Ornithologist Megan Buers holds up shells from a lancetooth and Pacific sideband snail, both of which are prey for western screech-owls. (Jessica Durling/News Bulletin)
Coastal screech-owls once flourished over the east coast of Vancouver Island, but now the subspecies has become a rare sight for birders.
Ornithologist Megan Buers recently presented to the Yellow Point Ecological Society about her research into western screech-owls, particularly the coastal western screech-owls, which have significant biological differences from their interior counterparts.
Both subspecies have been considered threatened for more than a decade, with the committee on the status of endangered wildlife in Canada noting that the coastal subspecies faces ongoing threats including predation from barred owls, as well as habitat loss where logging has altered the age structure of the forest. The coastal owls are physically smaller in mass, about 170 grams compared to up to 300 grams, and are also darker in colour.
"They were ubiquitous, they were everywhere at very high densities and not that long ago," Buers said. "I would say between 30-50 years ago, you could go in any forest here and you'd find them."
The Island's coastal screech-owls are heavily reliant on old growth, including coastal Douglas fir and Garry oak biomes, and as a result, while the owls exist on the east coast of the Island, the population can be more easily found on the west coast. The largest reason for the low number along the east coast, the scientist said, is land development.
"Those Garry oak ecosystems are highly degraded," she said. "If they were stewarded properly, if those native plants were reintroduced, some of that broom removed and some of the invasives controlled, we don't know whether those species would start to come back."
Buers spent her career studying the western screech-owl, shifting to the coastal variant in recent years. This past spring, she was part of a research study in partnership with B.C. Parks, Environment and Climate Change Canada, UBC Okanagan and the ministry of water, land and resource stewardship, testing the best method to tag and track the coastal owls. Due to their smaller size as well as the dense forest, there were challenges in researching the subspecies.
"[The coastal owls are] smaller to the point where you have to think about different tagging options, because if your tag is so big you need the bird to be so heavy to have the tag. The birds that we capture have to have a weight threshold to be tagged."
The owls were observed over about a hundred hectares of old growth land, foraging in bogs and intertidal systems, hunting small mammals as well as snails, salamanders, frogs, snakes and fish.
"The first question is where are they foraging, are they foraging in that stream, that riparian?" Buers said. "Are they going up to the bluffs with all that coastal Douglas fir old growth? Are they foraging in 40-year forests which have been re-planted? What habitats are they prioritizing for foraging and what do they need? That's a lot of what the tag data does."
These tags can also be used to study territorial overlap, which isn't well known, or overall home range size, meaning how much habitat a coastal screech-owl needs to thrive.
Currently, Buers believes Vancouver Island should be able to support "three or four times" the population of coastal screech owls that it has now.
Buers said she would like people to understand ecosystems aren't solitary and require bottom-up feeding. If there isn't enough prey, the owls aren't as likely to breed, aren't as likely to have as many young, and aren't as likely to be able to sustain the young.
"So if we lose our salamanders, our frogs, our songbirds then we're going to lose things like the charismatic screech-owl..." she said. "I want people to understand that it starts with the ecosystems, the native plants, the native systems that we have here and stewarding those lands and making those ecosystems healthier."
While individually, people can't do a lot to combat large-scale landscape change, beyond advocating or voting, she said individual changes can be made within backyards, such as planting native plants to attract pre,y keeping dead standing trees around when it is safe to do so, and placing nest boxes.
"There are many ways you can provide that habitat in your own backyards to facilitate more biodiversity and potentially offer more places for western screech-owls to be."