Swinhoe's Storm-Petrel Hydrobates monorhis

Medium-sized storm-petrel found primarily in the Pacific. Dark brown overall, with buffy carpal bars in upperwing and noticeable white primary shafts at close range. Tristram's and Matsudaira's are similar but noticeably larger (apparent with experience); dark-rumped Leach’s Storm-Petrel very similar but lacks white primary shafts, flies more erratically, on sharply crooked wings. Flight is often relaxed, on wings often held out farther from the body than in Leach’s. Inhabits deepwater areas but occasionally seen near shore during or after storms.