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Just a comment to Roy Harvey's and Tom Green's
message about the impact of Galah bark chewing on tree health.
No doubt, as was mentioned, bark chewing will
provide starting points for fungal growth, which in turn will weaken at least
part of a tree. However, hollows that could be useful for nesting, are chiefly
created when termites are involved as well. They hollow out ("pipe") trunks
and branches and parts of the hollowed out wood break off, thus exposing the
cavities. Presence of fungal rot often attracts termite activity, but as a
rule they follow only 'heart rot' (starting from the base in the
centre of the tree). [The story can be a bit more complex and variable, but the
above describes most of the situations.]
When I see big branches that have fallen from
eucalypts, I often check. In the majority of cases, some of the cross section of
the branches is rotten, only some have termite tunnels as well.
Coming back to the Galahs and their chewing
activity: p. 115 in HANZAB Vol. 4 gives a bit of detail about this behaviour
("Scarring"). The text indicates that it is restricted to the nest tree. I
certainly have seen the birds doing it to trees they are not nesting in, and
outside the breeding season. I still suspect the birds get some food value (sap)
out of it. No doubt an activity with several functions.
Michael Lenz
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