Four species of Pterodroma petrel (P. macroptera, P. cervicalis, P. pycrofti and P. nigrippenis) responded strongly to human calls (termed by us the "war-whoop" method). This response was greater in the larger species and included the following behaviour: more frequent calling, movement towards the observer, and fighting. The level of response in P. macroptera was greatest during courtship and incubation and decreased during the chick rearing stage. Our findings support Warham's (1988) hypothesis that mainly unpaired birds respond to human calls and that the birds associate these sounds with sexual advertisement.