DEMOGRAPHIC SHIFTS and the ROLE of CLIMATE WARMING in a SWITCH from MIGRANT to RESIDENT LIFE HISTORY By
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DEMOGRAPHIC SHIFTS AND THE ROLE OF CLIMATE WARMING IN A SWITCH FROM MIGRANT TO RESIDENT LIFE HISTORY by Hannah Visty B.Sc., The University of British Columbia, 2015 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (Forestry) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) November 2018 © Hannah Visty, 2018 The following individuals certify that they have read, and recommend to the Faculty of Graduate and Postdoctoral Studies for acceptance, a thesis/dissertation entitled: Demographic shifts and the role of climate warming in a switch from migrant to resident life history submitted by Hannah Visty in partial fulfillment of the requirements for the degree of Master of Science in Forestry Examining Committee: Dr. Peter Arcese, Forestry Supervisor Dr. Kathy Martin, Forestry Supervisory Committee Member Dr. Andrew Trites, Zoology Additional Examiner Additional Supervisory Committee Members: Dr. Scott Wilson, Environment Canada Supervisory Committee Member ii Abstract Identifying causes and consequences of variation in species life history should improve predictions about how climate and land use change will affect the demography and distribution of species in future. Sooty fox sparrows (Passerella iliaca unalaschcensis) were documented as obligate migrants, abundant in winter but with only three breeding records in coastal habitats of British Columbia and Washington prior to 1950. Because this subspecies has since established year-round resident populations in this region, I studied resident populations of sooty fox sparrows to test theory on how climate change and life history might affect the demography and distribution of a new partial migrant. I estimated demographic vital rates in one recently established resident population on Mandarte Is., BC, using color-banded birds. Annual fecundity (F) was higher than reported in migrant populations studied previously in Alaska and Newfoundland, supporting the hypothesis that residents invest more in reproduction on average than migrants within species. I also estimated high juvenile and adult overwinter survival (Sj = 0.32 ± 0.06, and Sa = 0.69 ± 0.05) and population growth (λexp = 1.61 ± 0.57), implying rapid population growth. I next tested the hypothesis that climate warming facilitated the establishment of resident populations by reducing the net benefit of migrating out of the wintering area to breed. Because resident sooty fox sparrows breed earlier and longer than migrants, I asked if climate warming during the pre-breeding period coincided with patterns of establishment by: 1) characterizing the pre-breeding climate niche of resident populations using species distribution models, occurrence data, and monthly climate records, and 2) testing if the emergence of the pre-breeding climate niche currently occupied by resident populations corresponds to the first reports of sooty fox sparrows breeding after 1920. Niche models suggest that the mild, near- shore climate niche now occupied by recently established resident populations expanded dramatically from 1920 to 2015 in a pattern matching early records of breeding by sooty fox sparrows within their historic wintering area from 1950. Whereas prior studies focus on climate warming affecting overwinter survival, my results suggest warming may also affect migration through improved fecundity and breeding niches. iii Lay Summary Climate warming is contributing to global declines and disruptions in animal migration, as species that once migrated long distances now remain resident year-round, migrate shorter distances, and occupy novel habitats. My work documents the loss of migration in some populations of a former migrant, the sooty fox sparrow (Passerella iliaca unalaschcensis), and uses theory to identify potential factors affecting migration tendency and its influence on population persistence and life history. I found that newly resident sooty fox sparrows bred earlier and had more nesting attempts annually than migrant fox sparrows, while maintaining high survival. These results suggest that sooty fox sparrows gain a reproductive benefit by remaining resident in their former wintering area, possibly facilitated by climate warming during the ‘pre-breeding’ season. My work illustrates the potential for climate change to influence trade-offs affecting the strategies of migrants and residents and the communities they occupy. iv Preface Chapter two of this thesis utilized 45 years of song sparrow data on Mandarte Island, British Columbia collected by dozens of field teams between 1960 and 2016, as well as 6 years of fox sparrow data collected between 2010 and 2016. I participated in data collection during the field season of 2017 to contribute to the dataset moving forward. A version of Chapter 2 of this thesis has been published: Visty, H., Wilson, S., Germain, R., Krippel, J., and Arcese, P. 2018. Demography of sooty fox sparrows following a shift from migratory to resident life history. Can. J. Zool. 96: 436-440. I conducted all analyses and wrote the manuscript. Dr. R. Germain and J. Krippel led the data collection between 2010-2016. Dr. S. Wilson advised on the data analysis and helped extensively with editing. Dr. P. Arcese advised on data analysis and design of the paper. All authors provided editing and writing input, especially Dr. P. Arcese and Dr. S. Wilson. The third chapter of this thesis utilized several years of point count data collected throughout southwest British Columbia and northwest Washington between 2007 and 2017 from multiple field teams. I collected all data in 2017. Dr. R. Schuster and Dr. T. Wang provided code and analysis help. Dr. P. Arcese provided input on experimental design and analysis. I created the final maps and models and wrote the manuscript. Extensive editing help was provided by Dr. P. Arcese. A version of this chapter will be submitted for publication with Drs. R. Schuster, T. Wang, and P. Arcese as co-authors. All protocols involving the use of animals in this thesis were approved by the UBC Animal Care Committee (A14- 0366). Permits for this work were obtained from Environment Canada (master banding permit no. 10596, sub-banding permit 10596 T). v Table of contents Abstract ........................................................................................................................................................ iii Lay Summary ................................................................................................................................................ iv Preface .......................................................................................................................................................... v Table of contents ......................................................................................................................................... vi List of Tables .............................................................................................................................................. viii List of Figures ............................................................................................................................................... ix Acknowledgements ....................................................................................................................................... x Dedication .................................................................................................................................................... xi 1. Introduction .............................................................................................................................................. 1 1.1 Climate warming impacts on demography and migration ................................................................. 1 1.2 Study region ........................................................................................................................................ 3 1.3 Sooty fox sparrows as a novel partial migrant complex ..................................................................... 4 1.4 Thesis overview ................................................................................................................................... 5 2. Demography of sooty fox sparrows (Passerella iliaca unalaschcensis) following a shift from migratory to resident life history ................................................................................................................................... 6 2.1 Introduction ........................................................................................................................................ 6 2.2 Methods .............................................................................................................................................. 7 2.2.1 Study system ................................................................................................................................ 7 2.2.2 Estimation of survival and fecundity ............................................................................................ 8 2.2.3 Stochastic estimation of population growth.............................................................................. 10 2.3 Results ............................................................................................................................................... 10 2.3.1 Clutch size and nest success .....................................................................................................