UNIVERSITY OF CALIFORNIA RIVERSIDE The Evolution of Quiet Flight in Owls (Strigiformes) and Lesser Nighthawks (Chodeiles acutipennis) A Dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Evolution, Ecology, and Organismal Biology by Krista Le Piane December 2020 Dissertation Committee: Dr. Christopher J. Clark, Chairperson Dr. Erin Wilson Rankin Dr. Khaleel A. Razak Copyright by Krista Le Piane 2020 The Dissertation of Krista Le Piane is approved: Committee Chairperson University of California, Riverside ACKNOWLEDGEMENTS I thank my Oral Exam Committee: Dr. Khaleel A. Razak (chairperson), Dr. Erin Wilson Rankin, Dr. Mark Springer, Dr. Jesse Barber, and Dr. Scott Curie. Thank you to my Dissertation Committee: Dr. Christopher J. Clark (chairperson), Dr. Erin Wilson Rankin, and Dr. Khaleel A. Razak for their encouragement and help with this dissertation. Thank you to my lab mates, past and present: Dr. Sean Wilcox, Dr. Katie Johnson, Ayala Berger, David Rankin, Dr. Nadje Najar, Elisa Henderson, Dr. Brian Meyers Dr. Jenny Hazelhurst, Emily Mistick, Lori Liu, and Lilly Hollingsworth for their friendship and support. I thank the Natural History Museum of Los Angeles County (LACM), the California Academy of Sciences (CAS), Museum of Vertebrate Zoology (MVZ) at UC Berkeley, the American Museum of Natural History (ANMH), and the Natural History Museum (NHM) in Tring for access to specimens used in Chapter 1. I would especially like to thank Kimball Garrett and Allison Shultz for help at LACM. I also thank Ben Williams, Richard Jackson, and Reddit user NorthernJoey for permission to use their photos in Chapter 1. Jessica Tingle contributed R code and advice to Chapter 1 and I would like to thank her for her help. I thank Dr. Pete Bloom for his guidance and training early in this program and Dr. Scott Weldy and the volunteers at the Orange County Bird of Prey Center for their enthusiasm and dedication to Chapter 2. Thank you to Jennifer Brown, Stephen Fetting, Justin Garcia, Carie Battistone, and Theresa Wisneskie for state and federal permits used iv in Chapter 2 and March AFB for the donation of a salvage Barn owl to use for feather imaging The research for Chapter 3 was performed at the University of California Natural Reserve System (Boyd Deep Canyon Desert Research Center) Reserve DOI: (doi:10.21973/N3V66D). I thank Chris Tracy for his help at Boyd Deep Canyon Research Center. I thank my advisor, Dr. Christopher J. Clark for his dedication to me and this research. He guided me through countless e-mails, meetings, and manuscript drafts, filled in for me when I needed it most, and was supportive and helpful throughout this process. This dissertation is based upon work supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. (DGE-1326120) awarded to Krista Le Piane. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. The text of this dissertation, in part, is a reprint of the material as it appears in Evidence that the dorsal velvet of Barn Owl wing feathers decreases rubbing sounds during flapping flight, 2020. The co-author, Christopher J. Clark, listed in that publication directed and supervised the research which forms the basis for this dissertation. v DEDICATION This dissertation is dedicated to my family, friends, and mentors. Thank you to my wonderful, supportive parents, Kim Le Piane and Karl Le Piane and my brother, Ryan Le Piane for encouraging me to keep going when I wanted to give up. Thank you to my grandparents, Patricia Weckerly, Allen Weckerly, Michelle Le Piane, and Patrick Le Piane for being my biggest cheerleaders. Thank you to my dear friends: Jessica Tingle, Ayala Berger, Anne Hilborn, Ming-Feng Ho, Yongda Zhu, and Mahdi Qezlou for lifting my spirits. Thank you to Sharon Newmann, my high school counselor for planting the seed of a PhD in my mind when I was in high school. Thank you to Gary Waayers for lighting the spark of a love for Biology and to Dr. Gita Kolluru for my undergraduate training. Thank you to Dr. Erin Wilson Rankin for encouraging and supporting me at pivotal moments in this process. Finally, thank you to my advisor, Dr. Christopher J. Clark for believing in me, even when I did not believe in myself. Without all of you, none of this would be possible. Thank you for lifting me onto your shoulders and supporting me through this journey. vi ABSTRACT OF THE DISSERTATION The Evolution of Quiet Flight in Owls (Strigiformes) and Lesser Nighthawks (Chodeiles acutipennis) by Krista Le Piane Doctor of Philosophy, Graduate Program in Evolution, Ecology, and Organismal Biology University of California, Riverside, December 2020 Dr. Christopher J. Clark, Chairperson All locomotion produces sound and flight is no exception. In owls, flight sounds are quieted by three wing and feather features: the leading-edge comb, a modified barb structure that projects dorsally from the front edge of the outermost primary feather (P10), the velvety dorsal surface of flight feathers, and the fringed vane of flight and tail feathers. There are two hypotheses for the evolution of quieting features: stealth and self- masking. Under the stealth hypothesis, we predict quiet flight evolved to aid owls in sneaking up on prey. Under the self-masking hypothesis, we predict quiet flight evolved to aid acoustic hunters in locating prey. To test these hypotheses, we investigated the relationship between leading-edge comb morphology and ecology (Chapter 1), tested the function of the dorsal velvet in Barn Owls (Chapter 2), and investigated the function of quieting features in Lesser Nighthawks, another nocturnal bird (Chapter 3). In Chapter 1, We used phylogenetic generalized least squares (pgls) to test the correlation between comb morphology and the stealth or self-masking scores. We found comb morphology to be correlated with both stealth and self-masking (pgls; DF = 66 test-statistic = -3.92; P- vii value = 0.0002). In Chapter 2, impairing the dorsal velvet of 10 feathers on 13 barn owls increased broadband sound production and the upstroke increased more than the downstroke, such that the upstroke of manipulated birds was louder than the downstroke, supporting the frictional noise hypothesis. Finally, In Chapter 3, we found Lesser Nighthawks initiated pursuit of prey at a greater distance than the audible detection distance of insects (0.5 m) both when hunting on the ground (1.1 ± 0.2 m; P-value = 0.02) and on the wing (2.5 ± 0.4 m; P-value <0.0001), suggesting they use visual cues to initiate pursuit of prey under these conditions. This dissertation contributes to a research area which has received little consideration: the role of sound and hearing in predation. viii Table of Contents: Introduction: ..................................................................................................................... 1 Chapter 1: Phylogenetic analysis suggests owl leading-edge comb evolved to reduce self- masking and aid in stealthy hunting.................................................................................... 3 Abstract: .......................................................................................................................... 3 Introduction: .................................................................................................................... 4 Methods: ......................................................................................................................... 8 Results: .......................................................................................................................... 22 Discussion: .................................................................................................................... 26 Figures: ......................................................................................................................... 34 Tables: ........................................................................................................................... 41 Chapter 2: Evidence that the dorsal velvet of Barn Owl wing feathers decreases rubbing sounds during flapping flight ............................................................................................ 45 Abstract: ........................................................................................................................ 45 Introduction: .................................................................................................................. 46 Methods: ....................................................................................................................... 50 Results: .......................................................................................................................... 58 Discussion: .................................................................................................................... 60 Figures: ......................................................................................................................... 67 Tables: ........................................................................................................................... 71 Chapter 3: Evidence that Lesser Nighthawks (Chordeiles acutipennis) use visual cues to hunt ................................................................................................................................... 75 Abstract: