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Oh
yes, clearly there are several factors applying to population changes of all
species, these two no less than others. One of the other things is soil
moisture. Starlings like feeding in damp substrate more than dry and the dry
conditions impact on them but it probably makes no difference on Mynas. Clearly
Michael or anyone else may choose to be surprised or see a connection as we see
fit. We can only consider if data supports or disproves things. I say Starling and Myna have very similar dynamics. Their annual
abundance pattern is very similar, their timing of breeding is very similar
(see the graphs in the GBS Report). Given a choice they will eat the same things
in the same places and nest in similar places. So I reckon of all the
species we have in Canberra for which we have a lot of data from the GBS, I find
it hard to come up with any other two species that are so similar in so
many ways, that do compete for both food and nesting sites (and nesting in
hollows creates much more competition than building a nest in a tree) for which
an increase in one matches so closely a decrease in the other, as we have in
this example. If anyone else can nominate another situation with anything like
as close a match, then I'd like to see it. There is certainly little if any
evidence from GBS trends that changes in either species have affected any other
species where we can suggest a credible link, where the evidence is so
supportive as it is with these two. Sure the Red-rumped Parrot and the
Kookaburra declined with the increase in the Myna and the Pied Currawong. Is
there a link? Well maybe but hard to be sure as there are so many other factors
operating and in each case any causation is based on just one
aspect.
Philip Veerman
24 Castley Circuit
Kambah ACT 2902
02 - 62314041
While there may certainly be possible interactions
between Mynas and Starlings (espec. regarding competition for nest sites), I
would still be surprised if there is overall a direct link in the rise or
fall of one of the species due to the fall or rise of the other
species.
Starling and Myna have very different dynamics. The
Starling decline was Canberra-wide and occurred in too many places without that
Mynas were present. And now Starlings are coming back in areas with still good
Myna numbers as I could also see last year during my Ainslie survey. Some
buildings had both species present as breeders.
Anyhow, perhaps Martin could do again his good work
and prepare, his time permitting, a graph on the A values for the Starling we
then could compare with the one for the Myna.
Michael Lenz
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