica) and Mexican primrose‐willow (Ludwigia octovalvis), and decreasing water depth. Overall, activity budgets suggest both managed wetlands and taro contribute to fulfilling daily and seasonal resource requirements for Hawaiian ducks. The increased range of activities, particularly courtship and copulation, performed in moist‐soil wetlands suggests that greater habitat diversity is provided by seasonal wetland systems. Future research aimed at food production and daily and seasonal patterns of movement and habitat use would expand our understanding of the relative role that taro and managed wetlands provide in meeting the annual habitat needs of Hawaiian duck. © 2018 The Wildlife Society.