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Aegolius Acadicus) in the Sierra Nevada Foothills WINTER ECOLOGY OF NORTHERN SAW-WHET OWLS (AEGOLIUS ACADICUS) IN THE SIERRA NEVADA FOOTHILLS OF CALIFORNIA ________________ A Thesis Presented to the Faculty of California State University, Chico ________________ In Partial Fulfillment of the Requirements for the Degree Master of Science in Biological Sciences ________________ by Julie Shaw Summer 2014 WINTER ECOLOGY OF NORTHERN SAW-WHET OWLS (AEGOLIUS ACADICUS) IN THE SIERRA NEVADA FOOTHILLS OF CALIFORNIA A Thesis by Julie Shaw Summer 2014 APPROVED BY THE DEAN OF GRADUATE STUDIES AND VICE PROVOST FOR RESEARCH: _________________________________ E. K. Park, Ph.D. APPROVED BY THE GRADUATE ADVISORY COMMITTEE: _________________________________ Colleen Hatfield, Ph.D., Chair _________________________________ Tag Engstrom, Ph.D. _________________________________ Raymond J. Bogiatto, M.S. ACKNOWLEDGEMENTS I would have not been able to complete this thesis without the help and support of many people. First and foremost, Dr. Colleen Hatfield has been instrumental in keeping me on track with making progress. She especially helped keep me sane when I was feeling overwhelmed, and has provided guidance on both research and personal matters. I also would like to thank Dawn Garcia who has put forth hours of additional help for this project. She was an amazing ally in planning and executing much of the field logistics of my research, and this project would have never gotten off the ground without her. I would also like to thank the remainder of my thesis committee-Jay Bogiatto, MS and Dr. Tag Engstrom, for accepting the extra work of taking on another graduate student. Dr. Kathy Gray has also been extremely helpful with the “statistical challenges” of my thesis. Thank you to Scott Weidendsaul for your expertise on eastern saw-whets, your knowledge and experience was truly appreciated in the early stages of my research. The BCCER staff-Jeff Mott, Scott Huber, and Dr. Paul Maslin were all extremely helpful, and I would like to thank them for allowing me access to the reserve in search of my owls. I would like to extend a special thank you to the iii BCCER funding committee for awarding me a grant to conduct this research for all three of my study years. Additionally, thanks to the Vesta Holt award committee for funding three of my transmitters. I would also like to thank the remaining Owl Banding volunteers-Steve and Raina King, Mike Fisher, and Colleen Martin for their enthusiasm for my project. My undergraduate students, Noah Strong, Cheryl Hausle, Nikki Ramey, Jeff Lauder, Cody Akana, and Tyrone Asencio were great assets in the field. Finally, I want to thank my friends Shannon Rich, Shannon McCamy and Will McCall, who were always willing to help, and my partner Glenn Woodruff, who continues to support me. iv TABLE OF CONTENTS PAGE Acknowledgments…………………………………………………………………………….............. iii List of Tables………………………………………………………………………………..................... vii List of Figures…………………………………………………………………………………………….. viii Abstract…………………………………………………………………………………………………….. x CHAPTER PAGE I. Introduction………………………..……………………………………………………... 1 Background……………………………………………………………….............. 1 Species Description…………………………………………………................. 9 II. Methods………………………………………................................................................. 14 Study Area........................................................................................................ 14 Telemetry Installation................................................................................. 18 Winter Roost Site Characterization....................................................... 19 Random Roost Site Characterization.................................................... 21 Pellet Dissection and Analysis.................................................................. 22 Statistics............................................................................................................. 23 GIS Analysis...................................................................................................... 27 III. Results……………………………………………………………………………………….. 29 BCCER Winter Residency Summary...................................................... 29 Northern Saw-Whet Owl Telemetry...................................................... 31 Habitat Use....................................................................................................... 31 Differences in Saw-Whet Owl Roosts Between Years.................... 33 Differences Between Predominant Roost Species and Others.......................................................................................................... 35 Random Roost Site Selection.................................................................... 39 Prey Analysis................................................................................................... 42 v CHAPTER PAGE GIS Analysis...................................................................................................... 46 Wintering Home Range............................................................................... 46 Habitat Use Analysis..................................................................................... 52 IV. Discussion……………………………………………………………………………......... 55 Telemetry.......................................................................................................... 55 Habitat Use....................................................................................................... 57 Home Range Analysis................................................................................... 64 Prey Selection.................................................................................................. 65 References..........……………………………………………………………………………………..……. 70 Appendices........................................................................................................................................ 76 A. Additional Tables...................................................................................................... 77 vi LIST OF TABLES TABLE PAGE 1. Descriptions and codes for the habitat variables used in the paired linear regression to compare saw-whet owl roosts and random roosts..................................................................................................... 25 2. Summary data for radio-tagged northern saw-whet owls, 2010-2012……………………………………………………………….............................. 30 3. Results of Kruskal-Wallis Tests for differences between toyon measurements and roosts other shrub measurements................ 38 4. Results of Kruskal-Wallis Tests for differences between canyon live oak measurements and other tree measurements............................. 39 5. Full paired logistic regression model with owl variable for random effects describing northern saw-whet owl shrub selection.......................................................................................................................... 41 6. Simplified logistic regression model with owl variable for random effects describing northern saw-whet owl shrub selection.......................................................................................................................... 42 7. Full paired logistic regression model with owl variable for random effects describing northern saw-whet owl tree selection.......................................................................................................................... 43 8. Simplified paired logistic regression model with owl variable for random effects describing northern saw-whet owl tree selection.......................................................................................................................... 43 9. Kernel density contour values (in hectares) for owls 5 and 12..................... 47 10. Total area of clipped habitat types for northern saw-whet owl roosts and random roosts....................................................................................... 53 vii LIST OF FIGURES FIGURE PAGE 1. Number of banded migrant saw-whet owls at both BCCER and BCEP banding stations, 2005-2013.................................................................................... 6 2. Study area map of both Big Chico Creek Ecological Reserve and Butte Creek Ecological Preserve, Butte County, CA.......... 7 3. Map of Big Chico Creek Ecological Reserve study area..................................... 15 4. Backpack harness to be fitted on a saw-whet owl.............................................. 19 5. Map of all diurnal saw-whet roosts, 2010-2012................................................... 32 6. Frequency of diurnal roost species used by northern saw-whet owls during the study, 2010-2012................................................. 34 7. Comparison of average (±SE) height of roosting owls compared to overall height of the roost plant for the two principle roost species; canyon live oak and toyon........................................................................ 35 . 8. Comparison of mean values for percent slope and canopy cover Between toyon roosts and other shrub roosts.................................................. 36 9. Comparison of mean values for roosting height and shrub height between toyon roosts and other shrub roosts................................................. 36 10. Comparison of mean values for percent slope and canopy cover between canyon live oak roosts and other tree roosts.................................. 37 11. Comparison of mean values between canyon live oak and other trees....
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