Understanding Colonial Wading Bird Metapopulation Dynamics in the NJ Meadowlands and NY Harbor

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

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

3. 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

4. Example outputs • These graphs have different global density dependence based on their global Θ value • Graph A has a global Θ=0.447214, 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 Graph A Number of Nests Graph B Time (year) *Different color lines represent different breeding populations