Breeding activity of Chatham Island taiko (Pterodroma magentae) monitored using PIT tag recorders

We developed a new automated recorder, powered by a 12-volt battery, to monitor activity patterns of wild animals marked with passive integrated transponders (PIT tags). The recorder was used to monitor Chatham Island taiko (Pterodroma magentae), a critically endangered seabird species with remote and dispersed breeding burrows. We collected information on annual return rates of individuals and pairs, dates of return and departure for the courtship and egg-laying periods, duration and dates of incubation shifts and also chick feeding visits. Taiko return to their burrows in September and October each year to mate. Return dates are independent of moon phase. Females can spend as little as one day ashore during the month-long courtship period. The pre-laying exodus averages 55 and 51 days for females and males respectively. The three main incubation shifts average 14–15 days each but some shifts can be as long as 19 days. Adults feed their chicks 32–35 times over a 3-month period, with males feeding their chicks more often than females. We discuss problems encountered during the development and field testing of the new PIT tag recorders, but also the benefits of these devices over conventional monitoring techniques for cavity-nesting birds.