Understanding Colonial Wading Bird Metapopulation Dynamics in the NJ Meadowlands and NY Harbor Mentor: Prof. Gareth J. Russell UBM Student: Abraham Rosales Research Goals To model the fluctuations of colonial breeding populations on islands by combining metapopulation dynamics with aggregation behavior.To model the fluctuations of colonial breeding populations on islands by combining metapopulation dynamics with aggregation behavior. Model Components (Hypotheses) Aggregation behaviorAggregation behavior Site fidelitySite fidelity Limit to nest density in patchesLimit to nest density in patches Global food resource limitation means some nests remain emptyGlobal food resource limitation means some nests remain empty Population agingPopulation aging

Great Egret Nesting Data Time (year) Number of Nests *Different color lines represent different breeding populations

Model Outline (one nesting season) Colony Development –Birds arrive in random order –Patch allocation by “attractiveness” function, based on Resource Availability (Nest sites) Desire to be with others (aggregation behavior ) Site Fidelity (where the individual was the year before) Reproduction –Reproduction Rate Follows the density-dependent Theta-Logistic model –λ= r(1-(N/K) Θ ) –Offspring Number Random Poisson Distribution with reproduction rate as its mean Death and Aging –Random accidental death –Death from old age

Example outputs Number of Nests Time (year) *Different color lines represent different breeding populations Graph A Graph B These graphs have different global density dependence based on their global Θ value Graph A has a global Θ= , strong density dependence Graph B has a global Θ=5, low density dependence What we are seeing in these graphs is that as global Θ value increase so does the number of fluctuating populations We are still trying to find out the reason for this kind of behavior