Cover

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Title page, Copyright, Dedication

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Contents

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pp. vii-xii

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Preface

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pp. xiii-xvi

In the early 1960s biologists began to realize that not only morphological structures but also social relationships and species-typical patterns of sociality were the product of natural selection. This was reflected in the first comparative studies of social organization in relation to environment (e.g., Orians, 1961; Crook, 1963) ...

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Acknowledgments

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pp. xvii-xviii

In twenty-seven years of studying communally breeding birds I have received aid from many people. One person has stood by me, always ready to help, for this entire period—my wife, Esther R. Brown. She has helped in every imaginable way, in field observations, in processing and analyzing data, ...

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1 Why Study Helping Behavior?

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pp. 3-7

Helping behavior has a special meaning in biology. It is not just any behavior that may appear to be helpful. Conventional usage of the term helping has been somewhat narrower than Skutch's definition above. Helping is parent-like behavior toward young that are not the genetic offspring of the helper. ...

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2. The Discovery of Helping Behavior and a Classification of Avian Communal Breeding Systems

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pp. 8-33

In 1935 Alexander Skutch wrote a brief paper titled "Helpers at the nest." In it he described the feeding of young Brown Jays, Bushtits, and Banded Cactus Wrens by more than two unhanded birds of their own species. Some of the birds must have been feeding young that were not their own; hence some were helpers. ...

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3 Climate, Geography, and Taxonomy

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pp. 34-44

Is the frequency of avian species that have communal breeding systems correlated with climate, geography, or taxonomy? Yes, there are rough patterns of correlation with each of these factors, but their meaning is not entirely clear. We hope to gain some insight into the origins of communal breeding by studying these patterns. ...

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4 Elements of Inclusive Fitness Theory for Field Studies

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pp. 45-61

In 1954 David Lack published his influential book, The Natural Regulation of Animal Numbers. Through this book and his many papers, Lack convinced many ecologists of the overpowering importance of selection at the level of the individual and of the weakness of the argument for reproductive restraint. ...

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5 Delayed Breeding Sets the Stage for Helping

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pp. 62-90

In order to understand the ecological factors that predispose a bird to perform alloparenting, it is necessary first to re-emphasize that helping occurs in a variety of situations and may, therefore, be favored by different combinations of factors in different cases. For example, even in one species, the Acorn Woodpecker, helping occurs by breeding males who share a female, ...

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6 Reduced Dispersal Sets the Stage for Helping

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pp. 91-101

Many communally breeding species are characterized by reduced dispersal, as well as delayed breeding and alloparental care. Dispersal is a critical process in the life of a bird because it often occurs in the transition from immaturity to breeding status. In order to place these events in a broader perspective, we consider briefly not only the movements of dispersal, ...

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7 Territorial Inheritance as Parental Facilitation

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pp. 102-115

Dispersal typically precedes breeding in vertebrates and is often crucial if the young animal is to obtain a favorable breeding position. In group-territorial species, however, the chances that a single young and naive individual, striking off on its own, can find good territories that are unoccupied are indeed slim. ...

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8 Mutualism, Cost-Sharing, and Group Size

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pp. 116-131

The addition of a breeding or nonbreeding helper to a group of two may effect a variety of costs and benefits beyond care of young. This is especially true in group-territorial species. Much has been learned about energy budgets of birds in recent years (Mugaas and King, 1981). ...

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9 Mutualistic Mating Systems Polyandry and Uncertain Paternity

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pp. 132-153

The study of mating systems in communal birds has opened new vistas into avian sociobiology. It has extended the classical view through the discovery of mating systems previously unknown in birds, such as cooperative polyandry (Galapagos Hawk) and polygynandry (Pukeko, Acorn Woodpecker), nest-oriented promiscuity (Noisy Miner), and semi-promiscuous monogamy (Ostrich). ...

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10 Mutualistic Mating Systems Joint Nesting and Uncertain Maternity

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pp. 154-168

Mate sharing in polyandrous systems may seem complex, but it is relatively simple compared to the systems considered in this chapter. When a second female is added to a polyandrous unit, polygynandry occurs, as in the Acorn Woodpecker and Pukeko. This possibility raises a new set of questions concerning the female in particular. ...

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11 Does Helping Really Benefit the Helped?

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pp. 169-189

It is generally understood that theories of helping which invoke indirect selection (Lack, 1968; Brown, 1969a, 1974; Emlen, 1982b; Maynard Smith and Ridpath, 1972; Ricklefs, 1975; Vehrencamp, 1979, 1980) require the recipient to benefit from the alloparental care provided by the helper. ...

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12 The Genetic Structure of Social Units

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pp. 190-214

The theory of inclusive fitness has in the two decades since its introduction (Hamilton, 1964) added a new dimension to population genetics, namely, the study of genetic structure within the deme. D. S. Wilson (1975, 1977) referred to the new view as one of structured demes. ...

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13 Indirect Selection for Helping

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pp. 215-223

In this chapter and the next we evaluate various hypotheses for the evolution of helping by nonbreeders. Here we consider theories that invoke indirect selection. In the following chapter we consider theories that exclude an important role for indirect selection. ...

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14 Direct Fitness, Mutualism, and Reciprocity

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pp. 224-249

In discussions about the evolutionary causes of helping, one view is that classical individual selection, or direct selection, is primarily responsible, and that the importance of indirect selection is negligible. In this chapter we explore some conceptual bases for this view and consider what facts are needed to test it. ...

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15 Parent-Offspring Relationships

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pp. 250-264

Perhaps surprisingly, the pioneers in the evolutionary study of parent-offspring relationships have been entomologists. Students of the social insects have long been impressed with the fact that in eusocial species the queens and male reproductives are given "royal" treatment during their development ...

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16 Infanticide. Dominance, and Destructive Behavior

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pp. 265-269

Communally breeding birds are not always cooperative. That they may act destructively toward the nest and eggs of others in their social unit has been known since nest robbing and egg destruction were described for the Mexican Jay (Brown, 1963a) and Australian Magpie (Carrick, 1963,1972). ...

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17 Diet and Group Territoriality

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pp. 270-275

Social defense of food resources occurs in a wide variety of orders and families of communal birds (Table 2 2) and mammals. According to a recent model (Brown, 1982a and Chapter 8), cooperative defense of food resources is profitable for such species when the benefits of cooperation in sharable tasks exceed the costs stemming from defense, vigilance, care of young, and the more rapid consumption of resources in a group than alone. ...

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18 Synthesis

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pp. 276-290

We have looked in some detail at a variety of topics and problems. Now it is time to draw together the main points, especially those that span several chapters. With a controversial problem, such as the ecological evolution of helping behavior, it is desirable to employ the scientific method rather than the method of advocacy. ...

Appendix

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pp. 291-296

Annotated Glossary

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pp. 297-308

Literature Cited

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pp. 309-336

Author Index

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pp. 337-342

Taxonomic Index

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pp. 343-351

Subject Index

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pp. 352-354