Breeding and fledging behaviour of the Chatham Taiko (Magenta Petrel)Pterodroma magentae, and predator activity at burrows

摘要

Breeding and fledging activity of the Chatham Taiko or Magenta Petrel Pterodroma magentae were observed from October 2000- May 2001 during 3696 h of video surveillance at 16 burrows. Additional video-monitoring was done during 1999/2000 (486 h), 2001/02 (703 h) and 2002/03 (590 h). Laying in one burrow, and incubation changeovers in three, were observed. Three chicks were fed on average every 3.86 days (March-April) until the desertion period. Parental visits, shared equally by the sexes, lasted 33 minutes - 26.3 h, and ceased between 22 April and 9 May, causing desertion periods averaging 16 days (range 9-23 d, n=6). Five chicks first emerged on 21 April-1 May. Time chicks spent outside the burrow increased approaching fledging, while wing-flapping rate increased, then decreased. Mean fledging date was 15 May (range 6-27 May, n=18). Desertion periods were longer on the leeward side of the colony (mean 22 days, n=3) than on the windward side (mean 11 days, n=3), and more leeward fledglings crashed attempting to leave (75% vs 33%). Rats ( Black Rattus rattus &/or Polynesian R. exulans) were the only predators observed on video. All 38 recorded rat visits seemed benign, although 63% involved burrow entry, but visitation rate was highest in April when chicks were large.