Trout Creek Pawnee Montane Skipper (Hesperia leonardis montana) Survey 2014

Transcription

1 Trout Creek Pawnee Montane Skipper (Hesperia leonardis montana) Survey 2014 December 2014

2 CNHP s mission is to preserve the natural diversity of life by contributing the essential scientific foundation that leads to lasting conservation of Colorado's biological wealth. Colorado Natural Heritage Program Warner College of Natural Resources Colorado State University 1475 Campus Delivery Fort Collins, CO (970) Report Prepared for: Wild Connections 2168 Pheasant Pl. Colorado Springs CO Recommended Citation: Sovell, J. R Trout Creek Pawnee montane skipper (Hesperia leonardis montna) survey Colorado Natural Heritage Program, Colorado State University, Fort Collins, Colorado. Front Cover: Male Pawnee montane skipper nectaring along Trout Creek, September 1, Colorado Natural Heritage Program, John Sovell 2

3 Trout Creek Pawnee Montane Skipper (Hesperia leonardis montna) Survey 2014 John Sovell Colorado Natural Heritage Program Warner College of Natural Resources Department of Biology College of Natural Sciences Colorado State University Fort Collins, Colorado

4 CONTENTS INTRODUCTION... 5 METHODS... 5 RESULTS... 6 DISCUSSION/RECOMMENDATIONS... 5 APPENDIX 1. DESCRIPTION OF PROJECT TRANSECTS... 7 LIST OF TABLES Table 1. Butterfly and vegetation data from each of the legs surveyed at both of the Trout Creek Trail transects surveyed during Table 2. The data collected from transects 1 and 2 at the Trout Creek Trail during the 2010, 2012 and 2014 surveys Table 3. Multivariate ANOVA results for Pawnee montane skippers, comma skippesr, total skippers, blue grama, dotted gayfeather, live trees and dead trees LIST OF FIGURES Figure 1. The Trout Creek transect and the location of each 200 m station along the transect. Station E designates the endpoint of each transect. The Polhemus fire and the estimated suitable habitat for the Pawnee montane skipper (Hesperia leonardus montana) butterfly are also shown Figure 2. The locations of the Pawnee montane skipper (Hesperia leonardus montana) butterfly and the unidentified skippers documented along the Trout Creek transect in The Polhemus fire and the estimated suitable habitat for the Pawnee montane skipper butterfly are also shown LIST OF PHOTOS Photo 1. The relatively flat, open, and sunny topography of transect 1, which parallels Trout Creek Photo 2. The narrow, deep, shaded, and steep sided gully of transect 2 where restoration is taking place.9 4

5 INTRODUCTION The Colorado Natural Heritage Program (CNHP) is Colorado s only comprehensive source of information on the status and location of Colorado s rarest and most threatened species and plant communities. CNHP tracks and ranks Colorado s rare and imperiled species and habitat and provides scientific information and expertise to promote the conservation of Colorado s biological resources. Established in 1979, the CNHP is a non-profit scientific organization affiliated with the Warner College of Natural Resources at Colorado State University. CNHP conducted field surveys in 2010 and 2012 for the Pawnee montane skipper (Hesperia leonardus montana) butterfly along two trail corridors adjacent to Trout Creek in the Pike National Forest, Douglas County, Colorado. This survey is an extension of those 2010 and 2012 surveys. Wild Connections contracted with Colorado State University - Colorado Natural Heritage Program (CSU-CNHP) to provide a survey to provide a survey of Pawnee montane skipper at this site. There were three objectives of these surveys: 1. Understand how restoration of a section of the trail corridor running east from the creek up a steep gully (designated Trout Creek transect 2 in this report) improves the habitat for the federally threatened Pawnee montane skipper butterfly. 2. Identify the abundance Pawnee montane skipper butterflies inhabiting the trail corridor on either of the two surveyed transects. 3. Identify the relative frequency on the two transects of blue grama (Bouteloua gracilis) and relative abundance of dotted gayfeather (Liatris punctata) stems, the larval host plant and primary adult nectar source, respectively, of the Pawnee montane skipper. METHODS Two 800-meter (m)-long belt transects were located along the corridor of the Trout Creek Trail (Figure1). The survey area width for each belt transect was 10 m (5 m on either side of the transect center line). The effective area surveyed was 8,000 m 2 (800 m x 10 m), which is equivalent to 1.98 acres. Trout Creek transect 1 runs parallel to Trout Creek, crosses relatively level ground along the trail corridor, is free of erosion, and has not required restoration work. Trout Creek transect 2 follows the trail corridor up a steep gully and the steep incline combined with heavy motorcycle use on this trail section has caused excessive erosion requiring extensive restoration work. The restoration was completed by Wild Connections in 2009 and Trout Creek transect 2 is also located within the boundary of the Polhemus Fire and the forest of transect 2 experienced a low intensity burn from that fire. Each of the 800-meter (m) belt transects were divided into four legs (A through D) of 200 m length creating five separate transect stations; one each starting at 0 m, 200 m, 400m, and 600m (Figure 1). Each 5

6 200 m leg was further divided into 10, 20 m sub-segments resulting in 40 separate sampling segments along each 800 m belt transect. Each 200-m leg was walked, and data were recorded for each of the10, 20-m sub-segments along the 200-m transect leg. The following data were collected along each 20-m sub-segment: - Tree counts. Live trees greater than 6 inches diameter at breast height (DBH) within the belt transect (5 m on each side of the transect center point) were counted to document the larger living trees along the transect in both burned and unburned areas. Also, dead standing trees greater than 6 inches DBH were counted and recorded in a separate category (particularly pertinent to transect 2 in the Polhemus Fire area). - Blue grama (Bouteloua gracilis) (Bogr) frequency. The presence or absence of blue grama was documented within a visually estimated 0.5-m-square rectangular quadrant that extended 0.5 m on either side of the observer s toe, and 0.5 m in front of the toe at the endpoint of each 20-m interval along the transect (10 recordings per 200-m segment). The observer marked + or for presence, 0 for absence in the appropriate space on the data sheet. - Dotted gayfeather (Liatris punctata) (Lipu) stem counts. Stems of blooming Dotted gayfeather were counted in each 20-m segment within the 10-m wide belt of the transect. Commonly there were multiple blooming stems emanating from the crown of an individual Liatris plant. Each stem was counted as a separate occurrence. - Adult skipper butterfly counts (Hesperia leonardus montana [Hlm] and Hesperia comma [Hco]). Individual skipper butterflies of either the Pawnee montane skipper or the common branded skipper were counted in each 20 m segment within the 10-m wide belt of the transect. The sex of the skipper was recorded if it was ascertainable. If the skipper species was unknown, its occurrence was entered as an unknown skipper, and the sex was recorded if it was ascertainable. RESULTS The 2014 field survey documented 8 Pawnee montane skipper butterflies along portions of both of the Trout Creek Trail transects (Table 1 and Figure 2). This is nearly as many Pawnee montane skippers as were observed on the same two transects in 2012 (11) and double the 4 that were observed in 2010 (Table2). Five of these Pawnee montane skippers were observed on Transect 1, while 9 were observed in 2012 and 3 in Three of the 8 Pawnee montane skippers were observed on Transect 2 in 2014 versus 2 in 2012 and 1 in Of the 8 Pawnee montane skippers recorded, 5 were males with 2 observed on Transect 1 and 3 on transect 2; 3 were females all observed on Transect 1 (Table 1). Additionally, 5 comma skippers were observed in 2014, while 5 were also observed in 2012, but 0 were seen in In 2014, there were also 9 skippers observed that could not be identified because of their fast flight and the short time they remained visible; 6 on Transect 1 and 3 on Transect 2 (Table 1 and Figure 2). In 2012, there were 11 skippers that could not be identified, while 6 could not be identified in In 2014, there were 22 Pawnee, comma, and unknown skippers observed on both transects, similar to the 27 observed in 2012 and over twice that of the 10 seen in

7 Table 1. Butterfly and vegetation data from each of the legs surveyed at both of the Trout Creek Trail transects surveyed during Transect Burn Intensity Date Year UTME UTMN Leg Start Time End Time Live Tree Dea d Bogr Lipu Hlm Mal Hlm Femal Hlm? Hco Male Hco Femal Hco? UNK male UNK femal UNK? TroutCr1 1 8/30/ A 9:55 10: TroutCr1 1 8/30/ B 10:18 10: TroutCr1 1 8/30/ C 10:33 10: TroutCr1 1 8/30/ D 10:50 11: TroutCr2 2 8/30/ A 11:06 11: TroutCr2 2 8/30/ B 11:20 11: TroutCr2 2 8/30/ C 11:44 11: TroutCr2 2 8/30/ D 11:58 12: Total Bogr = Bouteloua gracilis, Lipu= Liatris punctata, HIm = Hespena leonardus montana, Hco = Hespena comma and UNK = unknown skipper. Table 2. The data collected from transects 1 and 2 at the Trout Creek Trail during the 2010, 2012 and 2014 surveys. Sample Block Burn Date Year UTME UTMN Leg Start Time End Time Live Trees Dead Trees Bogr Lipu Hlm Hco UNK TOTAL TroutCr1 0 9/2/ D 10:42 11: TroutCr2 1 9/2/ D 11:55 13: TroutCr1 0 9/1/ D 11:24 12: TroutCr2 1 9/1/ D 12:46 14: TroutCr1 0 8/31/ D 9:55 11: TroutCr2 1 8/31/ D 11:06 12: Bogr = Bouteloua gracilis, Llpu= Liatris punctata, HIm = Hespena leonardus montana, Hco = Hespena comma, and UNK = unknown skipper.

8 A multivariate analysis of variance (MANOVA) performed on the data, comparing the number of Pawnee, coma and all skippers seen during the three years surveyed did not show any statistically significant differences between the two transects (Table 3). A MANOVA performed on live and dead trees, blue grama and dotted gayfeather found significantly more blue grama and marginally significantly more live trees on Transect 2 (Table 3). Table 3. Multivariate ANOVA results for Pawnee montane skippers, comma skippesr, total skippers, blue grama, dotted gayfeather, live trees and dead trees. Sum of Squares d. f. F P Transect 1 Mean Transect 2 Mean Pawnee montane skipper Transect Comma skipper Transect Total skippers Transect Blue grama Transect Dotted gayfeather Transect Live Trees Transect 15, Dead trees Transect Statistically significant at p = Statistically significant at p = 0.1. DISCUSSION/RECOMMENDATIONS The 2014 survey once again documented the occurrence of Pawnee montane skipper on both Trout Creek transects. Skippers decreased in 2014 compared to However, there were no statistically significant differences in the number of total, Common branded or Pawnee montane skippers observed between the two transects in 2014 versus either 2010 or There were more Pawnee montane skippers observed on Transect 2 in 2014 than in either 2010 or 2012 suggesting that the restoration effort may be increasing habitat quality for the skipper on Transect 2. In three years of sampling, there have been 17 Pawnee montane skippers observed on Transect 1 versus 6 on Transect 2. Empirically, the habitat of Transect 1 appears more suitable for Pawnee montane skippers than that of Transect 2, lending support to the data. For the purposes of this study, the detection of statistically significant increases in Pawnee montane skipper numbers on Transect 2 since completion of the trail restoration work would supply evidence that the restoration has benefitted the Pawnee montane skipper, increasing the suitability of the habitat of Transect 2 for the butterfly. The data is showing an increase of Pawnee montane skipper numbers on Transect 2. The changes to the environment realized through restoration of the trail may not lead to large increases in the butterfly s numbers. This is because they require open canopy ponderosa pine woodland with an understory that includes the larval host plant, blue grama, and presence of the primary adult nectar source, dotted gayfeather. Doted gayfeather was not observed on Transect 2 in 2012 and only 6 5

9 flowering stems were recorded in Additionally, there has only been an average frequency of 5% of blue grama on Transect 2 over all three years surveyed. This, combined with a dense forest canopy on the transect may be more limiting to the butterfly than are the benefits realized from restoration of the trail. Additional monitoring of the butterfly at the two transects will help clarify whether the trail restoration will increase numbers of the Pawnee montane skipper at the restored site. As mentioned in the previous reports, forest thinning might be the most beneficial management action for the Pawnee montane skipper on Transect 2. Years of fire suppression on the Pike National Forest has resulted in an overly dense tree canopy, which the Polhemus and Hayman fires were responding too. However, the actual reference state for tree density on this forest is unknown and tree density within the deep gullies of the forest may have been higher than on the less steep slopes and hilltops of the surrounding landscape. Forest thinning as has been prescribed to improve habitat suitability for the Pawnee montane skipper would benefit the Pawnee montane skipper at this site (Sovell 2014). Additional restoration at Transect 2 involving the reestablishment of native vegetation including blue grama and dotted gayfeather would improve the habitat for the Pawnee montane skipper and further reduce erosion on the steep slopes of the transect. Additional monitoring at the site could potentially find that Pawnee montane skippers continue to increase in numbers on Transect 2, the restored transect. 6

10 APPENDIX 1. DESCRIPTION OF PROJECT TRANSECTS Transect 1 This transects follows the base of the slope crossing relatively flat terrain along Trout Creek (Photo 1). The richer soils of this flat creek-side area and the high solar radiation resulting from an open forest canopy support abundant blue grama grass and moderate amounts of dotted gayfeather. Lower elevation, relatively flat areas, with abundant sunlight where the tree canopy tends to thin, support the largest densities of blue grama and dotted gayfeather, and this area is no exception. In three years of sampling there was a 61% frequency of blue grama along this transect, which represents an abundant amount of blue grama. Over 10 years of monitoring in the Hayman Fire area the average frequency of blue grama was 13% and the average density of dotted gayfeather was 67 stems/acre (Sovell 2012). The high frequency of blue grama and moderately abundant gayfeather (27 stems/acre) make this important habitat for maintaining the metapopulation dynamics of this rare butterfly. Conserving and restoring populations of blue grama and dotted gayfeather are vital to conserving the butterfly. Care should be taken to avoid broadcast spraying of pesticide and herbicides that could negatively impact the butterfly, its host plant blue grama, or dotted gayfeather the butterfly s primary adult nectar source. Photo 1. The relatively flat, open, and sunny topography of transect 1, which parallels Trout Creek. 7

11 Transect 2 Transect 2 is comprised of the restored trail segment that lies in a gully with a dense overstory of conifers, where shading is high and little blue grama was recorded (Photo1, Table 1, and Figure 1). In general, the habitat of transect 2 is less suitable for Pawnee montane skippers and this is evidenced by the high live tree count (260 in 2010, 122 in 2012, and 144 in 2014) and the low 5% frequency of blue grama recorded on the transect (7.5% in 2010, 5% in 2012 and 2.5% in 2014) compared to the 13% frequency recorded over 10 years of monitoring in the Hayman Fire area (Sovell 2012). In 2010, however, there was a moderate amount of dotted gayfeather with 31 stems or 15.7 stems/acre counted on the transect, but in 2012 dotted gayfeather was not observed on Transect 2 and in 2014 only 3 stems/acre were recorded. The oviposition flight of a female Pawnee montane skipper was observed on this transect in 2010 and there are patches of suitable habitat scattered along the hilltops crossed by the transect. The restoration project completed on transect 2 stabilized this segment of the trail corridor through the placement of water bars, check dams, erosion mat, and drainage swales, which prevented further erosion, helping to restore native vegetation to these eroded areas. Stabilization of the trail corridor will prevent erosion of upslope areas above and adjacent to the restored corridor. This should reduce erosion of the hilltop areas above the trail corridor that are adjacent to the restored areas. In this hilly and gullied topography it is these hilltop sites that the Pawnee montane skipper occupies. In this type of terrain the hilltop areas have richer soils and a higher content of soil moisture relative to the surrounding slopes, less dense tree cover, and less shading due to fewer trees and the relative flatness of the hilltop, all of which leads to higher solar radiation and more abundant blue grama grass and dotted gayfeather relative to the adjoining areas. 8

12 Photo 2. The narrow, deep, shaded, and steep sided gully of transect 2 where restoration is taking place. 9

13 REFERENCES Sovell, J. R Pawnee montane skipper post fire habitat assessment survey August/September Colorado Natural Heritage program, Colorado State University. Sovell, J. R Pawnee Montane Skipper Vegetation Study for the Upper South Platte Watershed Protection and Restoration Project - September Colorado Natural Heritage Program, Colorado State University. ADDITIONAL RESOURCES Sovell, J. R Trout Creek Pawnee montane skipper (Hesperia leonardus montana) survey August 31, 2010, Colorado Natural Heritage Program, Colorado State University. Sovell, J. R Trout Creek Pawnee montane skipper (Hesperia leonardus montana) survey November 2012, Colorado Natural Heritage Program, Colorado State University. ACKNOWLEDGEMENTS Grants from Cheyenne Mountain Zoo were awarded to Wild Connections to underwrite the 2010 and 2012 surveys and a grant from Prairie Biotic Research to John Sovell and designated funds from Wild Connections underwrote the 2014 survey. 10

14 FIGURES 1 and 2 11

15 Figure 1. The Trout Creek transect and the location of each 200 m station along the transect. Station E designates the endpoint of each transect. The Polhemus fire and the estimated suitable habitat for the Pawnee montane skipper (Hesperia leonardus montana) butterfly are also shown. 12

16 Figure 2. The locations of the Pawnee montane skipper (Hesperia leonardus montana) butterfly and the unidentified skippers documented along the Trout Creek transect in The Polhemus fire and the estimated suitable habitat for the Pawnee montane skipper butterfly are also shown. 13