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The Breeding Biology of the Flesh-Footed Shearwater Puffinus Carneipes

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The Breeding Biology of the Flesh-Footed Shearwater Puffinus Carneipes The Breeding Biology of the Flesh-footed Shearwater Puffinus carneipes. A thesis presented for the degree of Doctor of Philosophy. School of Biological Science and Biotechnology, Murdoch University, Western Australia Christopher D.L. Powell BSc (Hons) June 2004 Declaration I declare that this thesis is is my own account of my research and contains as its main content work, which has not previously been submitted for a degree at any tertiary education institution. …………………………………………………… Christopher David Lionel Powell Why do they get so fat? Abstract The Flesh-footed Shearwater Puffinus carneipes, a 625g (± 3) shearwater, was studied on Woody Island, off the southern coast of Western Australia, from 2000 to 2003, mainly during the chick-rearing phase. Flesh-footed Shearwaters arrive back at their breeding colony at the end of September/early October, dig burrows and court in October, before an unsynchronised pre-laying exodus through November. Eggs are laid in the last week of November, incubated in December and January, and then hatch mid- to late-January. The fledglings depart in late-April/early-May. Most nesting burrows were located in areas where soil depth was greater than 350mm (± 14), and were angled into a slope so that the average length was about 1050mm (± 16) long. Burrow activity, monitored with knock-down barricades, peaked around 83-86% of burrows visited nightly in late-October/early-November. Nightly visitation of burrows fell to 8-10% in the third week of November (the pre-laying exodus), and then rose rapidly to around 70% through late-November/early-December as laying commenced. Body mass was high 632g (± 5) during courtship, fell just before the exodus 606g (± 6), then rose again 620g (± 11) upon return. Parents incubate their egg alternately, each undertaking a shift of one to eight days. A few days after hatching, the nestling is left unattended by day in the burrow, where it receives a meal weighing 13-18% adult body mass every 1.4 nights, on average, during the 101 days (± 1) it spends there. Flesh-footed Shearwaters are strictly nocturnal visitors to their colony, although nightly proportions of nests entered were not adversely influenced by bright moonlight, climatic or oceanographic conditions. Initially, nestlings received small overnight feeds, but these increased in size and were delivered more frequently as nestlings grew. In consequence, although mean peak body masses attained by nestlings differed significantly between years, after an average period of 66 days (± 2) in the nest young attained masses equivalent to 135-160% mean adult mass. This coincided with deposits of body fat, but carcass analyses of nestlings revealed that a substantial proportion of mass accumulation was attributable to water, particularly as a component of body fat. Subsequently, nestlings lost 30-40% of their mass as the time of fledging approached, even though masses of food were generally no smaller, nor delivered any less frequently during this period. Mass recession occurred primarily as a result of water loss, mainly from the integument, but also, substantially from body fat. This is consistent with the view that mass accumulation is related to feather growth. Although the final body masses recorded differed between years, nestlings fledged at around 92- 98% mean adult mass, even though they retained a store of body fat. Nestlings continued to be fed to within one to two days prior to departure. The exception was if the peak mass attained was only 800g or less. Individuals in this low peak mass category lost a proportion of body mass similar to heavier chicks and therefore fledged correspondingly lighter than other fledglings. It is suggested that parent shearwaters “over-feed” their nestling so that the peak in body mass coincides with the period of maximum feather growth, and nestling obesity stems from both lipid and water accumulation. The Flesh-footed Shearwater nestling attains a high level of obesity, even though it is fed large meals almost nightly throughout its life ashore, even in poor years. This lends little support to those explanations for nestling obesity in shearwaters that are based upon buffering the young against erratic feeding schedules and long intervals between meals. Acknowledgments Thanks to Associate Professors Ron Wooller and Stuart Bradley for their guidance in formulating the program of study, the experimental design and, for supervising this project. To Ron for editing drafts as the chapters evolved, and for supplying items of field equipment and current literature. To Stuart for the generous provision of his time and expertise in analysing the large and complex data set. Thank you Gentlemen, it has been a pleasure. Without the generosity of Mackenzie’s Island Cruises this study would not have been possible. The donation of sea transport and accommodation was greatly appreciated, and field sites only a few minutes walk from a hot shower must certainly be rare. I particularly thank Fud Mackenzie for his vision and enthusiasm in supporting this project. He will hopefully be rewarded, not only by the persistence of the Flesh-footed Shearwater breeding population on Woody Island, but also by contributing, through this study, to the theoretical understanding of seabird life histories, which, in future, may greatly aid the informed management of vulnerable species. I am grateful to Sally and Casper Castledine for kindly sharing their home over the years and making me welcome in Esperance. Special thanks to Tori, Hannah and Alex for letting a Muttonbirdman stay in their cubby house. I also thank Michelle and Hugh Crisp, as well as Jessica and Samantha for their friendship and generous hospitality. Woody Island receives many visitors and, consequently, I have lost track of the many wonderful people who offered their assistance in the field. To avoid offending anyone, I make no attempt to thank everyone personally, but you know who you are, and your interest and help was well appreciated. However, I specifically thank Dr. Vi Saffer for her hard work and contribution to the banding program. Special thanks also, to certain bush nymphs for preventing the onset of cabin fever. I also thank Coral Turley for compiling the plant list, Kevin Howells for ongoing logistical assistance on Woody Island, and Peter Collins for transport to, and assistance on Muttonbird Island. The study was supported by a Murdoch University Research Studentship, and a Commonwealth Research Training Scheme place. Additional funds were kindly made available by Professor Ian Potter, courtesy of a Fisheries Research and Development Commission grant. This thesis is dedicated to my parents Ann and Lionel Powell, and to the memory of my sister Stephanie. “She might not show up, she might not call, She just loves to ride horses, and that’s about all”. (She loves to ride horses from the album The Dark by Guy Clark, 2002) Table of Contents Declaration Frontispiece Abstract Acknowledgements Chapter 1. Introduction 1 Chapter 2. The Puffinus Shearwaters 2.1 The Order Procellariiformes 9 2.2 The Puffinus Shearwaters 11 2.3 The breeding chronology of the Flesh-footed Shearwater Puffinus carneipes 16 2.3.1 The Flesh-footed Shearwater 16 2.3.2 The contra-nuptial season 17 2.3.3 Return to the breeding colonies 18 2.3.4 Courtship 19 2.3.5 The pre-laying exodus 20 2.3.6 Egg laying 21 2.3.7 Incubation 22 2.3.8 The hatchling 22 2.3.9 The brooding/guard stage 23 2.3.10 The nestling period 23 2.3.11 The desertion period 25 2.3.12 Fledging 26 Chapter 3. The field site and general methodology 3.1 The field site 28 3.1.1 The Archipelago of the Recherche and Woody Island 28 3.1.2 Climate and topography 30 3.1.3 Woody Island flora 32 3.1.4 Woody Island fauna 33 3.2 General methodology 34 3.2.1 The breeding colonies 34 3.2.2 Burrow monitoring 35 3.2.3 Daily weighing of nestlings 38 3.2.4 Linear skeletal measurements 38 3.2.5 Capture and banding of adults and pre-fledglings 39 3.2.6 Licences and authorities relevant to this project 39 Chapter 4. The breeding colony 4.1 Introduction 41 4.2 Methods 44 4.3 Results 50 4.3.1 Burrow density 50 4.3.2 Burrow geometry 51 4.3.3 Soil depth 53 4.3.4 Breeding success 56 4.4 Discussion 59 Chapter 5. The pre-laying, and laying to hatching periods 5.1 Introduction 63 5.2 Methods 68 5.3 Results 70 5.3.1 The pre-laying period 70 5.3.2 Laying 71 5.3.3 Incubation 71 5.3.4 Hatching 72 5.3.5 Brooding 73 5.4 Discussion 79 Chapter 6. The nestling period Chick provisioning: Measuring food delivery by repetitive frequent weighing 6.1 Introduction 83 6.1.1 Background 83 6.1.2 Matters concerning the methodology 86 6.2 Methods 89 6.3 Results 92 6.3.1 Total overnight food delivery 92 6.3.2 Factors relating to mass loss 92 6.3.3 Correction of mass loss 100 6.3.4 Maintenance of body mass 103 6.3.5 Identifying meals 104 6.3.6 Rate of food delivery 108 6.3.7 Effects of nutritional status on body temperature 110 6.4 Discussion 111 Chapter 7. The nestling period Chick provisioning: Estimating food delivery from 24-hourly mass observations 7.1 Introduction 115 7.2 Methods 116 7.3 Results 119 7.3.1 Predicting overnight feeds from 24-hour mass changes 119 7.3.2 Weekly variation in overnight feeds and 24-hour mass changes 125 7.3.3 Identifying meals from overnight feeds 126 7.3.4 Estimating frequency of meals per night 128 7.3.5 Weekly variation in overnight feeds and frequency of meals 141 7.3.6 Regulation of food delivery in response to nestling body condition 144 7.4 Discussion 148 Chapter 8.
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