Contrasting responses of male and female foraging effort to year‐round wind conditions

Abstract

Summary There is growing interest in the effects of wind on wild animals, given evidence that wind speeds are increasing and becoming more variable in some regions, particularly at temperate latitudes. Wind may alter movement patterns or foraging ability, with consequences for energy budgets and, ultimately, demographic rates.These effects are expected to vary among individuals due to intrinsic factors such as sex, age or feeding proficiency. Furthermore, this variation is predicted to become more marked as wind conditions deteriorate, which may have profound consequences for population dynamics as the climate changes. However, the interaction between wind and intrinsic effects has not been comprehensively tested.In many species, in particular those showing sexual size dimorphism, males and females vary in foraging performance. Here, we undertook year‐round deployments of data loggers to test for interactions between sex and wind speed and direction on foraging effort in adult European shags Phalacrocorax aristotelis, a pursuit‐diving seabird in which males are c. 18% heavier.We found that foraging time was lower at high wind speeds but higher during easterly (onshore) winds. Furthermore, there was an interaction between sex and wind conditions on foraging effort, such that females foraged for longer than males when winds were of greater strength (9% difference at high wind speeds vs. 1% at low wind speeds) and when winds were easterly compared with westerly (7% and 4% difference, respectively).The results supported our prediction that sex‐specific differences in foraging effort would become more marked as wind conditions worsen. Since foraging time is linked to demographic rates in this species, our findings are likely to have important consequences for population dynamics by amplifying sex‐specific differences in survival rates.

European shags optimize their flight behavior according to wind conditions

“…Climate models are predicting that mean wind speeds will increase in many regions (McInnes et al, 2011;Young et al, 2011), which may have important consequences on foraging energetics. A recent study on European shags suggests that daily foraging time decreased with increasing wind speed (Lewis et al, 2015), which suggests that increased wave action reduces prey capture rates such that it becomes less economical to continue feeding, and hence birds return sooner to land (Daunt et al, 2006). Here, we show that flight performance is also affected by wind.…”

From days to decades: short- and long-term variation in environmental conditions affect offspring diet composition of a marine top predator

“…The flight and diving performance of shags is affected by local weather, in particular wind conditions (Daunt et al 2006, Lewis et al 2015, Kogure et al 2016 and potentially rainfall, which in turn may affect diet composition as previously shown in other seabirds (Finney et al 1999, Stienen et al 2000. Therefore, we used hourly wind speed (m s ) and total daily rainfall (mm) on the day of sample collection.…”

“…There is also evidence that seabird diet composition is altered by short-term weather conditions such as wind speed (Finney et al 1999, Stienen et al 2000, mediated by effects on flight performance and prey behaviour and catchability (Sagar & Sagar 1989, Weimerskirch et al 2000, Lewis et al 2015, Kogure et al 2016. At intermediate temporal scales, diet composition may display seasonal patterns if alternative prey show different scheduling of key life-history events and associated availability (Lewis et al 2001a, Davoren & Montevecchi 2003.…”

“…Thus, a seasonal shift to the 0 group might be expected, in line with blacklegged kittiwakes Rissa tridactyla, Atlantic puffins Fratercula arctica and common guillemots Uria aalge breeding at the same colony (Lewis et al 2001a). In addition, foraging and flight performance of shags is affected by daily wind conditions (Daunt et al 2006, Lewis et al 2015, Kogure et al 2016). Accordingly, short-term weather may be important in determining shag diet composition if wind affects catchability or availability of different prey.…”

Within-pair similarity in migration route and female winter foraging effort predict pair breeding performance in a monogamous seabird

“…Females also spent more time in flight over winter, despite covering similar total distances to males, and this seemed particularly marked in mid-winter (November to December), just after pair members started to follow less similar routes. While this apparent mismatch between flight time and distance may be due to inaccuracy in estimating distance from geolocation data, it could also result from sex differences in flight efficiency at certain wind speeds (Lewis et al 2015, Cornioley et al 2016 or exposure to different wind conditions when sexes visit different areas. One of our key results is that while pair total foraging effort was a good predictor of future breeding performance (higher foraging effort was associated with earlier breeding), this was mainly due to the effect in females.…”