Periodic Reporting for period 1 - GROUP MOVEMENT (Vocal and visual mechanisms behind coordinated group movement)
Reporting period: 2018-05-15 to 2020-05-14
Contact calls are thought to be especially important in habitats with visual barriers like forests as calls travel a lot farther in those types of habitats and can provide information about many different individuals at one time. While vocal coordination of group movement in mammals is somewhat understood, evidence regarding how calls function to maintain group cohesion and coordinate group movement in social bird species is rare. To determine if anthropogenic noise masking contact calls can impact flocking behaviour, the mechanisms behind how these calls are used by individuals to coordinate group movement must be understood. To accomplish this, it is necessary to track not only the position of each individual in the flock, but to determine which individuals are calling from where and when. Combining this with controlled environmental manipulations of both the acoustic and visual environment, we can ask targeted questions about how flocks change their group behaviour and calls to maintain flock cohesion and coordinate movement.
Our objective with this project is to determine how anthropogenic noise may be causing declines in species diversity through masking contact calls. To accomplish this our goal is to answer the following two questions: (1) how to individuals and groups use calls to affect the behaviour of the group and coordinate group movement, and (2) how does the visual and acoustic environment affect the use of vocal coordination of group movement.
We conducted environmental manipulation experiments to address both questions. Each flock experienced four environmental conditions: good (silent, visually open), visually poor (silent, visually restricted), acoustically poor (noisy, visually open), and poor (noisy, visually restricted). To create these different environments, we used infrared-invisible clear and opaque barriers to control how far individuals could see when perching or foraging and playbacks of silence or road noise (which is often encountered in the wild) to control how easy it was to hear one another. By examining movement and calling data from the good condition, we will determine how individuals use calls to coordinate group movement in ideal conditions. By examining movement and calling data from the visually poor and acoustically poor environments we can determine the effects of reducing visual and acoustic contact separately in a controlled setting. Finally, by examining movement and calling data from the poor environment we can determine the effects of anthropogenic noise in many of the habitats birds live in (e.g. forests, etc.).
The sudden unavailability of one tracking method (acoustic tracking for positional location) necessitated a further development and piloting of the visual tracking method (VICON), resulting in a year delay. Therefore, while we have extracted all the data from the experiments, we are still in the process of developing more robust methods to process the raw positional data into 3D individual tracks and fine-tune the acoustic localization methods for starling calls. However, we continue to work towards robust data for analyses examining how individuals coordinate group movement using calls and the effects the visual and acoustic environment has on those calls. We are dedicated to looking at these results as we need to understand how anthropogenic noise affects group movement and contributes to species diversity loss before we can find solutions.
With the data from these experiments we will be able to include visual, acoustic, and physical impediments into models exploring the mechanisms of group movement that currently exist. Hopefully this will improve the ability for future models of group movement to incorporate different or multiple modes for individuals to maintain contact and bridge the gap between models’ empty space where theoretical movement occurs and ecological realities of cluttered space where group moving species exist. By better understanding both how individuals use calls to coordinate group movement, and how anthropogenic noise affects a group’s ability to do use these calls to maintain cohesion and coordinate, we hope to be able to develop solutions for masking problems arising from anthropogenic noise.