Roost habitat of a North Island blue duck ( Hymenolaimus malacorhynchos ) population | Notornis and Birds New Zealand

摘要

A survey was undertaken in the Te Waiiti Stream, Bay of Plenty, in summer 2002/2003, to identify blue duck (Hymenolaimus malacorhynchos) roost habitat. Thirty-six roosts were identifi ed along 18.5 km of stream channel, averaging three roosts per blue duck pair. Stable undercut banks were most commonly used as roost sites (42%), followed by log jams along stream banks (25%). Large woody debris (LWD) was a component of 50% of the roost sites, and there was a positive relationship between LWD loadings in the stream channel and number of LWD roosts. All roosts provided overhead and lateral cover, most likely an adaptive response to current and historic avian predators, and all were located at the water's edge. The location and composition of roosts provided easy access to the stream channel, discrete cover for rearing juveniles and for moulting, and daytime shelter. There were indications that channel morphology characteristics in the lower section of the survey reach may be limiting roost habitat availability and blue duck occupancy. Suitable roost habitat is a year-round requirement for blue duck and should be considered when evaluating their habitat.