Integration of Demographic Analyses and Decision Modeling in Support of Management of Invasive Monk Parakeets, an Urban and Agricultural Pest

Abstract

We investigated from 2003 to 2006 the population dynamics of Monk Parakeets (Myiopsitta monachus), an invasive, exotic, pest species inhabiting northeastern Spain. Our study focused on several colonies of parakeets in Barcelona. Starting in 2003, we trapped and marked birds at the main Barcelona colony in Ciutadella Park during 2 annual periods: winter (pre-nesting) and late summer (post-nesting), respectively. We marked 459 individuals, and subsequently reencountered marked birds at the colony via recapture, and additionally obtained resightings of parakeets throughout Barcelona (n = 381 recaptures and 570 resightings). We used a variation of the Robust Design in conjunction with reverse-time CR modelling to estimate survival and recruitment rates, and to determine the relative contribution of survival and recruitment to population growth rate. Due to high dispersal, apparent survival rates were low, so we used the combined recapture-resighting data to provide more realistic estimates of demographic survival. We then combined the projections with estimates of survival and recruitment elasticity from our statistical models in a decision model, in order to investigate alternative management scenarios for reducing damage from continued parakeet expansion. Given the logistical and social constraints under which managers operate, it appears that the most effective management strategy would be removal by trapping (in urban areas) or shooting (in rural areas) of birds during summer-winter period.