Roost characteristics of invasive mynas in Singapore

Abstract

We identified factors affecting the selection of roost sites by invasive white-vented (Acridotheres javanicus) and common (A. tristis) mynas in urban Singapore. In addition, we examined the effects of experimentally manipulating canopy cover and food abundance on roosting populations. Multivariate analysis, binary logistic regression, and the Akaike Information Criterion (AIC) showed that mynas selected roost trees with dense canopies that were closer by 603.5 m to food centers and surrounded by 2.6% more vegetation than random non-roost trees. Based on Wilks' Lambda, we ranked canopy density as the most important variable, followed by proximity to food centers. Canopy density and food abundance manipulation experiments showed that although both resulted in a decrease in the number of roosting mynas, canopy density reduction had a greater effect, as predicted by the roost-selection model. The canopy of existing roosts can be thinned to alleviate the problem caused by roosting mynas. Stringent control of refuse at food centers also should be implemented to make such areas less attractive to mynas. Planting large and densely covered trees, particularly angsana (Pterocarpus indicus) and tropical apple (Eugenia grandis), near food centers should be avoided by park and urban managers.