Birding-Aus Digest, Vol 42, Issue 20

Hi birders

Back in 2004 on Birding-Aus I wrote this:

“… /Some musing on that feral pest the Common Blackbird (Turdus
merula) in Victoria, Australia …./

/A couple of observations this Autumn have me wondering whether some
proportion of the Victorian Blackbird population might be migratory –
even if its just the kind of altitudinal migration seen in various
indigenous birds here. Let me elaborate …/

/At two sites I’ve visited in the last fortnight, I’ve come across
groups of Blackbirds (about 10 birds in each case) roosting/resting in
isolated patches of vegetation in farmland during the day. In one case
the patch was a cluster of pines in a vast dry grassy paddock, no
understorey – very un-Blackbird-like habitat (Craigieburn, northern
Melbourne). The others were laid up in a mess of Spanish Heath (Erica
lusitanica) underneath remnant Swamp Gums (Eucalyptus ovata) in farmland
(south of Colac, northern Otway Ranges foothills). Both sites were at
about 200m above sea level, and perhaps less than 50km from more upland
forest (>500m ASL). In both cases they flushed in groups, and didn’t
give the characteristic Blackbird cackle that usually accompanies such
disturbance./

/This seems vaguely like migrant behaviour to me. Thrushes like these
often migrate at night in their natural range, and lay up in various
copses of vegetation during the day. In the Craigieburn example, several
migrant Grey Fantails were noted in an adjacent patch in the paddock./

/I’d be interested in any comments on this matter. Does anyone live in
an upland kind of place with fluctuating Blackbird numbers which might
suggest regular short – medium distance movements? Any other similar
observations? The ‘big picture’ data presented in the New Atlas
publication are not finely resolved enough to address this question –
particularly if only some Blackbirds are migrating/moving/ …”.

There wasn’t much of a response, and nothing to corroborate my musings.
So until today I hadn’t thought about it much since. This morning
pre-dawn when I went outside briefly (Tylden, central Victoria, ~600m
above sea level) there was an unusual amount of Blackbird noise – more
than I’d expect from our apparently resident pair. Out walking with the
dog a few hours later, around 10am, I saw what could only be Blackbirds
migrating. Over a period of about 5 minutes, I estimated about 40
Blackbirds passed through in a loose stream, going N/NNE (and therefore
down in altitude) – much as you see with Yellow-faced and White-naped
Honeyeaters when they’re migrating – moving from one copse of trees to
another, stopping briefly before heading on. In this case both males and
females.

So why does it matter? Just a feral pest. It has been frequently stated
in the literature that Australian introduced populations of Blackbirds
are all sedentary. In their native range some populations are migratory.
Does that reflect here then that the source populations are from
different populations in Europe with respect to migration, or are local
environmental conditions just triggering latent migratory behaviour? I
can’t help but be interested …

If anyone else sees anything similar this autumn, I’d love to hear from you.

regards

—
address.html

< #*dr.-lawrie-conole*>/Dr. Lawrie Conole/

Tylden 3444, Victoria
Australia

lconole[at]gmail.com

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