Time, light and sound: nocturnal predators in landscapes of the anthropocene

Overview

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. 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. Simultaneously, we will quantify the lightscapes and soundscapes in which these raptors move, by around-the-clock, on-animal recordings using dedicated sensors. We will further collect data from nests about provisioning rates, delivered food items, assimilated diet, and breeding success. Specifically, this project has three fundamental objectives:
Objective 1: Timing of activities in city- and forest-dwelling owls: To quantify the plasticity in timing of Tawny owls. We predict that Tawny owls, whose activity commences in darkness, will contract their temporal niche in illuminated urban and suburban areas compared to dark forests, in response to increased urban noise.
Objective 2: Moving through urban lightscapes and soundscapes: To examine how sensory pollutants (light and noise) shape foraging behaviour and foraging efficiency. We predict that with increasing levels of artificial light and sound, owls will use space more selectively, hunting in quieter and possibly darker areas. Selectivity will be evident from on-bird measures of light and high-resolution GPS data, and from ground measurements of noise. Using these data, we will build movement models to identify spatio-temporal responses of owls to time-structured, anthropogenic changes to their habitats.
Objective 3: Links to diet and reproductive success: To identify how the modified use of time and space in urban areas impacts on diet and reproductive success. Decreased parental foraging efficiency, delivery of fewer or lower quality food items, and disrupted rest phases could all impact nestlings’ body condition. We predict: i) lower chick provisioning rate in urban than forest owls, ii) different diet in urban compared to forest owlets, iii) lower chick body condition and fledging success in urban owls.

Click on an image to expand

Image Captions

owls figure 1.png – Fig. 1. A Tawny owl fledgling (photo by Freya Coursey).
owls figure 2.png – Fig. 2. Movement tracks of two Barn owls obtained through GPS telemetry (courtesy of Kamiel Spoelstra). These pilot data was collected using the same tags we plan to use for this project.
owls figure 3.png – Fig. 3. Accelerometer data showing hourly activity levels of one female Tawny owl for a 10-day period. Not how activity is mostly confined during the night hours, although some activity bouts can be seen also during the day.

Methodology

We will study Tawny owls in urban and suburban plots in the Glasgow area, and in managed forest plots in the Loch Lomond and the Trossachs National Park. In the forest plots, Tawny owls breeding behaviour has been monitored for 10 years and a large dataset is already available through the collaboration with CASE partner Forestry and Land Scotland. Owls are routinely caught at least once a year, making an ideal system for biotelemetry studies. In Glasgow, owls will be caught at known long-term nesting sites. Moreover, 50 nest boxes have been recently installed in several urban parks and suburban areas, and more potential nesting sites have been recently identified from ground surveys.
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, collecting feather samples for physiological analyses. Laboratory work will involve analysing feather samples carbon and nitrogen isotope values. Pilot data exist (Figs 2-3) for owl movements and activity, and for lightscapes (www.lightpollutionmap.info). Techniques to analyse provisioning behaviour and diet via stable isotopes have been validated in other bird species (9).
We 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 will allow us to fully characterise the roles of time, space and explanatory variables, permitting projections and interpolations to non-censused areas. We will analyse changes in diet using stable isotope data and established generalised mixed-effect model (GLMM) approach. Finally, we will link spatio-temporal habitat use of urban and forest owls to changes in diet and reproductive success using GLMMs.

Project Timeline

Year 1

Literature review, field work to collect movement and activity data with GPS loggers (objective 1 and 2) and feather samples for stable isotope analysis (objective 3), attendance of workshops on Bayesian statistics and stable isotopes, visit to project partners.

Year 2

Field work as in year 1, analysis and write up for objective 1, initiate analyses for objective 2, laboratory analyses of stable isotopes samples (objective 3), attendance of workshop on analysis of spatio-temporal movement data, attendance of national scientific meeting (i.e. national conference on stable isotopes, Glasgow 2021), visit to project partners.

Year 3

Finalise analyses and write up for objective 2, conduct analyses and write up for objective 3, attendance of scientific writing courses, manuscript preparation, attendance of scientific meeting.

Year 3.5

Attendance of international scientific meeting, completion of manuscripts and submission of thesis.

Training
& Skills

The training provided by this project will cover a broad suite of important formal quantitative and computational approaches and their application. This, combined with extensive field work with birds, will provide the student with an extremely strong basis for pursuing independent research in their field(s) of interest or for a transition to roles in growth areas such as data science.
The scholar will be based within IBAHCM under the supervision of Dr Davide Dominoni. At IBAHCM the student will be exposed to a vibrant research environment that takes pride in its strong collaborative approach to scientific research. Several special interest groups are present in the institute that will help the student develop theoretical knowledge and practical skills, including the Avian Evolutionary Ecology group, the Spatial Ecology group and the Statistics group.
In year 1, the student will receive training on spatial modelling, GIS, management of large datasets, Bayesian statistics, by following dedicated courses offered within IBAHCM, by attending external specific workshops and courses, and through the support of the supervisors (DD and MB in particular). The student will also receive training on using the University of Glasgow computing cluster to enable rapid data processing. In year 2, the student will develop skills in spatio-temporal modelling of biotelemetry data, integrating different datasets on movement data and environmental variables, with training from MB. The student will also join retreat sessions on scientific writing and will start to lay out the first manuscript. He/she will also spend time with Dr Bogdanova at CEH to discuss analyses of movement data, and with Dr McGill at SUERC to perform stable isotope analyses and discuss the data. In year 3, through participation in Institute seminars and national and international conferences, she/he will also develop presentation and communication skills.

References & further reading

1. K. C. Seto, B. Guneralp, L. R. Hutyra, Global forecasts of urban expansion to 2030 and direct impacts on biodiversity and carbon pools. PNAS. 109, 16083-16088 (2012).
2. M. Alberti et al., Global urban signatures of phenotypic change in animal and plant populations. Proc. Natl. Acad. Sci., 201606034 (2017).
3. M. T. J. Johnson, J. Munshi-South, Evolution of life in urban environments. Science. 358, eaam8327 (2017).
4. B. Helm et al., Two sides of a coin: ecological and chronobiological perspectives of timing in the wild. Philos. Trans. R. Soc. London B.
5. D. Dominoni, J. Borniger, R. Nelson, Light at night, clocks and health: from humans to wild organisms. Biol. Lett. 12, 20160015 (2016).
6. D. M. Dominoni, B. Helm, M. Lehmann, H. B. Dowse, J. Partecke, Clocks for the city: Circadian differences between forest and city songbirds. Proc. R. Soc. B Biol. Sci. 280 (2013), doi:10.1098/rspb.2013.0593.
7. B. Kempenaers, P. Borgström, P. Loës, E. Schlicht, M. Valcu, Artificial night lighting affects dawn song, extra-pair siring success, and lay date in songbirds. Curr. Biol. 20, 1735-1739 (2010).
8. J. T. Mason, C. J. W. McClure, J. R. Barber, Anthropogenic noise impairs owl hunting behavior. Biol. Conserv. 199, 29-32 (2016).
9. C. J. Pollock, P. Capilla-Lasheras, R. A. R. McGill, B. Helm, D. M. Dominoni, Integrated behavioural and stable isotope data reveal altered diet linked to low breeding success in urban-dwelling blue tits (Cyanistes caeruleus). Sci. Rep. 7 (2017), doi:10.1038/s41598-017-04575-y.

Further Information

Applications: to apply for this PhD please use the url: https://www.gla.ac.uk/study/applyonline/?CAREER=PGR&PLAN_CODES=CF18-7316.

This project is in competition with others for funding, and success will depend on the quality of applicants. Funding includes tuition fee waiver for Glasgow University, a competitive stipend, and research support. To express interest please contact Dr Davide Dominoni (Davide.Dominoni@glasgow.ac.uk) by early January 2020, including: 1) a paragraph detailing your reasons for applying and how your experiences fit the project; 2) your CV with marks earned for previous degrees; and 3) contact info for two references. Only the best applicants will be asked to submit a full application, including two reference letters, by 16:00 on the 10th of January 2020.

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