Parrots, goats and sun: population dynamics of the yellow-shouldered amazon parrot (Amazona barbadensis) in Bonaire island, Dutch Antilles.

Abstract:

With the new status of special municipality Bonaire’s development aims have focused toward more efficient  sustainable policies. With centuries of human intervention, ecosystem degradation, pressure of invasive species and tourism industry, services associated with biodiversity are threatened by developmental needs. The Amazona barbadensis parrot is of special conservation concern due to the vulnerability to habitat degradation and poaching and its small range restricted to Bonaire and Northern Venezuela. We ask whether the spatial development plan of Bonaire (ROB) for the coming years has an either positive or negative effect on the parrot population in the island. We used METAPHOR, an individual-based stochastic population model in order to estimate the population trend for the next 200 years. We use two cases, poaching and no poaching, and four scenarios, Current, two scenarios contemplated in the ROB and one scenario of goat control and vegetation recovery that changes nest availability.For all the scenarios the model showed great stability around the year 100.Reducing poaching and controlling goats increased the population in each scenario with c. 50%. The ROB scenarios did not increase the population size or made it significantly lower, as only the (minor) impact on carrying capacity was taken into account. The estimated population size under current conditions was ~1800. Increasing poaching to 50% diminished this valued until 1000 while the poaching didn’t affect the age structure. Increasing availability of nests to 130 raised the population to 3000. The used survival of 87% for fledges and adults showed to be the most optimistic case in the sensitivity analysis warning about the real status of the population and the high uncertainty of the model. The control of the invasive goats has been a conservation success in other islands and showed to have the best outcome for the modelled population. Whether it is control of goats or vegetation restoration, increasing vegetation cover would favour conservationist and economic aims providing habitat for plant and animal communities and  providing more valuable services for terrestrial ecotourism.