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in the Arctic Tern - University of New Brunswick PDF

207 Pages·2012·1.4 MB·English
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Finding the "Arctic" in the Arctic Tern: breeding biology and diet across the latitudinal range of an iconic seabird by Kelly Anne Boadway B.Sc., University of Guelph, 2000 A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science in the Graduate Academic Unit of Biology Supervisors: Antony W. Diamond, Ph.D., Biology Department & Faculty of Forestry and Environmental Management Mark L. Mallory, Ph.D., Biology Department, Acadia University Examining Board: Simon C. Courtenay , Ph.D., Biology Department Graham J. Forbes, Ph.D., Faculty of Forestry and Environmental Management Les C. Cwynar, Ph.D., Biology Department, Chair This thesis is accepted by the Dean of Graduate Studies THE UNIVERSITY OF NEW BRUNSWICK March 2012 © Kelly A. Boadway, 2012 DEDICATION To Josh, who is always there for me, and who has been infinitely patient. ii ABSTRACT As climate change progresses in the Arctic, it is essential to have tools to warn of changing ecosystems. Arctic Terns are seabirds suitable as indicators of ecosystem health. Their breeding ecology has been studied intensively at low latitudes, but little at Arctic breeding sites. I studied the breeding ecology of Arctic Terns in High Arctic Canada, comparing them to those in Boreal Canada to determine if knowledge from low-latitude studies may be applied to Arctic populations. The Arctic population responded in predictable ways to presence of predators and lack of food, but had fewer predators and apparently higher functional food availability than the Boreal population. The Arctic population was generally more successful; however, I found each study differed from others in their oceanographic zones. I therefore concluded that because these birds show high phenotypic plasticity, responses at accessible temperate colonies cannot be used to infer responses in High Arctic colonies. iii ACKNOWLEDGEMENTS This thesis would not have been possible without the enthusiasm, ideas, and willpower (to ensure field seasons actually happened), and funding miracles of Drs. Mark Mallory and Tony Diamond, my co-supervisors. You have both taught me so much, from discussions in the field to those in offices and over the phone. Thank you. Thanks too to my other committee member, Dr. Rick Cunjak, who provided friendly advice, helped me figure out stable isotopes, and provided sample-sorting space and equipment. Field seasons were made fabulous by all of the amazing Arctic animals themselves, but also by everyone who helped with research throughout my years on the island: Josh, Mark, Jason, Dave, Mark the Young, Shanti, Al, Caroline, Kerrith, Siu-Ling, Val, Ted, Carolyn, Liv, Claudia, Terry, Claudine and Birgit. The field is my favourite place to be, and I thoroughly enjoyed sharing it and all of the laughs with each of you. My thanks for smooth field seasons goes to the teams at the Polar Continental Shelf Project, who kept us safe, fed us well, and ensured we got everything we needed to our field site and back. Thanks to the people of the SINLAB at UNB, for teaching me about the technical side of stable isotope analysis, answering all my questions, and ensuring my samples were run: Anne, Christine, Brittany, Katrina and Heather. Though he is not part of the SINLAB, my thanks also to Alex for his guidance on stable isotopes. Thanks for revisions and suggestions on early drafts of this thesis to Bill Tibble, Robin Hunnewell, Mandy Valois and, especially, Sarah Trefry and Alex Bond, who read all of the many chapters in this thesis. For all of the help, encouragement, commiseration, and iv laughter away from the field, I thank my labmates and friends Sarah Trefry, Emily McKinnon, Kevin Fraser, Robin Hunnewell, Travis Clarke, Kirsten Bowser, and Alex Bond, along with all of my other dear friends I met while in Fredericton. Thanks to my families, Ramster and Boadway, who were patient as I kept us away from home. Finally, thanks to my husband Josh, who travelled to the field each year with me, endured my frustrations, encouraged me, and helped me think. v Table of Contents DEDICATION .................................................................................................................. ii ABSTRACT ..................................................................................................................... iii ACKNOWLEDGEMENTS ............................................................................................. iv Table of Contents ............................................................................................................. vi List of Tables ................................................................................................................... ix List of Figures ................................................................................................................. xii Chapter 1: Introduction ..................................................................................................... 1 Seabirds and the effects of climate change ................................................................... 1 Arctic Terns: global seabirds with local influence ........................................................ 5 Current knowledge ........................................................................................................ 6 Objectives ...................................................................................................................... 8 Thesis structure ........................................................................................................... 10 Literature cited ............................................................................................................ 11 Chapter 2: Breeding biology of Arctic Terns in Canada's High Arctic .......................... 19 Abstract ....................................................................................................................... 19 Introduction ................................................................................................................. 19 Methods ....................................................................................................................... 21 Study Site ................................................................................................................ 21 Nest Initiation .......................................................................................................... 23 Nest monitoring and breeding phenology ............................................................... 24 Chick growth rates .................................................................................................. 25 Chick feeding rates .................................................................................................. 26 Adult body condition and morphometrics .............................................................. 26 Predators .................................................................................................................. 27 Statistical analyses .................................................................................................. 28 Results ......................................................................................................................... 33 Nests: initiation and incubation period ................................................................... 33 Clutch size ............................................................................................................... 36 Hatching success ..................................................................................................... 37 Eggs ......................................................................................................................... 38 Chick growth rates .................................................................................................. 41 Chick feeding rates .................................................................................................. 43 Adult weight ............................................................................................................ 44 Predators .................................................................................................................. 45 High Arctic colony comparisons ............................................................................. 47 Discussion ................................................................................................................... 49 vi Breeding and feeding: Effects of predators and food resources ............................. 49 High Arctic colony comparisons ............................................................................. 59 Literature cited ............................................................................................................ 62 Chapter 3: Diet of Arctic Terns in the Canadian High Arctic: stable isotopes reveal temporal specialization and income breeding ................................................................. 71 Abstract ....................................................................................................................... 71 Introduction ................................................................................................................. 71 Methods ....................................................................................................................... 76 Study site ................................................................................................................. 76 Sample collection .................................................................................................... 76 Sample analyses ...................................................................................................... 78 Statistical analyses .................................................................................................. 82 Results ......................................................................................................................... 87 Trophic positions ..................................................................................................... 87 Niche width ............................................................................................................. 91 Qualitative observations of tern diet ....................................................................... 94 Nutrient allocation ................................................................................................... 94 Discussion ................................................................................................................... 95 Trophic positioning and niche width ...................................................................... 96 Nutrient allocation ................................................................................................... 99 Literature cited .......................................................................................................... 101 Chapter 4: Machias Seal Island and Nasaruvaalik Island: a comparison of Arctic Tern (Sterna paradisaea) breeding ecology in the High Arctic and Boreal oceanographic zones .............................................................................................................................. 109 Abstract ..................................................................................................................... 109 Introduction ............................................................................................................... 110 Methods ..................................................................................................................... 113 Study sites ............................................................................................................. 113 Breeding parameters ............................................................................................. 114 Statistical analyses ................................................................................................ 115 Results ....................................................................................................................... 126 Nests: initiation and incubation period ................................................................. 126 Eggs: volume, clutch size and hatching success ................................................... 130 Chick feeding and growth rates............................................................................. 133 Adult body condition and morphometrics ............................................................ 135 Relative trophic positions ...................................................................................... 144 Oceanographic zone comparisons ......................................................................... 144 Discussion ................................................................................................................. 148 Good and poor years, food and predators: differences between the sites ............. 151 Nests: initiation and incubation period ................................................................. 153 Timing ................................................................................................................... 156 Eggs: volume, clutch size and hatching success ................................................... 158 Chick feeding rates ................................................................................................ 159 Chick growth rates ................................................................................................ 161 vii Adult body condition and morphometrics ............................................................ 164 Oceanographic zone comparisons ......................................................................... 165 Conclusions ........................................................................................................... 167 Literature cited .......................................................................................................... 168 Chapter 5: General Discussion ...................................................................................... 177 High Arctic colony .................................................................................................... 178 High Arctic and Boreal comparisons ........................................................................ 179 Literature cited .......................................................................................................... 182 Appendix A ................................................................................................................... 185 Literature cited .......................................................................................................... 189 Curriculum Vitae viii List of Tables Table 2-1: Incubation period for Arctic Terns at Nasaruvaalik Island in 2008 and 2009 were similar, while 2010 was significantly longer than both 2008 and 2009. Rows sharing a letter are not significantly different. ................................................................ 34 Table 2-2: Arctic Tern nest initiation on Nasaruvaalik Island in 2009 was earlier than 2008 and 2010. Rows sharing a letter are not significantly different. ............................ 34 Table 2-3: Arctic Tern hatching success at Nasaruvaalik Island declined among all years in which it was measured. Hatching success reported for 2009 was limited to early- nesters and was not the final hatching success, so may be biased high. Years with different letters in the right column are significantly different. ...................................... 38 Table 2-4: Arctic Tern chick feeding rates at Nasaruvaalik Island were compared between years, and the data are presented below. No statistically significant differences in chick feeding rates (# feeds/nest/hour) were found between years overall, nor between diurnal and nocturnal feeding. ........................................................................................ 44 Table 2-5: Nasaruvaalik Island Arctic Tern chick feeding rates (# feeds/nest/hour) from 2007 and 2008 data were pooled to increase sample size and power to compare diurnal and nocturnal feeding rates.No significant difference was found between diurnal and nocturnal feeding rates, though the power to detect a difference was low. .................... 44 Table 2-6: Mean of annual mean Arctic Tern clutch sizes at Nasaruvaalik Island as well as the mean of annual means from other studies in the High Arctic zone. Sources of these data are noted in Appendix A. ............................................................................... 48 Table 2-7: Arctic Tern egg volume index was significantly higher at Nasaruvaalik Island compared to Sand Island, as depicted by different letters in the right column. .............. 48 Table 2-8: Arctic Tern chick weight and wing growth rates on Nasaruvaalik Island (2008 and 2010 combined) and Sand Island (reported for 2008 only). Measures of variance were not available for the Sand Island data. ..................................................... 49 Table 3-1: Isotopic values for International Atomic Energy Agency (IAEA) and internal standards used at the University of New Brunswick's SINLAB and the University of Ottawa's G.G. Hatch Stable Isotope Laboratory to assess accuracy and precision of results obtained from stable isotope analyses. ................................................................ 81 Table 3-2: Differences in discrimination factor (D 15N, D 13C) between tissue types that were used as proxies for breeding colony nutrients (plasma) and wintering ground nutrients (feather), to adjust for tissue type prior to trophic position calculations, and to determine nutrient allocation to eggs. Diet-tissue fractionation values are the means reported for each tissue in the literature. As discrimination factors vary greatly with species and size of individuals (McCutchan et al. 2003), the studies listed below were ix chosen because they contained discrimination factors for closely-related species of similar size to Arctic Terns. Unfortunately, egg values are not common, so I used what was available for a seabird and landbirds. Tissue-tissue fractionation values are the differences of the mean discrimination factor for each tissue type. ................................ 86 Table 3-3: Stable isotope ratios for Arctic Tern tissues used in this study to determine trophic positions, niche width and nutrient allocation at Nasaruvaalik Island. These values are uncorrected for tissue-tissue discrimination factors. ...................................... 87 Table 3-4: Results of F-tests comparing sets of two variances (isotopic niche width) of Nasaruvaalik Island terns grouped by year, age and period of breeding season. ............ 93 Table 3-5: Proportional nutrient contribution to Arctic Tern tissue at Nasaruvaalik Island from local exogenous resources and distant endogenous resources as determined using SIAR, a Bayesian mixing model. In this model, blood acted as a proxy for the local breeding diet, and feathers acted as the distant wintering diet. ....................................... 95 Table 4-1: Data were not available from each of the two study sites, Nasaruvaalik Island and Machias Seal island, for the same years. Below are the years in which data were collected for each parameter compared between sites. ................................................. 114 Table 4-2: Summary data and test statistics of each Arctic Tern breeding parameter compared between sites overall. Test statistics are denoted by letters: U = Mann- Whitney rank sum test; z = generalized linear model; t = t-test; χ2= chi-squared test. Significant differences are marked with an asterisk at the end of each row. Medians are reported only for parameters for which non-parametric tests were used. ..................... 138 Table 4-3: Summary data and test statistics of each Arctic Tern breeding parameter compared between sites within good years. Test statistics are denoted by letters: U = Mann-Whitney rank sum test; z = generalized linear model; t = t-test; χ2= chi-squared test. Significant differences are marked with an asterisk at the end of each row. Medians are reported only for parameters for which non-parametric tests were used. ............... 139 Table 4-4: Summary data and test statistics of each Arctic Tern breeding parameter compared between sites within poor years. Test statistics are denoted by letters: U = Mann-Whitney rank sum test; z = generalized linear model; t = t-test; χ2= chi-squared test. Significant differences are marked with an asterisk at the end of each row. Medians are reported only for parameters for which non-parametric tests were used. ............... 140 Table 4-5: Summary data and test statistics of each Arctic Tern breeding parameter compared within Machias Seal Island between year-types. Test statistics are denoted by letters: U = Mann-Whitney rank sum test; z = generalized linear model; t = t-test; χ2= chi-squared test. Significant differences are marked with an asterisk at the end of each row. Medians are reported only for parameters for which non-parametric tests were used. .............................................................................................................................. 141 x

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Finding the "Arctic" in the Arctic Tern: breeding biology and diet across the latitudinal range of an iconic seabird by. Kelly Anne Boadway. B.Sc., University of
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