University of Nevada, Reno Sexual Dimorphism, Detection Probability, Home Range, and Parental Care in the Yellow-billed Cuckoo. A dissertation submitted in partial fulfillment of the Requirements for the degree of Doctor of Philosophy in Ecology, Evolution and Conservation Biology By Mary Murrelet Halterman Dr. Lew Oring/Dissertation Advisor May, 2009 © Copyright by Mary Murrelet Halterman 2009 All Rights Reserved i ABSTRACT The biology of many species of conservation interest is poorly understood. Often, little is known apart from population estimates. Yellow-billed Cuckoos (Coccyzus americanus) are a neotropical migrant, and due to loss of riparian breeding habitat, are of great conservation concern in the western United States. Little is known about their basic biology. In this study I looked at sexual dimorphism, responsiveness to call playback, home range size, and parental care. Determining sex of a study organism is fundamental to understanding almost every aspect of their biology and management. Although there has been speculation about methods of sexing adult cuckoos using measurements, vocalizations, and extent of white in the tail, we found the only reliable way to sex cuckoos utilized genetic markers. Females gave the ―coo‖ call, considered an advertisement call, significantly more than males. Although there have been extensive cuckoo surveys done in the western United States, there are no data on responsiveness or detectability using call playback surveys. We tested the standard call playback methodology with 18 radio marked adult cuckoos. Response rate during call playback tests averaged 59.5%, and was higher for males (72.7%, n=10) than females (40%, n=8). Detection rates were lower than response rates, averaging 32.4% overall, and were higher for males (43.2%, n=10) than females (16.7%, n=8). The low responsiveness and detectability of cuckoos may be influenced by their large home ranges. We monitored 28 cuckoos equipped with radio transmitters on the San Pedro Riparian National Conservation Area during 2001-2005. Average home range ii estimates were 95% KDE - 39 ha, 75% KDE - 17 ha, and 50% KDE 7.5 ha. There were large variances for all home range estimates, and females had significantly smaller home ranges than males. This may partially account for lower detectability of females. Cuckoo researchers have observed small clutch sizes, rapid development of young, and a third adult helping to raise young, but there are no previous studies of parental care with banded, known sex Yellow-billed Cuckoos. We followed 28 adult cuckoos with transmitters and placed video cameras on four nests. Although both parents constructed nests, incubated eggs, and cared for young, males did all nighttime incubation, provided the majority of food to nestlings, and all care to fledglings. Additionally, we confirmed the presence of a third adult providing care to nestlings. Occasionally during the nestling period females appeared to abandon a viable nest and initiate a nest with another male. Males may have larger home ranges in order to locate females, who may call to attract second males. This male may assist with the first nest effort, then leave with the female for a subsequent nest. These observations present a pattern of male-dominated parental care, and Yellow-billed Cuckoos appear to be facultatively serially polyandrous. iii DEDICATION To my parents, Carol and Joseph, for always supporting my endeavors, and for allowing me to pursue this strange career I‘ve chosen. My Grandpa in Indiana was probably is responsible for my love of birds, and Grandma Halterman was the strongest person I have ever known. She taught me that a person can overcome anything. iv ACKNOWLEDGEMENTS A dissertation is a mind-bogglingly huge project, and far, far bigger than I realized when I started. Without the support and encouragement of fellow students Juliana Bosi de Almeida, Meeghan Gray, and Angela White, and my advisor Lew Oring, I would never have been able to get through the last year of crouching in front of my computer late into the night, to emerge into the sunlight of finishing my dissertation. I also had statistical, logistical, and moral support from fellow grads Alex Hartman and Patrick Lemmons. A special thanks to Barbara Raulston, who trusted that all the funding she worked to secure would eventually result in a worthwhile body of work. I would like to thank Greg Clune and John Swett for providing logistical support and the US Bureau of Reclamation and Southern Nevada Water District for providing financial support for this project. Thanks to Jack Whetstone and the Sierra Vista BLM office for logistical support and access to the Riparian Conservation Area and to Gray Hawk Ranch for access to their property. Additional thanks to Dr. Kathleen Blair and Dick Gilbert of the U.S.D.I. Fish and Wildlife Service, BWRNWR for their assistance. Thanks to the personnel of the Southern Sierra Research Station for the flexibility and support to get through this huge undertaking. Thanks to my entire committee, Dr. Michael Collopy, Dr, Catherine Fowler, Dr, Mary Peacock, and Dr. Jim Sedinger for their editorial assistance and willingness to return comments quickly and change dates frequently. Lew and Kay Oring provided logistical support in addition to moral and editorial support. The Ecology, Evolution, and Conservation program at UNR provided critically important financial support. I had v unendingly cheerful support from the NRES office staff, Kerrie Medieros, Heidi McConnell, and Ronald Rocky. A special thanks to three hardworking and dedicated biologist who began as field assistants, but became cuckoo experts during their 4 years of work on the project - Shannon McNeil, Eli Rose, and Diane Tracy. They have the sense of humor and tolerance for frustration required for working with cuckoos, and they all stepped up to the challenges of managing field crews and data when I could not be there. Also, many thanks to my hardworking field assistants for invaluable assistance during this project. My time in Reno would not have been so pleasant if not for many friends who helped out numerous times during my stay here. Franko and Cynthia Ferris opened their hearts and homes to me, and helped me adjust to returning to school after many years away. The entire agility community of Reno helped keep me sane during this process, and Patrick and Cynthia Kennedy allowed me to stay with them, and have been great and supportive friends. Thanks to my martial arts friends, including everyone at High Sierra Jujitsu, and Larry and David at Ridgecrest Kung Fu for providing physical activity, and forcing me to use a very different part of my brain. Although my dogs haven‘t provided much in the way of logistical support, they kept me sane during this entire process. Between forcing me to go walkies (and get away from the computer), and leading me to agility out of self-defense, I was able to maintain some balance in life, as well as meet new friends. Thanks to my entire family, who have always been happy to see me, though I usually just showed up in time for the big meals! I love you all. vi TABLE OF CONTENTS ABSTRACT ................................................................................................................... i DEDICATION ............................................................................................................. iii ACKNOWLEDGEMENTS..........................................................................................iv TABLE OF CONTENTS .............................................................................................vi LIST OF TABLES ..................................................................................................... viii LIST OF FIGURES ......................................................................................................xi GENERAL INTRODUCTION ..................................................................................... 1 LITERATURE CITED ........................................................................................................... 4 Chapter 1. Sexing Yellow-billed Cuckoos .................................................................... 6 ABSTRACT ........................................................................................................................... 7 INTRODUCTION .................................................................................................................. 8 METHODS ........................................................................................................................... 12 RESULTS ............................................................................................................................. 15 DISCUSSION ....................................................................................................................... 17 CONCLUSION ..................................................................................................................... 20 ACKNOWLEDGMENTS ..................................................................................................... 21 LITERATURE CITED ......................................................................................................... 22 TABLES and FIGURES ....................................................................................................... 27 Chapter 2. Response Rate and Detection Probability of Yellow-Billed Cuckoos in Arizona ........................................................................................................................