The variety of social systems among the New World blackbirds (Family Icteridae) and the structural simplicity of their foraging environment provide excellent opportunities for testing theorics about the adaptive significance of their behavior. Here Gordon Orians presents the results of his many years of research on how blackbirds utilize their marsh environments during the breeding season. These results stem from information he gathered on three species during ten breeding seasons in the Pacific Northwest, on Red-winged blackbirds during two breeding seasons in Costa Rica, and on three species during one breeding season in Argentina.
The author uses models derived from Darwin's theory of natural selection to predict the behavior and morphology of individuals as well as the statistical properties of their populations. First he tests models that predict habitat selection, foraging behavior, territoriality, and mate selection. Then he considers some population patterns, especially range of use of environmental resources and overlap among species, that may result from those individual attributes. Professor Orianns concludes with an overview of the structure of bird communities in marshes of the world and the relation of these patterns to overall source availability in these simple but productive habitats.
| Preface | vii | |
| 1. | The Approach and the Subjects | 3 |
| 1.1. | The Players | 3 |
| 1.2. | The Theater | 8 |
| 1.3. | Materials and Methods | 18 |
| 2. | Marshes as Providers of Resources for Blackbirds | 25 |
| 2.1. | Quantity of Emergence | 26 |
| 2.2. | Temporal Pattern of Emergence | 34 |
| 2.3. | Abundance of Insects on the Uplands | 42 |
| 3. | The Adaptations: Selection of Habitats, Territories and Mates | 48 |
| 3.1. | Habitat Selection by Males | 50 |
| 3.2. | Habitat Selection by Females | 53 |
| 3.3. | Predictions and Tests about Habitat and Mate Selection | 56 |
| 3.4. | Sizes of Territories | 73 |
| 3.5. | The Cues Used by Blackbirds in Selecting Their Territories | 80 |
| 3.6. | Conclusions | 86 |
| 4. | The Adaptations: Foraging Behavior | 90 |
| 4.1. | Theory | 91 |
| 4.2. | Tests of Foraging Theory | 102 |
| 4.3. | Tests of CPF Theory | 131 |
| 4.4. | Conclusions | 138 |
| 5. | The Patterns: Variability in Use of Resources | 141 |
| 5.1. | Range of Lake Productivity Occupied | 141 |
| 5.2. | Range of Nest Sites Occupied | 149 |
| 5.3. | Breeding Seasons | 153 |
| 5.4. | Clutch Sizes | 155 |
| 5.5. | Variability in Foods and Foraging | 159 |
| 5.6. | Conclusions | 171 |
| 6. | The Patterns: Competition, Overlap and Community Structure | 173 |
| 6.1. | Short-Term Effects of Competition | 174 |
| 6.2. | Long-Term Effects of Competition | 186 |
| 6.3. | Competition and Size | 189 |
| 7. | Adaptations Among Argentine Marsh-nesting Blackbirds | 194 |
| 7.1. | The Species of Blackbirds Breeding in Argentine Marshes | 195 |
| 7.2. | Foods and Foraging | 210 |
| 7.3. | Patch Utilization While Foraging | 216 |
| 7.4. | Dietary Breadths | 222 |
| 7.5. | Competition and Overlap | 222 |
| 8. | Of Birds and Marshes | 226 |
| 8.1. | Significance of Marsh Structural Simplicity | 226 |
| 8.2. | Nonpasserine Birds in Marshes | 239 |
| 8.3. | Avian Social Systems in Marshes | 241 |
| 8.4. | Island Biogeography of Marshes | 242 |
| 8.5. | Effects of Blackbird Predation on Odonate Populations | 244 |
| 8.6. | Conclusions | 251 |
| General Conclusions | 253 | |
| Appendixes | 255 | |
| References | 275 | |
| Index | 291 |
Overview
The variety of social systems among the New World blackbirds (Family Icteridae) and the structural simplicity of their foraging environment provide excellent opportunities for testing theorics about the adaptive significance of their behavior. Here Gordon Orians presents the results of his many years of research on how blackbirds utilize their marsh environments during the breeding season. These results stem from information he gathered on three species during ten breeding seasons in the Pacific Northwest, on ...