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What does a detection mean? Spatial and behavioural context improves the use of passive acoustic monitoring for the conservation of a wide-ranging bird

  • Author / Creator
    Knight, Elly C
  • The culture of ecology is shifting towards collaborative, integrative approaches that use ‘big data’ to solve big problems. Passive acoustic monitoring (PAM) has the potential to play a role in this new paradigm because it uses in-situ autonomous recording units (ARUs) to collect a permanent archive of audio recordings. PAM research groups across the world are collecting vast amounts of acoustic data that could be integrated to understand ecological phenomena at a global scale; however, there are several hurdles that must be overcome. First, accurate algorithms that automatically scan acoustic recordings (hereafter, “recognizers”) are required to efficiently determine the species detected within the recorded soundscapes. Second, an understanding of the context of these recognizer-processed datasets is essential for data integration and can improve how recognizer data is used in ecology. Unlike survey data collected by human observers, recognizer data is typically treated as a binomial dataset with minimal context beyond date and time of observations. In this thesis, I demonstrate the importance of spatial and behavioural context of recognizer data using the common nighthawk (Chordeiles minor) as a model species. The common nighthawk is a crepuscular and highly mobile bird species that consumes aerial insects and is declining in most parts of its breeding range across North America. First, I demonstrate a fundamental principle that is crucial to using and integrating recognizer data. I show that the classification probability of species detections reported by a recognizer is related to detection distance, and that the classification threshold applied thus defines the survey area. Understanding this spatial context is necessary for estimating density from recognizer data and for integrating multiple datasets. Next, I show that the behavioural context of recognizer data can provide important insight into ecological analyses. I use VHF telemetry to show that the wing-boom display of the common nighthawk is a territorial signal, which I then use to study behaviour-specific habitat use of this species in the boreal forest. I use the wing-boom to separate territorial from home range behaviour and show that the scale that most strongly predicts habitat use corresponds to the movement range of that behaviour. I then use the wing-boom to separate territorial from extraterritorial behaviour to confirm that the common nighthawk is a ‘disturbance specialist’ species in the boreal forest, but only for nesting territories. Finally, I combine these spatial and behavioural contexts to demonstrate a novel method for density estimation that can be applied to single ARUs at broad spatial scales. The goal of this approach is to improve regional, national, or range-wide population estimates, especially for regions that are poorly covered by human surveys or for species that have large home ranges. Together, this density modelling approach and the spatial principles my thesis presents will facilitate future integration of PAM datasets collected with varying methodologies as well as with other data types. The behavioural context component of my thesis encourages PAM users to ensure they put their recognizer data into appropriate ecological context, particularly for wide-ranging species. Collectively, the ecological inferences in my thesis provide a major advance in understanding common nighthawk ecology in the boreal forest and the tools developed will help future research and conservation of this enigmatic species.

  • Subjects / Keywords
  • Graduation date
    Fall 2021
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.