Behavior and Energetics of Ospreys Nesting in Northern California
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BEHAVIOR AND ENERGETICS OF OSPREYS NESTING IN NORTHERN CALIFORNIA by Howard Levenson A Thesis Presented to The Faculty of Humboldt State University In Partial Fulfillment of the Requirements for the Degree Master of Science December, 1976 BEHAVIOR AND ENERGETICS OF OSPREYS NESTING IN NORTHERN CALIFORNIA by Howard Levenson Approved by the Master's Thesis Committee Chairman Approved by the Graduate Dean ACKNOWLEDGEMENTS I wish to thank Drs. James R. Koplin and David W. Kitchen for their friendship, their constant interest in my studies, and for critically reviewing the manuscript. Their enthu- siasm for ecological research provided me an extremely stimulating atmosphere in which to work. Jim Koplin, my major professor, deserves special thanks for directing my research; he deserves additional praise for directing various studies that have increased our understanding of birds of prey in general and of Ospreys in particular. I am most grateful to Dr. William R. Sise for his invaluable criticisms and witticisms of the manuscript. Dr. Roger J. Ledderer, of California State University at Chico, kindly gave me permission to use the facilities of the Eagle Lake Biological Station during my stay at Eagle Lake. My research at Eagle Lake was supported by a grant from the Frank M. Chapman Memorial Fund of the American Museum of Natural History (Grant #24464). I am grateful to Steve Berman for showing me the Chinese poem and for drawing the Chinese characters. I also would like to thank Kathy McDonough for drawing the map of the study areas and for the English calligraphy in the frontispiece. TABLE OF CONTENTS Page INTRODUCTION 1 Study Area 3 Geographic Location 3 Climate 3 Vegetation 6 METHODS 8 Field Observations 8 Definition of Behavioral Activities Observed 8 Data Analysis 12 Categories of Behavioral Activities 12 Stratification of Data 13 Computer Program and Statistical Analysis 14 Energy Expenditure 17 Estimated Energy Expenditure 17 Predicted Energy Expenditure 18 RESULTS 20 Time and Activity Budget 20 Seasonal Trends in Behavioral Activities 29 Nest Activities and Tree Activities 29 Perch on Nest and Perch on Trees 34 Nest Material Flight 38 Nest-building 38 Mounting and Copulation 43 Incubation and Brooding 43 Fishing 49 Feeding Activities 55 Aggressive Interactions 56 Diurnal Variations in Behavioral Activities 57 Date of Departure from Nesting Area 58 Energy Expenditure 59 DISCUSSION 65 Energy Expenditure 65 Time and Activity Budget of Ospreys 66 Breeding Behavior of Other Falconiforms 67 ii Page Evolution of Division of Labor of • Breeding Falc oni forms 69 SUMMARY 72 LITERATURE CI TED 76 APPENDICES 83 iii LIST OF FIGURES Page 1. Location of nest 1, Washington Gulch Creek, Humboldt County, California, and nests 2 and 3, Eagle Lake, Lassen County, California. 5 2. Composite time and activity budget of female Osprey at nest 1, Washington Gulch Creek, Humboldt County, California, in relation to phase of the 1974 breeding season. 22 3. Composite time and activity budget of male Osprey at nest 1, Washington Gulch Creek, Humboldt County, California, in relation to phase of 1974 breeding season. 22 4. Time and activity budgets of male and female Ospreys during the Pre-Incubation phase of the 1974 breeding season at nest 1, Humboldt County, California, compared to the time and activity budgets of male and female Ospreys during the Pre-Incubation phase of the 1975 breeding season at nests 2 and 3, Eagle Lake, Lassen County, California. 24 5. Percent of daylight time Ospreys engaged in Nest Activities in relation to phase of the breeding season, at nest 1, Washington Gulch Creek, Humboldt County, California, during the 1974 breeding season, and at nests 2 and 3, Eagle Lake, Lassen County, California, during the Pre-Incubation phase of the 1975 breeding season. 31 6. Percent of daylight time female Ospreys engaged in Nest Activities in relation to the number of days prior to egg-laying, at nest 1, Washington Gulch Creek, Humboldt County, California, during the 1974 breeding season, and at nests 2 and 3, Eagle Lake, Lassen County, California, during the 1975 breeding season. 33 7. Percent of daylight time male Ospreys engaged in Nest Activities in relation to the number of days prior to egg-laying, at nest 1, Washington Gulch Creek, Humboldt County, California, during the 1974 breeding season, and at nests 2 and 3, Eagle Lake, Lassen County, California, during the 1975 breeding season. 33 iv Page 8. Percent of daylight time Ospreys engaged in Nest Activities and Tree Activities in relation to phase of the breeding season, at nest 1, Washington Gulch Creek, Humboldt County, California, during the 1974 breeding season, and at nests 2 and 3, Eagle Lake, Lassen County, California, during the Pre- Incubation phase of the 1975 breeding season. 36 9. Numbers of items of nest material delivered per hour by female and male Ospreys in relation to phase of the breeding season, at nest 1, Washington Gulch Creek, Humboldt County, California, during the 1974 breeding season, and at nests 2 and 3, Eagle Lake, Lassen County, California, during the Pre- Incubation phase of the 1975 breeding season. 40 10. Numbers of mounts and copulations engaged in by Ospreys in relation to numbers of days prior to and after egg-laying at nest 1, Washington Gulch Creek, Humboldt County, California, during the 1974 breeding season. 45 11. Numbers of mounts and copulations engaged in by Ospreys in relation to number of days prior to and after egg-laying at nests 2 and 3, Eagle Lake, Lassen County, California, during the 1975 breeding season. 45 12. Relative percentages of daylight time each sex of Ospreys engaged in Incubation and Brooding in relation to number of days prior to and after egg-laying at nest 1, Washington Gulch Creek, Humboldt County, California, during the 1974 breeding season. 48 13. Relative percentages of daylight time sexes and different pairs of Ospreys engaged in Fishing in relation to phase of breeding season, at nest 1, Washington Gulch Creek, Humboldt County, California, during the 1974 breeding season, and at nests 2 and 3, Eagle Lake, Lassen County, California, during the Pre- Incubation phase of the 1975 breeding season. 51 14. Relative rates sexes and different pairs of Ospreys delivered fish to nest 1, Washington Gulch Creek, Humboldt County, California, during the 1974 breeding season, and to nests 2 and 3, Eagle Lake, Lassen County, California, during the Pre-Incubation phase of the 1975 breeding season. 54 v Page 15. Number of fish delivered per hour to nest 1, Washington Gulch Creek, Humboldt County, California, in relation to segment of the day during the 1974 breeding season. 60 vi LIST OF TABLES Page 1. Activities of foraging Ospreys while absent from nests located near Humboldt Bay, Humboldt County, California. 15 2. Relative percentages of the 24-hour day sexes and different pairs of Ospreys engaged in Flying and Non-flying activities at nest 1, Washington Gulch Creek, Humboldt County, California, during the 1974 breeding season, and at nests 2 and 3, Eagle Lake, Lassen County, California, during the Pre- Incubation phase of the 1975 breeding season. 25 3. Percent of daylight time Ospreys engaged in behavioral activities (including Unknown activities) at nest 1, Washington Gulch Creek, Humboldt County, California, during each phase of the 1974 breeding season. 26 4. Percent of daylight time Ospreys engaged in behavioral activities (including Unknown activities) at nests 2 and 3, Eagle Lake, Lassen County, California, during the Pre- Incubation phase of the 1975 breeding season. 27 5. Relative rates at which sexes and different pairs of Ospreys engaged in Nest Construction, Nest Alteration, and Digging at nest 1, Washington Gulch Creek, Humboldt County, California, during the 1974 breeding season, and at nests 2 and 3, Eagle Lake, Lassen County, California, during the Pre-Incubation phase of the 1975 breeding season. 41 6. Comparison of estimated and predicted energy expenditure of Ospreys at nest 1, Washington Gulch Creek, Humboldt County, California, during the 1974 breeding season, and at nests 2 and 3, Eagle Lake, Lassen County,. California, during the Pre-Incubation phase of the 1975 breeding season. 61 7. Predicted energy intake and predicted numbers of fish ingested (based upon predicted daily energy expenditure) by Ospreys at nest 1, Washington Gulch Creek, Humboldt County, California, during the 1974 breeding season, and at nests 2 and 3, Eagle Lake, Lassen County, California, during the Pre-Incubation phase of the 1975 breeding season. 63 vii LIST OF APPENDICES Page 1. Frequency of occurrence, percent frequency of occurrence, and mean elapsed time in minutes Ospreys were engaged in each behav- ioral activity at nest 1, Washington Gulch Creek, Humboldt County, California, during the 1974 breeding season. 84 2. Frequency of occurrence, percent frequency of occurrence, and mean elapsed time in minutes Ospreys were engaged in each behav- ioral activity at nests 2 and 3, Eagle Lake, Lassen County, California, during the Pre- Incubation phase of the 1975 breeding season. 87 3. Calculation of the percent of the 24-hour day the female Osprey at nest 1, Washington Gulch Creek, Humboldt County, California, engaged in Flying and Non-flying activities during the Incubation phase of the 1974 breeding season. 89 4. Estimated energy expenditure (calculated on the basis of food intake assimilated) of Ospreys at nest 1, Washington Gulch Creek, Humboldt County, California, during each phase of the 1974 breeding season. 90 5. Estimated energy expenditure (calculated on the basis of food intake assimilated) of Ospreys at nests 2 and 3, Eagle Lake, Lassen County, California, during the Pre-Incubation phase of the 1975 breeding season. 92 6. Percentage of fish delivered by and sub- sequently totally consumed by Ospreys at nest 1, Washington Gulch Creek, Humboldt County, California, during the 1974 breeding season, and at nests 2 and 3, Eagle Lake, Lassen County, California, during the Pre- Incubation phase of the 1975 breeding season.