Horned lark strigata subspecies (Eremophila alpestris strigata) recovery strategy: chapter 3

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2. Recovery

• 2.1 Rationale for Recovery Feasibility
• 2.2 Recovery Goals
• 2.3 Recovery Objectives
• 2.4 Approaches Recommended to Meet Recovery Objectives
  • 2.4.1 Broad strategies to effect recovery
  • 2.4.2 Narrative to support Recovery Planning Table
• 2.5 Performance Measures
• 2.6 Critical Habitat
  • 2.6.1 Identification of critical habitat
  • 2.6.2 Schedule of studies for the identification of critical habitat
• 2.7 Existing and Recommended Approaches to Habitat Protection
• 2.8 Effects on Other Species
• 2.9 Recommended Approach for Recovery Implementation
  • 2.9.1 Statement of when one or more action plans in relation to the recovery strategy will be completed

2.1 Rationale for Recovery Feasibility

Horned Lark strigata

Recovery of the Horned Lark strigata in Canada is technically and biologically feasible, as it meets all four criteria for determining recovery feasibility recommended in the draft Environment Canada Policy on Feasibility of Recovery (Environment Canada 2005). The U.S. population represents a potential source for either passive or active reintroduction of the subspecies in Canada. Although suitable habitat is likely limited at the present time, some suitable habitat likely exists and more could be made available through habitat restoration activities. In addition, there is significant potential for creation of new habitat through deposition of dredge spoils. It is possible to address or mitigate all known significant threats to the Horned Lark strigata through recovery actions at priority sites. Effective recovery techniques exist, including, but not limited to, invasive species removal and predator control.

Vesper Sparrow affinis

Recovery of the Vesper Sparrow affinis in Canada is technically and biologically feasible, as it meets all four criteria for determining recovery feasibility recommended in the draft Environment Canada Policy on Feasibility of Recovery (Environment Canada 2005). A small breeding population persists in British Columbia, the population appears to be self-sustaining, and an additional potential source population exists in the United States, with the next closest breeding population on San Juan Island, Washington, approximately 18 km to the south. Some additional suitable habitat may currently be available in British Columbia, and other areas are potentially available for restoration (e.g. Gulf Islands National Park Reserve). Effective recovery techniques exist, including, but not limited to, habitat restoration and population enhancement through invasive species removal and predator control.

2.2 Recovery Goals

Recovery goal for Horned Lark strigata

• Re-establish a breeding population of at least 10 breeding pairs at a minimum of three sites across its historical breeding range in Canada.

Historical occurrence and habitat availability data suggest that this species was never abundant, and was possibly ephemeral, in Canada; consequently, achieving a “minimum viable population” is not a reasonable goal, as such a small population will always be vulnerable to extirpation due to stochastic events in Canada or on the wintering grounds. Populations likely increased in the Fraser River valley as a result of anthropogenic activities that created temporary suitable habitat in the first half of the 20^th century. Subsequent agricultural intensification and urbanization in this region have resulted in the elimination of the vast majority of this habitat. Based on U.S. patch size data for Horned Lark strigata populations utilizing inland grassland sites (see Section 1.4), the remaining patches in the Fraser Valley are likely not large enough to be suitable. From this perspective, the historical breeding range should be limited to sparsely vegetated coastal dune or meadow habitats in the Lower Mainland and southeastern Vancouver Island. The recovery goal considers the limited available information on historical abundance and is believed to be achievable given the likely extent of remaining suitable and restorable habitat.

Goal for Vesper Sparrow affinis

• Re-establish a breeding population of at least 30 breeding pairs at a minimum of at least three sites within its historical breeding range in Canada.

Like the Horned Lark strigata,this species was likely never abundant, and was possibly ephemeral, in Canada; consequently, achieving a “minimum viable population” is not a reasonable goal, as such a small population will always be vulnerable to extirpation due to stochastic events in Canada or on the wintering grounds. However, given the existence of an apparently persisting population of 5–9 pairs at one site on southeastern Vancouver Island, it is reasonable to set a higher population target for the Vesper Sparrow affinis. The rationale is that there is an opportunity to exploit the existing population as a “source” from which to increase the overall Canadian population both at that site and at suitable neighbouring sites, thus increasing the probability of persistence from a metapopulation perspective. The goal is both reasonable in light of the limited available information on historical abundance and achievable given the extent of remaining suitable and restorable habitat.

2.3 Recovery Objectives

Recovery objectives for Horned Lark strigata

1. Identify and assess candidate sites featuring sparsely vegetated coastal dune or meadow habitat for suitability by 2008.
2. Analyze the feasibility of active reintroduction of the Horned Lark strigata to suitable unoccupied habitat by 2008.
3. Secure, restore, create, protect, or manage 3–6 of the most suitable sites by 2011.
4. Increase the probability of passive reintroduction from U.S. populations by 2009.

Objectives for Vesper Sparrow affinis

1. Analyze the feasibility of active reintroduction of the Vesper Sparrow affinis to suitable unoccupied habitat by 2008.
2. Increase the existing population by 2–3 pairs by 2010.
3. Assess candidate sites with appropriate structural characteristics for suitability by 2008.
4. Secure, restore, protect, or manage two additional sites of the most suitable candidates identified by 2010.

2.4 Approaches Recommended to Meet Recovery Objectives

2.4.1 Broad strategies to effect recovery

Broad strategies to effect recovery of the Horned Lark strigata and the Vesper Sparrow affinis are outlined in Tables 1 and 2, respectively.

2.4.2 Narrative to support Recovery Planning Table

Four threats identified in Section 1.5 are not addressed in the recovery planning tables. These are fire suppression, dyking, agriculture, and bird strikes. These threats were either historical or hypothetical. If they are shown to be current threats to the species, then an approach to address them will be developed.

2.5 Performance Measures

Measurable objectives are needed to evaluate the success of recovery efforts (Table 3). Many of these effectiveness measures will need to be derived from recommended habitat enhancements, site acquisition and management, inventory, monitoring, and research objectives outlined above. These performance measures are to be used as part of the mandatory five-year reporting requirement associated with this recovery strategy.

2.6 Critical Habitat

2.6.1 Identification of critical habitat

Horned Lark strigata

It is not possible to identify critical habitat for the Horned Lark strigata at this time.

No individuals are currently known to breed or over-winter within the historical range of this species in Canada. For the purposes of passive or active reintroduction, it is not known whether any sites with suitable or restorable habitat remain, although it is likely that some does. Passive reintroduction would involve colonization of currently suitable, restorable, or newly created habitat by dispersing individuals from U.S. populations. It is difficult to assess the likelihood of passive colonization at this time, in part because currently suitable or restorable sites have not been identified. Active reintroduction would involve direct reintroduction of birds captured and imported from U.S. populations and subsequent intensive management and monitoring. Methodologies for successful reintroduction of grassland passerines are currently not well developed. Also, there is uncertainty concerning the feasibility of introducing individuals from U.S. populations, as those populations are also at risk and the species remains a candidate for addition to the U.S. Endangered Species Act. Finally, the relative potential of natural (e.g. dune, natural grassland) versus anthropogenic (e.g. airports, dredge spoil islands) habitats to sustain populations of the Horned Lark strigata is unknown. Some anthropogenic habitat types (e.g. airports) may be population sinks for the Horned Lark strigata, in that populations breeding at these sites would need constant augmentation of new individuals in order to persist.

These knowledge gaps will be addressed in the manner described in the schedule of studies below (Section 2.6.2). It is recommended that no critical habitat be identified until candidate sites are assessed as being currently suitable or are restored to a condition of suitability.

Vesper Sparrow affinis

At the time that this recovery strategy is to be posted, the Vesper Sparrow affinis will be under consideration for listing on Schedule 1 of the Species at Risk Act. As such, critical habitat cannot be proposed for this species.

An updated recovery strategy for the Horned Lark strigata and the Vesper Sparrow affinis or an addendum to this strategy will be posted according to the timeline associated with the Vesper Sparrow affinis if the taxon is added to Schedule 1 of the Species at Risk Act. The update will deal specifically with potential critical habitat for the Vesper Sparrow affinis, as well as any other sites identified as critical habitat for Horned Lark strigata during the intervening time period.

2.6.2 Schedule of studies for the identification of critical habitat

Horned Lark strigata

1. Compile a list of candidate sites within the subspecies' historical range in Canada for consideration as potential habitat for the Horned Lark strigata by 2008.
2. With the assistance of species experts, identify and assess candidate sites as unsuitable, suitable, or restorable by 2007.
3. Identify, map, and prioritize suitable sites featuring sparsely vegetated coastal dune and meadow habitats for the Horned Lark strigata by 2007.
4. Identify, map, and prioritize coastal sites with habitat restoration potential for the Horned Lark strigata by 2008.

2.7 Existing and Recommended Approaches to Habitat Protection

Stewardship

Although the only known Vesper Sparrow breeding site in Canada is not formally protected and is actively managed as an airport, a stewardship agreement has, until recently, been in place between the Nanaimo airport and the Garry Oak Ecosystems Recovery Team's Vertebrates at Risk Recovery Implementation Group. Therefore, some consideration has been given to Vesper Sparrows in vegetation management decisions. However, airport management must adhere to Federal Aviation Authority rules, which stipulate heights of vegetation near the runway; therefore, some mowing during the breeding season is required, and this site can never be fully protected for sparrows.

An updated stewardship agreement is very important for recovery as are stewardship agreements with any other landowners now or in the future.

Secure suitable habitat areas

Securing areas through acquisition is costly, but ensures that they can be managed for long-term conservation purposes. In many instances, outright purchase may not be possible. Other options for securing habitat are conservation covenants or conservation or stewardship agreements.

Conserve and manage secured sites for the Horned Lark strigata and Vesper Sparrow affinis

1. Management plans for areas with open habitats need to specifically address threats to ground-nesting species.
2. Manage recreational activities on breeding sites to reduce or eliminate negative impacts. At sites with breeding populations, humans, vehicles, and domestic pets should be excluded during the breeding season.
3. Minimize impacts to nesting via management of mowing regimes at airports and other sites. Mowing is necessary to maintain airport safety. A mowing program also maintains habitat for both the Horned Lark and the Vesper Sparrow and therefore benefits these birds, provided all mowing is completed before the breeding season begins or after young have left the area (Vesper Sparrows fledge early, before they are able to fly, so fledging is not an indication that it is safe to mow). Mowing areas with short vegetation should be scheduled for before mid-March and again after the end of August.
4. Selectively control non-native and invasive shrubs at breeding site. Areas designated as potentially suitable Horned Lark habitat should have most shrubs removed. This may be done mechanically or, where practical, through controlled burning. Taller vegetation left at the edges of clearings or the occasional shrub missed in the clearing process should ensure that the habitat has potential for Vesper Sparrows as well.
5. Where Vesper Sparrows are the focus of vegetation management, shrubs should be thinned to create a mosaic of shrub cover and open spaces. Natural grasslands used by this species tend to have high variability, and no precise model exists for shrub cover versus open space for this species (Winter et al. 2005). Site-level managers should therefore provide a variety of options for these birds in terms of density of shrubbery (authors suggest a range of 1–50%).
6. Control predators. Feral and domestic cats in particular should be live-trapped and removed from breeding sites.

2.8 Effects on Other Species

Efforts to restore and protect open grassland and coastal sand dune habitats will be beneficial to many species that rely on these scarce and declining ecosystems. Any success in increasing habitat supply (area and quality) and reducing disturbance in these habitats will be especially beneficial to other ground-nesting birds that use sparsely vegetated habitats, such as Killdeer (Charadrius vociferus), Common Nighthawk (Chordeiles minor), and Savannah Sparrow (Passerculus sandwichensis).

Other listed species with similar habitat requirements include two arthropods. The Taylor's checkerspot (Euphydryas editha taylori) is listed as Endangered by COSEWIC and requires sparsely vegetated grasslands (Environment Canada 2006). The sand verbena moth (Copablepharon fuscum) is also listed as Endangered in Schedule 1 and is an obligate herbivore of yellow sand verbena (Abronia latifolia), a plant that occurs only in sand dune environments (Environment Canada 2006). Contorted-pod evening primrose (Camissonia contorta) was assessed as Endangered by COSEWIC in April 2006 and also utilizes dry, open, and sandy coastal habitats on southeastern Vancouver Island. Management of habitats for both the Horned Lark strigata and the Vesper Sparrow affinis can be compatible with the requirements of these three species.

There are, however, many species that do not favour sparsely vegetated habitats or that may be damaged by habitat restoration efforts (e.g. rare plant species affected by controlled burns). All sites will have to be carefully evaluated to determine which suite of species will benefit the most from restoration and management efforts. A balance will be required to ensure that all species have sufficient habitat areas for recovery and survival.

In the United States, the Horned Lark strigata now breeds on sites formerly used by Caspian Terns (Sterna caspia). Terns were removed from these sites prior to utilization of the sites by the Horned Lark strigata. Habitat creation through the deposition of dredge spoils may result in creation of tern habitat as well. Although Caspian Terns are not common in the Lower Mainland, at least one breeding colony does occur in the Fraser River delta. If the presence of terns reduces the suitability of newly created habitat, it may be necessary to manage these sites to prevent colonization by terns.

2.9 Recommended Approach for Recovery Implementation

Recovery of the Horned Lark strigata in Canada will likely prove to be more problematic than recovery of the Vesper Sparrow affinis. Larks require larger areas, no Canadian breeding sites currently exist, sites formerly used are almost completely lost or degraded, sites to be restored may need to be purchased, and new habitats need to be constructed. Despite these barriers, new nesting habitat may be created with relative ease from dredge spoils; this factor may compensate for other challenges in Horned Lark strigata recovery.

A more detailed action plan is needed to focus recovery efforts in Canada. A plan will be developed following identification and assessment of suitable or restorable sites for both species and evaluation of the best habitat enhancement/creation methods.

Conservation efforts in the United States have focused on identifying and monitoring existing populations, identifying habitat features important to successful breeding, testing methods for creating habitat, restoring degraded habitats, and restricting some human uses on breeding sites (Pearson and Altman 2005). Managers of potentially suitable sites in Canada should use habitat creation and restoration techniques that have proven successful south of the border.

It is recognized that most suitable habitat for these two subspecies in Canada and the United States occurs either at airports or on military reserves. Both land use types offer open areas with short vegetation and protection from disturbance by people and pets. Focusing recovery actions at airports and on military reserves may be problematic due to other management considerations. This strategy recognizes that public safety considerations clearly supersede those governing Species at Risk where the two are in conflict and that conservation actions such as habitat modification or enhancement must be compliant with Transport Canada regulations. Even with these restrictions, maintaining suitable habitat at airports and on military land will likely offer the best chance for successful recovery of these two species. Working relationships with land managers at these sites should be fostered and maintained.

Recovery actions should be coordinated with efforts to restore populations of these species in the United States.

Recovery actions should be coordinated with overall Garry Oak Ecosystems Recovery Team habitat mapping and restoration and species recovery efforts, in part to increase effectiveness of recovery actions and in part to eliminate any potential for conflicting recovery activities (e.g. damage to rare plant populations by controlled burning). To date, the Vertebrates at Risk Recovery Implementation Group of the Garry Oak Ecosystems Recovery Team has taken the lead in the conservation and management of habitats for these species on southeastern Vancouver Island and will continue to be involved with related issues in that region (Fuchs et al. 2002).

The Horned Lark strigata and Vesper Sparrow affinis Recovery Team may reconvene as a Recovery Implementation Group in order to expand the work initiated by the Vertebrates at Risk Recovery Implementation Group to include potential coastal dune sites on southeastern Vancouver Island and the Lower Mainland. Alternatively, habitat management, restoration, and/or creation could be implemented through formation of an additional Recovery Implementation Group, with specialization in dune and grassland habitats, especially if other listed species are determined to be affected. In this, the recommended approach, the Garry Oak Ecosystems Recovery Team Vertebrates at Risk Recovery Implementation Group would continue to implement recovery actions where appropriate (i.e. most recovery activities associated with the Vesper Sparrow affinis), but a coastal dune and related ecosystems Recovery Implementation Group would address conservation needs affecting the Horned Lark strigata as well as a suite of other federally and provincially listed species associated with this habitat type (e.g. sand verbena moth, contorted-pod evening primrose, pink sand verbena, Abronia umbellata, yellow sand verbena).

2.9.1 Statement of when one or more action plans in relation to the recovery strategy will be completed

An action plan will be completed by March 2009.