Eastern persius duskywing: COSEWIC assessment and status report: chapter 7

Habitat

Habitat Requirements

Erynnis p. persiusoccurs in jack pine (Pinus banksiana) barrens, pine-oak barrens, oak savannahs and other open woodland with populations of wild lupine (L. perennis) or wild indigo (B. tinctoria) (NatureServe Explorer 2001). In the United States, skipper is sometimes found along roadsides through forest (S. Daniels, pers. comm., 2002) and has been collected in seemingly unsuitable habitat away from any obvious populations of lupines (Borth 1997, Layberry et al. 1998, NatureServe Explorer 2001). Adults are believed to nectar at a variety of plant species (NatureServe Explorer 2001), but because the presence of the larval host plants is necessary for breeding, the species should be considered a habitat specialist. Older literature lists a variety of host plants for the species, including wild indigo, hairy ceanothus (Ceanothus oliganthus Nutt.), milkpea (Galactia sp.), bush-clover (Lespedeza sp.), birdsfoot trefoil (Lotus unifoliolata(Hook.) Benth.), poplars and aspens (Populus spp.), scrub oak (Quercus ilicifolia Wangenh.), tall prairie willow (Salix humilis Marsh.) and tree clover (Trifolium ciliolatum Benth.) (Tietz 1972). Scudder (1889) states he found E. p. persius in abundance on tall prairie willow and poplars, and Lindsey (1927) reports rearing it on poplar. This information was widely reported and believed until the late 1970s, when wild lupine was reported as the host plant of the Eastern Persius Duskywing (Balogh 1981). Since then, wild indigo has also been reported as a host plant for E. p. persius (D. Schweitzer, pers. comm., 2002). Because E. p. persius is sodifficult to identify, most early observers were likely not identifying Erynnis species correctly, and the early reports of a wide range of host plants are unlikely to be trustworthy, especially given the host-specific nature of other taxa within the complex.

Matt Holderbelieves that wild lupine (at least L. perennis) is the main host plant for E. p. persius in Canada, and populations of the skipper will be associated with populations of the plant. Wild lupines are known to occur at several locations in southwestern Ontario, usually in sites with tallgrass prairie or savannah habitats. Savannahs, such as those found in the Grand Bend area, are open areas interspersed with mature trees (especially oaks) that often grade into tallgrass prairie. Under natural conditions, these habitats are subject to frequent fires that prevent woody plants from colonizing and a significant shrub layer or understorey from forming. Lupinus perennis still persists in some locations in southern Ontario and it is to these locations that E. p. persius was likely restricted.

Many rare insect and plant species are also associated with tallgrass and prairie communities, including two butterflies designated by COSEWIC as Extirpated: Karner Blue (L. m. samuelis) and Frosted Elfin (Callophrys irus (Godart)). Although the Eastern Persius Duskywing’s tolerance to disturbance is unknown, the two other lupine butterfly species have shown intolerance to habitat change. Additionally, the Mottled Duskywing (Erynnis martialis) has been reported to require open habitats and to be absent from otherwise suitable sites that have more than 55% woody cover (Swengel 1994). It is reasonable to expect that the Eastern Persius Duskywing shares a similar intolerance, although this hypothesis is purely conjectural and the skipper may be restricted only by the presence and abundance of its host plant.

In addition to the presence of the host plant, E. p. persius appears to favour habitat with other characteristics. Swengel (1994) and others have identified that open woodland habitat, principally sandy areas with sparse vegetation interspersed with oak saplings, is key to E. p. persius (Kons 1997). Additionally, Iftner et al. (1992) report that E. p. persius will not oviposit on lupines in shade. However, Maxwell and Ferge (1994) found this skipper in both open and shady woodland habitat, and Kons (1995) believed that E. p. persius flies through closed forest to disperse to patches of lupine. It is likely that open areas with patches of lupine are necessary for oviposition, but forest is not a barrier to dispersal.

Although the spatial structure of E. p. persius populations has not been quantified, it appears that population dynamics, characterized by local extinctions and recolonizations as described by Givnish et al. (1988), exist at the landscape scale. In the past, open woodlands that hosted wild lupines were maintained through fire, and E. p. persius populations would only persist if individuals escaped to neighbouring unburned patches of lupine. However, in the absence of fire, it is possible that E. p. persius may be able to persist in isolated patches of suitable habitat if maintained through some other means (e.g., mowing after mid-July as part of a plan to inhibit woody plant colonization and to promote lupine growth). Most extant lupine sites in Ontario are isolated with few plants (P.A. Woodliffe, pers. comm., 2002; W. Bakowsky, pers. comm., 2002; D. Sutherland, pers. comm., 2002), although there are several locations with large patches of lupine, such as St. Williams and The Pinery. In Michigan, it is thought that at least 200 sq. ft. (approximately 20 m2) of suitable habitat with an abundance of lupines would be required to support a small population (M. Nielsen, pers. comm., 2005). Management through clearing of woody plants and replanting or reseeding of lupines in Lambton County and at St. Williams has maintained a patchy distribution of the host plants. Additionally, one small population (50-100 plants) in Peterborough County (Don Sutherland, pers. comm., 2002) has persisted on a roadside through standard roadside management (mowing).


Trends

Declines in savannah and prairie habitat are widespread in northeastern North America. Reasons for this decline include resource extraction, agricultural use and development, urbanization and fire suppression. In the Midwestern United States, where conservation of savannah and prairie habitat is considered the most progressive, less than 25% of original habitat survives, and then in a degraded state (Nuzzo 1986). Nuzzo (1986) estimated that 0.02% of the upper Midwest (Missouri northward) that supported oak savannah before European settlement still existed in a healthy state. Still, D. Schweitzer (pers. comm., 2002) reports that much of the existing habitat across northeastern North America that would appear to be capable of supporting E. p. persius lacks the species entirely.

In Ontario, widespread habitat change through urbanization, agricultural development and resource use has adversely affected many species. Indications are that prairie and savannah habitat occurred across much larger areas of southern Ontario than at present (Bakowsky 1999), probably hosting populations of wild lupine and potentially supporting E. p. persius populations. It is estimated that roughly 2000 km2 of prairie, savannah and open woodland occurred in Ontario prior to European settlement, but less than 20 km2 of this habitat remains (Varga 1999). Catling et al. (1992) believed the Rice Lake Plains north of Cobourg were composed of prairie and savannah habitat and had the most extensive lupine populations in Ontario. These plains could have hosted E. p. persius and other lupine feeders, such as L. m. samuelis (Catling and Brownell 2000), but the habitats had been destroyed by 1900 and now only relict populations of lupines survive in this area (Brownell and Blaney 1996, D.A. Sutherland, pers. comm., 2002). However, one large patch of existing tallgrass prairie and savanna habitat in the region hosts a sizeable population of several thousand lupines.

Other sites with lupine populations include High Park in Toronto, and Walpole Island. High Park has suffered from disturbance and habitat degradation, including poor habitat management in the past, invasion of non-native plants and human disturbance. Recent efforts have improved the habitat at High Park (City of Toronto 2002), but considering several factors (e.g., the distance from source populations of E. p. persius, and past habitat change), it is unlikely that E. p. persius will occupy this extant habitat by natural means. There are unconfirmed records (no specimens) of Erynnis p. persius from Walpole Island (Kulon et al. 1987), which had hosted a "substantial" population of wild lupines (Woodliffe and Allen 1988). However, this lupine population was destroyed in 2001 with the expansion of a sand extraction operation (P.A. Woodliffe, pers. comm., 2002). This site will not support E. p. persius without rehabilitation.

Habitat degradation in the St. Williams and Pinery areas has been well documented (e.g., Stead 1993). Human-induced forest succession, through tree planting and fire suppression, has been the primary cause of this habitat change. At least at The Pinery Provincial Park, extensive browsing by White-tailed Deer (Odocoileus virginianus (Zimmermann)) may also be responsible for declines in lupine populations (Hess 1992). Although browsing by White-tailed Deer is a natural factor, the tremendous population of this herbivore brought about by removal of deer predators and competitors and landscape change is exerting extreme pressure on lupines and other herbaceous plants in the prairie and savannah remnants of southern Ontario. St. Williams and the Pinery area were important to E. p. persius, and details on habitat change and rehabilitation efforts at these two sites are provided below.

Recent efforts have been put forth by Ontario Parks and Lambton Wildlife Incorporated to restore savannah habitat in North Lambton County, primarily for the purpose of conserving habitat for L. m. samuelis. However, these initiatives were implemented after suitable habitat had become sufficiently rare to cause the extirpation of L. m. samuelis and probably E. p. persius. In The Pinery Provincial Park, Ontario Parks has undertaken planning and management activities to promote the health of natural oak savannah (Ontario Ministry of Natural Resources 1986), which has resulted in a recovery of wild lupine populations. These efforts include population control of White-tailed Deer through an organized cull, creation and maintenance of a deer exclosure in open woodland near the south end of the park, and transplantation of wild lupines from a source population outside the park. As a result of these efforts, four small areas within The Pinery Provincial Park host lupine populations (Appendix 2).

There are several areas with wild lupine populations outside the park (Appendix 2). The most significant site is the Karner Blue Sanctuary near Port Franks, Ontario, a significant natural area owned and managed by Lambton Wildlife Incorporated. The site hosts hundreds of individual lupines, mostly in the open woodland of “The Bowl” found in the southeastern corner of the property, and has the highest quality of habitat for E. p. persius in the area. A management plan has been drafted (Banks et al. 2001) and is undergoing implementation with the intention of creating habitat suitable for a re-introduction of L. m. samuelis. Restoring the integrity of the oak savannah habitat at the Karner Blue Sanctuary has included prescribed burns, removal of woody vegetation and planting of wild lupines (Banks et al. 2001, P.M. Banks, pers. comm., 2002). Matt Holder believes this area has high quality habitat for E. p. persius.

Outside of The Pinery Provincial Park, the St. Williams Crown Forest hosts the largest area of savannah still remaining in the Carolinian life zone of Canada and possesses a very high diversity of plants and animals, many of them rare in Ontario and Canada (Draper et al. 2002). Although much of the area was forested in 1945, a large portion of the Manestar Tract, where considerable numbers of lupines presently grow, was clearcut by 1953 and sand was extracted between 1955 and 1972 (Draper et al. 2002). Throughout these years, savannah habitat persisted in certain southern sections of the property. These small remnants were subject to forest succession in the absence of a natural thinning process, but were thinned to savannah conditions in 1991 (Draper et al. 2002). The last observations of E. p. persius, C. irus and L. m. samuelis were made at one of these remnants. Elsewhere in the Tract, lupines and other plants with savannah/prairie affinities have continued to occupy open areas adjacent to ingrown savannah, particularly along access roads, open trails and the large field at the north end of the property.

Management for savannah at the Manestar Tract of the St. Williams Crown Forest has included vegetation removal and seeding of lupines. A management plan for the Manestar Tract exists in draft form (Allen 1992), but has yet to be finalized and implemented. Further recommendations for rehabilitating and managing the St. Williams Crown Forest are presented by Draper et al. (2002). The St. Williams Crown Forest will soon be a Conservation Reserve to be administered by Ontario Parks (OMNR 2005).


Protection/Ownership

Habitat suitable for breeding E. p. persius exists in the St. Williams area on Crown land managed by the Ontario Ministry of Natural Resources; in The Pinery Provincial Park, controlled and managed by Ontario Parks; and on property owned and controlled by Lambton Wildlife Incorporated, a conservation and naturalist group in Lambton County. Additional areas with wild lupines are controlled by First Nations (Walpole Island) and local government (e.g., in Norfolk County and Toronto), although the ownership of some sites is unclear. For most sites, it is unlikely ownership will change in the future, but the fate of lupine populations east of Delhi (Appendix 2) is to be determined. Roughly 80-90% of suitable habitat is protected from destruction, although management plans have not been created for many sites.

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