In 2021, the Friends of Cortes Island received funding from the Habitat Stewardship Program to seek out the elusive Western Screech Owls. This research is being guided by the Pacific Megascops Research Alliance, and biologists from the Ministry of Water, Land and Resource Stewardship are part of the team. The first season was spring 2022.
According to Cortes Island biologist Sabina Leader Mense:
“We know they’re here, why aren’t they talking to us? The research results we got: not a hoot, not a peep, not a call. Nothing but lots and lots of questions.”
“The autonomous recording units, the ARUs, are just being analyzed now. Whatever was picked up by them during February and March of this year, that information’s coming to us within the next month.”
“FOCI’s been very successful at getting funding, again from the Habitat Stewardship Program, for two more years. So we’ll be going out in February and March 2023, and we will have the information from the autonomous recording units. It is really important to know if there were Western Screech Owls calling at times when they just simply weren’t answering us.”
“People are seeing the birds in the Discovery Islands. While we were doing transects down here in February and March, there were Western Screech Owls up on Sonora Island calling in behind some greenhouses in the Diamond Bay area. There was a Western Screech Owl predation by Ravens observed at Port Maurelle on Maurelle Island.”
Cortes Currents: What about Read Island? Were there any sightings or hearings?
Sabina Leader Mense: “The researchers on Read ran transect lines. They had no calls in return, just as we had.”
“Possibly we have too many predating Barred Owls here and they have to remain quiet. Who knows? That’s why you do research and ask questions and get out there, because we weren’t able to answer those questions. So we just go at it again.”
“This year FOCI secured the monies for purchasing our own autonomous recording units. Last year we borrowed from the Ministry, and so this year we have purchased 10 of these ARUs and 3 ARUs will be going out to each of our partnered islands: Sonora, Maurelle, and Read Island.”
“We start in February and March during the breeding season of the Western Screech Owl.”
“We affectionately call them WESOs, bird abbreviations are always the first two letters of each of the common names.”
“This is a sweet little owl, about eight inches in length. It was historically very abundant. It’s a strictly nocturnal owl, so only active during the night. If you spread your fingers from your thumb to your little finger, that’s the length of this small little owl. Stocky body; square head; conspicuous ear tufts. It has excellent camouflage. It’ll either be grey or brown streaked on the belly and bright yellow eyes.”
“It was probably never very abundant on Cortes Island, though it historically was abundant from Baja all the way up to Alaska. What we have is are a lot of different subspecies of the Western Screech Owls.”
“We have historical records of Western Screech Owls here from the 1980’s on Cortes. Channel Rock, for example, was a big area. We have nesting records from areas close to that around the Gorge. The last documented observation was an audial observation that I heard up in the northern reaches of Cortes Island in 2017.”
“We’ve had these dramatic population declines of Western Screech Owl, throughout their range, over the last 20 years. The big question is why the decline?”
“One of the big reasons for that decline could be the increased predation by the Barred Owls on the Western Screech Owls. Everybody knows the Barred Owl. It’s the owl that everybody hears calling out ‘Who cooks for you’ every night on Cortes. This is an owl that lived on the East Coast and somehow managed to work its way across to the western coast of North America. It began moving west in the sixties. It arrived in Vancouver, on the coast here, sometime in the 1970s and 80s. They’re a big owl, 21 inches high and they eat all our small owls, including the Western Screech Owl. So this increased predation is one component of the decline of these birds.”
“Another component is loss of habitat. The Western Screech Owl is a forest owl and it’s very dependent on the complex structure of old forest. Everybody in BC knows that we have only pockets of old forest or old growth left anywhere in the province, let alone on Cortes Island.”
“The other component leading to its decline are the decline in its specific food sources. Amphibians are under assault with all kinds of disease and habitat loss. So, the amphibian food source is going down. Insects are very important to the Western Screech Owl, and that is going down as well.”
“What we need to do and what we’re doing, is going out there to determine how many are actually out there? Historically, where are they? They’re in forest areas. Well, they’re being beaten out of those areas or bullied out of those areas by the Barred Owls. They need to seek refuge.”
“One of the very interesting habitats or places that they’re going to seek refuge is in bog habitat. Some of the studies that have been done on the Bogs in Northern Vancouver Island, like Nawhitti Bog, where they have found these incredibly high concentrations of Western Screech Owls.”
There, they have all kinds of nesting cavities in the trees. Old forest surrounds most of these bog areas and wasn’t logged because it got too wet and too close to the bog. There’s lots of prey species, caddis flies and amphibians in the bog. So interestingly, we’re finding these really high densities of Western Screech Owls in Northern Vancouver Island bogs.
“No one ever saw Western Screech Owls in a bog before, but the bog provides really nice protection from predators. No Barred Owl is going to place himself up in the middle of a bog habitat. They’re always around people in disturbed areas picking off rats. So you are not going likely to have Barred Owls up there.”
“The reason the Ministry has interest in our work and the Pacific Megascops Research Alliance has interest in our work is because Cortes Island is part of the Discovery Islands and the Discovery Islands form this amazing bridge. It’s like stepping stones, from the mainland to Vancouver Island. A lot of really interesting things happen here, with respect to species and speciation.”
“The Discovery Islands represent one of the strongest, largest patches of unfragmented, what’s called Coastal Western Hemlock, xeric maritime one (CWHxm1). This is just a biogeoclimatic zone that’s determined by all those things, the biology, the geography, and the climate. We have this zone that is unique. It is the zone that surrounds the Salish Sea. The majority of that biogeoclimatic zone, CWHxm1, is disturbed, destroyed and impacted. Here in the Discovery Islands, we have these unfragmented areas like the whole northern reaches of Cortes. We’re also working together with Read Island, Maurelle Island, and Sonora Island, where there is also less impact, less fragmentation. That’s why the researchers are really interested in engaging with us. That’s why we are engaged.”
“They think that possibly we have fewer Barred Owls in this area. They want to know where the Barred Owl overlap happens with the Western Screech Owls. That’s why we’re engaged in the research and the research is standardized methodology used across the province, and up and down coastal BC.”
“We basically have two methods to determine if Western Screech Owls are in the neighborhood.”
“One is called ‘call playback.’ Call playbacks are where we go into the forest during the breeding season, February and March, and we play the call of a male Screech Owl. They’re very territorial and if there’s a male screech owl out there, he is going to call back, ‘what the heck do you think you’re doing in my territory?’ — and bingo, we know we have a Western Screech Owl.”
“The second method we use in areas where we can’t physically walk, is to put out ARUs, or little song meters, that are programmed to come on an hour and a half before dusk and stay active until an hour and a half after sunrise. They’re programmed to come on for three minutes every 12 minutes through that time period from dawn to dusk, and they passively record anything that’s calling out there. So a Western Screech Owl, a Pygmy Owl, a Saw-whet Owl, a Barred Owl, a Wolf: whatever is calling in the middle of the night.”
“In 2021, Friends of Cortes Island received funding from the Habitat Stewardship Program to support this research on Cortes.”
“In the spring of 2022, we established five transect lines. We walked three of them on land. For example, we would walk from Carrington Bay Road, from the parking area where you enter the Children’s Forest, to the western end of Blue Jay Lake. Every 800 meters we would be playing the call of the male Screech Owl and listening for a response.”
“The northern reaches of Cortes don’t have a lot of trail systems, it’s bushwhacking. You can’t do that in the middle of the night walking along trying to make calls.”
“So we had this brilliant idea of making transects down the center of Von Donop Inlet and Carrington Bay. Two of our transects were water transects, where we overnighted with a sailboat and we would go out in the night with a skiff. It’s a lot of fun. February was snowy this year. The head of Von Donop Inlet was frozen. We had great adventures up there, but we got the work done. The interesting thing is, we came back from those five transect lines, which we visited three times during the breeding season, every two weeks and we did not hear a single hoot or call from a Western Screech Owl. That got all the researchers scratching their heads going, ‘why weren’t they talking to you? Why were they quiet?’”
“We had Western Screech Owls up on Sonora Island; we had Western Screech Owls observed later on Maurelle Island: So they’re there. Is the predation pressure so great that they don’t dare to speak out? And if they don’t speak out during the breeding season, how do they find their mates to actually breed?”
“What we did find and was a surprise to us, we heard Barred Owls virtually on all of our transects in our most isolated areas, like at the bottom of Wiley Lake, Robertson Lake, Cork Lake. We had Barred Owls calling everywhere. That was not a good sign.”
“Maybe our Western Screech Owls have learned to use a different dialect and they don’t respond to what we were using on these broadcasts?”
The search will resume when mating season begins, two months from now.
Top image credit: Western Screech-owl on north Vancouver Island – Photo by Guy Monty, taken during surveys funded by the Ministry of Water, Land and Resource Stewardship
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