Introduction
This report concerns the Nothern Spotted Owl. British Columbia is the only province of Canada that harbors this species. Their habitat is composed by mature, old-growth and late successional forest.
Background of the research project
This species is considered “endangered” since 1996 by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). A study realized in 2002 estimated that the historical population in British Columbia counts 500 breeding pairs. The biggest threat for Spotted Owl seems to be their habitat availability which has been altered by several factors including among others hydroelectric development.
The study was conducted during the year 2004. The purpose was to survey and better understand Spotted Owl’s population distribution, occupancy, breeding, activity, population density and corridors that allows connectivity between discrete populations. All information and data collected could help for management and recovery strategies. Different restorations goals have been expressed by the Bridge Coastal Fish and Wildlife Restoration Program (BCRP).
Methods and study area
The study area was situated within the BCRP study area, in the Carpenter, Seton, Anderson and Bridge River watersheds. Due to diverse altering factors this area is composed of a mosaic of forests. Thirteen transects were determined. They were located in areas featuring suitable Spotted Owl habitat. Their disposition was chosen according to previous data, modeling and detections to establish uninterrupted covering of the area and target habitat of interest.
The method used to determine the species distribution is based on acoustic lure and follows the Ministry of Water, Land and Air Protection (MWLAP) survey standards and protocols. Along the transects, from established stations, recorded mature Spotted Owl territorial calls were emitted, all in the same time to reduce risk of repeated detection of the same owl. Those recorded calls usually attract territorial resident males that call in return and approach the emitting station. Survey standards are used to determine if an area is “occupied” or “vacant”. When results from those surveys indicate that the area is occupied, a breeding survey can be done. This survey is based on a visual method during day-time and aims to establish pair status (pair or solitary individual), breeding status (pair nesting or not) and nest location. Habitat data are collected for each day perch or nest location. If other raptors or Red- or Blue-listed flora and fauna were observed during the surveys, data were also collected. Three repetitions of these surveys where done for each transect.
Results
During this study, 39 owls from different species were observed, including Blue-listed species. Only 18 active Spotted Owl sites were determined even though more might exist. For one of those sites, near the Township of D’Arcy, along the East side of Anderson Lake, no previous detection of Spotted Owl had been detected. This site is great quality habitat for Spotted Owl. However only one call from adult male could be heard in this spot and the breeding survey did not lead to results in the area up to now. The breeding surveys on the other transects did not allow to detect any nest or day perch.
Informative lectures were presented in Lillooet and Victoria to educate local communities about Spotted Owl project and efforts of the BCRP. Successful relationships were made with those communities.
Discussion
This one-year survey’s results shows a low Spotted Owl detection frequency (3%) which seems confirmed by a larger inventory extending across the whole Province of British Columbia from 2004. Due to repetition of the surveys, the same owls were probably detected several times on the same transect. Repeated detection were used to estimate residency status in the area. Even the single Spotted Owl detection is relevant for recovery plans considering the low population rate of the species and the connectivity role of the area where it was detected. Logging and hydroelectric operations transform the habitat through forest clearing and fragmentation. This habitat change causes Spotted owls to be endangered by destroying nests as well as nesting and foraging habitat while supporting two other owl species that are competitors and predators of Spotted Owls. Results obtained for other owls species observations are really interesting and can be used as a basis for larger survey but can not be used to deduce or conclude anything about their population as this survey did not specifically focus on them.
Management recommendations/Suggested action
Four main recommendations are exposed in this report :
- First, the Seton-Anderson watershed including the Anderson lake where the single Spotted owl has been detected should be protected as it is an important connectivity corridor that allows genetic exchange between active populations.
- Second, in order to avoid further suitable Spotted Owl habitat loss it is essential that the different independent power producers and the province collaborate to share as much as possible the hydroelectric transmission corridors to limit the development of new ones.
- Third, the same survey should be done again for a second year to confirm that MWLAP protocol and standards have been respected and to confirm and raise information about the single Spotted owl detection.
- Fourth, new surveys targeting the other owl species especially the Blue-listed ones detected during this survey should be carried out to acquire more information that could be used for management plans.
Conclusion
Information collected by this study is important to improve the knowledge about this endangered species. The information will help to make management and conservation decisions and to implement the restoration plans of BCRP for the Seton and Bridge Watersheds.
- Source Vicky Young. Apr 2004. Report: Northern Spotted Owl Inventory and Monitoring - Project #: 04.W.Br.03. Prepared by Eco-Vision Consulting, for the Ministry of Water, Land and Air Protection. Available at : https://a100.gov.bc.ca/pub/acat/documents/r40727/04.W.Br.03_spotted_owl_1388774177903_8773771279.pdf [Accessed 03/2021].