Modeling Breeding Habitat Preferences of Tahiti Petrel <i>Pseudobulweria rostrata</i> on Ta‘ū, American Samoa

Understanding the prevalence and use of breeding habitat of seabird species is important for evaluating appropriate conservation and management strategies. Seabirds are one taxonomic group for which we have relatively few species distribution studies, particularly on remote islands. To address this limitation, the goals of this study were to (1) build and use a species distribution model to identify which differences in habitat structure, physical characteristics, and environmental conditions affect Tahiti Petrel Pseudobulweria rostrata nesting presence on the island of Ta‘ū, American Samoa; and (2) evaluate how important nesting habitat characteristics can identify the fine-scale extent and location of suitable Tahiti Petrel breeding habitat throughout the summit region of Ta‘ū. We found that closed canopy cover and higher altitudes best predicted Tahiti Petrel nesting locations. We classified the summit montane rainforest habitat above 650 m by the presence of canopy species using supervised image classification. Of the 774.7 ha (7.474 km2) of habitat classified, 63.8% was covered by canopy species, and a total of 254.1 ha (2.541 km2) of montane habitat was classified as most suitable for Tahiti Petrel nesting. Closed canopy cover was higher on the leeward side of the summit (80.02%) compared to the windward side (46.50%). This difference is likely caused by a combination of prevailing winds and disturbances from storm events, which can significantly alter the amount and distribution of canopy vegetation. This pattern highlights the importance of considering breeding habitat availability when assessing the conservation needs of Tahiti Petrels.