Cyclone avoidance behaviour by foraging seabirds

Abstract

In the context of climate change, how extreme climatic events, such as cyclones, will affect the foraging abilities of marine vertebrates is still poorly known. During the course of a study on the foraging behaviour of two tropical seabirds, red-footed boobies and great frigatebirds, several cyclones have affected their breeding grounds and foraging zones, allowing us to study their response to extreme wind conditions. We examined whether adults and young naïve birds were able to predict the arrival of a cyclone and behave accordingly to reduce mortality risks and optimise foraging. We show that when a cyclone approached, juveniles and adults of the two species differed in their decisions to leave the colony for the sea. When the winds reached gale force, the juveniles of both species and adult frigatebirds remained at the colony, whereas adult boobies continued their foraging routine. The mortality of the individuals remaining on land remained limited. When encountering at-sea gale conditions, adult birds were able to avoid the centre of the low pressure systems and moved westward to bypass the route of the cyclones and circumvent the moving cyclone. Frigatebirds climb to high altitudes when close to the eye of the cyclone to bypass it at high speeds. These movements likely reduce the mortality risk at sea but can temporarily cause birds to move outside their normal range at sea or over land masses. We discuss the potential consequences of an increase in cyclonic conditions on seabird populations.

Cascading effects of climate variability on the breeding success of an edge population of an apex predator

“…Cornioley, Börger, Ozgul, & Weimerskirch, 2016). Under unfavourable wind conditions, the energetic costs of foraging flights at sea during the breeding season may be too high as to impact population-level demographic processes, such as reproduction and survival (mostly of young individuals; Frederiksen, Daunt, Harris, & Wanless, 2008;Hennicke & Flachsbarth, 2009;Thorne et al, 2016;Weimerskirch & Prudor, 2019), and even increase the risk of extinction of some populations (Hass, Hyman, & Semmens, 2012). Therefore, changes in wind regimes may affect the future distributions of wind-dependent bird species.…”

Tropical cyclones alter short-term activity patterns of a coastal seabird

“…While the spatial impacts of macroscale events are relatively well-studied, effects of shorter-term acute drivers (e.g. local storms) are less known [14].…”

“…Species that occupy ecosystems regularly subjected to hurricanes demonstrate behavioral modifications for increasing survival during cyclonic activity, although direct studies appear limited [14]. For example, marine species commonly display one of two contrasting strategies for mitigating negative effects from intense but short-duration weather events; relocation and sheltering in place.…”

“…Of particular utility for examining differential responses to cyclonic events, seabirds present a group of taxonomically and morphologically diverse organisms often impacted by marine storms. For example, smaller-bodied pelagic seabirds may attempt to avoid or circumnavigate an approaching hurricane [14, 30]. Individuals unable to do so may be displaced far from their preferred habitat (often inland), leading to the observed wrecks of these species following major events (e.g.…”

“…Conversely, larger-bodied coastal-dwelling species may reduce daily activities and attempt to shelter during storm passage, but this remains unexamined. Variation in hurricane response may also differ by life stage in addition to morphology [14]. Understanding how various seabird species respond to large-scale environmental irregularities may therefore clarify apparent discrepancies in displacement susceptibility [30].…”