My
project involves studying the movement and survival of Star Finches on the
margins of the Parry Creek and King River floodplains in the Wyndham area.
In 2009, with the assistance of a grant from the WA Bander’s
Association, I colour-banded 706 juveniles, using three different colours
according capture-location. The
objectives were to investigate the juveniles’ mobility and how many survived
their first year.
Readers
may remember that, in my last report (Nov 2009), I referred to Star Finches as
being like sheep. Recce, put up a
mist-net and in they fly. Well,
the start of field work in February 2010 brought a sharp reality check – where
were the birds? It wasn’t a
matter of access – the poor wet season meant most sites were accessible- it
was about dispersal. When food and
water are available, Star Finches disperse widely. How widely I don’t know
yet, as I couldn’t find them!
The
poor Wet meant habitat dried rapidly, and by early March birds started to
re-appear. March banding efforts
led to some interesting discoveries: proof, via active brood patches because I
never found a nest, that some of last year’s juveniles were breeding, and that
a high proportion of females developed active brood patches in the same week –
the third week in March – which coincided with the ripening of their favourite
food – cane grass seed (Sorghum
stipoideum). This example of
synchronous breeding has been written up and will be published in the new Birds
Australia WA journal, Amytornis.
Between
March and September 55 banding sessions were held – usually involving one or
two nets in the vicinity of the 2009 banding sites. The aims were two-fold –
to recapture as many of last year’s juveniles as possible and to colour-band a
good-sized sample of this year’s juveniles, for checking on next year.
Finding two sites where large numbers of Star Finches (ie 100+) roosted
overnight was a surprising and useful development.
Surprising because both roosts were just patches of thick cane grass, not
obviously different from any other, and one was within 3 metres of the busy
Parry Creek Farm Road. And useful
because if I managed to creep up and erect my net without mishap in total dark
(at 4.30am), then before first light I could flush birds into it, because in the
dark they preferred to flutter through the grass rather than fly up. Too noisy, or an approach at the wrong angle, and
they fluttered in the wrong direction; too late and they flew up and away.
Too often? I didn’t like
to risk it! 4 catches on one roost
yielded 323 new birds, but only 19 retraps, implying perhaps that the original
birds left that roost and new ones took their place.
Then the whole area got burnt, as happens too often in the
Kimberley..............
No
problem with the second aim – the survival of 838 juveniles will be monitored
in 2011. No problem with the first
aim either, except how to interpret the result.
I managed to recapture 70 out of 703 of last year’s juveniles (3 were
known to have died in 2009). At a
minimum, I now know that one in ten juveniles survived.
Others were resighted out of their banding location (revealed by their
colour bands) but, as I also captured birds out of location its hard to know if
the birds sighted were the same or different ones.
But is this a good or bad rate of survival?
What does it tell me about the ongoing viability of that population of
birds? I now have a year to
work that out– all suggestions will be very gratefully received!
With
regard to the mobility of the population, lots of inter-site movements by adults
and juveniles within a restricted range (of up to 20kms) – linked, I believe
to the ripening of particular varieties of seed.
As waterholes dried up, also many movements into town to drink at the
sprinklers on the oval, the cemetery or at the crocodile park reservoir.
I’ve also spent many hours searching for colour-banded birds away from
the banding sites. Not
surprisingly, as water dries up, I’ve found birds banded on the margins of
Parrys floodplain moving to the remaining lagoons to drink.
But equidistant movements off the floodplains towards waterholes on more
wooded, slightly higher terrain do not seem to occur.
In
2011 the emphasis will be on evaluating the survival of 2010 juveniles and
confirming that, for most of the year, Star Finch are confined to floodplain
country. And, if I can find a
way to do it, making an estimate of the total Wyndham population.
If you think you can help, please get in touch!
Jan
Lewis
October
2010
