NESTING and MATING DECISIONS and THEIR CONSEQUENCES in the BAYA WEAVERBIRD Ploceus Philippinus
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NESTING AND MATING DECISIONS AND THEIR CONSEQUENCES IN THE BAYA WEAVERBIRD Ploceus philippinus By SUHEL QUADER 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 2003 Copyright 2003 by Suhel Quader To my parents and my brother for their support; and to the BSAP for starting it all. ACKNOWLEDGMENTS My advisor, Jane Brockmann, allowed me the freedom and independence to pursue my own research ideas. Without her intellectual contribution this project would have been impossible to complete. She shared advice and editorial comments freely; and her broad perspective on the field of animal behavior has enriched my education. Rich Kiltie, Doug Levey, Colette St. Mary, and Katie Sieving were wonderful committee members—their suggestions greatly improved my research, and their patience and understanding helped me through a busy last semester. I also thank Rebecca Kimball and Ginger Clark for comments on one of my chapters. Various agencies funded my research, including the University of Florida, the American Museum of Natural History, the American Ornithologists’ Union, and Sigma Xi. I am grateful to them. In India, V. C. Ambedkar, Lalitha Raj, and U. N. Ravi Kumar, helped me search for a suitable field site. I am very grateful to the Birdwatchers’ Society of Andhra Pradesh, and in particular Siraj Taher and Aasheesh Pittie, for facilitating and encouraging my research. Tom Hash and Fran Bidinger made my work at ICRISAT possible. Prashant Bhardwaj, Lydia Flynn, Cecile Grenier, Radha Ranganathan, A. Giridhar Rao, K. Hanumanth Rao, and many others made my stay a pleasure. I thank the Andhra Pradesh Forest Department for granting me permission to study baya weaverbirds. For advice and help in collecting and analyzing genetic material, I thank Dan Brazeau and Ginger Clark at the University of Florida and Jonathan Crouch, Hutokshi iv Crouch, Santosh Gurtu, Abdul Gafoor, Bryan Moss, and G. Soma Raju at ICRISAT. T.L. Prasad let me use his vehicle in 2000; without it, field work would have been very difficult, indeed. For help in the field, I thank Irfan Quader, Jane Brockmann, and especially Kavita Isvaran. The graduate students in Zoology have been a source of stimulating discussion and pleasant companionship. My intellectual development has been much advanced by my interactions with Becca Hale, Billy Gunnels, Ben Miner, Toshi Okuyama, April Randle, Sarah Schaack, Nat Seavy, Laura Sirot, Markus Tellkamp, Manjula Tiwari, Manuel Vélez, and Amy Zanne. I thank the staff of the Department of Zoology, and especially Karen Pallone, for all manner of help and advice over the years. Skye White helped draw some of the figures in this dissertation. Ben Bolker and Craig Osenberg teach challenging and inspiring courses in the Department of Zoology. Ben Bolker’s ecological models course helped me develop confidence in using various quantitative methods. I am grateful to them both. My parents and brother have always supported me in everything I have done. Their love and encouragement and interest in what I do have made my tenure as a graduate student all the more enjoyable and fulfilling. The person who has had the greatest influence on me over most of my adult life is Kavita Isvaran. I have learnt from her, and have attempted to follow her example in both professional and personal spheres of life. She is my closest colleague and companion; this dissertation is as much hers as it is mine. v TABLE OF CONTENTS Page ACKNOWLEDGMENTS ................................................................................................. iv LIST OF TABLES........................................................................................................... viii LIST OF FIGURES ........................................................................................................... ix ABSTRACT.........................................................................................................................x CHAPTER 1 GENERAL INTRODUCTION ....................................................................................1 2 SEQUENTIAL SETTLEMENT BY NESTING MALE AND FEMALE WEAVERBIRDS: THE ROLE OF MONSOON WINDS...........................................5 Introduction...................................................................................................................5 Methods ........................................................................................................................7 Results.........................................................................................................................11 Discussion...................................................................................................................14 3 DO FEMALE BAYA WEAVERBIRDS PREFER ELABORATE NESTS? EXPERIMENTAL AND CORRELATIONAL EVIDENCE ....................................25 Introduction.................................................................................................................25 Methods ......................................................................................................................27 Results.........................................................................................................................35 Discussion...................................................................................................................38 4 CONSEQUENCES OF NEST CHOICE: REPRODUCTIVE BENEFITS ASSOCIATED WITH NEST LOCATION AND STRUCTURE IN THE BAYA WEAVERBIRD..........................................................................................................52 Introduction.................................................................................................................52 Methods ......................................................................................................................55 Results.........................................................................................................................62 Discussion...................................................................................................................67 vi 5 RATES OF EXTRA-PAIR PATERNITY AND INTRASPECIFIC BROOD PARASITISM IN THE BAYA WEAVERBIRD.......................................................80 Introduction.................................................................................................................80 Methods ......................................................................................................................83 Results.........................................................................................................................89 Discussion...................................................................................................................91 6 GENERAL CONCLUSIONS.....................................................................................99 Nesting and Mating Decisions in Weaverbirds ..........................................................99 Female Choice and Nest Attributes ..........................................................................100 Comparative Studies—the Next Step? .....................................................................103 Conclusion ................................................................................................................104 LIST OF REFERENCES.................................................................................................106 BIOGRAPHICAL SKETCH ...........................................................................................116 vii LIST OF TABLES Table page 2-1 Nest bearing and nest-entrance orientation of helmet-stage nests chosen and not chosen by females. ...................................................................................................19 3-1 Summary statistics of attributes of helmet location and architecture.......................44 3-2 Morphometrical measurements on male and female baya weaverbirds...................45 3-3 Male morphological correlates of female choice, from GLMM analyses with male identity as random effect. ................................................................................46 3-4 Female choice in relation to male behavior at the helmet from GLMM analyses with colony identity as random effect. .....................................................................47 3-5 Female choice in relation to nest structure and nest location based on GLMM with colony as random effect. ..................................................................................48 4-1 Attributes of nest location and nest architecture. .....................................................73 4-2 Numbers of nests that survived until hatching and fledging, numbers that failed before hatching and fledging, and number whose fates were unknown. .................74 4-3 Correlates of nest survival based on Cox proportional hazards regression..............75 4-4 Results of GLMM analysis of predictors of fledging success, with colony identity as the random effect. ...................................................................................76 5-1 Polymerase chain reaction conditions for the three microsatellite loci used in parentage analysis, and measures of the variability of the loci................................96 viii LIST OF FIGURES Figure page 2-1 Hypothesized effect of nest-entrance orientation on the probability of losing eggs during strong winds..........................................................................................20