Historical records of passerine introductions to New Zealand fail to support the propagule pressure hypothesis

• Published in: Biodiversity and conservation Vol. 21; no. 1; pp. 297 - 307
• Main Authors: Moulton, Michael P, Cropper, Wendell P. Jr, Avery, Michael L
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 2012; Springer; Springer Nature B.V
• Subjects: Analysis; Animal populations; Archives & records; Biodiversity; Biomedical and Life Sciences; Birds; Brief Communication; Climate Change/Climate Change Impacts; colonizing ability; Conservation Biology/Ecology; ecological invasion; Ecology; extinction; Historic documents; Hypotheses; Introduced species; Life Sciences; Nonnative species; Passeriformes; Population ecology; population size; Species extinction; viability; New Zealand; Introduced birds; Propagule pressure; Historical records
• ISSN: 1572-9710; 0960-3115; 1572-9710
• DOI: 10.1007/s10531-011-0165-2

Blackburn et al. (Biodiver Conserv 20:2189–2199, 2011) claim that a reanalysis of passerine introductions to New Zealand supports the propagule pressure hypothesis. The conclusions of Blackburn et al. (2011) are invalid for three reasons: First, the historical record is so flawed that there is no sound basis for identifying the mechanisms behind extinction following introduction, or whether species were successful because they were introduced in large numbers or were introduced in large numbers because earlier releases succeeded. Second, the GLIMMIX analysis of Blackburn et al. (2011) is biased in favor of the propagule pressure hypothesis. Third, the population viability analysis presented by Blackburn et al. (2011) is based on unjustified and questionable assumptions. It is likely that the outcome of passerine bird introductions to New Zealand depended on species characteristics, site characteristics, and human decisions more than on a simple summing of the numbers introduced.