PhD: Understanding threatened seabird moves complex ocean energyscapes

Understanding how a threatened seabird moves across complex ocean energyscapes

The movements made by animals are a critical determinant of their access to resources and exposure to threats, with movement being one of the key primary responses of individuals to environmental change. Thus, understanding how individuals adjust their movement behaviour in response to changing environmental conditions is an essential step in linking environmental change to energetic and demographic consequences for individuals and ultimately populations (Nathan et al.

2008).

Seabirds are the most threatened group of birds globally (Dias et al. 2019), being exposed to a wide array of anthropogenic pressures. They are also often highly mobile, exhibiting very large-scale movements, particularly in the non-breeding season. Though there are documented areas characterised by winter seabird aggregations (Davies et al. 2021), we often do not know why these areas are suitable for non-breeding birds.

It is apparent that individuals can differ markedly in their destination and/or in the specific route taken to reach a common destination (Fayet et al. 2016, Phillips et al. 2017) and movements can vary in response to changing environmental conditions (Siddiqi-Davies et al. 2024). The non-breeding period is a critical one for seabird species in temperate regions, with the winter representing an energetically demanding period of the annual cycle due to lower temperatures, poor weather, reduced food availability, and shorter daylengths (Daunt et al.

2006, Fort et al. 2009). These factors can lead to conditions that directly impact on survival (Grosbois & Thompson 2005, Reiertsen et al. 2014) or can indirectly impact on subsequent breeding success via carry‑over effects (Fayet et al. 2017). Although there have been some recent studies investigating seabird energy expenditure during the non‑breeding season (Dunn et al. 2020, Buckingham et al.

2023, Leandri-Breton et al. 2025), understanding of how individual movement patterns affect both energy expenditure and energy gain, and what this may mean for survival or reproduction, is very limited. Consequently, we have limited knowledge of how changing marine conditions may affect individual energy balances and consequently lead to demographic impacts. This is primarily due to (i) historical challenges associated with gathering large and long‑term biologging datasets for seabirds in the non‑breeding season, from which movements and energetics can be estimated, and (ii) difficulties in linking seabird movement data with measures of energy gain (i.e., prey abundance and distribution).

This project will begin to fill this knowledge gap by bringing together a rarely available extensive paired biologging (geolocation‑immersion loggers) and demographic dataset collected across 18 years for black‑legged kittiwakes (Rissa tridactyla) from the Isle of May, Scotland, with a unique spatio‑temporal food abundance dataset. This dataset captures the large zooplankton energy across the kittiwake’s non‑wintering range, with prior diet and stable isotope analyses indicating that zooplankton are often a significant component of the diet in non‑breeding kittiwakes (Braune 1987, Lydersen et al.

1985, Charrier et al. 2024). In bringing these data together, this project will reveal how individuals both expend and gain energy as they move throughout the non‑breeding season and how they respond to environmental conditions. It will also provide a rare examination of the potential consequences of non‑breeding season movements for later breeding success. Specifically, the project will explore four key questions:

1. How do individuals gain and expend energy across their non‑breeding season movements and how are these patterns predicted by oceanographic conditions?
2. To what extent do individuals vary in the timing, route, or destination of non‑breeding season movements, and how does this relate to patterns of energy expenditure and gain?
3. Do differences in energy expenditure or gain have consequences for subsequent timing of breeding and productivity?
4. How are the drivers of kittiwake movements and energetics…