Celestial Moderation of Tropical Seabird Behavior

Abstract

Most animals, including birds, have cyclic life histories and numerous studies generally conducted on captive animals have shown that photoperiod is the main factor influencing this periodicity. Moon cycles can also affect periodic behavior of birds. Few studies have investigated the influence of these environmental cues in natural settings, and particularly in tropical areas where the change in photoperiod is slight and some bird species keep cyclic behaviors. Using miniaturized light sensors, we simultaneously investigated under natural conditions the influence of photoperiod and moon phases on the migration dates and at-sea activity of a tropical seabird species, the Barau's petrel, throughout its annual cycle. Firstly, we found that birds consistently started their pre- and post-breeding migrations at precise dates corresponding in both cases to a day-duration of 12.5 hours, suggesting a strong influence of the photoperiod in the regulation of migration behavior. We also found that mean population arrival dates to the colony changed from year to year and they were influenced by moon phases. Returns at their colonies occurred around the last full moon of the austral winter, suggesting that moon cycle is used by birds to synchronize their arrival. Secondly, variations of day-time activity were sinusoidal and correlated to seasonal changes of daylength. We thus hypothesize that the photoperiod could directly affect the behavior of the birds at sea. Night-time at-sea activity exhibited a clear cycle of 29.2 days, suggesting that nocturnal foraging was highly regulated by moon phase, particularly during the non-breeding season. To our knowledge, this is the first study to document a mixed regulation of the behavior of a wild bird by photoperiod and moon phases throughout its annual cycle.

Year-round distribution and habitat preferences of the Bugio petrel

“…When compared to other larger Procellariidae, such as different species of albatrosses, the Bugio petrel presented activity patterns only similar to those of the grey-headed albatross Thalassarche chrysostoma (Mackley et al 2010). With regard to the Bugio petrels' behaviour at night and its relation to the lunar cycle, we observed that these birds would spend more time in flight at night at times closer to the full moon; this is consistent with other species such as Barau's petrel Pterodroma baraui (Pinet et al 2011a), the streaked shearwater Calonectris leucomelas (Yamamoto et al 2008) and other larger species such as the white-chinned petrel Procellaria aequinoctialis (Mackley et al 2011). Bugio petrels could benefit from the increased visibility caused by the full moon to actively search for prey, therefore shifting from their 'sit and wait' foraging behaviour to 'active foraging' during these special days.…”

Route Fidelity during Marine Megafauna Migration

“…These significant periodicities are not unlike the period (range = 29.3-29.8 days) and semiperiod (range = 14.6-14.9 days) of the lunar illumination cycle (i.e., synodic cycle). Periodicities in these ranges are not entirely unexpected given the growing number of studies demonstrating that lunar illumination is strongly correlated with a variety of organismal behaviors including animal movement (e.g., Larkin and Keeton, 1978;Grau et al, 1981;Baird et al, 2003;Tsukamoto et al, 2003;DeVries et al, 2004;Fraser, 2006;Pinet et al, 2011;Erisman et al, 2012;Schmidt et al, 2012;Sudo et al, 2014).…”

Chronobiology by moonlight

“…Decreased lunar light is correlated with increased number of departures during fall migration of land birds [56]. The arrival date of Barau's petrel (Pterodroma baraui), a tropical seabird, to their breeding colonies, occurred around the last full Moon of the austral (Southern Hemisphere) winter, and their night-time sea activity exhibited a clear cycle of about 29 days, with higher activity during full Moon nights, suggesting that nocturnal foraging is regulated by Moon phase [57].…”