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Cuckoos, Cowbirds and Other Cheats
904
ANIMAL BEHAVIOUR, 60, 6
the political, scientific and economic complexities of whaling in two paragraphs. The critical conservation problems faced by the Florida manatee are given only passing mention. Once again, I believe the authors would have done better to treat regional problems in more detail. Readers will, in any case, go elsewhere for coverage of global issues. A large body of information on the status of marine mammals in the Gulf of Mexico, the stock assessment reports required under the Marine Mammal Protection Act (Waring et al. 1997), is neither extracted nor referenced here. The physical production and layout of the book are superb. The volume is very pleasing to the eye. Larry Foster’s paintings, the colour plates, other photographs and line drawings of skulls are all excellent. In the first sentence of the Prologue, the authors note that David Schmidly began this book more than 10 years ago. With such a long gestation, it is a shame that the end result is marred by a number of errors that should have been detected and corrected at the editorial stage. With a firm editorial hand, an expanded regional perspective within the Gulf, more detail on well-known species, and less general material, this could be a first-rate regional reference volume. I hope the next edition will address these issues. A. J. READ Nicholas School of the Environment, Duke University Marine Laboratory, 135 Duke University Marine Lab Road, Beaufort, NC 28516, U.S.A. References Mann, J., Connor, R. C., Tyack, P. L. & Whitehead, H. 2000. Cetacean Societies. Field Studies of Dolphins and Whales. Chicago: University of Chicago Press. Reynolds, J. E. III & Rommel, S. A. 1999. Biology of Marine Mammals. Washington, D.C.: Smithsonian Institution Press. Waring, G. T., Palka, D. L., Mullin, K. D., Hain, J. W. H., Hansen, L. J. & Bisack, K. D. 1997. U.S. Atlantic and Gulf of Mexico Stock Assessments—1996. NOAA Technical Memorandum NMFS-NE-114. Woods Hole, Massachusetts.
doi:10.1006/anbe.2000.1568, available online at http://www.idealibrary.com on
Cuckoos, Cowbirds and Other Cheats. By N. B. DAVIES. London: Academic Press (2000). Pp. x+310. Price £24.95. The butterfly Maculinea rebeli, the Psithyrus bumblebees, the Plagiolepis ants, the catfish Synodontis multipunctatus, the bird Cuculus canorus and many others, all share the same reproductive strategy: they are brood parasites. Brood parasites exploit parental care provided by unrelated individuals belonging to the same or to different species. Given the cost of parental care, it is easy to understand the benefits arising from this parasitic mode of reproduction. Brood parasitism has been extensively studied in birds where it occurs in about 1% of existing species. Aristotle was the first to note that cuckoos have a bizarre reproductive behaviour: females lay their eggs in nests of passerine species and the young cuckoo ejects all host eggs and chicks soon after hatching. Our understanding of the selective forces shaping brood parasitic
behaviour and host defences has improved a lot since Aristotle’s observations of cuckoo behaviour. In particular, in the last decade, several long-term studies of host– brood parasite associations have provided some of the best evidence of coevolutionary interactions in nature. Nick Davies’s book is the latest contribution to the study of brood parasitism. The book is a magnificent review of the suite of adaptations allowing brood parasites to exploit their hosts and allowing hosts to escape parasitism. The book contains detailed descriptions of parasite natural history but also provides a modern theoretical framework to explain brood parasitism with evolutionary arguments. Davies covers all the major questions related to brood parasitism in birds from its origin to the coevolutionary and ecological interactions with the hosts. The hypotheses are clearly presented and the evidence supporting or refuting them is extensively reviewed. The book begins with an introduction to the 100 species of avian brood parasites (cuckoos, cowbirds, honeyguides, parasitic finches and ducks) and their natural history. Most of our knowledge of brood parasitism comes from studies on the common cuckoo, including work conducted by Davies and collaborators, and it is therefore not surprising that this species takes a central part of the book. Davies describes the particular features that allow a cuckoo to exploit its hosts (speed and timing of laying, egg size and strength, egg removal), and the coevolutionary process between parasite trickery (egg mimicry) and host defences (egg recognition and ejection). For example, chapter 6 deals with one of the several seemingly paradoxical characteristics of host– brood parasite associations: the lack of chick discrimination by parasitized hosts. Although some passerine species parasitized by the common cuckoo possess astonishing capacities to recognize mimetic cuckoo eggs, they seem unable to discriminate against cuckoo nestlings. This is surprising given that, unlike eggs, cuckoo nestlings do not resemble host chicks. One possible explanation for this lack of host discrimination is that early imprinting on cuckoo nestlings would result in subsequent rejection of the host’s own chicks, certainly a maladaptive strategy. Incorrect imprinting is likely to occur in host species parasitized by cuckoos during their first reproductive attempt. Parasitic eggs usually hatch before host eggs and the young cuckoo evicts all host eggs within a few hours. As a consequence the cuckoo nestling is the only template for parents to imprint on. If this imprinting hypothesis is true we should expect that in species where parasitic chicks are raised along with the host chicks, parents should be able to compare their own and foreign nestlings. This might favour the evolution of chick recognition and, as for egg discrimination, select for chick mimicry. Overall, this appears to be the case. In particular, parasitic finches and screaming cowbirds exhibit the most extraordinary features of host mimicry. Parasitic finches parasitize African estrildids and are very host specific. Host chicks have a series of marks and dots in the gape which differ in colour and shape between species. Parasitic chicks have the same pattern of gape marks and dots as their specific hosts. Screaming cowbirds parasitize the only nonparasitic cowbird, the bay-winged cowbird. Adult birds of the two species differ in plumage colour and can easily by distinguished, but nestlings are identical. Host mimicry in parasitic finches and screaming cowbirds seems to be a parasitic adaptation rather than an ancestral trait. Recent molecular data
2000 The Association for the Study of Animal Behaviour
BOOK REVIEWS
indicate that parasitic finches did not cospeciate with their estrildid hosts and that screaming and bay-winged cowbirds are not sister species. Finally, the observation of reduced parental care of nonmimetic nestlings by estrildids and bay-winged cowbirds further supports the view of host mimicry as a parasitic adaptation. Recent advances in molecular techniques have also allowed the study of another peculiar characteristic of common cuckoos: the existence of populations (called gentes) adapted to a particular host species. Although the common cuckoo exploits several passerine species across its geographical range, each gens is specialized on one host species. This is because egg mimicry can only be achieved at the price of host specificity. Except for egg colour and spotting, and host choice, the different cuckoo gentes are identical with respect to morphological and behavioural traits. Molecular data suggest that gentes may evolve only along female lines, since gentes differ in their mitochondrial DNA sequences (with only maternal inheritance) but not in their nuclear DNA. The book ends with two chapters on intraspecific nest parasitism and the evolutionary forces at the origin of
brood parasitism across different taxa. These two areas are not as well covered as the chapters on coevolutionary interactions, but Davies provides a broad general overview that should stimulate further research. The book is wonderfully illustrated with line drawings by David Quinn. Among the very few criticisms one might make is that there is a paucity of figures and graphics. Many of the ideas and findings reported in the book could have been better illustrated by the original figures. However, this is only a very minor remark for a charming, interesting and well-written volume, which will be of much interest to evolutionary biologists and ornithologists. GABRIELE SORCI Laboratoire d’Ecologie, CNRS UMR 7625, Universite´ Pierre et Marie Curie, 7 quai St Bernard, Case 237, 75252 Paris cedex 05, France
905
ANIMAL BEHAVIOUR, 60, 6
the political, scientific and economic complexities of whaling in two paragraphs. The critical conservation problems faced by the Florida manatee are given only passing mention. Once again, I believe the authors would have done better to treat regional problems in more detail. Readers will, in any case, go elsewhere for coverage of global issues. A large body of information on the status of marine mammals in the Gulf of Mexico, the stock assessment reports required under the Marine Mammal Protection Act (Waring et al. 1997), is neither extracted nor referenced here. The physical production and layout of the book are superb. The volume is very pleasing to the eye. Larry Foster’s paintings, the colour plates, other photographs and line drawings of skulls are all excellent. In the first sentence of the Prologue, the authors note that David Schmidly began this book more than 10 years ago. With such a long gestation, it is a shame that the end result is marred by a number of errors that should have been detected and corrected at the editorial stage. With a firm editorial hand, an expanded regional perspective within the Gulf, more detail on well-known species, and less general material, this could be a first-rate regional reference volume. I hope the next edition will address these issues. A. J. READ Nicholas School of the Environment, Duke University Marine Laboratory, 135 Duke University Marine Lab Road, Beaufort, NC 28516, U.S.A. References Mann, J., Connor, R. C., Tyack, P. L. & Whitehead, H. 2000. Cetacean Societies. Field Studies of Dolphins and Whales. Chicago: University of Chicago Press. Reynolds, J. E. III & Rommel, S. A. 1999. Biology of Marine Mammals. Washington, D.C.: Smithsonian Institution Press. Waring, G. T., Palka, D. L., Mullin, K. D., Hain, J. W. H., Hansen, L. J. & Bisack, K. D. 1997. U.S. Atlantic and Gulf of Mexico Stock Assessments—1996. NOAA Technical Memorandum NMFS-NE-114. Woods Hole, Massachusetts.
doi:10.1006/anbe.2000.1568, available online at http://www.idealibrary.com on
Cuckoos, Cowbirds and Other Cheats. By N. B. DAVIES. London: Academic Press (2000). Pp. x+310. Price £24.95. The butterfly Maculinea rebeli, the Psithyrus bumblebees, the Plagiolepis ants, the catfish Synodontis multipunctatus, the bird Cuculus canorus and many others, all share the same reproductive strategy: they are brood parasites. Brood parasites exploit parental care provided by unrelated individuals belonging to the same or to different species. Given the cost of parental care, it is easy to understand the benefits arising from this parasitic mode of reproduction. Brood parasitism has been extensively studied in birds where it occurs in about 1% of existing species. Aristotle was the first to note that cuckoos have a bizarre reproductive behaviour: females lay their eggs in nests of passerine species and the young cuckoo ejects all host eggs and chicks soon after hatching. Our understanding of the selective forces shaping brood parasitic
behaviour and host defences has improved a lot since Aristotle’s observations of cuckoo behaviour. In particular, in the last decade, several long-term studies of host– brood parasite associations have provided some of the best evidence of coevolutionary interactions in nature. Nick Davies’s book is the latest contribution to the study of brood parasitism. The book is a magnificent review of the suite of adaptations allowing brood parasites to exploit their hosts and allowing hosts to escape parasitism. The book contains detailed descriptions of parasite natural history but also provides a modern theoretical framework to explain brood parasitism with evolutionary arguments. Davies covers all the major questions related to brood parasitism in birds from its origin to the coevolutionary and ecological interactions with the hosts. The hypotheses are clearly presented and the evidence supporting or refuting them is extensively reviewed. The book begins with an introduction to the 100 species of avian brood parasites (cuckoos, cowbirds, honeyguides, parasitic finches and ducks) and their natural history. Most of our knowledge of brood parasitism comes from studies on the common cuckoo, including work conducted by Davies and collaborators, and it is therefore not surprising that this species takes a central part of the book. Davies describes the particular features that allow a cuckoo to exploit its hosts (speed and timing of laying, egg size and strength, egg removal), and the coevolutionary process between parasite trickery (egg mimicry) and host defences (egg recognition and ejection). For example, chapter 6 deals with one of the several seemingly paradoxical characteristics of host– brood parasite associations: the lack of chick discrimination by parasitized hosts. Although some passerine species parasitized by the common cuckoo possess astonishing capacities to recognize mimetic cuckoo eggs, they seem unable to discriminate against cuckoo nestlings. This is surprising given that, unlike eggs, cuckoo nestlings do not resemble host chicks. One possible explanation for this lack of host discrimination is that early imprinting on cuckoo nestlings would result in subsequent rejection of the host’s own chicks, certainly a maladaptive strategy. Incorrect imprinting is likely to occur in host species parasitized by cuckoos during their first reproductive attempt. Parasitic eggs usually hatch before host eggs and the young cuckoo evicts all host eggs within a few hours. As a consequence the cuckoo nestling is the only template for parents to imprint on. If this imprinting hypothesis is true we should expect that in species where parasitic chicks are raised along with the host chicks, parents should be able to compare their own and foreign nestlings. This might favour the evolution of chick recognition and, as for egg discrimination, select for chick mimicry. Overall, this appears to be the case. In particular, parasitic finches and screaming cowbirds exhibit the most extraordinary features of host mimicry. Parasitic finches parasitize African estrildids and are very host specific. Host chicks have a series of marks and dots in the gape which differ in colour and shape between species. Parasitic chicks have the same pattern of gape marks and dots as their specific hosts. Screaming cowbirds parasitize the only nonparasitic cowbird, the bay-winged cowbird. Adult birds of the two species differ in plumage colour and can easily by distinguished, but nestlings are identical. Host mimicry in parasitic finches and screaming cowbirds seems to be a parasitic adaptation rather than an ancestral trait. Recent molecular data
2000 The Association for the Study of Animal Behaviour
BOOK REVIEWS
indicate that parasitic finches did not cospeciate with their estrildid hosts and that screaming and bay-winged cowbirds are not sister species. Finally, the observation of reduced parental care of nonmimetic nestlings by estrildids and bay-winged cowbirds further supports the view of host mimicry as a parasitic adaptation. Recent advances in molecular techniques have also allowed the study of another peculiar characteristic of common cuckoos: the existence of populations (called gentes) adapted to a particular host species. Although the common cuckoo exploits several passerine species across its geographical range, each gens is specialized on one host species. This is because egg mimicry can only be achieved at the price of host specificity. Except for egg colour and spotting, and host choice, the different cuckoo gentes are identical with respect to morphological and behavioural traits. Molecular data suggest that gentes may evolve only along female lines, since gentes differ in their mitochondrial DNA sequences (with only maternal inheritance) but not in their nuclear DNA. The book ends with two chapters on intraspecific nest parasitism and the evolutionary forces at the origin of
brood parasitism across different taxa. These two areas are not as well covered as the chapters on coevolutionary interactions, but Davies provides a broad general overview that should stimulate further research. The book is wonderfully illustrated with line drawings by David Quinn. Among the very few criticisms one might make is that there is a paucity of figures and graphics. Many of the ideas and findings reported in the book could have been better illustrated by the original figures. However, this is only a very minor remark for a charming, interesting and well-written volume, which will be of much interest to evolutionary biologists and ornithologists. GABRIELE SORCI Laboratoire d’Ecologie, CNRS UMR 7625, Universite´ Pierre et Marie Curie, 7 quai St Bernard, Case 237, 75252 Paris cedex 05, France
905