If it ain't broke, don't fix it: variable foraging behaviour is associated with low kittiwake reproductive success

Repeated use of a winning foraging strategy can be profitable when individuals use memory to return to successful food patches. However, in environments where patches are unpredictable, variable foraging behaviour may be more profitable. To test this idea, we explored how individual variation in foraging trip characteristics impacts breeding success in black-legged kittiwakes, Rissa tridactyla, on Middleton Island, Alaska, U.S.A., during a period of highly variable environmental conditions, the largest recorded marine heatwave. As anticipated, foraging trip characteristics were highly variable, within and between years and individuals. While characteristics of foraging trips alone did not influence annual breeding success, both age and variance in those trip characteristics explained variation in breeding success. Specifically, individuals with smaller variance in foraging trip characteristics among trips were more likely to fledge a chick. There was a maximum distance threshold in foraging implying that individuals searched within a restricted area, increasing foraging time rather than distance when searching was not profitable, and providing additional support for the idea that kittiwakes are most successful when foraging in known areas rather than exploring new areas. The Pacific Decadal Oscillation, which is associated with large scale shifts between cold and warm ocean climate and ecosystem regimes in the region, impacted breeding success but did not change foraging behaviour. However, mean breeding success decreased as mean time spent resting and in area-restricted search (intensive search) on foraging trips during incubation increased. Based on nearly a decade of data, we conclude that smaller variability in behaviour, even during challenging foraging conditions, enhances breeding success. As climate change and marine heatwaves continue to increase in intensity, individuals more variable in foraging behaviour may be unable to compensate. (c) 2024 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.