BALD EAGLES (Haliaeetus leucocephalus) NESTING IN OREGON AND ALONG THE LOWER COLUMBIA RIVER, 1978-2007 Final Report By: Frank B. Isaacs & Robert G. Anthony Oregon Cooperative Fish and Wildlife Research Unit Department of Fisheries and Wildlife Oregon State University Corvallis, OR 97331, USA 18 March 2011 BALD EAGLES (Haliaeetus leucocephalus) NESTING IN OREGON AND ALONG THE LOWER COLUMBIA RIVER,1978-2007 Final Report By: Frank B. Isaacs Oregon Cooperative Fish and Wildlife Research Unit Department of Fisheries and Wildlife Oregon State University Corvallis, OR 97331, USA [email protected] and Robert G. Anthony Oregon Cooperative Fish and Wildlife Research Unit Department of Fisheries and Wildlife Oregon State University Corvallis, OR 97331, USA [email protected] 18 March 2011 Suggested citation: Isaacs, F. B., and R. G. Anthony. 2011. Bald eagles (Haliaeetus leucocephalus) nesting in Oregon and along the lower Columbia River, 1978-2007. Final Report, 18 March 2011. Oregon Cooperative Fish and Wildlife Research Unit, Department of Fisheries and Wildlife, Oregon State University, Corvallis, Oregon, USA. 1 TABLE OF CONTENTS TITLE PAGE.....................................................................................................................1 TABLE OF CONTENTS...................................................................................................2 ABSTRACT .....................................................................................................................4 INTRODUCTION .............................................................................................................8 STUDY AREA................................................................................................................13 Boundaries.................................................................................................................13 Topography................................................................................................................14 Climate.......................................................................................................................14 Habitat Diversity.........................................................................................................15 Land Ownership and Forests .....................................................................................16 Shoreline....................................................................................................................17 Recovery Zones and Watersheds..............................................................................18 METHODS.....................................................................................................................20 Terminology ...............................................................................................................20 Protocol......................................................................................................................22 Data Management and Analyses ...............................................................................27 Population Size ..........................................................................................................28 Distribution .................................................................................................................30 Nesting Phenology.....................................................................................................31 Productivity ................................................................................................................32 Abandoned Breeding Areas .......................................................................................33 Aquatic Features Associated with Breeding Areas ....................................................33 Band Returns and Marked Eagles .............................................................................34 Columbia River Segments .........................................................................................35 Density of Breeding Areas .........................................................................................37 Distance from Water and Elevation of Breeding Areas ..............................................39 Historical Breeding Population ...................................................................................39 Mate Changes at Breeding Areas ..............................................................................41 Nest Building and Copulation.....................................................................................41 Nest Trees, Nests, Gaps in Use, and Nest Tree Changes.........................................42 New Breeding Areas ..................................................................................................43 Other Species and Bald Eagle Nests.........................................................................44 Ownership of Nest Trees ...........................................................................................44 Population Size by Month ..........................................................................................45 Year-To-Year Nesting Outcomes...............................................................................46 RESULTS......................................................................................................................47 Population Size ..........................................................................................................47 Distribution .................................................................................................................49 Nesting Phenology.....................................................................................................51 Productivity ................................................................................................................54 Abandoned Breeding Areas .......................................................................................56 Aquatic Features Associated with Breeding Areas ....................................................57 Band Returns and Marked Eagles .............................................................................58 2 Columbia River Segments .........................................................................................60 Density of Breeding Areas .........................................................................................62 Distance from Water and Elevation of Breeding Areas ..............................................64 Historical Breeding Population ...................................................................................66 Mate Changes at Breeding Areas ..............................................................................67 Nest Building and Copulation.....................................................................................68 Nest Trees, Nests, Gaps in Use, and Nest Tree Changes.........................................69 New Breeding Areas ..................................................................................................76 Other Species and Bald Eagle Nests.........................................................................77 Ownership of Nest Trees ...........................................................................................79 Population Size by Month ..........................................................................................81 Year-To-Year Nesting Outcomes...............................................................................81 DISCUSSION ................................................................................................................83 Population Size ..........................................................................................................83 Marked Eagles ...........................................................................................................89 Distribution .................................................................................................................92 Nesting Phenology.....................................................................................................96 Productivity ................................................................................................................99 Nest Trees and Nests ..............................................................................................103 MANAGEMENT IMPLICATIONS AND RECOMMENDATIONS ..................................107 Population Size ........................................................................................................108 Recommendation .................................................................................................109 Monitoring ................................................................................................................109 Recommendation .................................................................................................110 Habitat Management................................................................................................110 Recommendation .................................................................................................111 Occupation of Breeding Areas .................................................................................112 Recommendation .................................................................................................112 Nest Trees ...............................................................................................................112