The much-maligned mistletoe, a parasitic plant commonly seen on trees along Australian country roads, may play an important role in the Australian bush, according to Charles Sturt University researcher Dr David Watson.

"Its distribution could indicate the health of a patch of bush," Dr Watson said. "Mistletoes appear to be increasing in many parts of Australia, particularly among isolated trees in cleared paddocks and along roadsides. They are, however, relatively rare in undisturbed bush," Dr Watson said.

"Mistletoes are sensitive indicators of the health of an ecosystem - the more mistletoes present, the more trees appear to be stressed. Mistletoes are also pollinated, consumed and spread by native animals and killed by fire - all important parts of the Australian bush."

In coming months, Dr Watson will investigate many aspects of mistletoe distribution across a landscape, thanks to a $18 300 Australian Research Council grant.

"Contrary to popular belief, mistletoes are native to Australia, with 90 species found in all but the driest deserts. They are parasitic plants that depend on host trees such as gumtrees for all their water and minerals. All but two Australian species live on the stems and branches of the host," Dr Watson said after a review of worldwide research on the plants.

Being parasitic, mistletoes are not limited by water or minerals as much as other Australian plants. "Therefore, they often flower and fruit throughout the year in many areas, even during droughts," Dr Watson said.

Most mistletoes are pollinated and spread by birds, which in turn depend on the plants' highly nutritious nectar and fruit for food. Many native birds, including honeyeaters, lorikeets, bowerbids, emus and cockatoos, are known to feed on the plants. Possums, koalas, sheep, cattle and many insects also graze on the leaves.

The dense leafy clumps also make ideal nesting sites for many birds, as they are protected from bad weather and predators. Many bird species, including the endangered Regent Honeyeater, prefer nesting in mistletoe clumps. Australian mistletoes are sensitive to fire, so bushfires prevent their spread.

Dr Watson is an ecology researcher with the University's Johnstone Centre and based on the Bathurst Campus. The initial research is part of a long-term project investigating the importance of mistletoes to woodland birds, insects and mammals.