Acoustic Communication in Colonial Seabirds: Individual, Sexual, and Species-Specific Variation in Acoustic Signals of Pterodroma Petrels

Acoustic Communication in Colonial Seabirds: Individual, Sexual, and Species-Specific Variation in Acoustic Signals of Pterodroma Petrels

Acoustic communication in colonial seabirds: individual, sexual, and species-specific variation in acoustic signals of Pterodroma petrels Matthew W. McKown A dissertation submitted to the faculty of the University of North Carolina at Chapel Hill in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Curriculum in Ecology. Chapel Hill 2008 Approved by: R. Haven Wiley (Advisor) Sabrina S. Burmeister Karin S. Pfennig Theodore R. Simons Peter S. White ABSTRACT Matthew W. McKown Acoustic communication in colonial seabirds: individual, sexual, and species-specific variation in acoustic signals of Pterodroma petrels (Under the direction of R. Haven Wiley) Acoustic communication is an integral component of social interactions in procellariid seabirds (petrels), and a substantial amount of research has been devoted to the vocalizations and vocal behavior in this family. This work has shown that petrels' calls contain information about the species, sex, and identity of the caller. Experiments have confirmed that these features are used to recognize conspecifics, mates, and other individuals in many species. Relatively little is known, however, about vocalizations in the genus Pterodroma, which contains 40% of the species in the family. My research on Pterodroma externa in the Islas Juan Fernández confirmed sexual dimorphism in the calls of this species and showed that their burrow calls differ among individuals. Both Linear Discriminant Functions and Probabilistic Neural Nets classified individuals by their calls with high accuracy. Acoustic censuses in a mixed colony of Pterodroma externa and P. longirostris showed that both of these nocturnal species increased vocal activity on nights with moonlight. Different tradeoffs between the risk of predation and the risk of collision in the dark might explain differences in the timing of their nocturnal activity. In addition, I compared aerial vocalizations in a closely related group of Pterodroma species in the subgenus Cookilaria . The similarities in the calls produced by these species suggest that vocalizations can provide useful information for understanding the phylogenetic relationships ii of species in this genus. Differences among the calls and activity patterns of these species, on the other hand, suggest a range of adaptations to the different environments they inhabit. One implication of these findings is that each colony of seabirds on remote islands might have an optimal pattern of activity that differs from those of colonies elsewhere. If immigrant individuals cannot adjust, these colony-specific patterns of activity could contribute to reproductive isolation between populations and thus to speciation in these birds. iii DEDICATION To my grandmother, Helen McKown, for introducing me to birds, and to my father and mother, for encouraging my interest in the natural world. iv AKNOWLEDGEMENTS This work would not have been possible without the help, advice, and support of many wonderful people. My advisor, Haven Wiley, inspired me with his energy, knowledge, and curiosity about the natural world. I thank him for him helping me to learn, for his advice, his incredibly helpful editing skills, and for introducing me to so many wonderful natural places in the state of North Carolina. I would also like to thank my committee for their advice, tough questions, and support over these years. Wiley lab members helped me throughout my time at UNC, even from afar. I would especially like to thank Will, for taking me to my first shearwater colony and teaching me how to record petrels. None of this would have been possible without the help of Michelle Wainstein and Peter Hodum. Michelle and Peter provided funding and allowed me to work with them after only a brief e-mail exchange. In subsequent years, Michelle, and the Conservation, Research and Education Opportunities (CREO) NGO, provided the additional funding I required for my field work and research. Peter introduced me to the petrels and shearwaters (and lone storm petrel) of the islands and to the wonderful research site on Alejandro Selkirk. Joanna Smith agreed to collaborate with an unknown graduate student in the creation of a study colony. Thank your for the “morning traffic reports” on my burrow recorders and your v encouragement on that first day up the hill. Erin Hagen, was a good friend and helped behind the scenes with a lot of the logistics of my work in the Juan Fernandez. The Guardaparques at CONAF shared their knowledge of the archipelago, and their skills, for which I am immensely grateful. Guillermo Araya was particularly involved, and collaborated with the research on Pterodroma defilippiana . The people of San Juan Bautista lent great support to our work, and were very welcoming. To the Mas Afuerions; I will never forget your incredible community, your warmth, and your generosity. Amber Johnson, Coral Wolf, and Amanda Rogers all helped as field assistants. The Minority International Research Training Program (MIRT) provided funding for two field assistants, Coral Wolf and Amber Johnson. Tammy Steeves helped Jo collect blood samples on Selkirk at all hours, and in all conditions. Erin McClelland analyzed blood samples to determine the sex of our marked petrels, and Sharon Birks from the Burke Museum of Natural History loaned us tissue samples from known sex specimens to confirm that the analysis worked correctly. Paul Scofield collaborated with the work on P. defilippiana and provided me with a proper Christmas Holiday in NZ. Matt Rayner allowed me to work under his research permit on Hauturu. He also made hours of recordings of P. cookii from Codfish Island. Staff from the NZ Department of Conservation helped me with the logistics and gave me the permits to visit and record on Hauturu and Lady Alice Island. I would especially like to thank Andrea vi Booth, who helped me get to and from Lady Alice, helped me get the supplies I needed, and introduced me to the petrels on Lady Alice. The McPherson Natural History Unit Sound Archive provided recordings of P. leucoptera leucoptera , and P. l. caledonica, and Dick Watling of Environmental Consultant’s (Fiji) Ltd. Lent me his recordings of P. brevipes . The Linden berg Foundation at UW provided me with a travel grant, as did the UNC Graduate School. Finally, to my wife, Jessica. Thank you for your love and support throughout my PhD. We endured many months apart without communication…during my field work…and during the writing of this dissertation! Thank you for your support and encouragement. We’ve done it! vii TABLE OF CONTENTS LIST OF TABLES................................................................................................................. x LIST OF FIGURES ............................................................................................................. xii Chapter Introduction ...............................................................................................................1 1. Biotic and abiotic constraints on acoustic communication – a review of behavioral adaptations to the signaling environment ...........................................9 Abstract.....................................................................................................................10 Introduction...............................................................................................................11 Animal communication.................................................................................13 Biotic and abiotic constraints on animal communication.............................18 Do locally adapted signals lead to reproductive isolation?...........................30 Conclusion ............................................................................................................... 33 References.................................................................................................................36 Tables and Figures ....................................................................................................53 2. Individual and sexual variation in the burrow calls of the Juan Fernandez Petrel Pterodroma externa ......................................................................................56 Abstract.....................................................................................................................57 Introduction...............................................................................................................58 Methods.....................................................................................................................62 viii Results.......................................................................................................................78 Discussion.................................................................................................................88 References.................................................................................................................99 Tables and Figures ..................................................................................................106 3. Vocal activity at a multispecies petrel colony: effects of predators and ..... aerial collision on the costs of nocturnal behavior ............................................124 Abstract...................................................................................................................125 Introduction.............................................................................................................126

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