Journal Watch Online reports an interesting finding:

According to the “tens rule”, roughly ten percent of introduced species become established and ten percent of those become invasive. Only it doesn’t hold for mammals or birds, according to Jonathan Jeschke’s study, the findings of which are published in Diversity and Distributions.

The Ludwig-Maximilians-University, Munich, researcher found that fifty percent of introduced bird species become established, of which 34 percent become invasive. Mammals are even more successful colonists, with an amazing 79 percent finding a permanent home and 63 percent of those going on to become a pain in the proverbial for conservationists. That makes mammals almost fifty times more effective invaders than the tens rule predicts. How wrong can one be?

Source: Jeschke JM (2008) Across islands and continents, mammals are more successful invaders than birds. Diversity and Distributions DOI: 10.1111/j.1472-4642.2008.00488.x

I wonder what explains this difference between mammals and birds.  Is it something to do with biology or what species people move around?  It would be interesting to see how the patterns vary with body mass.

Another paper by Jeschke is also interesting.  Invasion success of vertebrates in Europe and North America – which showed that there does not seem to be ecological imperialism between vertabrates, and that invasion success is higher than expect.