The ghosts of Pacific avifauna

Diamond, J. 2007. Voices from Bird Bones. Science, 315:941–942. www.sciencemag.org (subscription required).

Jared Diamond reviews two recent publications on the Pacific's many extinct birds.

• "Extinct Birds of New Zealand" by Alan Tennyson and Paul Martinson (Te Papa Press, Wellington, New Zealand, 2006).


• "Extinction and Biogeography of Tropical Pacific Birds" by David W. Steadman (University of Chicago Press, Chicago, 2006).

The review of Tennyson and Martinson's attractive book is brief and complementary. "Martinson's gorgeously detailed paintings bring home the tragic loss of formerly breathing real animals in a way that descriptions of bones cannot achieve" (p. 941). Diamond presents it as a worthy companion to Trevor Worthy and Richard Holdaway's (2002) book, "The Lost World of the Moa".

"The New Zealand fossil avifauna is by far the most completely sampled in the world" (p. 941). Diamond is particularly fascinated by how the extinction of many of New Zealand's endemic birds was followed by a replacement by often related Australian species. He sees there being much to learn about the processes of community assembly from both the Pacific's prehistoric avifauna and the modern bird communities that have replaced them.

David Steadman's decades of excavations have revealed the details of how the Polynesian settlement of the Pacific Islands triggered a mass extinction of birds and other vertebrates. I well remember being stunned when I read Steadman's chapter in the 1997 book "Biodiversity II", with its description of the massive scale of bird extinctions in the Pacific following human arrival. Unfortunately, Diamond's opinion of Steadman's book is less than complementary, not due to any inaccuracies in the data behind the book, but rather regret at the superficial interpretation of this data. In Diamond's eyes, Steadman is stubbornly resistant to the modern analysis of his data and all the amazing things that could be learned from it. With the publication of "Extinction and Biogeography of Tropical Pacific Birds", this modern treatment may follow.

Fukami et al. (2006): Above- and below-ground impacts of introduced predators in seabird-dominated island ecosystems.

Tadashi Fukami, David A. Wardle, Peter J. Bellingham, Christa P. H., Mulder, David R., Towns, Gregor W. Yeates, Karen I. Bonner, Melody S. Durrett, Madeline N. Grant-Hoffman and Wendy M. Williamson. 2006. Above- and below-ground impacts of introduced predators in seabird-dominated island ecosystems. Ecology Letters Volume 9 Issue 12 Page 1299 - December 2006

Predators often exert multi-trophic cascading effects in terrestrial ecosystems. However, how such predation may indirectly impact interactions between above- and below-ground biota is poorly understood, despite the functional importance of these interactions. Comparison of rat-free and rat-invaded offshore islands in New Zealand revealed that predation of seabirds by introduced rats reduced forest soil fertility by disrupting sea-to-land nutrient transport by seabirds, and that fertility reduction in turn led to wide-ranging cascading effects on belowground organisms and the ecosystem processes they drive. Our data further suggest that some effects on the belowground food web were attributable to changes in aboveground plant nutrients and biomass, which were themselves related to reduced soil disturbance and fertility on invaded islands. These results demonstrate that, by disrupting across-ecosystem nutrient subsidies, predators can indirectly induce strong shifts in both above- and below-ground biota via multiple pathways, and in doing so, act as major ecosystem drivers.