Mardon Skipper Rangewide Distance Sampling Protocol: A FOUR YEAR REPORT ON TRENDS, ANALYSES, AND SUGGESTED NEXT STEPS Report from the Xerces Society to the Interagency Special Status/Sensitive Species Program (ISSSSP) Agreement L13AC00102, Modification 6 Mardon skipper (Polites mardon). Photo by Rich Hatfield, the Xerces Society. Bombus vosnesenskiiRich on Balsamorhiza Hatfield, sagittata. Candace Photo Fallon, by Rich andHatfield, Michele the Xerces Blackburn Society. The Xerces Society for Invertebrate Conservation February 2018 Contents Summary ........................................................................................................................................................................ 3 Introduction ................................................................................................................................................................... 3 Population trends and analysis ...................................................................................................................................... 4 Overall analysis .......................................................................................................................................................... 4 Individual sites ........................................................................................................................................................... 5 Implementation analysis ............................................................................................................................................... 9 Recommendations ....................................................................................................................................................... 13 Continue Distance Sampling at sentinel sites .......................................................................................................... 13 Conduct detection/no detection surveys ................................................................................................................ 13 Revisit site management plans ................................................................................................................................ 14 Further research .......................................................................................................................................................... 14 Site condition ........................................................................................................................................................... 14 Efficacy of management actions .............................................................................................................................. 14 Acknowledgements ..................................................................................................................................................... 15 Literature cited ............................................................................................................................................................ 16 Appendix: Site condition and detection/no detection datasheet ............................................................................... 18 Figures Figure 1: Mardon skipper population trends at each of the four sentinel sites in Oregon and Washington.. .............. 5 Figure 2: Flight period at each of the four sentinel sites from 2014-2017. ................................................................... 6 Figure 3: Four year population trends for (clockwise from upper left) each site. ......................................................... 7 Figure 4: Photo of the Windy Valley meadow after the Chetco Bar Fire (2017). .......................................................... 8 Figure 5: Geographic Areas and/or Administrative Units of respondents. ................................................................... 9 Figure 6: Role of the respondents in implementing the mardon skipper rangewide monitoring protocol. ................. 9 Figure 7: Response to the clarity of annual reports to date. ....................................................................................... 10 Figure 8: How the results of Distance Sampling population estimates has improved understanding. ....................... 10 Figure 9: How mardon skipper population estimates informed land management. .................................................. 11 Figure 10: Respondents indicated perceived barriers to implementing the detection/no detection sampling. ..... 121 Figure 11: Respondents indicated perceived barriers to implementing the Distance Sampling protocol. ............... 112 Figure 12: Response to the best next steps for mardon skipper monitoring on Administrative Units. ...................... 12 2 SUMMARY Over the past four years, the Oregon/Washington Bureau of Land Management (OR/WA BLM) and U.S. Forest Service Region 6 (USFS) have successfully implemented many aspects of the mardon skipper (Polites mardon) rangewide monitoring protocol (Hatfield et al. 2013a) with support from the Interagency Special Status Sensitive Species Program (ISSSSP). The information gleaned from this undertaking has led to an increased awareness of mardon skipper populations throughout the species’ range (within the purview of ISSSSP), and helped to inform land management at several sites. Annual Distance Sampling efforts have revealed a negative population trend at each of the four sentinel sites, though these trends are not significant (see Figures 1 and 3). Continued Distance Sampling is recommended to determine if this negative trend is indicative of decline or if it is merely reflective of normal insect population fluctuations. As the mardon skipper remains a State Endangered Species in Washington (WNHP 2017), and an OR/WA BLM and USFS Region 6 Sensitive Species (ISSSSP 2015), further monitoring efforts to inform population trends and land management would improve our understanding of this species’ habitat needs and increase the chances of long-term conservation. While we recognize that all of the below may not be possible given funding, personnel, and other conservation priorities, we identified the following as potential key next steps for this species: 1. Maintaining the Distance Sampling monitoring protocol at all four sentinel sites; 2. Utilizing the detection/no detection protocol to ensure that once-occupied meadows are surveyed at least once every 3-5 years; and 3. Revisiting sites with implemented site management plans to determine if further management is needed. Additionally, we identify two other avenues for future research that could help land managers better understand the conservation needs of this species: 1. Research and develop a site condition form that considers the management goals of this species and is in concordance with the habitat and host plant conditions necessary for long-term survival. Once developed, this site condition form could be added to the monitoring protocols for both Distance Sampling and detection/no detection surveys, and filled out for each site surveyed 2. Formally assess how management actions affect mardon skipper populations. This would better inform management actions and allow for evidence-based management decisions. INTRODUCTION Mardon skippers are grassland and open meadow obligates endemic to four distinct regions within Washington, Oregon, and California. Adults use a variety of nectar species, including Potentilla diversifolia, P. gracilis, Wyethia angustifolia, Dichelostemma capitatum, Eriogonum umbellatum, Delphinium spp., Horkelia fusca, Plectritis congesta, Vicia spp., and Calochortus spp., among others (Beyer & Black 2007; Kerwin 2011; Barrett 2015, pers. comm.; Fallon 2015, pers. obs.). Flight periods can vary from year to year based on population size and weather conditions, ranging from 10 days to more than a month (Potter et al. 2002 and Figure 2). The historic range of this species is poorly documented, but it is thought to be in decline (Hatfield et al. 2013a). The mardon skipper is currently known from four major areas: (1) southern Puget Sound, (2) the east side of the Cascade Mountains in Washington, (3) the Cascade Mountains in southern Oregon, and (4) in Del Norte California and the southern coast of Oregon. Although previously listed as a federal candidate species under the Endangered Species Act, it was removed in the fall of 2012 (DOI, FWS 2012). It remains a State Endangered Species in Washington (WNHP 2017), and an OR/WA BLM and USFS Region 6 Sensitive Species (ISSSSP 2015). It has a global rank of G2G3T2T3 (imperiled) and state ranks of S1 in Washington and S2 in Oregon (ORBIC 2016, WNHP 2017). 3 Additional research on the effects of different management actions is needed in order to develop long-term management strategies for this species. However, knowing the population estimates for each site is a critical first step. Distance sampling is a method of surveying that can provide an accurate population estimate since it incorporates the detectability of the butterfly, thus accounting for those butterflies that were missed in the course of a survey. In the case of a small, low flying butterfly like the mardon skipper, detectability in surveys is low (Potter & Olson 2012; Fallon & Hatfield 2014; Fallon & Hatfield 2015; Hatfield et al. 2016; Hatfield et al. 2017); thus incorporating detectability into population estimates is essential. In 2013, the Xerces Society made recommendations to the Interagency Special Status / Sensitive Species