Adaptations of the rare endemic Grey Falcon Falco hypoleucos that enable its permanent residence in the arid zone of Australia Jonny Schoenjahn Dipl.-Math. A thesis submitted for the degree of Doctor of Philosophy at The University of Queensland in 2018 School of Biological Sciences 2 Abstract The Grey Falcon Falco hypoleucos is an extremely rare and little known Australian endemic raptor. The Web of Science lists only two publications for this species, considered to be one of the five rarest Falco species of the world: a literature review and analysis of museum material (Olsen and Olsen 1986), and the results from the preliminary investigation that led to this study (Schoenjahn 2013). The difficulty in finding these rare birds (<1000 mature individuals), distributed thinly across much of Australia’s arid/semi arid zone (~5 million km2), hampers detailed studies and has deterred previous researchers from studying this species. The Grey Falcon is the only species of Falco to have its entire population confined exclusively to a hot arid environment. To understand the processes that help the species to persist in its extreme environment, I explore key aspects of its ecology, morphology, and anatomy, using observational data collected during 14 field seasons (2003–2016), involving 59 breeding events and satellite tracking data from seven individuals tracked for between 82 and 797 days. How do individuals, during the various stages of their lives, cope with extremely high ambient temperatures? Investigating whether the species is specifically adapted behaviourally and anatomically to its environment, I found that Grey Falcons keep physical exertion and thus activity levels low in each aspect of their day-to-day lives, and lack particular morphological or physiological characteristics that would help them to cope with heat better than other bird species do. A possible explanation of the behaviour to keep activity levels low is that this helps to keep endogenous heat production low which enables these birds to respond to extreme and unexpected environmental changes without delay. The breeding ecology of the Grey Falcon is characterized by a behaviour that is unique among birds of prey. The young often stay with their parents for up to 12 months or longer after fledging, i.e. well into the next breeding season, and some of these young were even fed by their parents at this advanced age. I show that this behaviour may be interpreted as a consequence of Grey Falcons of all ages keeping their activity levels low at all times. The movements of individuals is a further key aspect in the ecology of a species, particularly so in desert-living birds. The Grey Falcon lives exclusively in an area where at least 45% of the regularly breeding bird species are considered to be nomadic. I found that the movement patterns of the Grey Falcon are generally nomadic, but are characterized by a distinct and unusual element of reluctance. That is, if conditions become inadequate for 3 breeding these birds rather stay and forego breeding than embark on a search for more favourable conditions that may be far away, and could expose them to risk. Although capable of long-distance movement (one individual moved more than about 1000 km in nine days), Grey Falcons appear to move on only when environmental conditions become a risk to their survival, i.e. only when absolutely necessary, and when they do move on, they move no farther than necessary. I term this behaviour ‘reluctant nomadism’. An unexpected behaviour brought to light by this study is that Grey Falcons often roost on the bare ground at night. This behaviour was noted on 149 (26%) of 576 nights that Grey Falcons were recorded at locations other than the nest. They roosted on the ground at times even when trees (and their nest) were within view. I propose that this is also a consequence of the species’ behaviour of keeping activity levels low at all times. Night-roosting on the bare ground exposes these birds to predation by recently introduced cats, foxes, and dingoes. A further hitherto unrecognized threat to the species is suggested to be climate change. This threat derives from extreme climatic events that characterize the species’ environment, and is a consequence of the species’ behaviour to remain at all times in the arid/semi-arid zone. This hot environment is characterized by extreme and unpredictable climatic events, and these are predicted to increase in frequency, severity, and duration over time. In summary, in key aspects of its ecology, the behaviour of the Grey Falcon shows markedly low levels of physical exertion. The consistency suggests that the species’ ecology is, consequently, governed by the principle of keeping physical exertion low. I interpret this behaviour as an adaptation of the species to its hot arid environment, one that is characterized by extreme and unpredictable climatic events. Keeping levels of physical exertion low helps to keep endogenous heat production low. This enables these birds to respond to adverse climatic events without delay even under challenging circumstance, thus enabling the Grey Falcon’s permanent residency in the hot arid and semi-arid zone of Australia. 4 Declaration by author This thesis is composed of my original work, and contains no material previously published or written by another person except where due reference has been made in the text. I have clearly stated the contribution by others to jointly-authored works that I have included in my thesis. I have clearly stated the contribution of others to my thesis as a whole, including statistical assistance, survey design, data analysis, significant technical procedures, professional editorial advice, financial support and any other original research work used or reported in my thesis. The content of my thesis is the result of work I have carried out since the commencement of my higher degree by research candidature and does not include a substantial part of work that has been submitted to qualify for the award of any other degree or diploma in any university or other tertiary institution. I have clearly stated which parts of my thesis, if any, have been submitted to qualify for another award. I acknowledge that an electronic copy of my thesis must be lodged with the University Library and, subject to the policy and procedures of The University of Queensland, the thesis be made available for research and study in accordance with the Copyright Act 1968 unless a period of embargo has been approved by the Dean of the Graduate School. I acknowledge that copyright of all material contained in my thesis resides with the copyright holder(s) of that material. Where appropriate I have obtained copyright permission from the copyright holder to reproduce material in this thesis and have sought permission from co-authors for any jointly authored works included in the thesis. 5 Publications during candidature Conference abstracts 2016 Ecological Society of Australia Annual Conference ‘ESA16’, 28 Nov. – 2 Dec. 2016, Fremantle, Western Australia. Presentation title: ‘Can climate explain the delayed juvenile independence and slow behavioural development in the Grey Falcon?’ 2015 International Raptor Conference of the Raptor Research Foundation, 4–8 Nov. 2015, Sacramento CA, USA. Presentation title: ‘Delayed independence in young of the desert-dwelling Grey Falcon (Falco hypoleucos) of Australia: a description and possible explanation of a unique behavior in raptors.’ Publications included in this thesis No publications included. 6 Contributions by others to the thesis Gimme Walter and Chris Pavey contributed to this thesis in critically revising it so as to contribute to the interpretation. David Booth commented critically on early drafts. Statement of parts of the thesis submitted to qualify for the award of another degree None. Research involving human or animal subjects The study required animal ethics approval. The following overview summarizes the approvals for the states and territories involved, covering the fieldwork period of the PhD- programme (15/09/2014 to 15/09/2017). For the full names of the committees see the respective document. State/Territ. Agency Approving Reference number Start date End date Appendix # Committee NSW DPI DG’s ACEC 10/1354 22/03/2013 22/03/2016 6A DPI DG’s ACEC 16/350 22/03/2016 22/03/2019 6B NT CDU AEC of CDU A12018 16/04/2014 16/04/2016 6C CDU AEC of CDU A12018 30/03/2016 30/03/2020 6D Qld UQ NEWMA AEC SBS/308/14 15/09/2017 15/09/2017 6E DAFF DAFF AEC CA 2013/04/684 01/07/2013 30/06/2016 6F DAF DAF AEC CA 2016/04/955 01/07/2016 07/04/2019 6G SA DEWNR WEC 14/2013 01/07/2013 30/06/2016 6H DEWNR WEC 13/2016 26/05/2016 26/05/2019 6I Key to the abbreviations of the agencies’ names: CDU Charles Darwin University (NT) DAF Dept. of Agriculture and Fisheries (Qld) DAFF Dept. of Agriculture, Fisheries and Forestry (Qld) DEWNR Dept. of Environment, Water and Natural Resources (SA) DPI Dept. of Primary Industries (NSW) UQ The University of Queensland 7 Acknowledgements A study of such an elusive species spanning some 15 years while covering much of Australia’s remotest areas is impossible without the help of very many people, and my heartfelt thanks go to all these wonderful people who supported me and this impossible study over the years. I hope that they will continue to do so. More than 400 persons kindly shared their sightings and photos with me, patiently answering further and further questions about the details of their observations; many breeding sites I discovered by in situ-investigations of such reports. Many people went out of their way to check likely and unlikely sites for me, often at remote locations, thus adding crucial information to the research data.