The Causes and Consequences of Group Living in the Crimson Finch (Neochmia Phaeton)
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The causes and consequences of group living in the crimson finch (Neochmia phaeton) Catherine M Young A thesis submitted for the degree of Doctor of Philosophy of The Australian National University Research School of Biology Division of Ecology and Evolution Canberra, Australia © Copyright by Catherine Mary Young 2017 All Rights Reserved ________________________________________________________________________ Declaration I, Catherine M Young, hereby state that the research presented in this thesis is my own original work. I am the senior author and principal contributor of all the chapters. No part of this thesis has been submitted for any previous degree. ____________________________ Catherine Mary Young October 2017 Supervisory Team Panel Chairs: Professor Patricia Backwell & Dr Sarah Pryke Co-supervisor: Professor Robert Heinsohn Panel: Dr Kristal Cain Dr Nina Svedin 2 ________________________________________________________________________ Acknowledgements There is not enough time or paper to thank everyone who should be acknowledged here in the manner they deserve. This journey didn’t start where anyone may expect but rather around a campfire in the Kalahari where I was adamantly telling a colleague, Tom Flower that I wouldn’t do a PhD. Tom from memory said something along the lines of “don’t discount it completely” and by the end of the conversation I had changed my tune to; maybe, if I found the right project. Thank you to the extremely talented Sarah Pryke who helped me find that project and ultimately made all things possible. Pat Backwell who adopted me and is (in her own words) - bloody awesome and one of the prettiest woman I have ever met. Nina Svedin and Kristal Cain, where do I even start, there are no words, thank you for your patience, for being straight with me and helping with every aspect of my PhD. Rob Heinsohn, thank you for your support, it’s meant so much knowing that you are in my corner. Thanks must also go to Mike and Elisabeth Fidler for their generosity with advice and support. To my EE family 2012-2016, this department at ANU can only be described as family and I have been blessed to go on this journey with so many fantastic people. Thanks especially to department head Scott Keogh, Jan, Wes, Anna, Danswell, Hanna, Moos, Josh, Ana, Marta, Regina, Nina M and of course Will and Dan. Thomas Merkling and Liam Bailey, I can only think you worked on your own projects at night or when I wasn’t in the office because I spent much of my time at your desks with one of my many R/stats problems. Thank you for your endless patience and enthusiasm! My wonderful field assistants, Fiona Finch and Sophie Keats for sweating it out in the Kimberley wet season with me. Some country towns you need to live in for decades before you are considered a local but Wyndham felt like a second home from the first week. Thank you especially to Alan Pardoe-Bell and Jasper Kruse for making it so. To Kristy and Luke Connell for taking me in when I needed to get away from it all and my parents for their unwavering support (plus mom’s excellent proof reading). I’d also like to take the opportunity to thank Lee Ann Rollins who is helping me with the next stage of this project in the lab and my brother who has always been my inspiration. Lastly and definitely not least, my husband David Hamilton who has looked at more drafts than anyone, listened to me rant and get frustrated but never been anything but 110% supportive. I am so lucky to share this life with you. 3 ________________________________________________________________________ ABSTRACT This thesis consists of five chapters, each investigating an aspect of breeding biology, sociality or behaviour of a group living species of an Australasian grassfinch, the crimson finch (Neochmia phaeton). It primarily focuses on the effects of habitat structure and group size on reproductive behaviour, and the role of signalling in mediating conflicts. Much of our knowledge of the breeding behaviour of the crimson finch is based on observations in captivity, little is known about wild populations. Captive crimson finches are known for their highly aggressive nature. However, free-living birds live and breed in large social colonies, which seems counterintuitive. The first three chapters explore the ecology and colony structure of wild crimson finches, providing insight into the breeding system, nest predation and dispersal strategies. In chapters 4 and 5, we used field observations and experimental manipulations in captivity to determine the factors that cause, facilitate and maintain aggression and sociality in this species. Chapter One describes aspects of habitat use and breeding ecology from 14 distinct colonies, and contrasts these findings with other populations living in different habitat, which have been examined previously. Although we found many similarities between the populations in breeding biology, we also found some pronounced differences in the way crimson finches organise themselves socially and geographically in the divergent habitat structures. Chapter Two investigates the factors influencing nesting success, specifically the influence of nest site location and adult behaviour (predator defence) on nest success. Though there was no evidence that adult behaviour influences nest success, we found three features of nest site choice that were related to nest survival; nest visibility, vegetation height and distance to other vegetation. Chapter Three provides the first study of dispersal in crimson finches. We report that contrary to previous speculations, long-distance movements between colonies are common. The primary factor predicting two key decisions, whether to leave the natal group, and where to settle, was primarily related to the adult sex ratio of the colony. Chapter Four explores aggressive behaviour between adult males. Here we use correlative and manipulative approaches to understanding how plumage signals mediate aggressive behaviour. In particular, we investigate the role of melanin and carotenoid plumage pigments in signalling dominance and fighting ability. Chapter Five experimentally examines aggressive behaviour of both males and females at the nest, using mounts of conspecific and heterospecific intruders. Although crimson finches are said to be non-territorial they are known to defend the area immediately 4 ________________________________________________________________________ around their nest. We found no difference in levels of aggression between males and females, or towards conspecific and heterospecific intruders. The final section of this thesis summarises our findings and provides suggestions on future research to further investigate the costs and benefits of group living. 5 ________________________________________________________________________ TABLE OF CONTENTS 7 Introduction 15 Chapter 1 – Breeding of Crimson Finch (Neochmia phaeton) in the eastern Kimberley, Western Australia 34 Chapter 2 – Nest predation avoidance Young, C.M., Cain, K.E., Svedin, N.S., Backwell, P.R.Y. and Pryke, S. R. (2017). Nesting success in crimson finches: Chance or choice? Ethology. 123: 41-50 46 Chapter 3 – Natal dispersal between breeding colonies 65 Chapter 4 – Aggression in the non-breeding season Young, C.M., Cain, K.E., Svedin, N.S., Backwell, P.R.Y. and Pryke, S. R. (2016). The role of pigment based plumage in resolving contests. Journal of Avian Biology. 47: 167-175 76 Chapter 5 – Aggression in the breeding season Young, C.M., Cain, K.E., Svedin, N.S., Backwell, P.R.Y. and Pryke, S. R. (2017). Predictors of aggressive response towards simulated intruders depend on context and sex in Crimson Finches (Neochmia phaeton). Behavioural Processes. 138:41-48 100 Conclusion and future directions 6 __________________________________________________________________________________________ Introduction Introduction Feeding flock of crimson finches Picture © Catherine Young 7 __________________________________________________________________________________________ Introduction INTRODUCTION Coloniality, a social system in which individuals breed in groups, occurs in more than 13% of bird species (Lack 1968). The costs and benefits of colonial living in birds have been widely studied in many species, such as seabirds (e.g. Brown et al. 1990) and swallows (e.g. Brown and Brown 1996). In these systems, the benefits of group living are thought to include predator avoidance and increased foraging efficiency, whereas potential costs include increased disease susceptibility, competition for resources and predator attraction (reviewed in Davies et al. 2011). However, the resolution of conflicts within colonial groups, (for example, access to limited breeding sites, mates and food resources) has received much less attention. Within the colony, conflict resolution is likely to differ between individuals and to vary according to their age, sex, social status and relatedness. The interaction between dominance/aggression and social, reproductive or environmental factors can be complicated as demonstrated in the diagram below (Figure 1). The direction of influence is not always clear and may also depend on the interaction between a number of other factors. For example, group size can directly positively affect levels of aggression (e.g. Poot et al. 2012) but this effect may be mitigated by increasing habitat complexity (e.g. Basquill and Grant 1998). Extra-pair - copulations + Parental + Group investment sex ratio Reproductive + +/- - +/- Success - DOMINANCE +/- +/- +/- & AGGRESSION