Inventory and Monitoring of the Northern spotted, Western Screech and Flammulated Owls

The Northern Spotted, Western Screech, and Flammulated Owls are on the list of Canada’s Species at Risk. Identification of species distribution and habitat use is imperative to the conservation of biodiversity and and required habitat of rare, threatened, and endangered species. .The research of the Northern Spotted Owl in years between 1992 and 2001 showed that the population declined 49% in that time interval. By the year 2004 monitoring found only 17 active sites in the study area. It is estimated that at least 28% of the reduction was influenced by agriculture, urban development or resource extraction. Barriers such as train track and roads also contributed to the reduction in ideal habitat. The goals of this study were to monitor and observe these three threatened owl species suing call play back techniques to estimate the number and distribution of individual territories within the Bridge River, Seton and Coquitlam watersheds.

The most effective monitoring for these threatened and endangered species is call playback. Areas that were of typical owl habitat or showed owl territories in past studies were selected a priori.  Using call playback techniques field technicians are able to estimate the distance between the calling owl and the listener.  With this data territory size and distribution could be calculated.

Owls are most territorial from April until August, and especially earlier in this range during breeding season.  After randomly selecting locations for the 2-6 km long transects within suitable areas, survey points were placed at regular intervals along each transect.  At each survey point recorded owl calls were transmitted through a speaker system a number of times with intervals in between during which the field technician listened for responding owl calls.  There were on average 17 survey points per transect.

The number of owl observations is not accurate to the actual number of owl territories/sites as resident owls were likely to be discovered more than once during the repetitions running along each transect. To fix any territory number is based on owl home range sizes and present call events. Survey locations were determined by using Terrain Resource Information Management (TRIM) data, known habitat suitability modeling and existing known owl detections within the identified watersheds (Carpenter Lake, Bridge River, Anderson Lake, Seton Lake, Coquitlam, Carpenter Lake, Gold Bridge, and Lillooet watersheds).

132 owls were detected during the field portion of this study, and the highest rate of owl calls observed was by the Flammulated owls at 0.7 owls detected per hour. The Barred Owl was the most common owl detected at 39% of all detections. In descending order of abundance was Flammulated owls at 26% of detections, Great Horned owl at 22%, Northern Saw-whet Owl at 7% and Western Screech Owl at 7%

The research results from this study have been published to raise awareness about the statuses of local threatened and endangered species and how local groups and organizations can facilitate stewardship.  Future direction that was suggested in the report includes future studies regarding the effects of habitat fragmentation on the population declines of the Northern Spotted Owl in the province.  It is also recommended that future management plans take into consideration the sensitivity of these owl species to habitat modifications.

  • Source Doris Hausleitner, Vicky Young. November 2005. Inventory and Monitoring of the Northern Spotted, Western Screech and Flammulated Owls. Prepared by Seepanee Ecological Consulting and Eco-Vision Consulting, for British Columbia Conservation Foundation. Available at : [Accessed 03/2021].