Amended Recovery Strategy for the Horned Lark strigata subspecies (Eremophila alpestris strigata) and Recovery Strategy for the Vesper Sparrow affinis subspecies (Pooecetes gramineus affinis) in Canada - 2014 [Proposed]
Species at Risk Act
Recovery Strategy Series
Horned Lark strigata subspecies and Vesper Sparrow affinis subspecies
Table of Contents
- Executive Summary
- Recovery Feasibility Summary
- 1. Background
- 2. COSEWIC Species Assessment Information
- 3. Species Status Information
- 4. Species Information
- 5. Threats
- 6. Population and Distribution Objectives
- 7. Broad Strategies and General Approaches to Meet Objectives
- 8. Critical Habitat
- 9. Measuring Progress
- 10. Statement on Action Plans
- 11. References
- 12. Personal Communications
- Appendix A: Vegetation Range Summary for Other Vesper Sparrow Subspecies
- Appendix B: Effects on the Environment and Other Species
Environment Canada. 2014. Amended Recovery Strategy for the Horned Lark strigata subspecies(Eremophila alpestris strigata) and Recovery Strategy for the Vesper Sparrow affinis subspecies (Pooecetes gramineus affinis) in Canada [Proposed]. Species at Risk Act Recovery Strategy Series. Environment Canada, Ottawa. vii + 34 pp.
For copies of the recovery strategy, or for additional information on species at risk, including COSEWIC Status Reports, residence descriptions, action plans, and other related recovery documents, please visit the Species at Risk (SAR) Public Registry.
Cover illustration: Horned Lark strigata subspecies: Randall Moore
Vesper Sparrow affinis subspecies: Suzanne Beauchesne
Également disponible en français sous le titre
« Programme de rétablissement révisé de l’Alouette hausse-col de la sous-espèce strigata (Eremophila alpestris strigata) et Programme de rétablissement du Bruant vespéral de la sous-espèce affinis (Pooecetes gramineus affinis) au Canada [Proposition]»
© Her Majesty the Queen in Right of Canada, represented by the Minister of the Environment, 2014. All rights reserved.
Content (excluding the illustrations) may be used without permission, with appropriate credit to the source.
The federal, provincial, and territorial government signatories under the Accord for the Protection of Species at Risk (1996) agreed to establish complementary legislation and programs that provide for effective protection of species at risk throughout Canada. Under the Species at Risk Act (S.C. 2002, c.29) (SARA), the federal competent ministers are responsible for the preparation of recovery strategies for listed Extirpated, Endangered, and Threatened species and are required to report on progress within five years.
The Minister of the Environment and the Minister responsible for the Parks Canada Agency are the competent ministers for the recovery of the Horned Lark strigata subspecies and Vesper Sparrow affinis subspecies and have prepared this strategy, as per section 37 of SARA. It has been prepared in cooperation with the Government of British Columbia, Parks Canada Agency, Garry Oak Ecosystems Recovery Team, Nanaimo Area Land Trust, American Bird Conservancy, Vancouver Airport Authority, Nanaimo Airport Commission, and the State of Washington (Department of Fish and Wildlife). The British Columbia Ministry of Environment has reviewed and accepts this document as scientific advice.
Success in the recovery of these species depends on the commitment and cooperation of many different constituencies that will be involved in implementing the directions set out in this strategy and will not be achieved by Environment Canada and the Parks Canada Agency, or any other jurisdiction alone. All Canadians are invited to join in supporting and implementing this strategy for the benefit of the Horned Lark strigata subspecies and Vesper Sparrow affinis subspecies and Canadian society as a whole.
This recovery strategy will be followed by one or more action plans that will provide information on recovery measures to be taken by Environment Canada and the Parks Canada Agency and other jurisdictions and/or organizations involved in the conservation of the species. Implementation of this strategy is subject to appropriations, priorities, and budgetary constraints of the participating jurisdictions and organizations.
Gratitude is owing to the members of the Garry Oak Ecosystems Recovery Team’s Vertebrates at Risk Recovery Implementation Group for their ongoing work with respect to the conservation of the Horned Lark strigata subspecies and Vesper Sparrow affinis subspecies. All the members of the Horned Lark strigata and Vesper Sparrow affinis Recovery Team are thanked for the invaluable contribution of their time and individual expertise. The Recovery Team also benefited immeasurably from the expertise of Recovery Team advisors Dr. Scott Pearson and Bob Altman. These two individuals have generously shared information from their research on these species in Washington and Oregon and have actively participated in team meetings and provided extensive reviews of earlier drafts of this document. Past and present managers of the Nanaimo Airport are also thanked for granting access to the site and for their cooperation and assistance with vegetation management issues.
The members of the Horned Lark strigata and Vesper Sparrow affinis Recovery Team are:
- Bob Altman – American Bird Conservancy (advisor to the Recovery Team)
- Suzanne Beauchesne – Cooper Beauchesne and Associates Ltd
- Alaine Camfield – Canadian Wildlife Service, Environment Canada
- Trudy Chatwin – British Columbia Ministry of the Environment
- John Cooper – Cooper Beauchesne and Associates Ltd
- Wendy Easton – Canadian Wildlife Service, Environment Canada
- Kevin Fort (Chair) – Canadian Wildlife Service, Environment Canada
- Libor Michalak – Next Environmental Inc.
- Nicholas Page – Raincoast Applied Ecology
- Scott Pearson – Washington Department of Fish and Wildlife (advisor to the Recovery Team)
- Simon Robinson – Vancouver International Airport Authority
This revised recovery strategy outlines a multi-species approach for the Horned Lark strigata subspecies (henceforth: Horned Lark strigata) and Vesper Sparrow affinis subspecies (henceforth: Vesper Sparrow affinis). It was recognized that there is considerable overlap between these species with respect to current and historical distribution in Canada, general ecological requirements, and principal threats to the species and their habitat. In addition, many of the professional biologists involved have extensive knowledge of both species. Adopting a multi-species approach to recovery planning also represents an opportunity to make efficient use of conservation resources. Current and historical populations of both species are patchily distributed and, together with isolated populations in the United States, each comprises a single metapopulation in the Pacific Northwest. Thus, recovery of Canadian populations will contribute significantly to the global recovery of the two subspecies.
Horned Lark strigata
The Horned Lark strigata (Eremophila alpestris strigata) was assessed as Endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in 2003 and added to Schedule 1 of SARA in 2005.
The Horned Lark strigata is a subspecies of the Horned Lark, a small tan and yellow passerine with a black facial mask and ear tufts or “horns.” The Horned Lark strigata is an open habitat specialist, breeding in both dune and grassland habitats which have a high percentage of bare ground, short, sparse herbs or grasses, and few or no trees and shrubs. No individuals are currently known to occur or breed in Canada, but numerous confirmed historical breeding records exist. The historical distribution of the Horned Lark strigata in Canada is restricted to southwestern British Columbia, where it occurred only on southeastern Vancouver Island and in the lower Fraser River valley from Chilliwack west to the mouth of the Fraser River.
The population and distribution objective for this species is to establish and maintain a breeding population of a total of at least 10 breeding pairs distributed across a minimum of three sites within its historical breeding range in Canada.
Broad strategies to be taken to address the threats to the survival and recovery of the species are presented in the section on Strategic Direction for Recovery.
No critical habitat can be identified for the Horned Lark strigata at this time, as it is not known which specific sites with suitable or restorable habitat may be used. The persistence of this species in Canada is threatened primarily by loss or degradation of habitat due to urban and industrial development, increased disturbance at remaining suitable or restorable sites, modern agricultural practices, and infilling of most remaining open spaces by exotic vegetation. In addition, lark dune habitat has been lost due to improved dyking techniques in the Fraser River delta.
Vesper Sparrow affinis
The Vesper Sparrow affinis (Pooecetes gramineus affinis) was assessed as Endangered by COSEWIC in April 2006 and added to Schedule 1 of SARA in 2007.
The Vesper Sparrow affinis is a subspecies of the Vesper Sparrow, a large sparrow with a whitish eye ring, a chestnut shoulder patch, and white outer tail feathers. Like the Horned Lark strigata, the Vesper Sparrow affinis is a bird of open habitats, favouring areas with a high percentage of bare ground and short, sparse herbs or grasses. In contrast, however, it selects open habitats with scattered trees or shrubs, which it uses for singing perches and escape cover. In Canada, the Vesper Sparrow affinis currently breeds only on Vancouver Island at a single site. Historically, it has been reported during the breeding season on Vancouver Island from the Englishman River estuary in the north to Cobble Meadows and Mill Bay to the south. It was also formerly a local breeder in the Fraser Lowland on British Columbia’s southwest mainland coast.
Like the Horned Lark strigata, the persistence of this species in Canada is threatened primarily by loss or degradation of habitat due to urban and industrial development, and infilling of most remaining open spaces by exotic vegetation. In addition, future development at the Nanaimo airport and in surrounding properties may pose a threat to the persistence of the species in Canada, depending on the specific nature and on-site location of the development. It is acknowledged that conservation actions at the Nanaimo Airport site, such as habitat modification or enhancement, must be compliant with Transport Canada regulations. Public safety considerations supersede those governing the recovery of species at risk, in cases where the two are in conflict.
The population and distribution objective for this species is to establish and maintain a breeding population of a total of at least 30 breeding pairs distributed across a minimum of at least three sites (the current site, plus two additional sites) within its historical breeding range in Canada.
Broad strategies to be taken to address the threats to the survival and recovery of the species are presented in the section on Strategic Direction for Recovery.
Critical habitat for Vesper Sparrow affinis is identified in this recovery strategy at the site recently occupied by the species in Canada. The critical habitat is characterized by open areas with short, sparse grass or herbaceous cover and intermittent bare ground, needed for nesting and foraging. Scattered shrubs and small trees (as well as larger trees on the eastern periphery) are present on the site and used extensively by the birds as escape cover and singing perches.
Separate action plans for both species will completed by 2017.
Recovery of the Horned Lark strigata and 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 Species at Risk Act Policy. The criteria are as follows (Government of Canada 2009):
- Individuals of the wildlife species that are capable of reproduction are available now or in the foreseeable future to sustain the population or improve its abundance.
- Sufficient suitable habitat is available to support the species, or could bemade available through habitat management and restoration.
- The primary threats to the species or its habitat (including threats outside of Canada) can be avoided or mitigated.
- Recovery techniques exist to achieve the population and distribution objectives, or can be expected to be developed within a reasonable timeframe.
Horned Lark strigata
1. Yes, the U.S. population represents a potential source for passive recolonisation of the subspecies in Canada. Although reintroduction may appear unlikely, there was a sighting of an adult male in 2002, so it is not outside the realm of possibility. 2. Yes, 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. 3. Yes, it is possible to address or mitigate all known significant threats to the Horned Lark strigata through recovery actions at priority sites. 4. Yes, effective recovery techniques exist, including, but not limited to, invasive species removal and predator control.
Vesper Sparrow affinis
1. Yes, 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. 2. Yes, in addition to the currently occupied site, 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). 3. Yes, it is possible to address or mitigate all known significant threats to the Vesper Sparrow affinis in Canada through recovery actions at priority sites. 4. Yes, effective recovery techniques exist, including, but not limited to, habitat restoration and population enhancement through invasive species removal and predator control.
As the small Canadian populations of these subspecies occur at the northern part of their continental ranges, and the vast majority of their continental distributions and populations occur further south in the United States, it is important to note that population changes at the continental level may have a significant effect on recovery feasibility in Canada. As the continental populations of these species are experiencing ongoing downward population trends, their ranges may contract away from the current peripheries, and individuals may immigrate towards the centre of the ranges. In such a case, despite best efforts described in this strategy to ensure that sufficient suitable habitat is available and key threats are mitigated, the numbers of these species in Canada may continue to decline.
This recovery strategy outlines a multi-species approach for the Horned Lark strigata and Vesper Sparrow affinis. It was recognized that there is considerable overlap between these species with respect to current and historical distribution in Canada, general ecological requirements, principal threats to the species and their habitat, and biological expertise. Adopting a multi-species approach to recovery planning also represents an opportunity to make efficient use of conservation resources. This revised document represents an update to the earlier “Recovery Strategy for the Horned Lark strigata subspecies (Eremophila alpestris strigata) with consideration for the Vesper Sparrow affinis subspecies (Pooecetes gramineus affinis) in Canada”, which was published prior to the formal listing of Vesper Sparrow affinis subspecies on SARA Schedule 1.
2. COSEWIC1 Species Assessment Information
Date of Assessment:
Horned Lark strigata subspecies
Eremophila alpestris strigata
Reason for Designation:
Although this subspecies has always been rare in Canada, it has declined steadily throughout its range over the last 50 years and is now nearly extirpated from Canada.
COSEWIC Status History:
Designated Endangered in November 2003.
Date of Assessment:
Vesper Sparrow affinis subspecies
Pooecetes gramineus affinis
COSEWIC Status: Endangered
Reason for Designation:
This songbird, a subspecies of the Vesper Sparrow, is found in Canada only in coastal grasslands in the extreme southwestern corner of British Columbia, where it now breeds only at one site with a population of about 5 pairs. The taxon is declining in the United States as well, where it has a restricted distribution in western Washington and Oregon. Habitat loss is the greatest threat, both through direct destruction of habitat for urban development and through invasion by alien plant species.
COSEWIC Status History:
Designated Endangered in April 2006.
|Global (G) Rank||National (N) Rank||Canada Status||Sub-national (S) Rank||B.C. Conservation Status|
|Horned Lark strigata|
United States: N2
SARA : Schedule 1 (Endangered)
|British Columbia (SXB) |
|Vesper Sparrow affinis|
United States: N1B
SARA: Schedule 1 (Endangered)
|British Columbia (S1B) |
Oregon (S2B, S2N)
T: subspecies; X Presumed Extirpated; NR: Unranked; B: Breeding; G/N/S1: Critically Imperiled; 2: Imperiled; 3: Vulnerable; 4: Apparently Secure; 5: Secure.
B.C. CDC: British Columbia Conservation Data Centre
1 Goal 3: Maintain the diversity of native species and ecosystems. Priority 1: highest conservation priority.
Horned Lark strigata subspecies
The Horned Lark (Eremophila alpestris) is the only true North American member of the lark family (Alaudidae). It is a slender ground-dwelling passerine of open country. The adult male is distinctively marked with a dark facial mask and breast band that contrasts with the pale face and throat. The “horns” for which the species is named are tiny, black feather tufts that are apparent only at close range. The tail is square and blackish with pale central feathers and whitish edges that are evident in flight. The Horned Lark strigata is smaller than the other subspecies. The upperparts are dark brown and the nape is walnut brown. The bird has a yellow throat and eye stripe and yellowish underparts (Beason 1995). There is heavy brown streaking on the sides of the breast that should allow separation of males to subspecies in the field (Sibley 2000). In the hand, the longest uppertail covert is distinctly streaked (Pyle 1997). Adult females are similar to males, but they are duller and smaller and lack “horns.” Females cannot be separated to subspecies in the field. Juveniles of both sexes are generally duller than adult females (Sibley 2000).
Vesper Sparrow affinis subspecies
The Vesper Sparrow (Pooecetes gramineus) is a medium- to large-sized sparrow (length approximately 16 cm) with a chestnut shoulder patch (lesser coverts), white outer tail feathers, and a whitish eye ring (Sibley 2000). Sexes are similar in appearance. Juveniles are similar in appearance to adults, but duller, and they usually lack chestnut lesser coverts (Pyle 1997).
The three Canadian subspecies of Vesper Sparrow (P. g. confinis, P. g. gramineus, and P. g. affinis) are similar in appearance and cannot be reliably separated in the field, varying only in shading and measurements. The Vesper Sparrow affinis has medium greyish brown upperparts and white underparts with a buff tinge. Vesper Sparrow confinis, the common British Columbia interior subspecies, has pale greyish brown upperparts and creamy underparts. Vesper Sparrow affinis is slightly smaller overall than confinis and has a shorter tail (Pyle 1997).
Current and historical populations of both taxa in Canada, together with those in the United States, likely comprise a single metapopulation.
Horned Lark strigata subspecies
Horned Larks are found across much of North America and Eurasia. The breeding distribution of Horned Lark strigata, however, is restricted to the Georgia Basin/Puget Trough, the coast of Washington, and islands in the lower Columbia River (Beason 1995, Rogers 2000, Pearson and Altman 2005, Stinson 2005) (see Figure 1). The centre of its breeding distribution is the glacial outwash prairies of the south Puget Sound area of western Washington (Rogers 2000). The Canadian population is extremely small, and may be extirpated: the last observation of a Horned Lark strigata in Canada was made in 2002 (COSEWIC 2003). U.S. researchers have estimated that the Washington and Oregon population is likely fewer than 1000 individuals, based on recent breeding and winter surveys (Pearson and Altman 2005).
Figure 1. Current and historic Horned Lark strigata breeding localities and possible historic nesting or uncertain breeding season locations. All current breeding sites are in Washington and Oregon states. Map based on information from Altman 1999, Rogers 2000, Pearson and Hopey 2005, Stinson 2005.
The distribution of the Horned Lark strigata in Canada is restricted to southwestern British Columbia, where it historically occurred only on southeastern Vancouver Island and in the lower Fraser River valley from Chilliwack west to the mouth of the Fraser River (Campbell et al. 1997). The Horned Lark strigata is known to have bred in the lower Fraser River valley. Breeding records are concentrated near the mouth of the Fraser River on Sea Island, Iona Island, and Lulu Island. Other confirmed historical breeding localities include the University of British Columbia at Point Grey and near Chilliwack (Campbell et al. 1997). Breeding has not been documented on Vancouver Island or the southern Gulf Islands. However, it is possible that this subspecies did breed at these locations in the past, as some suitable habitat would have been available and birds were known to occur in the area (Munro and Cowan 1947, Beauchesne 2003, COSEWIC 2003). Central eastern Vancouver Island probably represents the northern limit of suitable habitat and range of this subspecies. Although most historical records for the Horned Lark strigata on Vancouver Island are not from the peak breeding season, it seems likely that these sightings were of breeding birds, occurring as they did in presumed nesting habitat. Historically, the Vancouver Island and lower Fraser River valley populations were likely very small and locally distributed. Given that these areas represent the northern extent of the geographic range of this taxon, it is also likely that not all apparently suitable habitats were utilized.
Trend information for the Horned Lark strigata subspecies, specifically, is not available through the Breeding Bird Survey (BBS); however, the Horned Lark (all subspecies) has undergone a significant range-wide decline (Sauer et al. 2008). Insufficient data exists to infer trend for Horned Lark in British Columbia (Sauer et al. 2008).
Vesper Sparrow affinis subspecies
Vesper Sparrows are widespread in appropriate habitat across North America. Vesper Sparrow affinis occurs in a disjunct population in the Pacific Northwest, separated from the interior populations (i.e., Vesper Sparrow gramineus, confinis ,and altus) by the Cascade Mountain Range. This subspecies’ current breeding range exhibits a patchy distribution from southeastern Vancouver Island south through western Washington and Oregon and possibly extreme northwestern California (Figure 2). Specifically, the subspecies bred in one location in Del Norte County, California; breeds rarely in coastal grasslands in Coos and Curry Counties, Oregon and in the Willamette and Umqua valleys, also in Oregon; and populations persist in the lower Columbia River, south Puget Sound, and the San Juan Islands in Washington. In Canada, the species occurred historically in the lower Fraser River valley and southeastern Vancouver Island, but is now limited to a single site on Vancouver Island. The Vesper Sparrow affinis is the only subspecies found west of the Cascade Mountains (AOU 1957, Pyle 1997, Cannings 1998, Rogers 2000, Campbell et al. 2001, Jones and Cornely 2002, Altman 2003).
In Canada, the Vesper Sparrow affinis is currently known to breed only on Vancouver Island at a single site: the Nanaimo Airport and immediately adjacent land, near Cassidy (Beauchesne 2002a, 2003, 2004a, 2010a). Historically, it has been reported during the breeding season on Vancouver Island from the Englishman River estuary in the north to Cobble Meadows and Mill Bay to the south. It was also formerly a local breeder in the Fraser Lowland on British Columbia’s southwest mainland coast. The last confirmed breeding record for that area is from 1968 (Campbell et al. 2001). The historical population size is unknown, but it is likely that the subspecies was never common in Canada, as it was never recorded in large numbers or from more than a few sites.
No population estimates exist for Vesper Sparrow affinis in Oregon or California, but a 1998 survey in Washington counted 125 singing males (Rogers 2000). In Canada, the population on southeastern Vancouver Island has ranged in recent years from three to 10 pairs (Beauchesne 2006, 2007, 2008, 2010b, 2011, 2012, 2013).
Trend information for the Vesper Sparrow affinis subspecies, specifically, is not available through the BBS; however, the Vesper Sparrow (all subspecies) has undergone a significant range-wide decline (Sauer et al. 2008). The trend for Vesper Sparrow in British Columbia is non-significant (Sauer et al. 2008).
Figure 2. Current and historic breeding distribution of the Vesper Sparrow affinis in Canada and the United States. Map prepared by Environment Canada based on Information from Rogers 2000, COSEWIC 2006, S. Pearson (pers. comm.), B. Altman (pers. comm.).
Horned Lark strigata
The Horned Lark strigata is a ground-nesting passerine. Across their range, Horned Larks are birds of open areas with short, low-density vegetation (Beason 1995). Horned Lark strigata habitat requirements are similar to those of other subspecies. The common characteristics of all breeding sites are short sparse vegetation dominated by grasses and forbs with very few or no trees or shrubs and a relatively high percentage of bare (i.e., non-vegetated) ground (Pearson and Altman 2005).
In Washington State, the Horned Lark strigata breeds primarily in the glacial outwash prairies of south Puget Sound. These prairies are remnant grasslands that likely developed shortly after the last ice age. Subsequent regional climate change, beginning about 6000 years ago, resulted in a shift to moister conditions that typically produced a succession to forest ecosystems. However, prairie conditions were maintained in some areas as a result of a high frequency of low-intensity fires, most set by First Nations peoples (Crawford and Hall 1997). The soils of these prairies are deep, have low nutrient levels, and drain rapidly. These characteristics, along with the frequent anthropogenic burning, also helped maintain the prairie grassland condition.
Other breeding sites in Washington and Oregon include airfields, dredge spoil islands in the Columbia River, sandy coastal beaches, and disturbed areas on military training bases (Rogers 2000, Pearson and Altman 2005). In the Willamette Valley of Oregon, the Horned Lark strigata breeds in agricultural fields, generally selecting sparsely vegetated fallow fields (Pearson and Altman 2005). The majority of the global population of the Horned Lark strigata is believed to winter along the lower Columbia River and in the Willamette Valley (Pearson and Altman 2005).
In British Columbia, larks have used agricultural fields, airports, beaches, sand dunes, short-grass playing fields, roadsides, and other areas with a high percentage of bare ground. Documented breeding habitat is restricted to short-grass fields in agricultural areas, airports, and estuaries and to sparsely vegetated, sandy beaches along the lower Fraser River (Butler and Campbell 1987, Campbell et al. 1997). Horned Lark strigata is believed to have used Garry oak ecosystems, especially those recently burned by First Nations peoples (Garry Oak Ecosystem Recovery Team 2003).
The size of the habitat patch is also likely important. Grassland sites may need to be very large to be effective (Vickery et al. 1994). In the United States, habitat patches in the Puget Lowlands grassland areas used by the Horned Lark strigata ranged in size from 131 to 390 ha. In coastal areas, the Horned Lark strigata breeds adjacent to expanses of open water; under these conditions, it uses habitat patches as small as 10 ha (S. Pearson, pers. comm.).
Availability of large patches of suitable breeding habitat with low levels of disturbance during the nesting period appears to limit the extant distribution of this species in Canada. In many areas with otherwise suitable habitat, activity of machinery, people, livestock, or domestic pets can destroy or depredate nests directly. Additionally, anthropogenic disturbance can lead to frequent flushing of nesting birds, resulting in nest abandonment and increased rates of nest predation (Pearson and Altman 2005).
Vesper Sparrow affinis
The Vesper Sparrow affinis is also a ground-nesting passerine. Like the Horned Lark strigata, the principal limiting factor for this species is believed to be the availability of suitable habitat with low disturbance levels during the nesting season. Vesper Sparrows are grassland birds, preferring dry, open areas with short, sparse grass or herbaceous cover, and patches of bare ground (Campbell et al. 2001, Dechant et al. 2001, Jones and Cornely 2002, Appendix A). Structural diversity of vegetation is important; however, taller vegetation such as scattered or edge shrubs or trees, is used for cover and for singing perches, whereas areas with shorter vegetation are used for foraging and nesting (Davis and Duncan 1999, Beauchesne 2002a, 2003, 2004a). In foraging areas of western Washington, the Vesper Sparrow affinis used sites with a mean cover of 32% bare ground, with the remaining cover consisting of grasses and forbs (Rogers 2000). Fence posts, wire fences, and other human-made structures may also be used as singing perches (Beauchesne 2002b). A combination of short-grass and herbaceous ground cover, bare dirt, and scattered taller vegetation seems to be preferred (see numerous citations in Dechant et al. 2001).
Several studies indicate that Vesper Sparrows avoid permanent pasture and hayfields (see Campbell et al. 2001, Jones and Cornely 2002) or areas where shrubs were completely removed and the site planted with grass (Castrale 1982). In Saskatchewan, Vesper Sparrows did occur in hayfields (mcmaster et al. 2005). However, sparrows initiated nesting in habitat that had clumps of short vegetation with considerable amounts of bare dirt until mid-June, after which the vegetation grew in height and density. On southeastern Vancouver Island, hayfields tend to support dense, tall vegetation early in the breeding season, precluding nesting by the Vesper Sparrow affinis.
Habitat patch size may also be important (Kershner and Bollinger 1996, Rogers 2000, Vickery et al. 1994). For example, in Washington, the Vesper Sparrow affinis is currently found primarily in large prairie areas, but not in small patches of similar habitat (S. Pearson, pers. Comm.). In eastern Oregon, however, Vesper Sparrows have been recorded breeding in areas smaller than 4 ha (B. Altman, pers. Comm.. In Jones and Cornely 2002), and on Vancouver Island, the extant population occurs in an area of suitable habitat of approximately 10 ha (Beauchesne 2002a). Populations of Vesper Sparrow affinis may therefore be able to persist in smaller habitat patches than those required for the Horned Lark strigata. However, the minimum habitat patch size requirement for Vesper Sparrow affinis is currently unclear. Studies of other Vesper Sparrow subspecies have suggested that patches should be larger than 10 ha to support a breeding population (Samson 1980, Herkert 1991).
On Vancouver Island, the plant community at the known breeding site includes both native and non-native flora. Birds frequently use clumps of introduced Scotch Broom (Cytisus scoparius) for singing perches and escape cover. They forage on the ground in adjacent open areas with gravelly soil and sparse forb and grass cover (Beauchesne 2002a, 2003, 2004b, 2006, 2007, 2010b, 2011, 2012, 2013). Nests monitored since 2005 have been associated with a range of native and non-native plant species, including English plantain (Plantago lanceolata) (Beauchesne 2006), mown Scotch Broom (Beauchesne 2006, 2007, and 2012), sparse grasses (Beachesne 2007, 2008, 2011), Trailing Blackberry (Rubus ursinus) (Beauchesne 2007), and thistle (Circium sp.) (Beauchesne 2008).
Multi-species Habitat Management
Given their similar habitat requirements, management of habitat at a single site for the Vesper Sparrow affinis and the Horned Lark strigata is possible. However, for management purposes, it is important to recognize that Vesper Sparrows require some shrub cover in open areas, whereas larks avoid shrubby areas. In many open habitats, the lark may nest in the middle of larger open areas and the sparrow may use the edges where both short and tall vegetation are available. This has been demonstrated at study sites in Washington State, where both species occur (Rogers 2000). In this recovery strategy, it is not expected that any sites be managed specifically for both species, as the currently most suitable candidate sites for each species are not likely to overlap geographically.
|Threat||Level of Concern1||Extent||Occurrence||Frequency||Severity2||Causal Certainty3|
|Habitat loss and degradation|
|Development||High||Widespread||Historic, Current and Anticipated||Continuous||High||High|
|Livestock grazing and cultivation||Low||Widespread||Historic||Continuous||Moderate||Medium|
|Small Population / Distribution Effects||High||Widespread||Current and Anticipated||Continuous||High||Medium|
|Bird strikes||Moderate (Horned Lark strigata)|
Low (Vesper Sparrow affinis)
|Localized||Historic and Current||Recurrent||Moderate (Horned Lark strigata)|
Low (Vesper Sparrow affinis)
|Changes in Ecological Dynamics or Natural Process|
|Fire suppression||Moderate||Widespread||Historic, Current||Continuous||Unknown||Low|
|Exotic, Invasive, or Introduced Species|
|Disturbance or Harm|
|Human intrusion||Low||Localized||Current and Anticipated||Recurrent||Low||Medium|
|Pesticides||Low||Localized||Historic and Current||Recurrent||Unknown||Low|
1 Level of Concern: signifies that managing the threat is of (high, medium or low) concern for the recovery of the species, consistent with the population and distribution objectives. This criterion considers the assessment of all the information in the table).
2 Severity: reflects the population-level effect (High: very large population-level effect, Moderate, Low, Unknown).
3 Causal certainty: reflects the degree of evidence that is known for the threat (High: available evidence strongly links the threat to stresses on population viability; Medium: there is a correlation between the threat and population viability e.g. expert opinion; Low: the threat is assumed or plausible).
Threats ranked as “low concern” in Table 2 are not described in this section.
Habitat Loss and Degradation
Loss of high-quality breeding habitat is considered the primary threat for both species. Although the extent of breeding habitat in the Georgia Basin for the Horned Lark strigata has always been limited, suitable open habitats, including 95% of the Garry oak and associated ecosystems (Fuchs 2001), have been lost as a result of industrial, commercial, and residential developments and dyking (Campbell et al. 1997). It is assumed that prior to European settlement, Garry oak ecosystems, prairies associated with Garry oak ecosystems, and other sparsely vegetated or burnt areas would have been the key open habitats used by the breeding Vesper Sparrow affinis. At the Nanaimo airport, the existing breeding Vesper Sparrow affinis population uses an area that is away from the vicinity of buildings and human activity. However, habitat in this area is vulnerable to potential future activities, such as airport expansion (new or longer runways), construction of new airport infrastructure (airport buildings, aircraft hangars, parking areas for vehicles and equipment), and expansion of ancillary commercial operations (expanded recreational vehicle sales or other new businesses). As the airport (and immediately adjacent land) is the only extant breeding site for the subspecies in Canada, future development at this site may pose a threat to the persistence of the species in Canada.
In addition to absolute habitat loss, development has resulted in changes to the size and spatial configuration of suitable habitat patches. The minimum patch size for the Horned Lark strigata may vary depending on the landscape context. Although the Horned Lark strigata may require patches no larger than 10 ha within an open landscape (e.g., dunes, coastal island or coastal prairie habitats), a suitable habitat patch would likely need to be larger if surrounded by forest, buildings or other tall structures that reduce visibility (Ribic et al. 2009). In general, U.S. data suggest that smaller patches are suitable only in habitats directly adjacent to the coast, whereas inland sites must be much larger (S. Pearson and B. Altman, pers. Comm.). The Vesper Sparrow affinis appears to use smaller areas of suitable habitat (Altman 2000), within an appropriate landscape context (Vickery et al. 1994). For example, at the Nanaimo Airport (and immediately adjacent land), the population is breeding in an area less than 10 hain size (Beauchesne 2004a) within an open, largely treeless, grass and forb dominated landscape. Recent habitat inventory work within a 20 km radius of the existing population has confirmed that similar sized patches of suitable or restorable habitat are scarce but do exist (Hill 2009). However, none are directly adjacent to the airport site, and many are not being currently managed in a way that is favourable to Vesper Sparrow breeding. These factors likely combine to reduce the chances of the current population expanding into any of these neighbouring sites, should the population at the airport increase beyond the site carrying capacity (Beauchesne 2003, 2004a, 2010a).
Small Population/Distribution Effects
A recent estimate of Horned Lark strigata population size in the United States, based on breeding and winter surveys, by U.S. researchers put the population at less than 1000 individuals (Pearson and Altman 2005). Genetic work suggests that the remaining birds are genetically distinct, while also having remarkably low genetic diversity. Samples all shared the same haplotype2, whereas all other Horned Lark subspecies exhibited multiple haplotypes (Drovetski et al. 2005). Genetic data do not currently exist for the Vesper Sparrow affinis, although patterns of genetic differentiation for other coastal grassland species suggest that this subspecies will be genetically distinct and isolated from subspecies occurring elsewhere in North America (Ruegg and Smith 2002, Drovetski et al. 2005). Small population size and low genetic diversity cause these subspecies to be especially vulnerable to stochastic events, such as severe weather events or disease outbreaks. Given that source populations for the Horned Lark strigata in British Columbia are now remote (i.e. nearest populations are in south Puget Sound in Washington State), the probability of recolonization after a catastrophic event would be extremely low. The nearest U.S. population of the Vesper Sparrow affinis is on the San Juan Islands, but that population has suffered severe declines, and only a few individuals are thought to remain there. The Vesper Sparrow affinis population in the Willamette Valley in Oregon State is comparable with that of the Horned Lark strigata there (i.e., about 400 individuals) (B. Altman, pers. comm.). However, as the Vesper Sparrow affinis is more abundant at the southern end of the range, the total population of the subspecies is estimated to be larger than that of the Horned Lark strigata.
Because the Vesper Sparrow affinis currently occurs in very small numbers at a single site in Canada, this population is particularly vulnerable to extirpation. A single catastrophic event on the airport grounds or adverse weather conditions on the wintering grounds have the potential to eliminate the entire breeding population.
U.S. military reports indicate that Horned Larks are the most commonly reported aviation bird strike victim of any species (BASH 2006). Horned Lark flight behaviour, including a tendency to fly at considerable altitude during mating displays, likely exposes them to a greater risk than that experienced by other grassland species. Horned Larks (strigata subspecies) have been found dead along the runways of military airport breeding locations in Washington State (Pearson and Altman 2005). During the breeding season, the Horned Lark strigata is also vulnerable to automobile strikes, as it often selects nest sites on or directly adjacent to gravel roads (S. Pearson and B. Altman, pers. comm.).
As the Vesper Sparrow affinis is not known to frequent roadside habitats, the risk of automobile strikes for this species is likely lower. Despite the subspecies’ presence at the Nanaimo Airport, air strikes are also less likely, as Vesper Sparrows do not engage in high-altitude flights to the same extent as do larks. Also, they tend to frequent areas farther away from runways at this site, since the shrub component is removed from areas within 100 m of the strip.
Changes in Ecological Dynamics or Natural Process
The effects of predators may also limit these species. Predation was the primary source of nest failure in the Horned Lark strigata at nearly all sites studied in the Puget Lowlands, Washington coast, Columbia River, and Willamette Valley (n = 166 nests: Altman 1999, Pearson and Hopey 2005). Vesper Sparrow researchers have found that predation is a major cause of nest failure, with rates of up to 63% (reviewed in Jones and Cornely 2002). For both species, urbanization and other human activities tend to lead to increased predation pressure from introduced predators, particularly domestic and feral cats (George 1974, Cooper 1993, Coleman et al. Undated), as well as some native predators, such as corvids (Marzluff and Neatherlin 2006). No nest predation information is available for the Vesper Sparrow affinis population at the Nanaimo airport, although domestic and feral cats have been observed at the site (S. Beauchesne, pers. comm.). Predation by corvids and feral cats is a known and ongoing threat for both species, wherever they occur. For both species, the proximity of any known or potential suitable sites to urbanized areas increases the risk of predation from introduced and some native predators.
Fire suppression is a prevalent policy around developed areas. Historically, some ecosystems burned frequently, but current practices have allowed natural succession to infill open habitats that were historically maintained by fire. For both species, suitable habitat in the Georgia Basin may have been more abundant in the past due to more frequent fires, both natural and of First Nations origin. Fire suppression has resulted in the infilling of previously suitable habitats by native plants, such as Douglas-fir (Pseudotsuga menziesii) and Common Snowberry (Symphoricarpos albus). In a recent controlled burn experiment in the United States, the Horned Lark strigata was more abundant in burned plots versus control plots in the post-breeding period (Pearson and Hopey 2005). Late summer burns appear to be more beneficial for the Horned Lark strigata, as regeneration of vegetation is not as vigorous, possibly allowing birds to locate and capture invertebrate prey more easily.
Exotic, Invasive or Introduced Species
The introduction of invasive plants such as Scotch Broom, Common Gorse ( Ulex europaeus), Himalayan Blackberry ( Rubus discolor), and tall non-native grasses has led to infilling of important habitats for Horned Lark strigata and Vesper Sparrow affinis. This change in vegetation structure has reduced the suitability of most of the remaining old-field, Garry Oak, and sand dune habitats for the Horned Lark strigata (Fraser et al. 1999). Because the Vesper Sparrow affinis requires a combination of short vegetation, bare ground, and shrub cover, this species tolerates some infilling by invasive species such as Scotch broom and will even use that plant as a singing perch and for escape and nest cover (Beauchesne 2002a, 2003, 2006, 2007, 2012). However, Vesper Sparrows are excluded from areas where shrubs completely dominate open areas (Jones and Cornely 2002). If left unmanaged, Scotch Broom can degrade formerly open habitats to the point where they become unsuitable. Other invasive plant species may have structural similarities to native species and may not be detrimental to breeding birds of either species. For example, Vesper Sparrow affinis nests in and adjacent to the Nanaimo Airport have been situated directly adjacent to English Plantain (Beauchesne 2006).
The role of invasive plant species at the Nanaimo Airport site is complex. Although ingrowth of Scotch Broom at the Nanaimo Airport site appears to threaten habitat quality in some areas, others areas (presumably with lower soil quality) appear to maintain a stable level of shrub density favoured by the birds. It is important to emphasize that optimal habitat quality for Vesper Sparrow affinis likely lies somewhere in the middle of a continuum of shrub density. It should be noted that ongoing management may be required in order to prevent natural succession from occurring at this highly disturbed site. Although not native, Scotch Broom is used by the birds and, at appropriate densities, appears to meet the structural shrub requirement of Vesper Sparrow affinis at the Nanaimo Airport site.
Population and Distribution Objective for Horned Lark strigata
- Establish and maintain a breeding population of at least 10 breeding pairs distributed across a minimum of three sites within its historical breeding range in Canada.
Historical occurrence and habitat availability data suggest that this species was likely never large enough to be self-sustaining, and was possibly ephemeral, in Canada; and likely always depended on immigration from the United States. Consequently, achieving a “minimum viable population” is not a reasonable objective; 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 20th 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 4.3), the remaining patches in the Fraser Valley are likely not large enough to be suitable. From this perspective, the effective potential breeding range should now be limited to sparsely vegetated coastal dune or meadow habitats elsewhere in the Lower Mainland and southeastern Vancouver Island. The population and distribution objective considers the limited available information on historical abundance and is believed to be achievable given the likely extent of remaining suitable and restorable habitat. Three sites are believed to be the minimum number that still allows for some redundancy and accounts for the possibility of stochastic events which could destroy one or more sites. This objective is considered achievable in part because of the likelihood that suitable sites will benefit a suite of species at risk, and therefore not require incremental recovery efforts specifically for this species. The three sites for Horned Lark strigata will not necessarily be the same sites used for Vesper Sparrow affinis
Population and Distribution Objective for Vesper Sparrow affinis
- Establish and maintain a breeding population of at least 30 breeding pairs distributed across a minimum of at least three sites (including the current site, plus two additional 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 objective, because such a small population will always be vulnerable to extirpation due to stochastic events in Canada or on the wintering grounds. However, the Vesper Sparrow affinis was historically more abundant and widespread (than it is currently), so an increase in the population and distribution is appropriate. While few of the remaining suitable or restorable sites could support more than the ~10 pairs supported by the one extant site, expanding the number of occupied sites is important in order to increase the probability of persistence from a metapopulation perspective. Expanding the population to three sites is realistic because the existing population can be exploited as a “source” from which to increase the overall Canadian population both at that site and at suitable neighbouring sites. Three sites are believed to be the minimum number that still allows for some redundancy and accounts for the possibility of stochastic events which could destroy one or more sites. The three sites for Vesper Sparrow affinis will not necessarily be the same sites used for Horned Lark strigata.
- The Nanaimo Regional Airport has participated actively in stewardship of Vesper Sparrow nesting habitat, previously through a stewardship agreement, and recently through the development of a site management plan (Beauchesne 2002c and Radcliffe 2010).
- Specific activities ongoing at the Nanaimo Airport include: habitat restoration work to reduce infilling of habitat by invasive exotic species, research to better document habitat used by the breeding Vesper Sparrow affinis, and annual inventory of the breeding population (Beauchesne 2002a, 2003, 2006, 2007, 2008, 2009, 2010b, 2011, 2012, 2013).
- The Nanaimo Area Land Trust (NALT) has developed a stewardship program with some of the local landowners adjacent to the Nanaimo Regional Airport. In addition, a landowner contact program was initiated in 2007-8, focused primarily on identification of additional suitable or restorable habitat for Vesper Sparrow affinis within 20 km of the Nanaimo Airport. Several potential suitable or restorable sites were identified, but further work is required to determine whether current land use is consistent with Vesper Sparrow breeding requirements. Previously, NALT has also held public information events and conducted media interviews to increase awareness and identification of the species, and to promote stewardship.
- The Garry Oak Ecosystems Recovery Team (GOERT) is coordinating conservation and recovery of Garry oak ecosystems in British Columbia. The Vertebrates at Risk Recovery Implementation Group of the Garry Oak Ecosystems Recovery Team is coordinating recovery actions for five species of birds associated with these ecosystems, including the Horned Lark strigata and the Vesper Sparrow affinis (Beauchesne 2004b).
- Habitat restoration work is underway in a number of areas managed for the purpose of conservation within the range of the Horned Lark strigata and the Vesper Sparrow affinis, some of which will benefit these species and other ground-nesting birds.
|Threat or limitation||Priority||Recommended approaches to meet recovery objectives|
|Broad Strategy 1: Complete an assessment of candidate sites featuring sparsely vegetated coastal dune or meadow habitat for suitability.|
|Knowledge gap on the identification of suitable sites.||Urgent|
|Broad Strategy 2: Secure, restore, create, preserve, or manage three of the most suitable sites.|
|Broad Strategy 3: Collaborate with international partners.|
Small population/ distribution effects
Knowledge gap related to U.S. threats
|Threat or Limitation||Priority||General Description of Research and Management Approaches|
|Broad Strategy 1: Manage and protect the habitat at the existing occupied site to support the current population and facilitate an increase in the existing population at the same site by 2–3 pairs|
|Broad Strategy 2: Complete an assessment of candidate sites with appropriate structural characteristics for suitability.|
|Broad Strategy 3: Secure, restore, preserve, or manage two additional sites of the most suitable candidates identified by 2015|
|Broad Strategy 4: Analyze the feasibility of active relocation of the Vesper Sparrow affinis to suitable unoccupied habitat.|
|Small population/ distribution effects||Beneficial|
|Broad Strategy 5: Collaborate with international partners.|
|Small population/ distribution effects||Beneficial|
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 in Canada. For the purposes of passive recolonization, some sites with suitable or restorable habitat remain, although they are widely dispersed, uncommon, and their relative suitability for future occupancy by Horned Lark strigata still needs to be assessed. Passive recolonization would involve colonization of currently suitable, restorable, or newly created habitat by dispersing individuals from U.S. populations, the likelihood of which is unknown; although an observation of an individual male in 2002 indicates it is possible. The recovery team has determined that an active reintroduction program is not feasible. 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. However, U.S. research to date has not been able to determine whether anthropogenic sites differ in habitat quality from natural habitats, due in large part to insufficient data with respect to relative adult survival in these habitat types (S. Pearson, pers. comm.).
The schedule of studies outlines how these knowledge gaps will be addressed. It will not be possible to identify critical habitat until candidate sites are assessed as being currently suitable or can be restored to a condition of suitability.
Vesper Sparrow affinis
In Canada, the Vesper Sparrow affinis is currently known to breed only on Vancouver Island at a single site near Cassidy, British Columbia (Beauchesne 2002a, 2003, 2006, 2007, 2009, 2010b, 2011, 2012, 2013).
The population and distribution objective for Vesper Sparrow affinis is to establish populations at three sites in Canada (maintain the currently occupied site, plus establish two additional sites). In this recovery strategy, critical habitat is only identified at the Nanaimo Airport site. Other habitats with potentially suitable or restorable habitat have not yet been identified and assessed. Consequently, the material here only represents a partial identification of critical habitat, based on the best available information. A schedule of studies (see section 8.2) has been included to complete the identification of critical habitat.
To carry out its life processes, the Vesper Sparrow affinis requires habitat for nesting, foraging, perching, and singing. These can all occur in one area, or it is possible to have perching and singing habitat in an adjacent area (within a territory) that is not suitable for nesting. Foraging can occur opportunistically anywhere within a territory. In addition, an open area ≥ 10 ha in size is required to support breeding Vesper Sparrows (Samson 1980, Herkert 1991).
The biophysical attributes of the nesting and foraging habitat consists of open areas with short, sparse grass or herbaceous cover, and intermittent bare ground. While the data gathered on Vesper Sparrow affinis has been insufficient to quantify suitable amounts of grass, forb, bare ground, and shrub cover specific to the subspecies, suitable amounts can be inferred from studies of the gramineus and confinus subspecies (Appendix A). The biophysical attributes of the perching and singing habitat are scattered shrubs and small trees.
At this site, the shrub component is dominated by Scotch Broom, a non-native invasive species that is targeted for removal in other parts of south-eastern Vancouver Island. It is important to note that this plant provides an important element of habitat structure without which the site would not be suitable as Vesper Sparrow affinis breeding habitat. Other native species could presumably perform this function equally well, but it remains unclear whether replacement of the Scotch broom and other non-native vegetation with native species would improve habitat quality or suitability for Vesper Sparrow affinis at this site. While native plant species may be desirable for a broader range of biodiversity values, and may possibly result in the reduction of ongoing vegetation management efforts, non-native plants including Scotch Broom and English Plantain will be tolerated within Vesper Sparrow affinis habitat at the Nanaimo Airport (and immediately adjacent land) until habitat restoration strategies at this site are further evaluated and developed (see Table 4).
Critical Habitat Identification
The area within which critical habitat is identified for the Vesper Sparrow affinis contains all actively defended territories3 observed between 2002 and 2012. (Beauchesne 2002a, 2003, 2004a, 2006, 2007, 2008, 2010a, 2010b, 2011, 2012, 2013). The methodology (for monitoring the population at the airport site) consists of intensive searches for Vesper Sparrows and their nests during the breeding period (i.e., early May to late July). Territory location and size estimates were derived by observing habitat features and singing perches used by the birds. An ongoing bird-banding program commenced in 2005, allowing for identification of individual birds, and greater certainty in mapping of individual territory boundaries.
Location of Vesper Sparrow affinis Critical Habitat
Critical habitat for Vesper Sparrow affinis is identified for one site found at the Nanaimo Airport (and immediately adjacent land) in British Columbia. The area containing critical habitat is represented in Figure 3. Within the represented area, critical habitat is defined as any habitat that possesses the biophysical attributes outlined above.
Figure 3. Critical habitat for Vesper Sparrow affinis near the southern portion of the Nanaimo Airport near Cassidy, British Columbia. Critical habitat occurs within the 1 km x 1 km UTM grids indicated (red outline), where the biophysical attributes set out in Section 8.1 are found.
Horned Lark strigata
Vesper Sparrow affinis
This recovery strategy has only partially identified critical habitat for Vesper Sparrow affinis, in that the population and distribution objective requires that populations be established at a minimum of three sites. It should be noted that the utility of identification of additional sites does not hinge on the development of active re-introduction techniques, as natural re-colonization of identified sites via dispersal from the extant breeding population is thought to be possible. Consequently, it may be possible to identify additional critical habitat following the completion of the following studies:
Activities that are likely to result in destruction of critical habitat are based on known habitat needs and habitat-related threats. Destruction would result if part of the critical habitat were degraded, either permanently or temporarily, such that it would not serve its biological function for the species. Destruction may result from single or multiple activities at one point in time or from the cumulative effects of one or more activities over time.
Vesper Sparrow affinis requires sparse grass or forb cover with intermittent bare ground for nesting and foraging, and shrubs and trees for song perches and escape cover. Examples of activities that are likely to result in the destruction of critical habitat, through the elimination of one or more of these key features include, but are not limited to, those listed in Table 5.
|Activity||Habitat feature destroyed||Biological function lost|
|Nesting and foraging habitat|
|Mowing during the breeding season (April 1-August 20)||Sparse grass or forb cover||Nesting and foraging|
|Seeding of rhizomatous mat-forming grasses||Sparse grass or forb cover and intermittent bare ground||Nesting and foraging|
|Perching and singing habitat|
|Significant shrub and/or tree removal||Trees and shrubs||Song perches and escape cover|
|Both habitat types (nesting and foraging and perching and singing)|
|Complete vegetation removal||All||All|
The performance indicators presented below provide a way to define and measure progress toward achieving the population and distribution objectives. Specific progress towards implementing the recovery strategy will be measured against indicators outlined in subsequent action plans.
Every five years, success of recovery strategy implementation will be measured against the following performance indicators:
Horned Lark strigata:
- Has a breeding population of at least 10 breeding pairs distributed across a minimum of three sites been established and maintained?
Vesper Sparrow affinis:
- Has a breeding population of at least 30 breeding pairs distributed across a minimum of three sites been established and maintained?
Separate action plans for each species will be completed by 2017. The previously posted recovery strategy indicated that an action plan would be completed for Horned Lark strigata by March 31, 2009. The reason the date is being amended is that more work is required to assess the candidate dune sites for suitability for Horned Lark strigata. This work will be completed along with other remaining steps in the schedule of studies between 2013 and 2016, with additional time allowed for the preparation and posting of the action plan.
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|Area||Mean grass cover (%)||Mean forb cover (%)||Mean bareground (%)||Mean shrub cover (%)||Mean height (cm)||Reference|
|Successful nests |
(n = 15)
|23.7 (7.6)||26.9 (18.6)||32.9 (20.7)||64.0 (14.5)||Wray and Whitmore (1979)|
|Unsuccessful nests |
(n = 24)
|23.1 (9.2)||20.5 (15.6)||44.8 (20.1)||67.1 (21.0)|
|Central British Columbia|
|Successful nests |
(n = 77)
(n = 43)
|High success territories |
(n = 124)
|42.8 (15.6)||37.0 (15.6)||21.9 (7.8)||37.6 (16.7)||Vickery et al. (1992)|
|Low success territories |
(n = 28)
|45.2 (32.3)||40.3 (32.3)||23.0 (15.9)||38.4 (26.5)|
A strategic environmental assessment (SEA) is conducted on all SARA recovery planning documents, in accordance with the Cabinet Directive on the Environmental Assessment of Policy, Plan and Program Proposals. The purpose of a SEA is to incorporate environmental considerations into the development of public policies, plans, and program proposals to support environmentally sound decision-making.
Recovery planning is intended to benefit species at risk and biodiversity in general. However, it is recognized that strategies may also inadvertently lead to environmental effects beyond the intended benefits. The planning process based on national guidelines directly incorporates consideration of all environmental effects, with a particular focus on possible impacts on non‑target species or habitats. The results of the SEA are incorporated directly into the strategy itself, but are also summarized below in this statement.
This recovery strategy will clearly benefit the environment by promoting the recovery of the Horned Lark strigata subspeciesand Vesper Sparrow affinis subspecies. The potential for the strategy to inadvertently lead to adverse effects on other species was considered. The SEA concluded that this strategy will clearly benefit the environment and will not entail any significant adverse effects.
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; COSEWIC Threatened), 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 on Schedule 1 of SARA and requires sparsely vegetated grasslands (Environment Canada 2006). The sand verbena moth (Copablepharon fuscum) is also listed as Endangered on SARA 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) is listed as Endangered on Schedule 1 of SARA 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 conservation and recovery.
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 tern.
1 COSEWIC – Committee on the Status of Endangered Wildlife in Canada
2 A set of closely linked genetic markers present on one chromosome which tend to be inherited together.
3 Active territory defense includes singing from regular perches along the territory periphery as well as physical interactions with neighbouring territory-holders.
- Date Modified: