Chemicals may put barn owls at risk
Sofi Hindmarch, (currently in the U.K., returns Dec. 29; reachable via e-mail to arrange Skype call); sofi.hindmarch@gmail.com
John Elliott, SFU adjunct prof, 604.940.4680; john.elliott@ec.gc.ca (also best reached by e-mail)
Marianne Meadahl, PAMR, 778.782.4323; marianne_meadahl@sfu.ca
Rodenticides used to kill rats may be putting the Lower Mainland’s barn owls at risk, while their grassy habitats are shrinking, says a former Simon Fraser University graduate researcher.
Sofi Hindmarch completed her graduate thesis on barn owl habitat in SFU’s Centre for Ecology this spring, but is continuing her research. She is working with SFU adjunct professor John Elliott to assess the extent and impact of potential rodenticide harm.
A 2009 study co-authored by Elliott, a scientist with Environment Canada, discovered that six of 164 owls found dead in Western Canada had rodent-formulated pesticide levels high enough to kill them, causing fatal stomach haemorrhaging. As many as 70 per cent showed detectible levels of rodenticides, ingested while eating contaminated rats, in their livers.
Fifteen to 30 per cent of the owls had notable levels of toxicity that would likely have debilitated them in some way, possibly being a factor in their deaths.
Hindmarch, whose thesis focused on agricultural change and its effect on owl habitat, is working with researchers to monitor the owls’ diets, take blood samples and study their foraging behaviour.
Besides testing their blood for poison and fitting the owls with radio transmitters to determine where they are feeding, researchers, including a team of SFU biology student volunteers, are collecting pellets to see if the owls are eating more rats and mice, suggesting a higher likelihood of secondary poisoning.
The researchers hope to add barred and great horned owls to their study next year.
The data is also beneficial to conservation research, says Hindmarch. Her earlier thesis research found that highways and increased traffic volume are having negative impacts on the occupancy of potential nesting sites and that breeding success was also negatively impacted by the amount of urban development within the owls’ home range.
Last week, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) recommended that the status of the western barn owl population, which exists mainly in the lower Fraser Valley, be changed from being a species of special concern to a threatened species.
“It’s important that we get word out about what’s happening to our declining barn own population,” says Hindmarch. “Barn owls living in the Lower Mainland’s urban landscapes are making use of remaining grass areas within urban centres while those in the Fraser Valley and rural areas of Vancouver Island also face the pressure of increasing development.
“Unfortunately with increasing urbanization, including highway development, these areas are shrinking,” Hindmarch adds. “Through our work we have witnessed how owls that used to be present in urban areas are no longer there as their habitats have been rezoned for shopping malls and condo development.
“Such development is inevitable, but a little more thought into how areas become developed - incorporating more greenbelts throughout a city and allowing grass in certain areas in parks to grow longer to mimic old grass habitat, could help maintain habitat for owls and other species.”
Hindmarch also advocates for the roadway designs with wildlife corridors and visual barriers to prevent birds from flying in front of traffic, and better evaluation of how rodent infestations are managed, from waste management methods to which rodenticides are used and how they are deployed.
-30-