British Columbia Nocturnal Owls Survey

Birds Canada
https://www.birdscanada.org

British Columbia Ministry of Environment
http://www.gov.bc.ca/env/

Project name: BC & North Nocturnal Owl Survey

Goals : The Nocturnal Owl Survey and Western Screech-Owl Survey monitor trends in owl populations through road-based methods similar to those used in the Breeding Bird Survey. By collating existing data on NatureCounts and managing the database, the programs make survey results available and ready for analytical purposes. They aim to investigate population trends and factors affecting owl occupancy and detection probability.

Dataset summary : The British Columbia-Yukon-Northwest Territories Nocturnal Owl Survey (NOS) consists of roadside surveys. All protocols have a silent listening period (2 min) at the beginning, followed by call-playbacks for some protocols. The dataset includes survey station locations, owl species, number of owls detected, environmental and anthropogenic conditions (e.g., noise and light) affecting detection probability, binned distances and direction of initial detection, observer ID, date and time of survey, and survey notes among other details. Regarding the Western Screech-Owl survey dataset, it was developed as an initiative of the Pacific Megascops Research Alliance (PMRA) and was made possible by volunteer effort from PMRA, funding from ECCC’s Habitat Stewardship Program (HSP), and administrative and technical support from Ausenco Sustainability North America (previously Hemmera Envirochem). The Western Screech-Owl Survey also consists primarily of roadside surveys including a silent listening period (2 min) at the beginning, followed by call-playbacks which are longer in duration (15 min) compared to the NOS playback to align with British Columbia Research Inventory Standards.

Status : Active

Year started : 2000

Years (comments) : 2000 for the Nocturnal Owl Survey program, 2021 for Western Screech-Owl Surveys

Season(s) and frequency : Annually and ongoing

Frequency : Annually

Geographic area covered : British Columbia, Yukon and Northwest Territories. The protocol “Southern Coastal BC” includes sites on the Lower Mainland, Sunshine Coast, Vancouver Island and Gulf Islands (surveys in February). The protocol “Interior BC, YK, & NWT” includes sites in the following regions: Okanagan-Similkameen (March), Thompson-Nicola (March), Kootenays (March), Cariboo-Chilcotin (April), Northwest BC (April), Northeast BC (April), Yukon (April), Northwest Territories (April). The protocol “Western Screech-Owl Surveys” includes sites in coastal British Columbia: Vancouver Island and other coastal islands, mainland coast and east to the Coastal Mountains (late February to April).

Type(s) of habitat : all rural and forested habitats

Primary species covered : All owl species are targeted (Barn Owl, Flammulated Owl, Western Screech-Owl, Great Horned Owl, Northern Hawk Owl, Northern Pygmy-Owl, Burrowing Owl, Barred Owl, Spotted Owl, Great Gray Owl, Long-eared Owl, Short-eared Owl, Boreal Owl, Northern Saw-whet Owl). Surveyors also help record grouse and nightjar species.

Sampling Design : Randomly selected routes/transects. Monitoring stations or stops are spaced 1.6 km apart (800 m apart for Western Screech-Owl Surveys) and located primarily in forested/rural areas. Western Screech-Owl Surveys call for repeated surveys within the breeding season to assess detection probability in addition to occupancy.

Field methods : Two volunteers drive pre-determined route, stopping at fixed intervals along roadside. At each stop, 2-minute listening periods. The protocols “Southern Coastal BC” and “Western Screech-Owl Surveys” use call broadcasts (using the Western Screech-Owl territorial call) to elicit the response of owls. Surveyor identifies and records all owls seen or heard during each listening period. Surveys begin one half hour after sunset during a single evening in spring and take 1 to several hours to complete (not including travel time to and from the survey route).

Analysis methods : Counts are used for statistical analysis of population trends, occupancy estimates, habitat associations, possibly population numbers. Trends are calculated every 10 years or so. Summary reports and annual newsletters are provided and sent to partners and participants.

Data validation : Data reviewed on paper dataforms or online forms, and uploaded into an Access database, accessible on request. Data are summarized for reports and submission to provincial database (BC’s wildlife species inventory). Data are formatted into BMDE format.

Data caveats : Data users should pay attention to data collected with or without call-playback, and implications for variation in survey effort. For Western Screech-Owl Surveys, data users should pay attention to data entered under “minute playback stopped” for the same reasons.

Publications : For the general program: https://www.birdscanada.org/bc_yk_nwt_owls For Western Screech-Owl Surveys specifically: https://www.pacificmegascops.org/methods

Users of the information : Birds Canada, BC government biologists, YT, NT and CWS biologists, other conservation organizations, raptor biologists. Data are used for provincial databases, state of environment reports, environmental assessments.