June 20 (UPI) -- Thanks to a new study, researchers are beginning to understand what makes alien species and why some places are more susceptible to invaders than others.
For the study, a team of researchers in Australia and the United States compiled a database of 4,000 alien bird introductions. Using complex statistical analysis, scientists examined the importance of local environment factors, species traits and the size of the invasion in predicting the success of the alien birds.
Their survey showed the characteristics of the local environment were the most important factors in determining the success of the invasion. Researchers determined alien birds were more likely to establish a population if the new habitat already hosted alien species and was similar to their native range.
"Alien birds are more likely to establish populations in areas that already have more aliens of other sorts," lead researcher Tim Blackburn, a professor of invasion biology at University College London, wrote in The Conversation. "This is consistent with the 'invasional meltdown' hypothesis that previous invasions help facilitate future alien arrivals."
But while previous studies have suggested human degradation of the environment can make ecosystems more susceptible to invasive species, the latest data showed alien birds were more likely to invade less-degraded habitat.
Environmental disturbance -- like a big storm, for example -- diminished the odds of an invading bird species' success.
Researchers found alien bird species have greater success invading habitat that have some but not a lot of native birds living there. An insect-eating invader, for example, is likely to have more success invading habitat where a few insect-eating native species are taking advantage of a local insect population. But overall, native plant and animal diversity had only a small effect on the success of an invader.
Scientists hope their work -- published this week in the journal Nature -- can help conservationists identify and better protect habitats most susceptible to invasion.
"We know alien species are the main driver of recent extinctions in both animals and plants so there is a clear and urgent need for better biosecurity measures to prevent or mitigate the impact of future invasions and protect endangered native species," said David Redding, a research fellow at UCL. "With increased global trade, more species are being transported around the world either purposefully or as stowaways, which creates more opportunities for alien species to establish themselves in new habitats."