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HomeMy WebLinkAboutAddenda - RFP - P982 BOBCAT RIDGE TRAIL DESIGN AND CONSTRUCTON (2)Chapter 4. Wildlife Bobcat Ridge Natural Area has several habitat types characteristic of the Colorado Front Range foothills which in turn supports a diversity of wildlife. Examples of significant species that are known to occupy Bobcat Ridge include: elk, deer, black bear, mountain lion, black-tailed prairie dog, golden eagle, grasshopper sparrow, and black-chinned hummingbird. The Moss’s elfin butterfly and Townsend’s big-eared bat are state-listed species of concern that are found at Bobcat Ridge. The natural area is also potential habitat for dusted skipper and rhesus skipper butterflies, tracked by the Colorado Natural Heritage Program, and federally threatened Preble’s meadow jumping mouse. Maintaining and enhancing the diversity of wildlife requires careful management especially as the site is managed for visitor use. Bobcat Ridge provides important winter forage for elk, mule deer and wild turkey. The natural area also supports black bears and mountain lions which raises the potential for human-wildlife conflicts. It is imperative to carefully balance the location and timing of recreation in order to limit interactions. Another possible management decision that will impact wildlife is grazing. Consideration will be given to fence and stock tank design to help minimize injury or loss of wildlife. The location and design of fences will be adjusted to accommodate wildlife movement if necessary. Rescue ladders will be placed in all water stock tanks to assist small mammals and birds that may not otherwise be able to escape the tank. The following sections provide specific conservation and management strategies for Bobcat Ridge’s wildlife. Mammals There are a wide variety of mammals present in Bobcat Ridge Natural Area. Significant species known to be present on the site are listed in Table 4.1 below. Other species that may possibly occur in the natural area, based on their habitat requirements and the habitats present, are listed in Table 4.2. While these tables are not comprehensive, knowledge of the presence or likelihood of these species will assist in management decisions. A complete list of mammal species at Bobcat Ridge Natural Area is in appendix IV. Table 4.1. Significant mammalian species present Common Name Scientific Name Habitat Types* Elevation Range (ft) CDOW Status American Elk Cervus elaphus 2 - 6 6,000 –13,000 Big-Game Mule Deer Odocoilus hemionus 2 – 6 3,000 – 13,000 Big-Game Coyote Canis latrans 1 – 7 3,000 – 14,500 Furbearer Red Fox Vulpes vulpes 1 – 2 4 – 6 3,000 – 14,500 Non-Native Furbearer Black Bear Ursus americanus 2, 4 – 7 4,500 – 11,500 Big-Game Mountain Lion Puma concolor 2 – 6 3,000 – 12,500 Big-Game Bobcat Lynx rufus 2 – 7 3,000 – 14,500 Furbearer Black-tailed Prairie Dog Cynomys ludovicianus 1, 3 – 4 3,000 – 6,500 State Species of Concern Townsend’s Big-eared Bat Corynorhimus townsendii pallescens 1,2,4,5 3,000 – 9,500 State Species of Concern *Habitat Types: 1. Urban and Croplands 2. Riparian/ Wetlands 3. Grasslands 4. Shrublands 5. Fore 6. Tundra 7. Unvegetated, Exposed-Rock Table 4.2. Significant mammalian species of possible occurrence Common Name Scientific Name Habitat Types* Elevation Range (ft) CDOW Status Gray Fox Urosycon cinereoargenteus 2–5 & 7 5,500 – 13,000 Not-Listed Western Spotted Skunk Spilogale gracilis 4–5 & 7 4,000 – 8,000 Not-Listed White-tailed Deer Odocoileus virginianus 2–5 3,000 – 12,000 Big-Game Yellow-Bellied Marmot Marmota flaviventris 2 & 4–7 5,400 – 14,500 Small-Game American Badger Taxidea taxus 2–6 4,500 – 14,500 Furbearer Preble’s Meadow Jumping Mouse Zapus hadsonius preblei 1-3 4,000-8,500 Federal and State Threatened * Habitat Types: see footnote for Table 4.1. Ungulates Deer and elk routinely occupy most areas within Bobcat Ridge Natural Area. However, their specific densities, critical range and movement corridors require further investigation. Vegetative indicators of plant health need to be established to help monitor plant and community response to grazing by deer, elk and domesticated cattle. Similarly, conservation targets such as native grassland remnants should be actively monitored for the purpose of maintaining or improving health and condition. Figure 4.1. Elk at Bobcat Ridge Natural Area (photo Hunting and grazing may play a role in the management of resources at Bobcat Ridge. The interplay of grassland and forage resources, grazing by wild and domestic ungulates, and management actions will require more specialized planning, inventory, and monitoring to ensure proper stewardship of both the wildlife and habitat resources. Conservation Target Elk and Deer Objectives Optimize habitat value and protect critical range(s). Natural Processes/ Functions/ Interactions Species will prosper through reproduction, recruitment, and ability to disperse. Naturally occurring in a healthy ecosystem. The combined effect of regional habitat loss, reduced natural predation and increased competition and grazing intensity with domestic grazers act to negatively impact habitats. Threats & Stresses (Sources of Stress)  Chronic Wasting Disease (CWD).  Competition for vegetative and water resources with cattle.  Disturbance from humans during critical times (e.g., calving season).  Migration corridors can become impeded by inappropriate or unnecessary fences, roads, or canals.  The absence of predation may stress the biological community through increased competition and grazing pressure from native species. Strategy/ Action  Become familiar with CWD and its impacts. Research and inter- agency cooperation will be employed.  Manage both native and domestic grazing activities to ensure health of grassland and forage resources. Implement sound grazing practices to prevent overgrazing and protect water resources.  Identify and protect critical areas from unnecessary disturbance. Designate seasonal off-limit or limited-access areas where appropriate.  Identify and take informed corrective measures to avoid impeding animal movement.  Evaluate the relationship between cattle grazing and perpetuating healthy grassland and riparian plant communities.  Identify indicators for population threshold to best maintain a diverse and sustainable system. Measure of Success To be determined by estimating annual population densities, vegetative analysis, and hydrology disturbance. Conservation Plan  Monitor for animals exhibiting symptoms of CWD; work with CDOW to mitigate any outbreaks.  Determine the densities, distribution, and critical range of deer and elk.  Establish a monitoring plan to identify the dynamics of the ecosystem response to management decisions.  Implement corrective measures to protect habitat (e.g., riparian areas, remnant grasslands) before or as soon as degradation occurs.  Employ management measures to prevent disturbance during mating and calving seasons.  Identify movement/migration throughout the natural area. Remove unnecessary fencing to minimize species movement.  Identify critical indicators that would trigger the need to reduce herd number.  Enhance habitat condition by creating “patches” of grasslands (5 acres in size) within the burned forest matrix. Black-tailed Prairie Dog Recently, the black-tailed prairie dog was removed from the US Fish and Wildlife Service’s Federally Threatened Species candidate list. Despite its removal from the federal list this species remains on the Colorado State Species of Special Concern list. Prairie dogs are a prey and habitat base for a suite of grassland wildlife. Educational information regarding these benefits should be part of the human experience when interacting with nature at this site. Location of trails or other activities should not interfere with opportunities for a healthy predator/prey relationship. The identified prairie dog colonies at Bobcat Ridge are shown in Figure 4.5 (at the end of this chapter). Conservation Target Black-tailed Prairie Dogs Objectives Maintain stable populations that are balanced with other conservation targets. Natural Processes/ Functions/ Interactions Species will prosper through reproduction, recruitment, and ability to disperse. Naturally occurring in a healthy ecosystem. The combined effect of habitat loss, reduced natural predation and increased competition and grazing intensity with domestic grazers reduces habitat quality. Threats & Stresses (Source of Stress)  Increase in animal densities and distribution could reduce available resources.  Bubonic plague, an introduced disease from Europe.  Poisoning or translocation resulting from human conflict.  Lack of native predators to help maintain stable population densities. Strategy/ Action  Maintain stable populations through management of prairie dog population densities.  Identify locations of concern and monitor for unusual fluctuations in population density.  Educate people regarding the benefits of prairie dogs to the ecosystem.  Encourage or influence natural predation. Measure of Success To be determined by estimating annual population densities. Analysis of vegetative resource health would also help establish a benchmark from which to measure the level of success. Conservation Plan  Determine sustainable prairie dog densities and implement a plan to maintain the recommended numbers.  Determine intervention measures to be taken in the event of a plague epizootic.  Install educational interpretation regarding the benefits of prairie dogs to their environment.  Reduce disturbance and fragmentation of habitat and place predator enhancements where needed to encourage a balanced predator/ prey relationship. Preble’s meadow jumping mouse Portions of the Bobcat Ridge Natural Area fall within the Colorado Natural Heritage Program’s Big Thompson River Potential Conservation Area (PCA). The Big Thompson River PCA identifies potential habitat for the Preble’s meadow jumping mouse (Zapus hudsonius preblei), a member of the Federally Threatened Species List. Although not currently documented at Bobcat Ridge, Preble’s meadow jumping mice have been documented in nearby riparian areas at elevations from 5,085 to 7,400 feet (see appendix IV for a detailed description of the Big Thompson River PCA). Habitat for this species consists of riparian vegetation dominated by willow (Salix spp.) with scattered stands of cottonwood (Populus spp.). Also found in these mesic habitats are snowberry (Symphoricarpos occidentalis), wild rose (Rosa woodsii), and mountain mahogany (Cercocarpus montanus). Stream banks have native sedges (Carex spp.) and rushes (Juncus spp.). Surrounding uplands are generally mid-grass prairie with stands of ponderosa pine (Pinus ponderosa). This habitat has been identified at Bobcat Ridge Natural Area (Figure 4.5). In August 2004, the City’s Natural Areas Program contracted with Jan Peterson, Ph.D. to conduct a trapping survey on city-owned portions of Buffum Canyon. From August 24 to August 28, 175 traps were laid out in two transects, one on each side of the stream. During the total of 700 trap-nights, 135 rodents were captured; 10 long-tailed voles (Microtus longicaudus), 18 Mexican woodrats (Neotoma mexicana), 97 deer mice (Peromyscus maniculatus), and 10 Northern rock mice (P. nasutus). No Preble’s meadow jumping mice were detected at this site, however, the survey was limited to the immediate vicinity of CR 32C in Buffum Canyon, at the entrance and parking lot area of the site. The results are not applicable to any other area of Bobcat Ridge (see appendix IV for the full survey report). Surveys of the potential habitats on the interior parts of Bobcat Ridge will need to be conducted. The Colorado Natural Heritage Program has identified urban/rural development, recreational use, and management of water resources as the most likely threats to this species. Recreational use is heavy throughout the Big Thompson River PCA, and such impacts to riparian and upland grassland habitats could reduce jumping mouse abundance. The Preble’s meadow jumping mouse has been shown to tolerate low levels of recreational use (hiking trails) in riparian communities, but such impacts should be mitigated to improve riparian shrubland and herbaceous cover. In areas where creeks and streams no longer flow at historic levels the riparian habitat is reduced in size and density. Such water flow impacts can jeopardize the persistence of jumping mice by decreasing the amount of available riparian habitat. Maintaining historic flows or increasing the water table in such areas can restore the riparian vegetation and maintain jumping mouse abundance. Conservation of riparian areas in Bobcat Ridge will include restoring historic flows (removing stock tanks and other such impacts), as well as dealing with erosion from the burned area and cattle grazing in the riparian areas. To ensure the persistence of jumping mouse populations, it is essential that development in and around riparian corridors provide both riparian and upland habitat for jumping mice. Jumping mice have been documented using upland habitats. It is possible that habitats lacking adjacent upland grassland are insufficient for local survival of the jumping mouse. Minimizing the extent to which riparian areas and adjacent upland habitats in Bobcat Ridge are impacted will ensure a suitable habitat remains available for the jumping mice should they return to the area. Management strategies restricting impacts such as excessive grazing and compaction of soils near riparian systems will likely increase the possibility of jumping mouse populations. Grazing can restrict the expanse of riparian shrub communities, and thus, restrict the ability for Preble’s meadow jumping mice to utilize the area. However, mild grazing pressure may not affect a population. Conservation Target Preble’s meadow jumping mouse (Zapus hudsonius preblei) Objectives Optimize habitat quality of riparian areas and adjunct grasslands to encourage the establishment of native jumping mice. Natural Processes/ Functions/ Interactions Species will prosper through reproduction, recruitment, and ability to disperse. Naturally functioning hydrology is essential in riparian areas. Threats & Stresses (Source of Stress)  Artificial manipulation of hydrology and/or overgrazing in these areas can expose a site to invasion by opportunistic weedy species.  Soil erosion and/or increased runoff from severely burned areas can negatively alter water quality and decrease bank stability. Strategy/Action  Restore natural hydrology to all drainages. This could include removal of stock tanks and implementing soil erosion prevention practices.  Eliminate grazing from riparian areas and buffer 100 feet back to provide for adjacent grassland. This may require some form of fencing to exclude cattle while the grazing lease is active.  Advance soil protection measures to ensure severely burned areas are not sediment loading drainages or eroding stream banks. Measure of Success Colonization of the area by Preble’s meadow jumping mice would indicate success, though there are likely off-site factors (proximity to existing population, lack of migratory corridors, etc.) that may impede success of colonization. Conservation Plan  Determine the presence of jumping mice at interior locations of Bobcat Ridge. If not found, determine whether known mice populations would be able to colonize portions of Bobcat Ridge.  If occurrences of Preble’s are documented or if migration corridors exist that would connect Bobcat Ridge with locations of known populations, investigate the functioning condition of riparian areas and adjacent grasslands on the property.  Inventory and examine the sources of hydrology (overland runoff, springs and seeps) to determine the extent of impacts that may be related to cattle grazing. Determine sources of erosion and erosion damage along drainages and stream banks.  If populations exist or are able to access Bobcat Ridge, restore natural hydrology to drainages, restrict grazing from riparian and adjacent grassland areas, and implement soil protection measures.  If a population were to become established, monitor and coordinate with the US Fish and Wildlife Service. Carnivores Coyotes, black bear, red fox, mountain lion and other species have been sited at Bobcat Ridge. It is highly probable that most of these species use Bobcat Ridge and adjacent areas as they have large home ranges. There are no known dens or other critical habitat features; however it is likely that some exist. Sensitive habitat such as these will surveyed to ensure protection of the sites from human disturbance. An example of one possible site is a rocky outcrop near Mahoney Park that is referred to by locals as the “cat box.” Seasonal wildlife closures of identified areas accompanied by buffer zones that protect predators, prey and visitors should be implemented. Education and enforcement of closure areas by staff rangers will be essential for the protection of wildlife and prevention of human conflicts. Conservation Target Carnivores Objectives Optimize and protect habitat (e.g. den sites). Natural Processes/ Functions/ Interactions Species will prosper through reproduction, recruitment and the ability to capture prey Threats & Stresses (Source of Stress)  Unnecessary disturbance from human activities (e.g., recreation).  Habituation to human activities (e.g., trash).  Conflictive encounters with humans.  Absence of other native carnivores.  Reduction of available prey. Strategy/ Action  Identify den sites and other sensitive areas.  Restrict or minimize human activities that could potentially lend themselves to habituation.  Inform recreational users and staff of potential for encounters with predators.  Identify prey species and protect their availability and accessibility for predators. Measure of Success May be determined by estimating annual population densities and analysis of behavioral response to increased human activities. Conservation Plan  Identify sensitive habitat and ensure its protection.  Strictly enforce regulations regarding “Leave No Trace.”  Educate through interpretation (e.g., signage and pamphlets).  Allow and manage for returning predators to return.  Establish buffer zones and avoid fragmentation of areas where prey is abundant. Bats Townsend’s big-eared bat (Corynorhimus townsendii pallescens) has been observed on the property and is a species of special concern at the state and federal level. Other bats are likely to occur and hunt in the area. Roost and possible hibernation sites should be identified and protected, as all bats are considered species of concern. Working with other agencies, like the US Geological Survey (USGS), Colorado Bat Society (CBS) and Bat Conservation International (BCI) will assist in our efforts to protect sensitive habitat for these species. Conservation Target Bats (Corynorhimus townsendii pallescens) Objectives Optimize habitat value. Natural Processes/ Functions/ Interactions Species will prosper through reproduction and ability to hibernate and migrate and are naturally occurring in a healthy ecosystem. Threats & Stresses (Source of Stress) Disturbance to roost sites from human activity. Strategy/ Action  Become familiar with species that occupy the area, their habits and roost sites.  Protect existing and potential roost and hibernation sites Measure of Success May be determined by estimating annual population and species diversity. Conservation Plan  Work with the USGS, CBS and BCI to determine species and roost sites.  Identify and protect existing and potential roost and hibernation sites. Birds Bird surveys conducted between June and December 2004, found 91 species of birds at Bobcat Ridge Natural Area (see Appendix IV for the complete list. Note: the current list does not include spring migrants) indicating a wide variety of bird species. This may be attributed to the diverse habitats found at Bobcat Ridge. Each plant community playing a critical role in supplying breeding, nesting, and feeding grounds, or migration stop-over point. Additionally, specific areas within each plant community may have special importance to known species or serve as potential habitat for new species. For example, the alfalfa field in the southeast corner of Bobcat Ridge supported a large number of grasshopper sparrows (figure 2) which are likely nesting in the area. Likewise, the burn area of the 2000 Bobcat Gulch Fire produced a large number of standing-dead trees, supplying important habitat for primary and secondary cavity nesters. This area also has the potential to draw three-toed woodpeckers, a species considered “uncommon to rare” by expert ornithologists. The Figure 4.2. Grasshopper sparrow. mountain shrub community found provides important habitat for a number of resident migratory species including bushtits, sage thrashers, and Wilson’s warbler. Riparian corridors provide important nectar sources during the spring and fall migration of species like black-chinned and broad-tailed hummingbird (Selasphorus platycercus). The cliff faces around the site serve as potential nesting habitat for white-throated swifts (Aeronautes saxatalis), cliff swallows (Petrochelidon pyrrhonota) and a variety of raptors like golden eagles, red-tailed hawks, and prairie falcons. A list of noteworthy bird species (locally common species not shown) found at Bobcat Ridge is shown in Table 3. Table 4 provides a list of significant birds that may occur. Both lists are presented for consideration as management decisions are made and actions implemented. It is important to understand that these lists are not comprehensive and will be added to as further observations are made. Table 4.3. Noteworthy bird species at Bobcat Ridge (not a complete list) Group Common Name Scientific Name Habitat Types* Elevation (ft)/ Range Nesting Preference American Vultures Turkey Vulture Cathartes aura 1 - 7 3,000 – 9,000 Breeding Cliff Ledge Kites, Eagles Golden Eagle Aquila chrysaetos 1 – 7 3,000 – 14,000 Year-round Cliffs and Trees Accipiters Sharp-shinned Hawk Accipiter striatus 1 - 6 3,000 – 11,500 Year-round Forest Cooper’s Hawk Accipiter cooperii 1 – 7 3,000 – 10,000 Migrant & Winter Forest Buteos Red-tailed Hawk Buteo jamaicensis 1 – 7 3,000 – 13,500 Year-round Cliff Falcons and Caracara Prairie Falcon Falco mexicanus 1 - 7 3,000 – 14,000 Year-round Cliff Grouse & Turkey Blue Grouse Dendragapus Table 4.4. Significant bird species of possible occurrence Group Common Name Scientific Name Habitat Types* Elevation (ft)/ Range Nesting Preference Kites, Eagles Bald Eagle Haliaeelus leucocephalus 1 - 6 3,000 – 8,000 Winter Cliffs and Trees Buteos Swainson’s Hawk Buteo swainsoni 1 - 7 3,000 – 10,000 Breeding Trees Rough-legged Hawk Bueto lagopus 1 - 6 3,000 – 9,500 Winter Trees Ferruginous Hawk Buteo regalis 1 – 7 3,000 – 9,000 Year-round Trees Owls Burrowing Owl Athene cunicularia 1 – 4, 6, 7 3,000 – 9,000 Summer Underground burrows Woodpeckers Three-toed Woodpecker Picoides tridactylus dorsalis 2, 5 8,000 – 11,500 Year-round Cavity *Habitat Types: See footnote for Table 4.3. Conservation of bird species (on-site) will likely depend on restoration efforts to enhance existing habitats In addition, threats such as West Nile Virus will require monitoring such that management action may be taken to mitigate negative impacts. Measures will be taken to avoid the use of insecticides as broad-spectrum chemicals may negatively the prey base for insectivorous birds. Figure 4.3. Lewis’ woodpecker Photo courtesy of Cole Wild Conservation Target Birds Objectives Optimize habitat value and protect breeding, migration, summer, winter and year-round ranges. Natural Processes/ Functions/ Interactions Species will prosper through reproductive success and ability to forage, migrate or over-winter. Threats & Stresses (Source of Stress)  West Nile Virus.  Human and domestic animal disturbance.  Habitat loss or change (i.e. alfalfa field, burn area, riparian areas, neighboring developments). Strategy/ Action  Monitor health of species and become familiar with measures to protect or avoid exposure to infection.  Identify sensitive areas and implement seasonal or annual closures to reduce potential disturbance.  Manage to maintain or increase important habitat.  Prohibit dog walking at Bobcat Ridge. Measure of Success May be determined by continuing surveys for estimating diversity and densities. Analysis of behavioral response to human activity. Conservation Plan  Monitor for presence of mosquito-borne virus or other diseases.  Establish buffer zones and close sensitive areas in need of protection.  Maintain and monitor agricultural field in southeast corner for Grasshopper sparrow habitat.  Manage burned areas to provide standing dead trees for primary and secondary cavity nesters.  Maintain or restore the mountain shrub communities to provide for resident and migratory species.  Manage for increasing nectar sources for resident and migrating hummingbirds.  Maintain or restore the riparian corridor communities to provide for resident and migratory species.  Install wildlife “escape ladders” in water stock tanks. Moths and Butterflies As part of the biological survey done by Colorado Natural Heritage Program (CNHP) in the summer of 2004, an inventory of moths, butterflies and their habitats was conducted (Drummond 2004). The Colorado Front Range is the fourth richest butterfly region in the United States (Opler 1994; Opler and Krizek 1984). This is likely due to the variety of environmental conditions at the convergence of the Rocky Mountains and Great Plains, including moist and arid zones, mountain and plains habitats and forest and grassland communities. Table 5 summarizes the major butterfly habitat types in Bobcat Ridge Natural Area. Table 4.5 Major butterfly habitat types at Bobcat Ridge Natural Area Habitat Types Notes Rating (1 = low, 5 = high) 1. Foothills canyons, with water present Sections of east-draining canyons with steep granite walls, running water, plunge pools; with stonecrop [Sedum lanceolatum] for Moss’s Elfin and wild hops [Humulus lupulus] for Hops Azure. [Note: Sedum was present, but Humulus was not seen.] 3 2. Native short-grass and mixed grass prairies None seen 1 3. Grassy openings in coniferous forests On upper ridges between east-draining canyons and along the upper North road and upper Power Line Road (leading to Mahoney Park.) 3 4. Old fields, pastures, roadsides, power-line cuts Areas west of the Hanson Feeder Canal in the southern portion, with better examples further north to the west of the historic cabin. These are very disturbed with little native vegetation. 2 5. Rocky outcrops, serpentine areas Extreme NE corner of property, to the ENE of the historic cabin, has good sandstone outcrops culminating in a tiny plateau rich in wildflowers, especially Asteraceae, and with some native grasses. 4 6. Wet meadows, bogs, fens, marshes and stream sides Mahoney Park has extensive wet meadows with representative wetland vegetation. Brooks Canyon is very disturbed riparian. 3 Bobcat Ridge Natural Area was surveyed for butterflies on April 16, 2004, and on May 21, 2004. A total of 19 species of butterflies were recorded from 11 hours of observation (Table 4.6). This is a very low number of species to be observed for a spring survey in the Colorado foothills. No single species was very common, and fully a third of the recorded species were represented by a single observation. Table 4.6. Butterfly species observed in April and May in Bobcat Ridge Natural Area Common Name Scientific Name Habitat Types* Number observed 4/16 5/21 Anise Swallowtail Papilio zelicaon 6 1 0 Colorado Marble Euchloe ausonides coloradensis 1,6 6 9 Colorado White Pontia sisymbrii elivata 4 3 0 Painted Lady Vanessa cardui 4 0 1 Mourning Cloak Nymphalis antiopa 1,6 11 0 Milbert's Tortoise Shell Nymphalis milberti 1,6 1 0 Hoary Comma Polygonia gracilis 1,6 10 0 Aphrodite Fritillary Speyeria Aphrodite 3,4 0 8 Gorgone Checkerspot Chlosyne gorgone 3 0 12 Field Crescent Phyciodes campestris 4,5 0 3 Silvery Blue Glaucopsyche lygdamus 2 0 Sheridan's Green Hairstreak Callophrys sheridanii sheridanii 1 1 0 Western Pine Elfin Callophrys eryphon eryphon 1 4 0 Moss's Elfin Callophrys mossi schryveri 1 4 0 Melissa Blue Lycaeides melissa 3 0 2 Boisduval’s Blue Plebejus icariodes 6 0 1 Persius Duskywing Skipper Erynnis persius 6 0 1 Taxiles Skipper Poanes taxiles 6 0 1 Common Checkered Skipper Pyrgus communis 6 0 1 *Habitat Types: see Table 4.5. CNHP is currently tracking 15 butterfly species known from Larimer County that occur in low- to mid-elevation habitats, such as those being studied in this year’s Larimer County Inventory (Table 4.7). Of these, nine are normally active as adults within the period of mid- April to the end of May over the range of habitats encompassed by Bobcat Ridge. Only one of these tracked species was found; the additional 13 species encountered are neither rare nor sufficiently unique in their habitat requirements to warrant monitoring or tracking. Table 4.7. Butterflies tracked by CNHP that could be expected to fly in April and May in Bobcat Ridge. Common Name Scientific Name Habitat Type* Expected Flight Period APRIL MAY Moss's Elfin Callophrys mossi schryveri 1 Hops Azure Celestrina humulus 1 Sandhill Fritillary Boloria selene sabulocollis 6 Mottled Dusky Wing Skipper Erynnis martialis 2,3 Simius Roadside Skipper Amblyscirtes simius 2,3 Dusted Skipper Atrytonopsis hianna 2,4 Cross-line Skipper Polites origines 2,4 Rhesus Skipper Polites rhesus 2 Arrowhead Skipper Singa morrisoni 3,5 *Habitat Types: see Table 5 However, Moss’s elfin (Callophrys mossii schryveri), a globally vulnerable subspecies was documented during the April site visit (Figure 4.4). Moss’s elfin flies in April and occurs in foothills canyons with its host plant stonecrop (Sedum lanceolatum). At Bobcat Ridge, the butterfly and its host plant were found in two canyon locations within the Ponderosa Pine Savanna system (Figure 4.5). It is likely that similar canyons nearby may also host the butterfly. A characterization abstract for the butterfly is attached (see Appendix IV). Poor habitat quality, adverse climatic factors, and/or sampling factors are possible explanations for the low numbers of butterflies observed. Climatic factors are the most likely reason: 1. Butterfly species throughout Colorado have suffered from the past several years of prolonged drought. 2. A mild spring may have resulted in the early emergence of many butterfly species, advancing the flight season by about two weeks in 2004. 3. Erratic weather patterns due to a mild spring likely increased butterfly mortality whose immature stages are susceptible to viral and bacterial infections during cold rainy periods, and whose adults experience high mortality during hot dry windy conditions. Spring 2004 had both in alternating abundance this year. As a result, butterfly species diversity and population sizes are down throughout Larimer County. Figure 4.4. Moss’s elfin Photo by Paul Opler In fact, the variety of habitat types within the Bobcat Ridge boundaries would suggest that butterfly diversity should be fairly high --- as many as 100 to 120 species could be expected in the area. The two-day survey produced less than 20% of this total, although the total fauna would be spread out over a flight season of nearly six months, not all flying at once. The two sample dates chosen should encompass active adult seasons of at least 50% of the butterfly fauna of the area. Thus, the 19 species recorded represent almost a third of the number of species expected to be present. Butterfly conservation at Bobcat Ridge Natural Area should focus on creating quality habitat suitable for individual species. This may include enhancing or expanding the extent of intact native plant communities and ensure the preponderance of larval host plants and nectar sources. Species characterization abstracts will help identify essential habitat elements or ecological processes that sustain the species. Figure 4.5. Map of Wildlife Habitats Conservation Target Moths & Butterflies Objectives Maintain occurrences of documented rare butterfly species and provide for habitat requirements of those species listed as possible occurrences. Natural Processes/ Functions/ Interactions Presence of the proper microclimate, interactions with larval host plants, nectar sources and other habitat features are all critical to the life cycle of moths and butterflies. Threats & Stresses (Source of Stress)  Extended drought and/or erratic weather patterns.  Improper use of insecticides (mosquito control).  Artificial manipulation of hydrology and/or overgrazing in riparian areas.  Replacement of native plants by opportunistic weedy species. Strategy/Action  Determine habitat requirements for rare butterfly species.  Restore natural hydrology to all drainages. This may include removal of stock tanks, and implementing soil erosion prevention practices.  Eliminate grazing from riparian areas, and buffer these areas 100 feet back as to provide for adjacent grassland. This may require some form of fencing while grazing lease is active. Measure of Success Persistence of Moss’s Elfin and re-colonization of Bobcat Ridge by species that are expected to be there. Conservation Plan  Ensure that larval host plants and nectar sources are available.  Investigate the life cycle requirements of the butterfly species tracked by CNHP that could be expected at Bobcat Ridge.  Evaluate whether those habitat requirements are physically represented at Bobcat Ridge.  Continue surveying and monitoring for species and habitat elements.  Restore habitat areas suitable for colonization and migratory stopover. Chapter References Drummond, Boyce A. 2004. Bobcat Ridge Natural Area Inventory: Preliminary Results of Larimer County Inventory. Fort Collins, CO: Colorado Natural Heritage Program. Opler, P.A. 1994. Conservation and management of butterfly diversity in the United States. Office of Information Transfer. U. S. Fish and Wildlife Service, Fort Collins, Colorado. Opler, P.A. and G.O. Krizek. 1984. Butterflies East of the Great Plains: an illustrated natural history. Johns Hopkins Press, Baltimore. obscurus 1 - 6 6,000 – 13,000 Year-round Ground Wild Turkey Meleagris gallopavo 1 - 7 3,000 – 8,000 Year-round Ground Hummingbirds Black-chinned Hummingbird Archilochus alexandri 1 – 5 7 5,500 – 7,000 Rare/ Breeding Trees Woodpeckers Lewis’ Woodpecker Melanerpes lewis 1 – 7 3,000 – 8,000 Breeding Cavity Bushtits Bushtit Psaltiparus minimus 1 - 7 5,000 – 8,500 Rare Trees or Shrubs Thrashers Sage Thrasher Oreoscoooptes montanus 1 - 7 3,000 – 14,000 Rare/ Migration Shrubs or Ground Warblers Wilson’s Warbler Willlsonia pusilla 1 - 6 3,000 – 13,500 Breeding Dense Moist Thickets/ Tangles Grosbeaks, Buntings, Sparrows Grasshopper Sparrow Ammodramus savannarum 1 – 4 6 - 7 3,000 – 6,000 Breeding Ground *Habitat Types: 1. Urban and Croplands 2. Riparian/ Wetlands 3. Grasslands 4. Shrublands 5. Forestlands 6. Tundra 7. Unvegetated, Exposed-Rock courtesy of Rob Meining).