Forest Investment Account (FIA) - Land Base Investment Program
FIA Project 6752003

    Northern Goshawk Nest Monitoring in TFL 37
Project lead: Sandford, Jeff (Western Forest Products Inc.)
Contributing Authors: Manning, E. Todd; Chytyk, Paul
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Land Base Investment Program
The coastal subspecies of Northern Goshawk, the (Accipiter gentilis laingi), is an uncommon forest raptor that is currently on the British Columbia Red List as a candidate species for Endangered or Threatened status. It is also an Identified Wildlife Management Species under the BC Forest and Range Practices Act. Federally, A. g. laingi is designated as Threatened by the Committee on the
Status of Endangered Wildlife in Canada (COSEWIC). Population trends of this subspecies are unknown in British Columbia, but the subspecies was listed due to its estimated small populations size (<1000 mature individuals) and threats to populations from forest harvesting. In Western Forest Products (WFP) Inc. TFL 37 on north-central Vancouver Island, 53 nest trees in 13 confirmed goshawk territories and 2 suspected goshawk territories, have been found between 1994- 2006. In 2006, TFL 37 was transferred from Canadian Forest Products (Canfor) Ltd. to WFP. Previous to 2006, Canfor had committed to managing habitat for this species through an Adaptive Management Strategy involving approved Wildlife Habitat Areas (WHAs), which vary in size from approximately 135-538 ha. Ten goshawk WHAs were established in TFL 37 by the BC government in March 2003.
Between 4-8 June and 3-8 July 2008, surveys to determine the breeding activity status were conducted in 12 known goshawk territories in TFL 37. All known territories were visited at least twice during the survey period (once during the nestling period (4-8 June) and once during the fledgling period (3-8 July) to determine the activity status and number of fledglings in each nesting territory. All surveys followed Resource Inventory Standards Committee standards for raptor surveys (RIC 2001), and consisted mainly of call playback and nest search surveys. A total of 105 call playback stations were completed during the survey period in 2008. Estimated survey hours in each known nest territory ranged from 1.5-16.5 hrs; total hours spent surveying was approximately 108.0 hrs.
Six goshawk detections occurred during surveys in 2008, which resulted in four active nests being located in the following territories: CT-060, John, Loon Lake and Toad. The other two goshawk detections occurred in Kaipit and Vernon territories, but did not result in active nests being found. Overall during 2008, 50.0% (6/12) of surveyed territories were occupied; this was consistent with the long-term average (1995-2008) of 48.0% (n=51/113) occupancy for known nest territories in this area over a 14 year period (E. McClaren, BC MoE, unpublished data). In 2008, most of the active goshawks nests in TFL 37 were thought to have successfully fledged 3 young, except for the John territory where only 2 young were confirmed. Average productivity for 2008 was 2.75 fledglings/nest, which is the highest productivity in TFL 37 since monitoring began in 1994. The mean long-term productivity rate (1994-2008) for known nest territories in TFL 37 was 1.61 young fledged/active nest/year.
Including the 2008 surveys, there are now 64 known nest trees (including 6 nest starts or partially built nests in Kaipit) in TFL 37 that have been documented or are thought to be those of goshawks. Of these, 62 are located in 13 confirmed goshawk nest territories, and two are found in suspected goshawk nest territories (BC-224 and Surprise Creek). Eight new nest trees were found in TFL 37 in 2008: Hoomak nests #5 and #6 (both old nests), John nest #7 (new active nest), and Kaipit nests #8-
12 (all nest starts). 2008 Northern Goshawk Monitoring of WFP TFL 37, Woss, British Columbia Manning, Cooper and Associates Ltd. August 2008
ii Three other raptor species (Merlin, Northern Pygmy-Owl and Sharp-shinned Hawk) were detected in 2008 during goshawk surveys in TFL 37.
Total prey species detection rates (77.1 potential prey species/100 call stations) were 38.8% lower in 2008 compared to the 2003-2006 average of 126.0 potential prey species/100 call stations in TFL 37. Scatter plot graphs were also used to compare red squirrel detection rates per 100 call stations against percent goshawk territory occupancy in order to obtain a linear correlation function (y = 1.9547x + 23.838). This analysis showed a positive correlation (R2 = 0.6331) between the number of red quirrel detections in a given year and the number of known goshawk territories that were occupied in TFL 37; however, the same analysis conducted for data collected between 2003-2006, showed a much higher positive correlation (R2 = 0.9832). These comparisons demonstrate the high degree of variability among years.


Final Report (1.2Mb)

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Updated August 16, 2010 

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