Adaptive Functions of Fleshy Ornamentation in Wild Turkeys and Related Birds
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ADAPTIVE FUNCTIONS OF FLESHY ORNAMENTATION IN WILD TURKEYS AND RELATED BIRDS By RICHARD BUCHHOLZ A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 1994 "That's the whole problem with science. You've got a bunch of empiricists trying to describe things of unimaginable wonder." Calvin ACKNOWLEDGEMENTS My advisor, Jane Brockmann, has gone above and beyond the call of duty in helping me with this project I will always be grateful for her enthusiasm, advice, instruction, guidance, constructive criticism and support. Little did I know that an academicumwelt is learned as well as innate, just like everything else. This study would not have been possible without the help of the rest of my committee. Ellis Greiner kindly taught me parasitology and allowed me to use his lab. He has also been very tolerant of the strange questions we ask over on this side of Archer Rd. Rich Kiltie has thought carefully about the theoretical underpinnings and techniques I have used to study fleshy structures. He directed me at several crucial turning points and made me realize the consequences of my assumptions (although I suspect he does not find turkeys very aesthetically pleasing). Doug Levey has always encouraged and helped me by considering even my wackiest ideas with tact He is also my secret source for everything "birdy." Brian McNab taught me about physiological ecology and generously allowed me to use his lab. Dave McDonald has served as a "ghost" committee member and a friend during my entire graduate career. Literally dozens of people helped catch, handle and process wild turkeys. I am grateful for their help. This study would not have been possible without it. In particular I would like to thank those who helped me several times, including Laurie Eberhardt Ron Clouse, Paula Cushing, and Monica Marquez. Farol Tomson and Frank Nordlie found a place to keep the turkeys, the Department of Zoology paid the costs of maintaining them, and Chris Wilcox and her crew helped care for the turkeys when I was out of town. The Florida Museum of Natural History, University Athletic Association and Frank Maturo in generously allowed me to use their facilities to house the turkeys. My dad, Eduard Buchholz helped improve the turkey cages. Margaret Byrne and Gerry Ryan helped build new cages. My studies of free-living wild turkeys were done under permit from the Florida Department of Natural Resources and Florida Game and Freshwater Fish Commission. Permits were facilitated by Dan Pearson and David Cobb. I thank them and the staffs at Paynes Prairie State Preserve and Camp Blanding Wildlife Management Area, particularly Jim Weimer and Jack Gillen. The National Wild Turkey Federation provided wild turkey transport boxes free of charge. Several pilot studies did not pan out in the long run. Nevertheless I would like to thank those who assisted me in these preliminary efforts. John Eisenberg kindly provided permission to conduct preliminary research at the Katharine Ordway Preserve. Peter and Denise Buchholz figured out how to catch jungle fowl on Kauai. Steve Nesbitt taught me all about sandhill cranes, shared his data and let me tag along on crane capturing trips. Marilyn Spaulding, Don Forrester and Sam Telford helped with my earliest attempts at parasitology. I hope they will continue to encourage students as they did me. At times graduate school is a very frustrating and unrewarding place. I must thank the family and friends who have supported, laughed and commiserated with me over the years and made it better. All have been instrumental in keeping me (somewhat) sane and (usually) happy. Nothing would have been possible without the love and generosity of my parents, Eduard and Elisabeth Buchholz. I hope someday they understand why I had to do this. Gratitude goes to their son Peter, who reaffirmed our brotherhood despite having chosen a different path. Thanks go to Marianne von Osten and Susan Edelbach, my "aunt" and "sister," for always welcoming me home. Special thanks go to fellow cohort member, peer advisor and buddy Laurie Eberhardt. I will miss her (boo!) and Peter. Carlita Restrepo is a kindred spirit. I thank the expatriates, Tes Toop and John Donald, for being funny, stabilizing and never dull. They tell me that in Australia Occam's razor is used to cut IV Gordian knots. Monica Marquez made sure I finished my NSF grant application and has always been an encouraging friend. Margaret Byrne and Gerry Ryan have been kind to me in many ways. I value my friendship with each of them and hope they figure out what they are looking for. Renee Calarco and Barbara Crute helped me get here, helped keep me here, and were always there. Maggie and Ted would not be happy about being mentioned in the same sentence, but I cherished them both. John, Tom, Bubba and Jane taught me alot about turkeys; may they rest in peace. Last, but not least, I thank the office staffs: Carol "Sweet Cheeks" Binello, Alice "Glamour Girl" McClaughry, Janet "Green Thumb" Zeigler, Lynda Everitt, Lori "Where Are You Going?" Clark, Ruth Ann Czerenda, Evelyn Rockwell, Kenetha "I've Got my Eye on You" Johnson, Tangelyn "You're Crazy" Mitchell and, of course, Gracie "Babes" Kiltie. Also thanks to Pete in the stockroom. They kept life in Bartram and Carr interesting and smoothed over the red tape. Keep up the great job! My research was funded by the Department of Zoology at the University of Florida, a Frank M. Chapman Memorial Fund Grant in Ornithology from the American Museum of Natural History, a grant-in-aid of research from Sigma Xi, the Animal Behavior Fund of the University of Florida Foundation, the Cracid Breeding and Conservation Center, and a Threadgill Dissertation Fellowship from the College of Liberal Arts and Sciences at the University of Florida. TABLE OF CONTENTS ACKNOWLEDGEMENTS iii ABSTRACT viii CHAPTERS 1 GENERAL INTRODUCTION 1 2 A COMPARATIVE ANALYSIS OF THE ADAPTIVE SIGNIFICANCE OF FLESHY STRUCTURES IN THE GALLIFORMES 5 Hypotheses and Predictions 7 Inter-individual Assessment 7 Immediate benefits 9 Good genes models 10 Fisher's runaway selection 13 Thermoregulation 13 Fleshy structures as heat sinks 14 Solar collector 14 Methods 15 Results 18 Inter-individual Assessment 18 Immediate benefits 18 Good genes models 18 Thermoregulation 22 Fleshy structures as heat sinks 22 Solar collector 22 Discussion 22 3 ADAPTIVE FEMALE CHOICE FOR MALE FLESHY ORNAMENTATION IN WILD TURKEYS 25 Introduction 25 Methods 30 Study Species 30 Mate Choice Experiments 31 Live male experiment 32 Male model experiment 37 Correlates of Ornamentation in Wild Males 39 Results 40 Live Males Experiment 40 Male Models Experiment 42 vi Correlates of Ornamentation in Wild Males 43 Discussion 46 4 MALE DOMINANCE AND VARIATION IN FLESHY HEAD ORNAMENTATION IN WILD TURKEYS 51 Introduction 51 Methods 53 Live Males 54 Male Model Trials 56 Results 57 Live Male Trials 57 Male Model Trials 62 Discussion 62 5 THE THERMOREGULATORY ROLE OF THE UNFEATHERED HEAD AND NECK IN MALE WILD TURKEYS 66 Introduction 66 Methods 67 Subjects and Apparatuses 67 Experimental Design 69 Results 71 Discussion 79 GENERAL DISCUSSION 82 LIST OF REFERENCES 85 BIOGRAPHICAL SKETCH 94 vn Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy ADAPTIVE FUNCTIONS OF FLESHY ORNAMENTATION IN WILD TURKEYS AND RELATED BIRDS By Richard Buchholz August, 1994 Chairman: H. Jane Brockmann Major Department: Zoology Wattles and other types of unfeathered fleshy ornamentation in birds are puzzling to evolutionary biologists because these structures increase the bird's susceptibility to blood- feeding insects and heat loss, without providing any obvious benefits. This study tests sexual and nonsexual hypotheses for the evolution and maintenance of fleshy ornamentation in galliform birds, particularly the wild turkey (Meleagris gallopavo) . A comparative study of the elaboration of fleshy structures in the avian order Galliformes identified the evolutionary pressures under which fleshy structures may have evolved. After controlling for the effects of body size and shared phylogeny, the lack of clear cut associations between fleshy ornamentation and other types of ornaments suggests that sexual selection has not played an important role in the evolution of these structures. Strong negative correlations with latitude, on the other hand, are supportive of a thermoregulatory role for these characters. Sexual selection for the maintenance of fleshy ornamentation was tested in mate choice and dominance trials using wild turkeys raised in captivity. If the wild turkey's viii fleshy structures are maintained by female choice, females are expected to mate non- randomly with respect to these characters. Females chose males with greater snood lengths and skullcap widths. Males with longer snoods were more likely to be dominant in dyadic encounters. In complementary field studies in north central Florida, male snood length was found to be a "good genes" indicator of coccidia infection and body condition. Thus the turkey's snood appears to be maintained by female choice for males who signal their genetic quality. The extensive vascularization of fleshy ornamentation suggests that it may function in thermoregulation. By insulating the unfeathered bare heads and necks of wild turkeys, I tested whether the fleshy ornamentation of this species is important in heat dissipation. Insulated turkeys increased their oxygen consumption and experienced higher body temperatures relative to uninsulated controls. These results concur with those of the comparative study and suggest avian fleshy structures function in heat dissipation as well as sexual selection. Nonsexual hypotheses for the maintenance of ornamentation in animals are rarely proposed, but are necessary to understand the evolution of these costly characters.