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Changes in non-randomness in the expanding introduced avifauna of the world

Authors

  • Tim M. Blackburn,

  • Kevin J. Gaston,

  • Mark Parnell


T. M. Blackburn (tim.blackburn@ioz.ac.uk), Inst. of Zoology, ZSL, Regent's Park, London NW1 4RY, UK. – K. J. Gaston and M. Parnell, Biodiversity and Macroecology Group, Dept of Animal and Plant Sciences, Univ. of Sheffield, Sheffield S10 2TN, UK. (Present address of M. P.: 38 Talbot Street, Sheffield, S2 2TG, UK.)

Abstract

The identities of bird species introduced to areas beyond the limits of their native geographic ranges have historically depended on a combination of societal demands for species with certain characteristics, and the availability of species for capture, transport and release. However, both societal demands and availability have changed over time, which should also change the characteristics of species more recently added to the list of introduced birds. Here, we quantify temporal changes in selectivity of introduced bird species by comparing the characteristics of 423 species listed in the seminal catalogue of introduced birds (Long, J. L. 1981. Introduced birds of the world. – David and Charles, London) with those of 122 species that have been introduced but are not listed in Long (1981). We demonstrate differences between these two groups of species in the frequencies with which different taxa are represented, in the geographic range sizes of species, and in their biogeographic regions of origin, but not in body mass. Both groups also differ from bird species in general in terms of geographic range sizes, body masses, and taxonomic composition. We relate the observed differences in the characteristics of species listed or unlisted in Long (1981) to changes in the changes in attitudes, legislation and vectors of transport relating to exotic species. We conclude by noting that the utility of published catalogues of introduced bird species is increasingly being eroded by the continued liberation and establishment of bird species.

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