Cassin’s Sparrow (Aimophila cassinii): A Technical Conservation Assessment Prepared for the USDA Forest Service, Rocky Mountain Region, Species Conservation Project April 13, 2006 Janet Lynn 705 Birch Ave. #1 Flagstaff, AZ 86001 Contracted by: Ecosphere Environmental Services 2257 Main Avenue Durango, CO 81301 Peer Review Administered by Society for Conservation Biology Lynn, J. (2006, April 13). Cassin’s Sparrow (Aimophila cassinii): a technical conservation assessment. [Online]. USDA Forest Service, Rocky Mountain Region. Available: http://www.fs.fed.us/r2/projects/scp/assessments/ cassinssparrow.pdf [date of access]. ACKNOWLEDGMENTS I would like to thank Mike Fitzgerald at Ecosphere Environmental Services for the opportunity to participate in the USDA Forest Service Species Conservation Project and all those who were involved in the development of this assessment. I would particularly like to thank Jennifer Holmes and Matt Johnson for their input and support. I also thank Lynn Alterman for her comments and editing and Sandy Friedley for all the administrative and technical support in the office. AUTHOR’S BIOGRAPHY Janet Lynn has been researching and studying migratory songbirds for the last 12 years. She received a B.S. in Wildlife Biology from Colorado State University in 1995 and a M.S. Degree in Forestry at Northern Arizona University. She is currently working as the Research Project Coordinator for the Ecological Monitoring & Assessment Program & Foundation at Northern Arizona University. COVER PHOTO CREDIT Cassin’s sparrow (Aimophila cassinii). Photograph by Greg Lasley. Used with permission. 2 3 SUMMARY OF KEY COMPONENTS FOR CONSERVATION OF THE CASSIN’S SPARROW Due to an overall declining trend in abundance, the Cassin’s sparrow (Aimophila cassinii) is listed as a species of concern and/or a priority species by several federal and state agencies and organizations for the central shortgrass prairie and semi-desert grasslands of the Great Plains and southwestern United States. This trend is validated by the Breeding Bird Survey trend analysis presented in the Population Trends section of this assessment, which shows significant survey-wide declines in abundance. With approximately 17 percent of the Cassin’s sparrow population located within Region 2, conservation of this species should be a high priority throughout the region. Habitat loss and fragmentation due to the conversion of shrub grasslands to agricultural fields and development of urban areas pose the greatest threats to the conservation of the Cassin’s sparrow on its breeding grounds. Management practices, such as intense livestock grazing, shrub removal, and fire, also contribute to the fragmentation and degradation of grassland ecosystems and negatively impact Cassin’s sparrow distribution and abundance. Due to the continued degradation and loss of habitat from these activities, remaining shortgrass and mixed- grass prairies within Region 2 become extremely important to the conservation of this species. Management activities alone or in combination with natural events can have profound effects on habitat suitability and Cassin’s sparrow populations. An endemic grassland bird, the Cassin’s sparrow requires grassland habitats with scattered shrubs, necessary for perching and skylarking. They avoid overgrazed and recently burned areas. Future management practices and conservation efforts for the Cassin’s sparrow should focus on mimicking natural disturbances and habitat distribution by conserving and/or creating a landscape mosaic of grassland parcels of different grass heights and densities throughout this species’ breeding range. 2 3 TABLE OF CONTENTS ACKNOWLEDGMENTS ..............................................................................................................................................2 AUTHOR’S BIOGRAPHY............................................................................................................................................2 COVER PHOTO CREDIT .............................................................................................................................................2 SUMMARY OF KEY COMPONENTS FOR CONSERVATION OF THE CASSIN’S SPARROW............................3 LIST OF TABLES AND FIGURES ...............................................................................................................................6 INTRODUCTION ..........................................................................................................................................................7 Goal............................................................................................................................................................................7 Scope..........................................................................................................................................................................8 Treatment of Uncertainty ...........................................................................................................................................8 Publication of Assessment on the World Wide Web ..................................................................................................8 Peer Review ...............................................................................................................................................................8 MANAGEMENT STATUS AND NATURAL HISTORY .............................................................................................8 Management Status ....................................................................................................................................................8 Existing Regulatory Mechanisms, Management Plans, and Conservation Strategies.............................................10 Biology and Ecology................................................................................................................................................11 Systematics and general species description.......................................................................................................11 Distribution and abundance.................................................................................................................................12 Global current and historical distribution and abundance..............................................................................12 Regional current and historical distribution and abundance ..........................................................................13 Population trends.................................................................................................................................................14 Activity pattern and movements .........................................................................................................................16 Circadian, seasonal, circannual ......................................................................................................................16 Broad scale movement patterns......................................................................................................................17 Potential links to, or isolation from, other segments of the population; connectivity....................................17 Habitat .................................................................................................................................................................17 Effects of climatic variability on habitat ........................................................................................................19 Geographic distribution and changes over time in habitat .............................................................................19 Food habits ..........................................................................................................................................................19 Breeding biology.................................................................................................................................................20 Phenology and behavior of courtship and breeding .......................................................................................20 Demography........................................................................................................................................................22 Genetic issues .................................................................................................................................................22 Recruitment, survival, immigration, age at reproduction...............................................................................22 Lifecycle graph and model development (prepared by David B. McDonald) ...............................................22 Spacing, defense, and size of area..................................................................................................................28 Dispersal.........................................................................................................................................................28 Factors limiting population growth ................................................................................................................28 Community ecology ............................................................................................................................................28 Predators and relationship to habitat use........................................................................................................28