Supplementary Feeding

Supplementary Feeding

Effect of supplementary feeding on female hihi (Notiomystis cincta) reproductive success at Maungatautari Ecological Island, Waikato, North Island, New Zealand

Maungatautari Ecological Island                                                                                                                                                                                              September 2012 to December 2013

Hihi (Notiomystis cincta) are nectarivorous birds, originally found throughout mature forests in the North Island of New Zealand.  The effects of habitat loss and introduced mammalian predators caused this species’ distribution to shrink to Little Barrier Island by the 1880s. Translocation of hihi from Little Barrier Island to predator-free reserves such as Tiritiri Matangi, Karori, Kapiti Islands, Bushy Park, and Maungatautari Ecological Island has been successful in establishing secondary populations. The majority of these sites require extensive management. This involves providing nest boxes and supplementary food in the form of sugar water because large portions of the forest are in early stages of regeneration.

Supplementary feeding has proven to be a successful conservation tool for many species, including hihi. Previous research has shown supplementary feeding to substantially increase hihi reproductive success at regenerating sites but suggested that it would have reduced benefit in mature forest habitat.  Maungatautari Ecological Island differs from other reserves in that the 3,400 ha of the mature forest provides adequate natural nest cavities and potentially a more reliable year-round food supply. This study was the first was to evaluate whether supplementary feeding of sugar water affects female hihi reproductive success at in mature forest.

During the 2012/2013 breeding season, 17 females nesting attempts were closely monitored to determine the effect that supplementary feeding had on female reproductive success (nest success, number of first-clutch fledglings per female and the total number of fledglings per female). The females naturally divided themselves into non-feeder users (nine females) and feeder users (eight females). The 45 fledglings produced by the 17 females including 27 fledglings from feeder users (an average of 3.4 fledglings/female) and 18 fledglings from non-feeder users (an average of 2.5 fledgling/female).  Feeder-using females fledged 3.7 times as many fledglings as non-feeder-using females in their first-clutch attempts (95% CI 1.6-8.8), and 1.8 times as many fledglings in total (95% CI 1.0-3.5). None of the feeder-using females had failed clutches, while 7 out of the 16 clutches failed in non-feeder users. Counter to expectation our results suggest that supplementary feeder use has a significant impact on reproductive success in mature forest habitat. At least for Maungatautari, providing supplementary food in mature forest habitat appears to greatly reduce the probability of hihi nest failure, and increase the number of young a female can fledge. This outcome has important ramifications for hihi management. Supplementary feeders should perhaps be available at all translocation sites regardless of habitat type, at least early in the establishment phase. While hihi can clearly reproduce to some extent without supplementary food, it is clear that supplementary food increases reproductive output, and may be needed for population growth.