Correlations between human-made structures, boat-pass frequency and the number of New Zealand dabchicks (Poliocephalus rufopectus) on the Rotorua Lakes, New Zealand

Negative effects of human presence and activities on breeding success and survival of many water bird species are well documented. The New Zealand dabchick (Poliocephalus rufopectus) is a protected endemic New Zealand grebe, confined to the North Island mainland and classified as vulnerable. A third of the total New Zealand dabchick population live on the lakes of the central volcanic plateau, where there is potential conflict between humans and dabchicks. We used data from two independent surveys describing the distribution of New Zealand dabchicks to investigate the effect that human-made structures (i.e. jetties and houses) and human recreational activities (i.e. boating) have on the numbers of New Zealand dabchick pairs, chicks and nests in the bays of Lake Rotoiti, Tarawera and Okareka. Our results suggest that human-made structures and recreational activities are not significantly affecting the numbers and distribution of New Zealand dabchick pairs or nests at this time. Furthermore, the number of human-made structures was positively correlated with the number of chicks in the sampled bays. Humans and dabchicks may be distributed similarly around the lakes because factors such as wind exposure and shoreline topography made certain sites preferable for both species. Alternatively, humanmade structures may provide protected nesting environments and/or cover for chicks from predators, refuges from harassment by other bird species, or other benefits. Pairs may therefore be able to raise chicks to the fledging stage more successfully. However, little is currently known about dabchick life history or population dynamics. We recommend that a method of capturing and marking be developed so that further monitoring of behavioural and population changes can be carried out. It is also necessary to conduct research on how boats and human activities at jetties affect incubating dabchicks and their young during the nesting phase.