Williams Lake, Colombie-Britannique
This site encompasses the valley walls of the Fraser and Chilcotin Rivers from their junction, about 30 kilometres southwest of Williams Lake, westward to the mouth of Big Creek and northward to the mouth of Williams Lake River. Valley walls consist of alternating steep slopes, flat benches and occasional rocky outcrops. Mature and old growth Douglas-fir woodlands are interspersed with open grasslands, and patches of big sagebrush are common in valley bottoms. The Cariboo Plateau to the east and the Chilcotin Plateau to the west are largely underlain by Tertiary lava flows of Miocene age. There are also areas of aeolian sand dune deposits and silt and sand hoodoos. This site supports California Bighorn Sheep and the most northerly populations of Spotted Bat, Small-footed and Fringed Myotis (a rare grassland bat species).
Chilcotin Junction was designated an IBA because it was thought to support a nationally significant population of Flammulated Owls, a species determined to be Special Concern by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC; wildlife species that have been assessed as at risk by COSEWIC may qualify for legal protection and recovery under Canada's Species at Risk Act). The owls breed in the mature to old-growth Douglas-fir forests that are found along the Fraser and Chilcotin River valley walls and this species is at the northern limit of its range here. At the time the site was designated, it contained one of the highest known concentrations of Flammulated Owls in Canada (100 pairs were estimated for the entire Cariboo Region, van Woudenberg 1999). An intensive survey of areas throughout the IBA in 1995 detected 22 calling Flammulated Owls within the IBA boundary (Roberts and Roberts 1995). In 1996, a follow up survey of similar areas found nine confirmed pairs and a further six singing males (a total 24 owls) (Waterhouse, M. pers comm.). A volunteer Nocturnal Owl Survey conducted in early June 2013 detected 13 calling Flammulated Owls along four routes within a small portion of the IBA. It is very likely that the actual numbers of Flammulated Owls within the IBA are higher than the numbers reported here, but an accurate estimate is not possible due to the survey methodologies used and the fact that many, but not necessarily all, singing males represent pairs. More consistent surveys are needed to better quantify the number and distribution of owls within the IBA and monitor change over time.
Other Species of Interest
Special Concern (COSEWIC) Long-billed Curlews breed annually in Chilcotin Junction IBA. The BC Ministry of Environment led a three year volunteer based survey for Long-billed Curlews between 2002 and 2004, which demonstrated that the Cariboo-Chilcotin region supported a minimum population of 211 Long-billed Curlews (VanSpall and Steciw 2005). Provincially rare Prairie Falcons nest and hunt in the IBA. Provincially vulnerable Sharp-tailed Grouse columbianus subspecies also nests within the IBA. Threatened (COSEWIC) Lewis's Woodpeckers and Common Poorwill breed or are regularly detected in the IBA, which is the northern extent of their range. Provincially vulnerable Dusky Horned Lark merrilli subspecies also occur in the IBA.
The greatest potential threats to Flammulated Owls within this IBA are habitat loss and degradation due to forest harvesting, wildfires/fire suppression activities, and forest health issues such as drought and insect infestation.
Interior Douglas-fir forests will be under increasing logging pressure as the forest industry shifts from salvaging mountain pine beetle-killed pine to green timber in this biogeoclimatic zone. Much of the forested portion of this IBA occurs in mule deer winter range. Partial-cut logging under General Wildlife Measures under the Forest and Range Practices Act promotes uneven-aged stand structure and retention of the oldest stems and might be complimentary to maintaining Flammulated Owl habitat. Stand tending treatments (thinning) that markedly reduce the density of Douglas-fir thickets, however, might compromise habitat quality (van Woudenberg 1999). Cavity trees are at risk of being cut as danger-trees during forestry activities. Much of the forested habitat is situated on steep slopes that are unfavourable to logging activities. There are no tree cutting restrictions on private land within the IBA and so mature trees on private land are at risk of being cut.
Wildfire poses a big risk to these forests. While old Douglas-fir trees are resistant to low intensity fires, the terrain and fuel abundance in these stands increases the risk of fire-induced mortality. A wildfire completely consumed mature Douglas fir forest only a few kilometers west of the IBA boundary in 2010. The fire suppression tactic of creating fire guards (exposure of mineral soil) with heavy equipment could create linear swaths of disturbance in both grassland and forest environments and introduce weeds.
Application of Bacillus thuringensis kurstaki (Btk) aerial sprays to control Western Spruce Budworm infestations would reduce but not eliminate lepidopteron prey availability for Flammulated Owls. A minimal area along the upper topographic benches within the IBA boundaries was treated in 2013. The budworm infestation appears to be waning and the Regional Entomologist for the Cariboo Region is committed to avoiding treating areas within the IBA boundary (Jodi Axelson, pers comm.). Old Douglas-fir trees are susceptible to Douglas-fir bark beetle-induced mortality. Douglas-fir growing on southern exposures are potentially at risk of drought-induced mortality.
The southern part of the site (4,573 ha) is protected within Junction Sheep Range Provincial Park. Two small Ecological Reserves overlap with the IBA (Big Creek Ecological Reserve and Doc English Bluff Ecological Reserve). Some of the IBA overlaps with Old Growth Management Areas (OGMA), in which forest harvesting activities are very restricted.
The last comprehensive Flammulated Owl survey was conducted in 1993-1996 by the Ministry of Forests. Local volunteer Caretakers established four Nocturnal Owl Survey routes within the IBA in 2013 and plan to survey the routes annually to confirm presence and locations of owls within the IBA. A breeding bird survey transect crosses the IBA. The Ministry of Forests, Lands and Natural Resource Management has recently monitored Sharp-tailed Grouse populations and grassland habitat within the IBA.