Leo is an Australian ornithologist and evolutionary biologist. He works on the evolution of Australian and New Guinean birds.
He is particularly interested in what we can learn from the record in DNA sequences of how bird species have come to be distributed across the region the way they are and how the evolution of the Australian and New Guinean region itself has shaped the evolution of the bird fauna.
A part of this is to understand how ecological diversity of birds has evolved by better understanding the evolutionary history fo the brids themselves. He became interested in birds through the spectacular parrots of our region and retains a fondness for that group.
He has also worked on South American birds and did so while living in Uruguay from 1994-97 and then again while at the Academy of Natural Sciences, Philadelphia from 1997-2005 where he was Chair of the Department of Ornithology
Whitley Award, 2009, for best Natural History book in Australia - jointly with Libby Robin and Robert Heinsohn