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NORTHERN SPOTTED OWL (Strix occidentalis caurina)

11. Ecological and Technical Feasibility of Species Recovery

A number of key policies require that the SORT assess the biological and technical feasibility of recovering the Northern Spotted Owl in British Columbia:

  • The National Framework for the Conservation of Species at Risk includes the goal to        “… prevent any species from becoming extinct as a consequence of human activities.”
  • The Accord for the Protection of Species at Risk states that a “lack of full scientific certainty must not be used as a reason to delay measures to avoid or minimize threats to a species at risk.”
  • The RENEW Recovery Handbook specifies use of a precautionary approach, where          “… species for which recovery feasibility is unknown would be considered recoverable until proven otherwise.”

Accordingly, the SORT has evaluated the feasibility of recovering the Northern Spotted Owl in British Columbia and has determined that recovery is biologically and technically feasible.  

Based on the examination of potential recovery actions, the SORT believes there is sufficient suitable habitat to support the existing small but endangered population of Spotted Owls until the recovery plan can be implemented.  Some of these recovery actions (e.g., definition and protection of critical habitat) should be implemented as soon as possible, and should address the factors that contributed to the Spotted Owl’s current population status to reduce the likelihood of extirpation. Over time, additional suitable habitat could be recruited in a spatial distribution that could enhance the population’s chances of reaching the recovery goal.  However, early attempts at modeling (Blackburn, pers comm.) suggest that, while feasible, meeting the recovery goal of 250 adult owls may require some level of population augmentation in addition to improved habitat conservation.  Moreover, it should be made clear that reaching the recovery goal will be a long-term project, likely measured by decades or even longer, rather than years, and that the recovery goal itself needs to be re-evaluated every five years. Ongoing modeling may refine the timeframe that this might entail.

Although the SORT believes that recovery is biologically feasible, it is recognized that Spotted Owls face several significant logistical, societal and economic challenges to recovery, and that even if all these challenges are met, there is no guarantee that recovery will occur.  The likelihood that the Spotted Owl will recover naturally (without human intervention) to numbers sufficient to down-list the species is considered to be extremely low, and therefore, active human intervention is recommended.  Population augmentation measures could have a major effect on the rate of recovery.  Challenges to recovery include the loss of habitat, the effects of resource competition with Barred Owls, the potential effects of habitat fragmentation on dispersal success, and demographic factors that are especially critical when populations are small (e.g., low reproductive and juvenile survival rates).  Most importantly, populations continue to decline on both sides of the Canada-United States border and the current small population size in British Columbia is extremely susceptible to stochastic environmental, demographic, and genetic events (see sections 4 and 5).  Recovery actions need to be undertaken in several areas; the time available to stabilize populations is short, and costs could be significant.

While the task at hand seems daunting, there are several examples of species at risk being successfully brought back from the brink of extinction or extirpation.  The Whooping Crane and California Condor populations were both reduced to a few dozen individuals.  Intensive recovery efforts, including captive breeding and release, have succeeded to reverse these population trends and increase their chances of recovery.  The Vancouver Island Marmot is currently on the brink of extinction and major recovery efforts including intensive research, captive breeding, predator control and habitat management are being used.  The Peregrine Falcon (subspecies Falco peregrinus anatum) was once extirpated from much of its world-wide range due to exposure to organochlorine contaminants.  Due to bans on the use of these chemicals and the use of captive-breeding and release techniques, it has now been down-listed or de-listed in most jurisdictions.  The Burrowing Owl is declining throughout much of its North American range and is considered Endangered in Canada.  It was extirpated from British Columbia, but has now regained a foothold thanks to an ongoing intensive captive breeding, controlled release and habitat stewardship program.  This program has enabled the species to breed in the province while habitat research and management efforts continue to search for ways to accommodate a naturally sustaining population.  The North American Waterfowl Management Plan is an excellent example of a successful major habitat conservation initiative that focuses on increasing and improving wetland habitats across North America to return waterfowl populations back to the levels of the 1970s.  This involved habitat creation and restoration efforts on a massive scale.  All these examples point out that recovery of wildlife populations is feasible as long as the species is extant and suitable habitat exists or can be created, and that success is dependent on having dedicated agencies and individuals collectively address the factors causing the decline.

In the sections that follow, we outline some of the issues that appear to most strongly influence the health of Spotted Owl populations in British Columbia. We briefly describe the issues and discuss some of the management activities that might be used to address them. These descriptions address the general feasibility of the noted activity, but, as noted above, the implementation of the activities, singularly or in combination, does not guarantee success. Importantly, detailed evaluation and analysis will be required to identify and prioritize the most appropriate activities and the most effective means for successful implementation. These assessments and analyses will contribute to, or be identified in, the recovery action plans.

 

Demography:

Northern Spotted Owls are long-lived birds, but reproductive output is low relative to most other species of birds, juvenile survival to breeding age is low, and in British Columbia populations are very small and birds are becoming increasingly spatially isolated.  Because of these, factors it seems possible that a “natural” recovery would take longer and contain more risk than a recovery that included some form of augmentation. For this reason, various forms of augmentation were identified as possible means to reduce this risk and expedite recovery.  These augmentation activities included holding juveniles in captivity over the winter to reduce winter mortality, tracking juveniles over winter to check their condition and perhaps supplement their diets, and captive breeding and subsequent release into the wild.  These activities are all feasible, but if implemented, would need to be conducted in concert with efforts to address the factors that currently limit the population.  Some of these recovery actions would likely be most effective in the near-term, when the population is most vulnerable to extirpation or delayed recovery due to its small size and uneven distribution.

 

Habitat:

There appears to be a sufficient amount of suitable habitat already protected to support the existing small population of Spotted Owls.  However, the current amount and spatial distribution of protected habitat is considered unlikely to be sufficient to recover the population.  Protection of some additional owl habitat and recruitment of new habitat to infill between tracts or patches of existing suitable habitat is required to enable recovery, to foster successful dispersal and reduce competitive pressures.  Recruitment of habitat would be a long term process because second-growth stands in British Columbia need to be at least 100 years old, and probably 120 years or older, before they become suitable for Northern Spotted Owls (SOMIT 1997a,b). 

The recovery goal of 250 adult owls could theoretically be met by creating 125 territories with each occupied by a potential breeding pair.   At roughly 3200 ha per territory, this scenario could be realized by managing 400,000 ha for the species.  The current Spotted Owl Management Plan includes 363,000 ha of habitat at various levels of protection. Suitable habitat exists outside the plan area that could be incorporated to increase the amount of area managed for the owl.  In addition, territory overlap of up to 12% has been recorded for the species, so careful planning of the spatial distribution of habitat could reduce the total amount needed to meet the recovery goal.  Therefore, it seems possible to attain the amount of habitat required.  Although these are theoretical values, continuing work on habitat models may help identify numbers of pairs and territories needed to facilitate recovery. The most difficult aspect will be to create the spatial distribution of habitat best suited for population recovery.  Recruiting and conserving sufficient amounts of suitable habitat for maintenance and recovery will continue to be the most contentious management issue.  The SORT is developing a spatially explicit habitat model that should help us address these issues, as well as related issues including habitat function, habitat quality, and the importance of connectivity both within British Columbia’s population and between our population and those in the United States.

 

Barred Owls and other threats:

Barred Owls first entered British Columbia in the 1940s (Campbell et al, 1990).  There is concern that wherever the two species’ ranges overlap, the Barred Owl is a significant competitor with the Spotted Owl.  Excluding Barred Owls from Northern Spotted Owl habitat in the short-term would require direct and repeated removal of Barred Owls. While this is technically feasible, and existing provincial policy enables the removal of wildlife predators in order to facilitate recovery of endangered species, it may not be publicly acceptable except on small scale, site-specific projects.  As the relationship of these two species is not clearly understood, we cannot conclude that the Barred Owl will prevent the feasibility of recovery for the Spotted Owl.

Threats posed by global warming may be largely beyond human control.  Changes imposed on British Columbia’s forests may improve Spotted Owl habitat in some areas and decrease it in others.  Overall, although changes in the forest are anticipated, they are not expected to diminish the feasibility of recovery because the Spotted Owl is distributed across a broad geographical and ecological range.

The threat posed by West Nile Virus (WNV) is potentially great but at this time is unknown and cannot likely be effectively mitigated.  The effectiveness of vaccines for species like the Spotted Owl has not been demonstrated, and the ability to locate and capture all owls to apply the vaccine on an annual basis would be a daunting task.  Currently, it is not possible to estimate the impact of WNV on the feasibility of recovery for the spotted owl.

After considering the factors above, the SORT concludes that the following actions are all biologically and technically feasible, and collectively have the potential to benefit Spotted Owls and thus increase the size of the population:

  • recruit new habitat to connect home ranges
  • increase or reconfigure the amount of protected habitat in landscapes
  • enhance the development of currently unsuitable or less suitable habitat;
  • translocate Spotted Owls into more suitable habitat, and to increase local populations;
  • provide supplemental prey to juvenile owls over winter to increase survival and recruitment
  • possibly overwinter juveniles and establish a captive breeding program; and
  • if and where necessary, implement other actions that address threats of predation, competition, and disease.

In summary, Northern Spotted Owls are capable of persisting and recovering in British Columbia given the right circumstances. Concerns about recovery potential are not about the basic biology of the owl, but mainly reflect the small population size, the current effectiveness of dispersal habitat, the time frame to effectively implement habitat improvements, and the difficulty in removing or reducing threats of competition from Barred Owls. Intensive population management may be needed to bridge the gap until these factors are adequately addressed.

In this context, and following the guidance of the policy directives stated at the beginning of this section, the SORT deems it biologically and technically feasible to recover the Spotted Owl.  It should be noted, however, that substantial recovery efforts and financial resources are needed immediately. Until action is taken and success demonstrated, options for recovery diminish and there remains a high risk of extirpation.