Recently published research by Julia Shonfield, a PhD student in Erin Bayne’s lab:
Shonfield, J & Bayne, EM. 2017. The effect of industrial noise on owl occupancy in the boreal forest at multiple spatial scales. Avian Conservation and Ecology, 12 (2): 13. doi: 10.5751/ACE-01042-120213.
Photo 1 – Barred Owl, one of three species of owls I’m studying in this project.
Energy development creates several types of disturbance that can impact wildlife, including the physical footprint of the infrastructure and the chronic noise from facilities. Chronic noise sources can pose problems for animals that communicate vocally because the noise can mask important signals.
Owls use vocal communication to attract mates and defend territories, and hunt by listening for acoustic cues made by prey (e.g. mice scurrying along the forest floor). Chronic noise has been shown to negatively affect owl hunting success and ability to detect prey. So this suggests that noise can have negative effects on owls, but we don’t know whether this affects where owls are distributed on the landscape.
For part of my PhD work in Erin Bayne’s lab, I wanted to know if owls avoid chronic industrial noise sources. To get at this question, I used autonomous recordings units (ARUs) to survey for owls.
Photo 2 – An autonomous recording unit (ARU) all set up and ready to record some owls calling.
These units were programmed to record every hour for 10 minutes throughout the night for up to 2 weeks at each site. I surveyed at three types of sites in northern Alberta:
- Chronic noise sites – with a compressor station or oil processing facility at the center of the site
- Intermittent noise sites – with a road bisecting the site
- No noise sites – with no traffic noise or industrial noise sources
I processed the recordings using recognizers I developed in a program called Song Scope to detect the calls 3 owl species found in northern Alberta: Barred owls, Great Horned owls and Boreal owls.
Photo 3 – An example of the call of the Great Horned owl, shown as a spectrogram in the program Song Scope.
Once I obtained the owl detections from the recordings, I analyzed the data using occupancy models. I analyzed the data at two spatial scales, at a larger scale that is roughly equivalent to an owl’s home range size, and a smaller scale representing an area within a home range.
Photo 4 – The two spatial scales that I analyzed to determine owl occupancy. The small white circles are ARU stations.
I found that the occupancy of all three owl species was not different between sites in the three noise categories at the larger scale. I also found that at the smaller scale, owl occupancy was not affected by industrial noise levels.
Photo 5 – Results of the owl occupancy models at the larger scale, showing occupancy estimates for each of the three noise categories of sites.
At the spatial extent I assessed there was no evidence of noise effects on owls, suggesting that noise is not likely to have negatively affected owl populations at current noise levels.
- Photos and blog post written by Julia Shonfield