Seasonal variability of the acoustic activity of two nocturnal species of seabirds: the fork-tailed Oceanodroma furcata and the leach's O. leucorhoa storm petrels

Seabirds seem to be good indicators of the marine ecosystem conditions. However the patterns of colony attendance in nocturnal seabirds are still not clear for many species that prevent the population monitoring. I studied seasonal vocal activity on the colony in two nocturnal seabirds, fork-tailed Oceanodroma furcata and Leach’s O. leucorhoa storm-petrels, and tested the impact of abiotic factors. I found that storm-petrel acoustic activity varies greatly from night to night, but increased significantly from June to August. However I didn’t find any significant effect of most of the study abiotic factors (humidity, cloud cover, wind speed and sea state) on the vocal activity in both species. Vocal activity variables of two species were quite divergent (e.g., the time of maximum vocal activity for O. furcata - 156.8±29.8 min and O. leucorhoa - 256.4±62.0 min after sunset) and the differences increased from June to August. The possible impact of the study for acoustic monitoring of storm-petrel populations was discussed.