I saw this article on another website and was very suprised. www.bmad.com.au.
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another example of human interference leading to altered species abundances and distributions...
Dieback has been around for a while, I think the main cause is fungal infection of the tree's vascular system, followed by a whole host of secondary infections such as bell miners and psyllids. I think the main cause is soil degredation and other soil issues. In my area the main secondary infection is longicorn tree borers, but the dieback symptoms vary a lot in different areas. There are precautions such as disinfecting boots in some areas, personally I think this is unlikely to be effective. Bell miners may be associated with dieback in some areas but are unlikely to be the cause, the whole thing is a bit mysterious at this stage.
These are just my opinions, not scientific facts.
There's a bit of confusion, Dieback usually refers to phytophora cinnamomi root rot, a completely unrrelated oomycete infection, though in general terms it could refer to any tree decline hence the problem with common names.
The Bell Miner associated tree decline is an interesting one though, call me a cynic but
'However, increases in Bell miner populations and their distribution, in addition to other factors such as tree stress, psyllid infestation, dense forest understories, forest structure as well as weed invasion, drought, logging, pasture improvement, soil nutrient changes, frost and changing fire and grazing regimes have all been implicated in the spread of dieback'.
sounds to me like a classic case of falling back on the old 'we don't know what's wrong so we'll include every possible factor that could conceivably be involved', reminds me of the purported reasons for the extinction of the Paradise Parrot and decline in Gouldian Finch populations... though certainly each idea floated warrants investigation.
I wonder if the over-abundance of Bell Miners has a similar cause to the over-abundance or domination of Noisy Miners where understorey has been destroyed.
Yes, phytophthera is usually blamed but it isn't root rot, it is the whole vascular system of the tree. In most cases there is no systematic investigation of the causes so there is no way of knowing what is happening. When a tree dies in the forest, no-one notices. It can be very hard to distinguish primary from secondary causes of tree death.
Yes by adopting a one size fits all approach of 'it's phytophthora' we risk being blinded to other causes which may be at play.
I believe Bell Miners reach highest populations on the perimeters of forests and increased fragmentation by habitat destruction has favoured them, Woko.
I'm not so sure they don't like understorey, I've seen them nesting in low shrubs, the site linked in the original post claims they are promoted by weed colonisation such as Lantana which would also be encouraged by disturbance events.
And is the so-called BMAD largely on the perimeters of forests, zosterops?
I totally agree that there are other causes at play here which we still don't understand.
"There is likely to be no single or simple management solution. In managing forests, it is necessary to recognise that there is a complexity of connections and interactions, many of which have yet to be deciphered. Because BMAD is associated with interacting disturbances, concentration on particular management regimes in isolation is unlikely to resolve the BMAD problem."
An old paper (2006) but worth reading on the subject of BMAD. http://www.bmad.com.au/publications/LiteratureReview.pdf
As for the nesting preferences of Bell Miners.
"Nests are built in low dense mid-storey vegetation below three metres. They are cup shaped and made of grass, rootlets, fine twigs and spiders web and are around 10 cm wide."
http://www.bmad.com.au/publications/BMAD_tech_note_1.pdf
Samford Valley Qld.