University of Adelaide
Ecology and conservation of a nomad: A case study using the
Australian bustard
Summary | Landscape-scale
distribution and monitoring | Habitat use,
feeding and reproductive ecology | Exploded lek
mating system | Movements | Techniques for monitoring growth pulses |
Aboriginal knowledge and harvesting | Supervisors |
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Terms used on this page:
Nomadic: fauna that move in an
opportunistic ways across the landscape, usually in response to
factors such as rainfall, fire etc.
Dispersive: movements made following
breeding where large numbers of birds disperse from breeding
areas.
Irruptive: Describes an organism that
can demonstrate a sudden change in the density of its
population.
Off-reserve conservation:
Conservation activities that take place outside designated parks
and reserves.
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Australian bustard: large, conspicuous and with some interesting
mating habits
Photo: Mark Ziembicki
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A large proportion of birds in the monsoonal and arid grasslands
of Australia are characterised by dispersive, nomadic movements and
large population fluctuations in response to variable climatic
conditions. These characteristics, along with poor knowledge of the
movements of Australian birds, make monitoring their populations
complicated. Conservation and reserve design for such species are
also difficult since there is no guarantee that an area set aside
for conserving them will remain suitable through time.
This project aims to use a typical nomad, the Australian
bustard, to develop methodology that will help monitor the
distribution, movements and status of such highly mobile birds and
their habitats on landscape scales and thereby aid in off-reserve
conservation of highly mobile populations.
This broad scale approach is complemented by a detailed
investigation of the ecology of the species at selected sites in
northern Australia in relation to key threatening processes,
including altered fire regimes, grazing impacts, hunting and
habitat alteration due to woody weed infestation. Additionally,
documenting Aboriginal knowledge of the status, distribution and
ecology of the species and current harvest rates is an important
part of the project.
Bustards are particularly suitable to a study of responses by
birds to climatic variability on a landscape-scale because of their
conspicuousness (therefore they are readily identifiable by
landowners), large size (enabling radio and satellite tracking),
existing databases of bustard distribution, and their nomadic,
irruptive nature.
Furthermore, the species is representative of a suite of birds
that have undergone significant population declines in the northern
and arid grassland regions of Australia.
This component of the study aims to develop and assess
techniques for efficiently monitoring the growth pulse in arid and
monsoonal grasslands, with an emphasis on its use for detecting the
widely scattered, ephemeral and temporally variable habitat of
breeding bustards. Such areas can then be targeted for protection
and management at critical times in the bustard's life cycle.
Distributional data for bustards collated from numerous sources
will be related to mapped landscape features and remotely sensed
data that measure and compare growth pulses at particular sites and
over broad landscape and temporal scales.
Progress in 2002–3
Distributional data for bustards has been collected and includes
information from large scale mail surveys to remote pastoral and
other landholder properties in rangeland WA, SA, NT, Qld and
western NSW. Other sources of information have come from the Birds
Australia Atlas surveys, state and territory government agency
record schemes and museum records. Compilation of remote sensing
and mapping information is almost complete and final analyses are
due for completion by November 2003.
A detailed, site-specific investigation into the ecological
relationships between bustards and different fire regimes, land
uses and land productivity, especially as these relate to the
species feeding and reproductive ecology is under way at two sites
of varying rainfall; the Victoria River District and the
Douglas-Daly River regions. Assessment of habitat use, diet and
food resource availability in different habitats in relation to
fire history and grazing is an important part of this work.
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A couple of male bustards step out to impress
the females
Photos: Mark Ziembicki
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Bustards are unique among Australia's birds in that they exhibit
what is known as an exploded lek mating system. Leks are
aggregations of males that come together to display in specific
areas, which females in turn visit to find mates—sort of like
the local pub! The difference being that males are usually well
separated from each other and are more spectacularly dressed than
the ladies.
It's an exploded lek because males are usually well spaced
apart—from 100m up to a kilometre. Generally, among lekking
species it's the larger males, with more elaborate displays, that
are more successful in the mating game.
This has important implications for harvesting bustards, because
if bigger birds, (the larger, more successful males) are preferred
for harvest, then the breeding performance of the species as a
whole may suffer.
Just as we have our preferred watering holes so too bustards may
have preferred breeding or lekking sites. If this is the case then
those areas are of vital importance for protecting the species.
Accordingly, one aim of my research is to determine whether
individuals keep to preferred breeding and lekking sites over
time.
To perform their elaborate displays males prefer open areas of
good visibility so females can see them. For this reason, the birds
may benefit (to some extent) from grazing and periodic fires, which
open up country. Females may then preferentially seek nesting sites
within more sheltered, vegetated areas within the general area,
which they especially require when raising young, who are almost
immediately mobile. A variety of habitats in a breeding area may
therefore be an advantage to bustards.
Progress in 2002-3
Progress in the past year has focused on continuing the study of
the species ecology. Information has been collected on the diet and
habitat use of bustards and the seasonal variability in bustard
numbers at each site. Intensive field work during the following
breeding season commencing in September will focus on the breeding
biology of the species in addition to work already in progress on
other aspects of the bustard's ecology.
Local-scale movements and ranging behaviour are currently being
investigated using radiotelemetry and marking of individual
bustards using wing tags with particular emphasis on determining
responses to experimentally induced fires, delineating daily
activity and habitat use patterns and determining territory sizes,
particularly with regard to configuration and use of leks. A grant
through the Herman Slade Foundation was obtained in early 2003 to
facilitate satellite tracking of individual bustards in the arid
and monsoonal grasslands regions of northern Australia. This work
is due to commence in August and aims to identify large scale
movements and possible cues for so-called nomadic movements in
relation to primary productivity, rainfall, fire management,
grazing intensity and horticultural developments on
landscape-scales.
This component of the study aims to develop and assess
techniques for efficiently monitoring the growth pulse in arid and
monsoonal grasslands, with an emphasis on detecting the widely
scattered, ephemeral and temporally variable habitat of breeding
bustards.
Distributional data for bustards collated from numerous sources,
including bird atlases, government fauna record schemes, aerial
surveys and a large mail-out survey to remote properties, will be
related to remotely sensed data that measure and compare growth
pulses at particular sites and over broad landscape and temporal
scales.
Mapped features that may influence bustard habitat use in the
form of GIS layers and a digital elevation model (to account for
topographical preferences) will be incorporated into the analysis.
This information should allow for the development of a tool for
predicting and locating optimal habitat for bustards and thereby
aid in targeting specific areas for protection and management at
critical times in the bustard's life cycle.
Bustards are an important cultural and food resource to many
Aboriginal communities throughout central and northern Australia.
The decline of bustards in these regions, which has been partly
attributed to breakdown over controls of traditional hunting, is of
concern to many indigenous communities. Part of the project
therefore seeks to:
- determine whether such concerns are justifiable in the study
site regions,
- draw on the knowledge and perspectives of Aboriginal
communities regarding the status, distribution and ecology of the
species
- examine changes in bustard numbers in specific areas over time,
and to
- determine whether current harvest rates are sustainable
Progress in 2002–3
Communities and Aboriginal land care units are involved in the
project in the two main study regions. Work to date has focussed on
collecting information on the status, distribution, habitat use and
diet of bustards from knowledge of individuals and from collection
of stomach contents from birds harvested.
It is hoped that this research, by assessing the ecology and
habitat requirements of bustards, in conjunction with a
landscape-scale analysis of their distribution and movements, will
improve our knowledge of the conservation and management
requirements of the species, as well as our understanding of
ground-dwelling birds and other nomadic species and their habitats
in Australia's arid and monsoonal grasslands.
Dr John Woinarski, NT DIPE
Dr David Paton, Adelaide University
