Perch deterrents in Grasslands National Park

Imagine all the species that call the vast prairie grasslands home. Now imagine that you are specially adapted to one of the most endangered biomes in the world. In Canada, greater sage-grouse have seen more than a 90% decline over the past 40 years, and they occupy about 7% of their historic range. As a result, these birds are listed as Endangered under the federal Species at Risk Act (SARA).

Since 2023, only one lek remains active in Saskatchewan and it is located in Grasslands National Park’s East Block. A lek in the West Block was last active in 2022, however wild greater sage-grouse are still observed in other areas of the west block occasionally. The lek in the East Block has undergone declines in the last few years making it vulnerable to also going inactive.

In addition to these challenges, imagine you are also vulnerable to non-traditional predators. Great-horned owls are a known predator of adult greater sage-grouse. They would have been in low abundances on the prairies historically but have benefitted from the human infrastructure that is now present, such as planted trees and tall infrastructure they can perch on, such as road signs. This makes limiting predator advantages through human infrastructure particularly important.

Grasslands National Park started a perch deterrent program in 2017. The overarching goal of this program is to mitigate the risk of predation of greater sage-grouse by avian predator. This is tricky when structures that are used as perches, such as road signposts and signs themselves, cannot be removed due to their need for visitor safety and park management.

Different research designs have been implemented to study the effectiveness of perch deterrents. The initial Perch Deterrent Effectiveness Study in 2018/19 used a before and after model. In 2018, no perch deterrents were installed, and remote cameras were set-up to detect birds perching on the signs. In 2019, commercially available perch deterrents were installed on signposts and remote cameras again were set-up. This allowed staff to compare the number of perching events and duration of perching events when perch deterrents were present to when perch deterrents were absent.

The main conclusions resulting from the study were that the commercially available perch deterrents were ineffective against predators of adult greater sage-grouse and that a new post-top perch deterrent be developed.

Through subsequent effectiveness testing, the post-top perch deterrent that was identified as being effective against large raptors is a large metal pyramid that covers the post-top with a tall metal chopstick protruding from the centre. The metal chopstick prevents large raptors from being able to centre themselves over the tip of the pyramid. Additionally, the metal chopstick is too smooth for large raptors to grip. The owls were unable to gain stability and immediately gave up on perching on the metal chopstick variant of the deterrent. As a result, the park has been working at installing the metal pyramid with metal chopstick post-top deterrents

Keep an eye out for these funny looking contraptions the next time you are in the park, and as always, if you see any wildlife remember to report your sightings to park staff or to the iNaturalist app.