Breeding Biology of Tristram's Storm-Petrel Oceanodroma tristrami at French Frigate Shoals and Laysan Island, Northwest Hawaiian Islands

We investigated Tristram’s Storm-Petrel Oceanodroma tristrami on Laysan Island and French Frigate Shoals, Northwest Hawaiian Islands, in the first detailed study of this species’ breeding biology. Breeding extended through the boreal winter from mid-October to mid-June. The mean hatching success on Laysan Island was 0.35 in 2004 and 0.46 in 2005; on Tern Island, it was 0.53 in 2005 and 0.61 in 2006. Fledging success was 0.45, and breeding success 0.16 at Laysan in 2004. At Tern Island, mean fledging success during 2005–2008 was 0.48 (range: 0.47 to 0.51) and overall breeding success in 2005 and 2006 was 0.27 and 0.28 respectively. Egg abandonment was common at both locations, but no relationship was evident between abandonment and frequency of visits by researchers. In addition to abandonment, weather and competition with larger burrowing seabirds for nest sites affected breeding success. Tristram’s Storm-Petrel appears to have a low reproductive rate compared with other storm-petrels, but whether the population is declining as a consequence is unknown. More research into demography and basic biology, including foraging niche, is recommended.