Wednesday, March 18, 2015

Bell Miners and Dieback



A favourite nearby short walk takes me through a small patch of bush that is occupied by Bellbirds or Bell Miners.


Bell Miners are an aggressive native honeyeater and are closely related to that other aggressive species, the Noisy Miner. Both birds spend an inordinate amount of time chasing away other species of insectivorous birds – in fact I have seen Noisy Miners chasing herons!?

Bell Miner in mid-call, see link below.

The Bell Miner feeds on the lerps on the leaves of eucalypts. Lerps are the crystallized structure of honeydew produced by sap sucking insects called psyllids.

Sugary secretions or lerps.
A tiny psyllid is just visible.

Much work is being done on the dieback effect in some areas produced by the loss of canopy foliage due to psyllid attack. One theory directly connects the Bell Miner. The birds chase away the insectivorous species to protect their ‘lerp zones’, so allowing the psyllid numbers to increase beyond normal proportions. The resultant loss of canopy foliage puts the trees under stress and may eventually cause them to die.

Of course, as the trees die in one area the psyllid population is reduced and the Bell Miner numbers will reduce by attrition or by migration. Studies are underway in many places to determine if the trees might recover naturally and so the whole thing becomes cyclical.

Bell Miner Associated Dieback WorkingGroup.
Australian Museum, The Bell Miner.
Birds In Backyards, The Bell Miner call

Gouldiae

2 comments:

  1. Interesting link between Bell Miners and dieback. Given how long Bell Birds would have been around I would suspect the real problem may be the relatively small areas of remnant forest in which such cycles are expected to operate.

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  2. Indeed Mosura. I think as much of the material on dieback points out, there are numerous factors that may be involved singularly or in combination. In some instances, Bell Miners definitely contribute apparently.
    Gouldiae

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