The extinction of several fruit eating birds as a result of habitat loss or predation by exotic mammals has prevented rainforest shrubs in the island nation from spreading their seeds to new sites the usual way.
But now, a new study by Jeff Foster and his colleagues has revealed that the Japanese white-eye and red-billed leiothrix widely disperse the seeds of these native shrubs.
The scientists analysed the stomach contents of the birds and discovered that they extensively snacked on native fruit.
Seed traps revealed that the birds were dispersing the seeds widely, allowing native shrubs to reclaim the "understorey" of Hawaiian forests.
"People tend to think of native species as good and exotic ones as bad, but it's just not that simple," said Foster.
The research appears in the current issue of the journal Conservation Biology, reports New Scientist magazine.