Effects of investigator disturbance on hatching success and nest-site fidelity in a long-lived seabird, Leach's storm-petrel

Abstract

Long-lived animals are expected to reduce reproductive effort when breeding conditions are unfavorable, therefore seabirds may be especially sensitive to investigator disturbance. In a non-threatened procellariiform, Leach's storm-petrel Oceanodroma leucorhoa, we examined whether the frequency and the time of day of investigator disturbance influenced hatching success, and if disturbance affected hatching success and nest-site fidelity in the subsequent breeding season. Birds used in this study had received little or no investigator disturbance during the prior decade. Hatching success was significantly influenced by the frequency, but not the time of day, of disturbance. Weekly and daily handling of parents reduced hatching success by 50 and 56% compared to the control group. Most failures (91%) were caused by egg desertion, and all the deserted eggs belonged to pairs in the weekly and daily groups. During the subsequent breeding season, the hatching success of disturbed pairs that continued to breed together returned to normal levels. However, 37% more disturbed pairs than control pairs deserted the nesting burrows they had used in the previous year. Since most changes in nest site also result in mate change, investigator disturbance may have had long-term negative effects on reproductive success as well. Our results demonstrate that both weekly and daily investigator disturbance during incubation greatly reduced the hatching success and subsequent nest-site fidelity of naı̈ve Leach's storm-petrels.