Australasian bird invasions: accidents of history?

Abstract

Exotic bird introductions to Australia, New Zealand and surrounding islands, have been aggregated into one of the best documented and most completely analysed datasets available on biological invasions. Of the >242 species introduced by Europeans to Australasia during the 18th-20th centuries, at least 32% established long-term viable populations. A review of the literature reveals the most robust predictors of introduction success to be total number of individuals liberated, and the number of separate attempts at introduction. Using generalized linear modelling on a combined regional dataset, I confirm this result, and demonstrate that together these two characteristics of historical introductions correctly explains the observed outcome in 89.3% of cases in Australasia. Further, I show that a simple stochastic population dynamics model, derived for a sub-set of 44 species from entirely independent longterm studies, is also able to achieve a high degree of predictive success (83%). Finally, a suite of meta-analyses have shown the strongest life history and environmental correlates of introduction success to be large body size, low propensity to migrate, climatically matched habitats across the native and invasive geographical range, sexually monochromatic plumage, dietary generalism, and greater behavioural flexibility. The collective results of these analyses on Australasian introductions provide a potentially powerful framework for predicting the probable outcomes of future bird invasions worldwide.