Using the prey captured by breeding Crested Terns to assess the availability of forage fish for other coastal meso-predators

J. Nic Dunlop; Erin Clitheroe; Donna Chapman

doi:10.1071/PC24056

RESEARCH ARTICLE (Open Access)

Next Contents Vol 31(2)

Using the prey captured by breeding Crested Terns to assess the availability of forage fish for other coastal meso-predators

J. Nic Dunlop ^A , Erin Clitheroe

^A ^B ^* and Donna Chapman ^A

+ Author Affiliations

- Author Affiliations

^A WA Seabird Conservation Network, 162 Swansea Street, East Victoria Park, Perth, WA 6101, Australia.

^B School of Environmental and Conservation Sciences, Murdoch University, Perth, WA, Australia.

^* Correspondence to: erinclitheroe@hotmail.com

Handling Editor: Dr Rochelle Steven

Pacific Conservation Biology 31, PC24056 https://doi.org/10.1071/PC24056

Submitted: 1 August 2024 Accepted: 19 January 2025 Published: 10 February 2025

© 2025 The Author(s) (or their employer(s)). Published by CSIRO Publishing. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)

Abstract

Context

The diets of seabirds are an effective indicator of changes in forage fish abundance and availability providing insight into how changing fish stocks impact the meso-predators that consume them. Non-invasive methods for monitoring seabird diets are a valuable tool in conservation.

Aims

We aimed to assess the availability of forage fish that were carried by Crested Terns for the threatened Little Penguins (Eudyptula minor) and other meso-predators on Penguin Island, Western Australia.

Methods

We used digital photography with 400–500 mm telephoto lenses to identify prey carried to Crested Tern (Thalasseus bergii) colonies on Penguin Island during the 2021, 2022 and 2023.

Results

Crested Terns breeding on Penguin Island captured a wider range of prey (62 species) than recorded in other diet studies at other colonies in southern Australia and South Africa. Blue Sprat (Spratelloides robustus) and Sandy Sprat (Hyperlophus vittatus) dominated the forage fish taken by the terns in 2021 and 2022 breeding seasons with Sardines (Sardinops vagax) and Anchovies (Engraulis australis) becoming more common in 2023.

Conclusions

A recruitment event was recorded in Sandy Sprats in 2021 after a near record winter rainfall in the region. This recruitment event was significant as Sandy Sprats, a critical resource for Little Penguins breeding on Penguin Island, were thought to have been unavailable in local waters since a marine heatwave event in 2011.

Implications

Early indications were consistent with Crested Tern diet influencing Penguin breeding performance; however, this can only be confirmed with a longer time series. Ongoing monitoring of forage fish using bill-loading Crested Terns may have an important role in the future management of the Little Penguin colony on Penguin Island.

Keywords: citizen science, Crested Tern diet, digital telephoto photography, forage fish availability, Little Penguin conservation, monitoring, non-invasive sampling, Sandy Sprat.

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