IAP-24-034

Nocturnal predators in landscapes of the Anthropocene: how light and sound pollution affect movement ecology and diet of Tawny owls (Strix aluco)

Urbanisation is one of the most pervasive forms of habitat change. More than half of the world’s human population now resides in urban areas, and urban land cover is projected to triple between 2000 and 2030 (1). This poses major threats to single species, biodiversity and ecosystem services (1). Nevertheless, some species may be able to establish in urban areas, where they usually display strong physiological and behavioural changes compared to their counterparts living in natural habitats (2). Ultimately, the future of these urban populations will depend on their ability to adapt to city life (3).
There is increasing recognition that urbanisation can profoundly modify not only the spatial environment, but also the temporal one (4). Particularly critical are artificial light at night and locally elevated sound levels, which can affect the natural rhythmic environment, disrupt organismal clocks, interfere with sensory perception, and ultimately lead to associated changes along the food chain (for example, behaviour of prey) (5). However, such evidence comes mostly from diurnal species, which have been found to expand their activity into the night to extend foraging time and increase mating success, exploiting the presence of light pollution to see and move through the urban night (6, 7). In contrast, there is a surprising lack of data from nocturnal species. Nocturnal species may also be strongly affected by light at night, especially in the case of prey that want to avoid being seen by predators. Moreover, nocturnal predators often hunt using acoustic cues, which makes them susceptible to anthropogenic noise, too (8). On one hand, these acoustic hunters may be forced to forage during quieter periods of the night, for instance by avoiding activity at noisy rush hours. On the other hand, they might switch between sensory cues and rely more on visual hunting in noisy areas, perhaps even exploiting areas polluted by anthropogenic light to find their prey. Distinguishing between these competing, although not fully exclusive hypotheses, will provide novel and exciting insights into how species may adapt to anthropogenic temporal environments.

This project will approach this unique challenge by studying Tawny owls (Strix aluco) (Fig. 1), a nocturnal predator that usually prey by sound. We will combine innovative biotelemetry tools with DNA metabarcoding of faeces and pellets (9) to analyse movement ecology and diet of Tawny owls along an urban gradient in Glasgow, Scotland. Individual owls will be tracked around-the-clock, using accelerometers to detail behaviour (Fig. 2), GPS to detail space use (Fig. 3), and soundmeters and lightmeters to detail the sensory environments experienced by the birds. We will then collect faecal samples as well as pellets and perform DNA metabarcoding and assess which dietary items were consumed by individual birds. Lastly, we will use the two datasets to test the hypothesis that movement behaviour is related to diet diversity and abundance. Specifically, this project has three fundamental objectives:

• Objective 1: Moving through urban lightscapes and soundscapes: To examine how sensory pollutants (light and noise) shape foraging behaviour by tagging individual owls with GPS + accelerometer + light sensor tags.
• Objective 2: Dietary shifts: Describe the diet of Tawny owls via DNA metabarcoding and assess how urbanisation, light and noise pollution might alter the diversity and abundance of dietary taxa.
• Objective 3: Links between movements and diet. To identify how the modified use of time and space in urban areas impacts on diet.

The study is a partnership between Dr Davide Dominoni at the University of Glasgow (urban ecologist) and Prof Andreanna Welch from Durham University (molecular ecologist). Moreover, the project has been running for a number of years and other collaborators have been involved, such as Patrik Karell (Lund University, Sweden), Barbara Helm (Swiss Ornithological Institute, Switzerland) and Petra Sumasgutner (Konrad Lorenz Institute, Austria). Thus, there will be ample opportunities for the student to expand their research network and thus the project itself (including new ideas and methodologies), and to be exposed to a vibrant research environment.

Field work will be conducted in Scotland (Glasgow and surrounding forest areas) under the supervision of Dr Dominoni. Tawny owls breed in nestboxes, and we have a network of ~ 200 nestboxes that owls use, making an ideal system for studies combining monitoring of reproductive activities with catching and tagging animals for biotelemetry data collection and collection of faecal samples and pellets.
This project will use novel biotelemetry technology consisting of tags fitted with GPS, accelerometer and light logger sensors, produced by project partner Technosmart. Field work will involve monitoring of breeding events, catching and ringing adults and chicks, tagging adults, recording of provisioning behaviour and diet via nest-cameras. Pilot data exist (Figs 2-3) for owl movements and activity, and for lightscapes (www.lightpollutionmap.info).
In the lab, the student will conduct diet DNA metabarcoding of faecal samples collected from both the parents and the chicks, and pellets collected at or around the nestbox. In this approach, DNA from diet items is extracted from faecal/pellet samples, and then sequenced on a next-generation, high throughput platform, to obtain the sequences of hundreds of diet items from up to 200 birds simultaneously. This will provide high-resolution detail of the diets consumed by the birds both during the breeding season. Powerful bioinformatics approaches will identify the taxonomy of the diet items and potentially information about abundance, and then statistical analyses will be carried out to identify significant effects of light and noise pollution.
The student will identify an appropriate framework to model both temporal and spatial effects of sensory pollutants on activity levels, home range and characteristics of hunting behaviour (e.g. Generalised Additive Models with auto-regressive terms, or Bayesian state-space models). This shall allow to fully characterise the roles of time, space and explanatory variables, permitting projections and interpolations to non-censused areas. Finally, using GLMMs links will be made between spatio-temporal habitat use of urban and forest owls to changes in diet.

Year 1

Fieldwork (primarily spring breeding season but also at intervals throughout the year), assembly of movement data, preliminary metabarcoding lab work to fine-tune methodology, preliminary animal movement models.

Year 2

Additional fieldwork, finalising metabarcoding lab work, bioinformatics and data analysis, finalising animal movement models, national scientific meeting or workshop attendance.

Year 3

Data analysis, manuscript preparation, international scientific meeting attendance

Year 3.5

Finalize manuscripts and submit/defend thesis

Through this project the student will develop many highly desired and transferrable skills. From Dr Davide Dominoni in Glasgow, the student will gain experience planning a field season, skills in ethical handling, tagging and use of animals in research, current technologies for monitoring animal behaviour and movements, and training in advanced statistical analyses. From Dr Andreanna Welch the student will learn the general lab and cutting-edge DNA sequencing skills that will be important for a research career in ecological and evolutionary genetics, but provide a strong foundation for careers in environmental testing, molecular biology, agricultural biotechnology, and medical testing/research. Numeracy and computer programming, two widely desired traits, will be well developed through use of sophisticated spatial ecology and bioinformatics approaches and implementation of rigorous statistical analyses. Scientific writing and attendance at professional meetings will aid in development of key networking and communication skills. Additionally, organisation and time management skills necessary for this project are widely applicable in all industries.