Negative effects of wind speed on individual foraging performance and breeding success in little penguins

Abstract

Most effects of environmental and climate variability on predator life history traits and population dynamics result from indirect effects mediated through the food chain. There is growing evidence that wind strength might affect seabirds while foraging at sea. Here, we investigated the effect of wind speed on the foraging performance of a flightless marine predator, the little penguin (Eudyptula minor). To this end, we used satellite‐derived wind data collected over 11 breeding seasons during which the daily attendance and body mass changes of more than 200 penguins breeding at Phillip Island (Victoria, Australia) were recorded by an automated penguin monitoring system. Over 17 363 foraging trips, we found that wind speed had important effects on foraging and provisioning parameters in breeding adults. During incubation and chick‐guard, stronger winds were associated with decreased foraging efficiency (lower body mass gain). During chick‐guard, stronger winds were furthermore associated with lower meal sizes provided to the chicks, but parental body reserves appeared unaffected. Under extreme wind conditions (>14 m/s) during the post‐guard phase, adults maintained their body reserves by shifting towards longer foraging trips, while providing chicks with smaller meals. Chick meal size and foraging trip duration during chick rearing had direct effects on breeding success, suggesting that the influence of wind on individual fitness was mediated by changes in foraging performances and success. Furthermore, using a long‐term wind data series spanning 150‐yr from a coastal wind station, we found a slight decline in wind speed and a decrease in wind speed variability in the Bass Strait where little penguins forage. Interestingly, based on this wind data, we found birds to be more directly affected by punctual events of strong winds (e.g. storms or gales), than by an overall change in wind patterns over time. Potential candidate mechanisms mediating the effects of wind speed on foraging efficiency may include swell formation, energy costs of travelling and thermoregulation, and a possible disruption of thermoclines, which may be important for little penguins. Plasticity in foraging strategies allowed parents to partially compensate for negative wind effects.

Oceanic thermal structure mediates dive sequences in a foraging seabird

“…Despite having a significant effect on some foraging parameters of little penguins (e.g., foraging effort, trip duration; Berlincourt & Arnould, 2015b; Saraux et al., 2016), wind speed had only a marginal effect on diving behavior in our study. Stronger wind speed was only associated with higher stochasticity in foraging sequences (for only one model) in guard stage.…”

“…This is consistent with the other results described in this study in which penguins exhibited higher stochasticity in foraging sequences in response to challenging environmental conditions. However, we only detected such effect during the guard stage and it could be explained by the fact we did not record extreme wind speeds (>14 m/s), representative of storm conditions (Dehnhard et al., 2013; Saraux et al., 2016), during this study.…”

“…Among Bass Strait's upper‐level predators, little penguins are useful models for investigating the relationship between environmental variability and complexity in foraging behavior, as it has already been shown that they are sensitive to changes in SST (Berlincourt & Arnould, 2015b; Carroll, Everett, Harcourt, Slip, & Jonsen, 2016), thermal stratification of the water column (Pelletier, Kato, Chiaradia, & Ropert‐Coudert, 2012; Ropert‐Coudert, Kato, & Chiaradia, 2009), and wind (Berlincourt & Arnould, 2015b; Saraux, Chiaradia, Salton, Dann, & Viblanc, 2016). Overall, relatively higher SST, stratified waters, and weak winds are likely favorable for little penguins as they result in higher abundance or predictability of prey patches because prey are aggregated nearby a thermocline (Carroll et al., 2016; Cox, Embling, Hosegood, Votier, & Ingram, 2018).…”

Within-colony spatial segregation leads to foraging behaviour variation in a seabird

“…size of foraging area, prey encounter depth, prey encounter rate and body mass gain) suggest that Penguin Parade birds foraged more efficiently in more profitable foraging grounds. Higher body mass gain after foraging trips mean larger chick meals (Saraux et al 2011(Saraux et al , 2016. From albatrosses to little penguins, when chicks receive large and frequent meals they have a higher probability of fledging (Huin et al 2000, Saraux et al 2016.…”

Linking oceanographic conditions, migratory schedules and foraging behaviour during the non‐breeding season to reproductive performance in a long‐lived seabird

“…This adjustment in behaviour coincided with higher breeding success, suggesting that foraging performance may be a key link between environmental changes and vital rates. Yet, the mechanisms by which variation in environmental conditions affects foraging behaviour and subsequently demographic parameters have only recently started to be explored and studies have mostly been focusing on the breeding season of the individual life cycle (Jenouvrier et al, 2015;Kowalczyk, Reina, Preston, & Chiaradia, 2015;Saraux, Chiaradia, Salton, Dann, & Viblanc, 2016;Weimerskirch et al, 2012).…”