Seabird reproductive responses to changing climate and prey communities are mediated by prey packaging

Y Watanuki,M Yamamoto,J Okado,W Sydeman,M Ito

doi:10.3354/meps13943

Y Watanuki, M Yamamoto + Show 3 more

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https://doi.org/10.3354/meps13943

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Abstract

Climatic factors drive changes in forage fish communities and may influence the productivity of piscivorous predators, but specific mechanisms of response remain poorly known. Between 1984 and 2020, we studied the rhinoceros auklet Cerorhinca monocerata, a seabird breeding in the western North Pacific at Teuri Island, Japan. We tested the hypothesis that climate-mediated prey-switching affects ‘food packaging’ (i.e. the way energy is brought to dependent offspring) and breeding success by quantifying relationships between climate, prey energy density, amount of food delivered, and the growth and survival of chicks. Prey composition switched 4 times: 1988-1992, 1997-1998, 2013-2014, and 2017-2018. All but the last of these switches were associated with (lagged) shifts in seawater temperature/Pacific Decadal Oscillation. Rhinoceros auklets brought multiple fish in each meal-load to chicks, and numbers were inversely correlated with the size of the fish. These relationships varied between fish species. The heaviest meal-loads were achieved when diets were dominated by anchovy Engraulis japonicas, which occurred during warm phases (1992-2013). Chick production, growth rates, and mass at fledgling were also highest during the warm phases. This study shows that climate affects seabird reproduction by shifting the manner in which food is selected relative to changes in forage fish community structure and abundance.

Highlights

Climate forcing of marine environments changes ‘bottom-up’ trophic effects that may influence the reproduction and population dynamics of top predators through changes in forage fish communities (Aebischer et al 1990, Barbraud & Weimerskirch 2001, Boyd & Murray 2001, Sydeman et al 2015)
Rhinoceros auklets bring multiple prey items in each meal-load. They can compensate for potentially small prey size by bringing more fish, and may have the ability to mitigate the effects of changes in prey energy density by increasing the mass of the mealload
We explored whether the timing of the change in prey use co-occurred with recent quasi-decadal scale climate shifts indicated by the Pacific Decadal Oscillation (PDO) index and seawater temperatures

Summary

Introduction

Climate forcing of marine environments changes ‘bottom-up’ trophic effects that may influence the reproduction and population dynamics of top predators through changes in forage fish communities (Aebischer et al 1990, Barbraud & Weimerskirch 2001, Boyd & Murray 2001, Sydeman et al 2015). Mar Ecol Prog Ser 683: 179–194, 2022 despite their name, belong to the puffin tribe of the Alcidae (Gaston & Jones 1998) They dive to 65 m depth and prey on a variety of species, such as sardine Sardinops spp., anchovy Engraulis spp., sand lance Ammodytes spp., capelin Mallotus sp., and squid, which they bring back to their colonies to provision chicks in nest burrows (Burger 1991, Gaston & Jones 1998, Kuroki et al 2003, Thayer et al 2008, Sydeman et al 2017, Cunningham et al 2018). They can compensate for potentially small (large) prey size by bringing more (less) fish (see Fig. 1), and may have the ability to mitigate the effects of changes in prey energy density by increasing the mass of the mealload

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