Forest Investment Account (FIA) - Forest Science Program
FIA Project Y091102

    Are northern goshawks and forest harvesting compatible? An examination of the effects of different harvest practices on northern goshawk nest productivity
Project lead: Harrower, William (Thompson Rivers University)
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
The northern goshawk is a species of concern in the southern interior of British Columbia for the following reasons. First, it is strongly associated with mid-elevation, mature conifer stands comprised of tall, large diameter trees with high canopy closure, namely the stand types often targeted for timber harvest[1]. Second, like the grizzly bear, it is a wide-ranging species with low reproductive rates. Third, the goshawk has been assessed as a candidate for endangered species listing twice in the United States, and there is considerable controversy about the conservation status of this species[2]. Forth, the Canadian Intermountain Joint Venture, a partnership of government agencies, First Nations, non-governmental organizations, universities, industry and landowners established to provide regional implementation of the Partners-in-Flight Bird Conservation Plans in the intermountain area, has identified the goshawk as a focal species for coniferous forests based on its habitat associations and population trajectories. Finally, the goshawk is of particular concern in southern interior BC because of the changes in the forested landbase associated with the escalating mountain pine beetle infestation, and a similar increase predicted in wildfire frequency due to climate change. In order to maintain goshawk habitat, steps must be taken now to ensure appropriate features are maintained on the landscape.

This project builds up the work we have been conducting on goshawks in the East Kootenay since 2001. To date, 48 nest areas have been located and monitored annually for occupancy (presence of a nesting pair) and productivity (number of young produced). Given that goshawk nests are extremely difficult to find, and the majority of published goshawk studies are based on 30 or fewer nests, we have a high number of nest areas to work with. Our past research on goshawks has been extremely successful. When we began this research, we identified three main questions: (1) what stand types and habitat features do goshawks select for nesting at multiple scales; (2) what habitat features are linked to the successful occupancy and rearing of goshawk young; and (3) how do goshawks respond to timber harvesting in the vicinity of their nest areas?

Question 1 has been well-addressed through a recent MSc thesis[3] under a previous FSP project. This project determined the forest types selected by adult and juvenile goshawks around individual nests at different spatial scales. Results were presented at an international conference, in a workshop to local biologists and foresters, and three papers are being prepared for submission to peer-reviewed journals. Habitat selection was found to be scale-dependent: within 200 m of the nest, adult goshawks selected for areas with a high proportion of closed canopy forest (> 40 % crown closure). Within 500 m of the nest, adults selected only for relatively smaller patches of forest, and within 1100 m, they selected only for relatively higher amounts of edge. Although selection for stands with high canopy cover was not significant at distances larger than 200 m, the proportions of the total area in this stand type remained on average about 50% up to 1100 m from the nest. Other variables such as the distance to roads and cutblocks were also significant, although these features were generally located outside the 200 m core area. Selection by fledgling goshawks differed from that of adults. Fledglings remain close to the nest during their first summer and during this time are completely reliant on their parents for food. Our results showed that fledgling goshawks avoided cut blocks and other forest openings, but selected stands 40-80 years old, a forest type generally avoided by their parents.

We are now poised to address the second of our three major questions, using our previous work as a foundation for more sophisticated analyses. Our previous data suggest that a core area of forest with high canopy cover exists around goshawk nests, but that goshawks also select nest sites with specific habitat features up to 1100 m from their nest1. Based on this, we have been able to make preliminary recommendations for management around goshawk nests. However, the scope of this research did not include linking the occupancy or productivity of nests to habitat: we simply analyzed the habitat around each nest, regardless of whether it was continuously occupied for 6 years, or only occupied once during this time. Our monitoring data show large variability in occupancy and productivity rates among the 48 nest areas; some were occupied continuously, some sporadically, and others for only one year. Average occupancy rates varied between 18 and 83 %[4]. During 3 years of intensive investigation, we found the survival of hatched young to vary between 70 and 100 percent[4]. With these data, it is now possible to address our Question 2, and determine the factors associated with differences in occupancy and productivity, and if the habitat surrounding high-quality goshawk nest areas (those with high occupancy and productivity) differs from that around low-quality areas. Since we also know from other studies that factors such as weather and prey availability can affect goshawk occupancy and productivity rates[5,6], these factors (or surrogates for them) can be examined concurrently. In order to develop management guidelines for this species, we need to know which factors influence occupancy and productivity, and which forest management activities are associated with high-quality nest areas.

Linked to this, it is also now possible for us to address Question 3, namely, how do goshawks respond to timber harvesting? In addition to monitoring occupancy and productivity at our goshawk nests, we have implemented an adaptive management program for the logging occurring near the nests. This program consisted of instituting a variety of site-level practices, including:
• no harvest within 500 m of the nest
• reserving the nest area in a large (10-30 ha) patch, connected to the adjacent contiguous forest
• reserving the nests in small (<2 ha) patches connected to the contiguous forest
• reserving the nests in small (<2 ha) patches, isolated from contiguous forest
• reserving the active nest tree, but harvesting around it (Pl removal only for MPB)

We can now analyze which of these practices resulted in the highest occupancy and productivity rates following harvest, while accounting for other factors such as weather, prey availability, and habitat around the nest at larger spatial scales.

Finally, we will then apply the model resulting from the above analysis to the forested landbase to determine the current amount and distribution of goshawk habitat in the East Kootenay. Model predictions will be verified (ground-truthed) and validated through the collection of new data. Once refined, the model will be linked to existing projections of historic and future habitat, based on current forest management practices, to assess a component of risk to goshawk habitat supply. For example, if the amount of current or future habitat is low relative to that projected to occur under historic disturbance conditions, risk to the goshawk population would be considered relatively high. Similarly, if projected future habitat declines significantly compared to current habitat, risk also would be considered high.

Together, this new information resulting from our analysis will be used to develop management strategies for goshawk nest areas specific to the southern interior. These ‘best management practices’ will be developed in collaboration with strategic and operational foresters, government agencies, and goshawk researchers, in order to ensure a scientifically defensible, useful and workable product. In the current results-based regulatory environment, the process we have chosen to disseminate the results of scientific investigations to directly forest managers is essential to producing real on-the-ground change.

Related projects:  FSP_Y102102FSP_Y113102
Contact: Harrower, Bill, (250) 434-4390,


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Updated May 02, 2011 

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