Climate change may impact habitat complementation and cause disassociation for mobile species

Abstract

Context: As complementary terrestrial and aquatic habitats are pulled apart by environmental change, animals will have to adjust their behaviours to successfully track their fundamental niches. We introduce a novel example of how climate change impacts can drive separation between complementary foraging and breeding habitats in seabirds. Objectives: We evaluated how Black Noddies (Anous minutus) modified their movement behaviour across the seascape to access complementary habitat types during a period of local food scarcity; and whether this influenced their breeding success. Methods: We quantified characteristics of foraging behaviour relating to energy consumption (time, distance and area covered) over four breeding seasons for Black Noddies (A. minutus) and compared favourable years (2019, 2020 and 2021) to an unfavourable year (2022). We also quantified and compared chick health and survival rates over the same period. Results: In 2022, severe reduction in local food abundance on Heron Island led breeding Black Noddies to forage further by an order of magnitude, utilizing a remote wooded island (Bushy Islet) as an overnight roosting location. This was a novel and completely unexpected response to the altered environmental conditions. At the same time, 2022 saw significant increases in chick mortality and decreases in chick health compared to other years. Conclusions: We show how a growing mismatch between nesting, roosting, and foraging sites pushed individuals in a breeding tropical seabird population to extend their foraging range by an order of magnitude, with direct negative consequences for juveniles. Our findings highlight the need to explicitly consider habitat complementation in land- and seascape conservation initiatives and planning.