Acoustic Bat Monitoring at a Southern Alberta Wind Farm

We deployed acoustic monitoring stations throughout a wind farm in southern Alberta to determine general and species-specific bat activity during spring and fall migratory periods, as well as the summer breeding period (March... [ view full abstract ]

We deployed acoustic monitoring stations throughout a wind farm in southern Alberta to determine general and species-specific bat activity during spring and fall migratory periods, as well as the summer breeding period (March through October). The wind farm is located along a major migratory pathway for birds and bats, and therefore poses a high mortality risk to wildlife. The wind farm has been under post-construction monitoring for two consecutive years, which includes weekly carcass searches and seasonal carcass persistence and searcher efficiency trials to assess mortality rates at each turbine. However, little is known about how the area is utilized by Alberta’s bat species in general throughout the year. Carcass searches only provide information about mortality rates, which may not be a good indicator of activity levels of different species. Each species has a unique ecology, which may lead to biases in which species are affected by wind turbines (e.g. forest species vs. open field species, gleaning species vs. species that hunt on the wing, etc.). Through the use of acoustic monitoring techniques we are able to provide a glimpse of the activity levels of different species of bats throughout the year, including bats that breed in area, as well as bats using the area as a migratory pathway. This information could be useful for determining when threatened or endangered species are present and at risk in the area. This includes specific times of the year and hours of the night where they are most active, which could be useful for informing mitigation decisions. We used Wildlife Acoustic Song Meters to record bats on a nightly basis from sunset to sunrise every night at five locations. We analyzed data with Kaleidoscope Pro (Wildlife Acoustics) and Analook (Titley-Scientific) software packages. Bat calls were identified using both autoID and manual ID techniques. Preliminary results show that different species tend to arrive and have peak activity levels at different times of year. Silver-haired bats and big brown bats tended to arrive first to the area (April) and had peak activity levels in August and September, whereas Myotis spp. bats appeared slightly later (May) and peaked in July. Hoary bats also arrived early (April) and peaked in July. Activity dropped steeply in October, with no bats detected past October 17th. Peak hourly activity throughout the night varied depending on the month, but in general was highest from 21:00 to 01:00. Bats were active for a longer portion of the night during the height of the breeding season (22:00 to 04:00 in July) and during the fall migration (21:00 to 05:00 in August and September). These data are useful for determining baseline activity levels of different species of bats in southern Alberta, an area where wind farm development is growing quickly. Mortality data from carcass searches alone may not be enough to make informed decisions about future wind farm developments and mitigation techniques, and acoustic monitoring could be a useful passive technique to help us understand and protect Alberta’s bats.