6 Jul 2015
Predicting the distribution and impacts of non-native birds in the Iberian Peninsula

BRANTA — Martin Sullivan

Predicting the distribution and impacts of non-native birds in the Iberian Peninsula

Institution: University of East Anglia, UK
Supervisors: Aldina Franco, Richard Davies
Details: PhD 2014 (completed)


Subject Keywords: Invasive species, species distribution modelling, dispersal, competition
Species Keywords: Common Waxbill Estrilda astrild, Black-headed Weaver Ploceus melanocephalus, Yellow-crowned Bishop Euplectes afer, Red Avadavat Amandava amandava,

Thesis Online here


Increasing numbers of species are being transported beyond their natural range boundaries by humans. These non-native species can have severe negative impacts on native biodiversity. In order to guide management of these species it is important to be able predict where non-native species will spread to, and what impact they will have. This thesis aims to improve our understanding in both these areas, using the expansion of non-native birds in the Iberian Peninsula as a study system. The number of non-native passerines in the Iberian Peninsula has increased in the late 20th century, with the Common Waxbill Estrilda astrild, Yellow-crowned Bishop Euplectes afer, Red Avadavat Amandava amandava and Black-headed Weaver Ploceus melanocephalus all established as breeding species since 1960.

Methods to (1) account for dispersal limitation when modelling the distribution of spreading non-native species and (2) evaluate the likely transferability of native trained species distribution models were developed. The consistency of the species-environment relationship during expansion in the non-native range was also examined. The ability of vacant niches to facilitate the spread of non-native species was tested, and a framework for detecting the early impacts of non-native species was developed.

Species distribution models of the potential distribution of non-native species are improved by incorporating dispersal. Dispersal is an important constraint on the distribution of non-native species, and interacts with environmental suitability to alter the species-environment relationship between the range-margin and the range core, and over time. Despite accounting for dispersal limitation in their evaluation, the performance of native-trained species distribution models was poor when most environmental conditions that were analogous to the species native range were within the species niche.

Non-native birds in the Iberian Peninsula utilised similar resources to native seed-eating birds, but small differences in resource utilisation allowed them to exploit rice fields, where resources were under-exploited by native species. Non-native birds could also interact with native reedbed nesting passerines, and indeed aggression between black-headed weavers and native Acrocephalus warblers has been recorded. However, we did not find evidence for competition between these species at current population densities of black-headed weavers.

Further work on non-native species needs to extend the hybrid dispersal-species distribution models developed here, and also to conduct more assessments of the impacts of non-native species in the early stages of their invasion.


Grundy, J.P.B., Franco, A.M.A. & Sullivan, M.J.P. 2014. Testing multiple pathways for impacts of the non-native Black-headed Weaver Ploceus melanocepahlus on native birds in Iberia in the early phase of invasion. Ibis , 156: 355-365.
Sullivan, M.J.P., Grundy, J.P.B. & Franco, A.M.A. 2014. Assessing the impacts of the non-native Black-headed Weaver on native Acrocephalus warblers. Ibis , 156: 231-232.
Sullivan, M.J.P., Davies, R.G., Reino, L. & Franco, A.M.A. 2012. Using dispersal information to model the species-environment relationship of spreading non-native species. Methods in Ecology and Evolution , 3: 870-879.

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