Understanding space and habitat use of the Near Threatened Eurasian Curlew to inform the value of habitat restoration schemes for the species' conservation

Mander, Lucas

Abstract

Intertidal habitats and terrestrial habitats connected to estuaries are subject to multiple anthropogenic pressures including the indirect effect of climate change (i.e., sea-level rise). To build sustainable coastal defences and create intertidal habitats in estuaries, managed realignment (MR) sites are created. These habitats are of potential value for wintering waders yet we know little about their long-term development and utilisation by waders (Charadriiformes; also referred to as shorebirds), for example, Eurasian curlew (Numenius arquata). The species is categorised as Near Threatened by the International Union for Conservation of Nature (IUCN) and uses both estuarine and non-estuarine habitats in winter. Understanding small-scale spatial patterns in the use of estuaries and of created intertidal habitats is essential in predicting the impact of habitat loss and designing effective compensatory sites for waders. In ecological models, e.g., individual-based models (IBMs), assumptions about animal movements are often made using a priori information on space use and habitat use. The first chapter of the thesis (Chapter 1) aims to provide background to the project and to review the use of modern telemetry and predictive modelling in assessing the success of estuarine habitat creation for waders. This thesis then examines the long-term suitability of managed realignment sites for waders in response to physical changes (i.e., in the elevation of created intertidal areas) (Chapter 2), and uses high-resolution tracking data to examine individual, sexual and temporal variation in the winter home range (Chapter 3) and habitat selection (Chapter 4) of Eurasian curlew. Furthermore, movement data – derived from GPS-tracked curlew – were incorporated to define parameters of an individual-based model, developed to predict the impact of managed realignment and other environmental changes. Using data on behaviour and fine-scale habitat use from the GPS-tracked Eurasian curlew, I also validated the model's predictions (Chapter 5). I found the foraging numbers of the four key waterbird species that colonised the MR site to decline above a certain elevation, and thus over time with accretion of the site, with this effect being most pronounced for the Eurasian curlew (Chapter 2). Using a sample of 21 GPS-tagged birds, I found Eurasian curlew to be faithful to foraging and roosting areas on their coastal wintering grounds, including a habitat creation site. Home range of Eurasian curlew was small (555.5 ha +/-SD 557.9 ha) and varied slightly in size through the non-breeding season (September to March). Home range sizes were greater at night than in the day, and showed high inter-individual variability which was not related to sex and thus potential differences in resource use (Chapter 3). I also found that Eurasian curlew’s core ranges were restricted to one to two distinct patches on intertidal flats with some overlap. Eurasian curlew preferentially selected saltmarsh and the MR site at night, presumably for roosting (Chapter 4). Finally, I successfully parameterised an individual-based model (Chapter 5). The model was able to successfully predict the impact of habitat creation on the abundance of waders supported by a discrete area of the Humber Estuary. Our overall results provide a collective understanding of the responses of waders to the creation of the managed realignment site and of the space and habitat use of Eurasian curlew. The results have been crucial in informing and validating simulations from the individual-based model.

Citation

Mander, L. (2023). Understanding space and habitat use of the Near Threatened Eurasian Curlew to inform the value of habitat restoration schemes for the species' conservation. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4320699

• Thesis Type: Thesis
• Deposit Date: Jun 30, 2023
• Publicly Available Date: Jun 30, 2023
• Keywords: Biological science ; Marine science
• Public URL: https://hull-repository.worktribe.com/output/4320699
• Award Date: May 1, 2023