ANNUAL SPATIAL ECOLOGY OF HERRING GULLS (LARUS ARGENTATUS) IN EASTERN NORTH AMERICA by Christine M. Anderson B. Sc. Trent University 2013 Thesis Submitted in partial fulfillment of the requirements for the Degree of Master of Science (Biology) Acadia University Spring Graduation 2017 © by Christine M. Anderson, 2017 ii This thesis by Christine M. Anderson was defended successfully in an oral examination on 25 April 2017. The examining committee for the thesis was: This thesis is accepted in its present form by the Division of Research and Graduate Studies as satisfying the thesis requirements of the degree Master of Science (Biology). …………………………………………….. iii I, Christine M. Anderson, grant permission to the University Librarian at Acadia University to reproduce, loan or distribute copies of my thesis in microform, paper, or electronic formats on a non-profit basis. I, however, retain the copyright in my thesis. iv Table of Contents Table of Contents --------------------------------------------------------------------------------- iv List of Tables --------------------------------------------------------------------------------------- v List of Figures ------------------------------------------------------------------------------------- vi Abstract --------------------------------------------------------------------------------------------- ix Acknowledgements-------------------------------------------------------------------------------- x Chapter 1 – General introduction and methods ---------------------------------------------- 1 Background -------------------------------------------------------------------------------- 1 Herring Gull ------------------------------------------------------------------------------- 4 General Methods ------------------------------------------------------------------------- 10 Objectives -------------------------------------------------------------------------------- 14 Chapter 2 – Are Herring Gulls residents or migrants? ------------------------------------- 21 Introduction------------------------------------------------------------------------------- 21 Validating methods with simulated data ---------------------------------------------- 24 Applying methods to Herring Gull data ----------------------------------------------- 27 Conclusion -------------------------------------------------------------------------------- 29 Chapter 3 – Do short and long distance migrants use different migration strategies? 35 Introduction------------------------------------------------------------------------------- 35 Methods ----------------------------------------------------------------------------------- 38 Results ------------------------------------------------------------------------------------ 41 Discussion -------------------------------------------------------------------------------- 44 Chapter 4 – Does winter habitat use differ by population? -------------------------------- 65 Introduction------------------------------------------------------------------------------- 65 Methods ----------------------------------------------------------------------------------- 67 Results ------------------------------------------------------------------------------------ 70 Discussion -------------------------------------------------------------------------------- 73 Chapter 5 – General Discussion --------------------------------------------------------------- 87 Findings ----------------------------------------------------------------------------------- 87 Applications and future directions ----------------------------------------------------- 88 References ---------------------------------------------------------------------------------------- 93 Appendix: R code for Chapter 2 simulations -----------------------------------------------115 v List of Tables Table 1-1: Adult Herring Gull survival estimates found in previous studies. -------------- 16 Table 1-2: Details of tracking device deployment for collecting Herring Gull movement data used in this thesis. -------------------------------------------------------------- 17 Table 3-1: Migration characteristics of Herring Gulls tracked from Nunavut (n = 8 [autumn], 1 [spring]), Newfoundland (n = 6, 9), Sable Island (n = 17, 11), and the Bay of Fundy (n = 11, 10). All summary statistics are presented as mean ± SD (range). Range and SD are absent for all Nunavut spring summaries because only one individual was tracked for the full migration period. ------------------------------------ 56 Table 3-2: Model averaged parameter estimates (β, 95% confidence intervals) and cumulative Akaike weights (Σ ωi) for generalized linear mixed models examining the effects of population and season on the migration characteristics for Herring Gulls tracked from Nunavut (NU; n = 8 autumn, 1 spring), Newfoundland (NL; n = 6, 9), Bay of Fundy (BF, n = 11; 10) and Sable Island (SI; n = 17, 11) during autumn (A) and spring (S). Individual is included as a random effect in all models except for directness. Estimates of conditional r2 (fixed effect only) and marginal r2 (fixed and random effects) are presented for the global model of each candidate set. Population and season are both categorical variables; the intercept is the predicted value for Herring Gull from Nunavut in the autumn, which then acts as the reference level for the other parameter estimates.--------------------------------------------- 58 Table 3-3: Arrival and departure dates for autumn and spring migrations of Herring Gulls tracked from Nunavut (n = 8, 1), Newfoundland (n = 6, 9), Sable Island (n = 17, 11), Bay of Fundy (n = 11, 10). Colony departure and arrival dates of Great Lakes Herring Gulls (n = 10, 5) included for comparison. All summary statistics are presented as mean ± SD (range). ---------------------------------------------------------------- 59 vi List of Figures Figure 1-1: Herring Gull (Larus argentatus) distribution in North America (BirdLife International and NatureServe 2014). Breeding distribution is shaded in yellow, year-round distribution is shaded in blue, wintering distribution is shaded in red, and migration distribution is hatched grey. ----------------------------------------------- 18 Figure 1-2: Schematic of state-space model structure, adapted from Jonsen et al (2013). The process model evolves through time as a random walk, starting at x1 and ending at xn. At times t1, t2, …., tn, measurements y1, y2, …, yn are taken as described by the observation model. An arrow from one variable (for example x1) to a subsequent variable (for example x2) indicates that x2 is expressed in terms of the conditional probability distribution of x2 given x1. Note that in the process model, all observations of x are dependent on x at the previous time step. Observations of y are independent of one another, and are dependent on x at the same time step. ------------------------------------------------------------------------------------ 19 Figure 2-1: An example of a) random movement by resident population and b) directed movement by a migrating population, simulated for n = 10 individuals. -------- 31 Figure 2-2: Coulson and Brazendale’s (1968) method for differentiating between migrants and residents requires all available non-breeding locations to be grouped into distance zones extending outwards from the breeding colony. Demonstrated for Herring Gulls breeding in the Great Lakes. Distance zones are at 100 km intervals, extending to a maximum of 1500 km ---------------------------------------------------------- 32 Figure 2-3: Top panels show the relationship between distance from the breeding colony and the proportion of locations in that distance zone or greater for one simulation of a resident or migrant population (n = 10). Simulated data are displayed in grey, fitted logarithmic function is displayed in red. Bottom panels show quantile plots of the r2 value for 1000 simulations of each sample size for resident and migrant populations.--------------------------------------------------------------- 33 Figure 2-4: The relationship between distance from the breeding colony and the proportion of locations in that distance zone or greater for Herring Gulls breeding in the Great Lakes (n = 8), the Bay of Fundy (n = 10), Sable Island (n = 8), Newfoundland (n = 3) and Nunavut (n = 8). Observed data are displayed in grey, fitted logarithmic function is displayed in red. ------------------------------------------------ 34 Figure 3-1: Scatterplot illustrating variation in a) directness, b) overall migration speed, and c) total stopover days between populations and seasons for Herring Gulls tracked from Nunavut, Newfoundland, Sable Island, and the Bay of Fundy. Herring Gulls breeding in Nunavut are represented in yellow, Herring Gulls breeding in Atlantic Canada are represented in red. ------------------------------------------ 60 vii Figure 3-2: Map of migration routes for Herring Gulls breeding in Nunavut. Stopover days are represented in yellow, and travel days are represented in blue. Breeding site on Southampton Island, NU is indicated by a pink triangle. ---------------- 61 Figure 3-3: Map of migration routes for Herring Gulls breeding in Atlantic Canada. Stopover days are represented in yellow, and travel days are represented in blue. Breeding sites are indicated by a pink triangle, from north to south: Newfoundland (3 sites), Sable (1 site), and Bay of Fundy (2 sites). ------------------------------------------ 62 Figure 3-4: Map of stopover sites used by Herring Gulls in Nunavut. Stopover days are represented