The pet trade could pose a risk to native species as alien birds are introduced into unnatural environments, researchers say.
For the first time a global map of alien bird species has been produced by a UCL-led team of researchers.
Human activities are shows to be the main reason for the amount of alien birds living in an area.
The study looked at the 1,000 alien bird species that were introduced over the past 500 years.
The annual rate worldwide has continued to increase constantly over the last 200 years, according to the study.
“One of the main ways humans are altering the world is by moving species to new areas where they do not normally occur.
“Our work shows why humans have been moving these ‘alien’ bird species around for the last 500 years – primarily through colonialism and the increasingly popular cage bird trade – and why some areas end up with more species than others,” explained supervising author, Professor Tim Blackburn (UCL Genetics, Evolution & Environment and ZSL).
The international team involved researchers based at UCL, ZSL, University of Adelaide, University of Cambridge, University of Exeter, The University of Queensland, and Imperial College London. The research was funded by the Leverhulme Trust and King Saud University.