Just a few observations mainly from my GBS site which to me illustrate how
observations can vary locally. I should add that we've been very wet, if
fact we've had close to 500 mm since the start of October, and it's been so
wet for the first time since the fires I've largely had to give up surveys
of Cooleman Ridge etc, also due to very long grass and also a dearth of
birds the few times I've gone there.
No sign of a food shortage here for nestlings, in fact the local Pied
Currawong pair has raised 3 chicks without appearing too stressed in
obtaining food, with the fledged young staying in the same small area for a
few weeks. No shortage of other dependent young being fed within 0.5 km
either. In addition Magpie-larks have bred successfully in my GBS for the
first time in a number of years, also raising 3 young in super quick time to
the point where they now have dispersed and the parents are revisiting the
nest, possibly to breed again. However, the Superb Fairy-wren may have been
a victim of wet nests, there has been a very secretive male round for a
couple of months, I've been waiting for his jenny to appear with young, but
last week she joined him again without any sign of progeny.
As in the past 4-5 years Koels are not really much in evidence here despite
the abundant ripe prunus, I've heard them in the distance six times or so,
the closest and most persistent being in Rivett last Saturday afternoon. I
suspect the reduced recording of at least the familiar call is because there
are enough females visiting now to make pairing much easier (as illustrated
by Geoffrey, Barbara and Matthew Frawley). Of course whether this leads to
more breeding success remains to be seen.
Jack Holland
-----Original Message-----
From: Michael and Janette Lenz
Sent: Friday, December 10, 2010 7:41 PM
To: David McDonald ; chat line
Subject: Impacts of rain on breeding success?
David,
Just a few comments and a bit of speculation, no science.
From my days in Germany it was evident that wet summers meant poor breeding
success in many species, notably the aerial feeders (swifts, swallows,
martins), and species with open cup nests. There are difficulties in finding
sufficient food (for the parents, let alone the young) and keeping the nest
content dry and warm. Prolonged wet weather can be very energy-demanding
particularly when 're-fuelling' is difficult.
Here I have found the Pied Currawong to be quite sensitive to wet
conditions, with fewer young reaching fledgling stage than were in the nest
at the start (incl. finding dead young under the nest). This year I have not
seen many young P. Currawongs, and if so, at the most 2 young/pair. At the
recent December woodland survey at Mt Ainslie I saw only a few fledglings
from any species, and I assumed that the very wet weather has reduced
breeding success (but several species were still on nests, several of those
were most likely replacement brood attempts). Even the Dusky Woodswallows
(Jack Holland's nest workshop in Campbell Park in mid November showed them
as abundant), were no longer very evident. Also there are only few
indications of breeding success in the wider surroundings of my GBS site in
Lyneham, on Lyneham Ridge etc. incl. common species (e.g. Magpie, Red
Wattlebird) (a key exception so far are the Noisy Miners at the ANU; they
seem to be indestructible!).
Even species which may have "dry" nest sites, incl. many cavity nesters, may
still be experiencing difficulties in finding enough food (e.g. Dollarbird,
Rainbow Bee-eater and others) with consequences for their overall breeding
success.
I have also been wondering why Koels have only given brief, fleeting
appearances this year in some of the areas where they have been breeding
successfully in the past (e.g. Ainslie, Lyneham). Is this also weather
related? Perhaps a reflection of limited numbers of suitable host nests at
the right stage/time for dropping eggs in? With the mild winter/spring and
some early welcome rains, several species have started nesting earlier than
usual, this would have been followed by difficult conditions for follow-up
broods (e.g. Red Wattlebird, Magpie-lark, Noisy Friarbird, potential hosts)?
We also have to keep in mind that rainfall in different parts of Canberra
can vary greatly; hence conditions and circumstances are not uniform across
town. What may apply to some parts of our area, may not be relevant in
others.
Michael Lenz
--------------------------------------------------
From: "David McDonald" <>
Sent: Thursday, December 09, 2010 4:48 PM
To: "CanberraBirds" <>
Subject: Impacts of rain on breeding success?
Hi, I'm wondering what science tells us about the impacts of extended wet
periods, such as we are now experiencing, on bird breeding success, and
the mechanisms involved. Anyone out there on top of this topic?
Thanks - David
--
David McDonald
Canberra Ornithologists Group email lists manager
T: 02 6238 3706
M: 0416 231 890
E:
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