Forest Investment Account (FIA) - Land Base Investment Program
FIA Project 6224020

    Managing for goshawks in TFL 39 on Haida Gwaii/Queen Charlotte Islands: goshawk and marbled murrelet habitat suitability
Project lead: Weyerhaeuser Company Ltd.
Author: Doyle, Frank I.
Imprint: Telkwa, BC : Wildlife Dynamics Consulting, 2004
Subject: Forest Investment Account (FIA), Marbled murrelet, British Columbia, Queen Charlotte Islands, Habitat, Goshawk, Vancouver Island, Forest Management
Series: Forest Investment Account (FIA) - Land Base Investment Program
The Queen Charlotte Goshawk (Accipiter gentilis laingi) and Marbled Murrelet (Brachyramphus marmoratus) have been identified as species that are threatened by the harvesting of the mature-old growth forest on Haida Gwaii/Queen Charlotte Islands. This project uses the available Ecosystem mapping and Forest Cover information used by Weyerhaeuser, to develop predictions for goshawk and Marbled Murrelet habitat. These predictions if strong can then be used allow the licensee to more effectively manage the forest for these threatened species. Over the last two years, 183 habitat assessment transects, focused on goshawk and Marbled Murrelet habitat requirements, have been conducted within the range of mapped Site Series and Forest Cover polygon boundaries. These transects have included not only structural habitat assessments, but also counts of known goshawk prey and prey sign, and Marbled Murrelet potential nest platform counts. In mature-old growth forest habitat suitability ranking for goshawks was seen to be linked to sites with better growing conditions. The range of Forest Cover and Site Series types that were suitable for goshawk nesting was found to be far larger than for foraging. For nesting only the wetter and Cedar leading sites ranked low. For foraging, the richer growing spruce leading and flood plain sites ranked the highest, while most of the drier zonal, hemlock, spruce sites ranked moderate. Wetter, cedar leading sites again ranked the lowest for foraging. Feed sites and middens of the Red Squirrel main goshawk prey on Haida Gwaii in summer, was also highest in the spruce leading, floodplain sites, while sign of the sapsucker, secondary prey, was most abundant in mixed hemlock, spruce, cedar stands, and Hairy Woodpeckers sign was most abundant in mesic hemlock and hemlock, spruce sites. Marbled Murrelet habitat suitability ranking was primarily driven by platform density. This ranking was also highest in richer spruce, spruce hemlock sites, with the highest ranked Site Series were in flood plains. Suitability ranking was lowest in the wet forest Site Series and Cedar dominated stands. In second growth forest 46 habitat assessment transect were conducted in stands ranging from 1-60 years of age, stands older than this are largely absent on the islands. The older harvested sites were all the richer growing sites, and in these forests goshawk nesting habitat suitability ranked as moderate between 40-49 years in unmanaged stands. After 60 years Marbled Murrelet habitat nesting suitability was still ranked at NIL as no potential nest platforms were present. Goshawk foraging is primarily a combination between prey abundance and its availability (forest structure). After 30-40 years the abundance of feed sites of its main prey, the Red Squirrel was higher than seen in mature-old growth forest, Hairy Woodpecker sign was highest in mature-old growth and sapsucker feed sites were even across age classes. Goshawk access (availability) to this prey was moderate ranked after 40 years. Comparisons between space and not spaced stands, suggests that goshawk availability to the squirrels in these young stands can be provided 10 years earlier. This provides the possibility, that the older second growth sites can become a critical source of prey for 10 years or more prior to harvesting.


Goshawk and Marbled Murrelet Habitat Suitability Report (0.2Mb)

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Updated August 16, 2010 

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