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Best-fit regression equations for estimating body-fat levels from morphological measurements of maned
ducks (Chenonetta jubata) were developed. The cube of [body weight/(sternum x tarsus x bill length)]
plus the square of skinfold thickness was the best predictor of body fat in females (r*2=0.81). The
cube of (body weight x skinfold thickness) was the best predictor in males (r*2=0.75). These regression
equations accurately estimated fat level in all seasons except females in winter, when estimated values
were significantly higher (paired t test, P<0.02) by 18% than actual levels. Body weight alone
predicted protein content well in males (r*2=0.81) and less well in females (r*2= 0.61). These equations
enable long-term and relatively cheap monitoring of body condition in trapped maned ducks.

Waterbirds at four northern tableland swamps were counted at monthly intervals. Populations were shown to vary.

Rainfall patterns and habits of individual species were postulated as the major factors causing this variation.

We derived 10 best fit regression equations for estimating body fat mass in maned duck carcasses.
Body fat can be estimated from abdominal fat mass (females, R*2=0.86; males, R*2=0.81), percentage
water (combined sexes, R2=0.83), and the Child-Marshall index (combined sexes, R*2=0.91). We
recommend that body fat be estimated by the Child-Marshall equation where carcasses can be dried,
and by abdominal fat equations otherwise.

Bag sizes of game ducks in New South Wales between 1977 and 1984 were compared with antecedent
annual rainfall in eastern Australia. Mean bag size is equivalent to 'catch-per-unit-effort', an index of
population abundance. Annual rainfall is an index of habitat availability for waterfowl. Bag sizes of
Pacific black duck and all game species combined were significantly (P<O.05) related to antecedent
rainfall. Rates of increase (computed from annual catch-per-unit-effort) of black duck, maned duck
and all species combined were significantly related to rainfall difference between the preceding 2 years.
This study indicates that prior rainfall is a useful predictor of duck numbers in New South Wales.

Body weights and fat levels of non-breeding maned ducks on the southern tablelands of New South
Wales and in the Australian Capital Territory were high during spring and summer, and low during
autumn and winter. During the non-breeding season, paired females were fatter than unpaired females
but fat levels of paired and unpaired males did not differ. Protein levels of females did not vary
significantly with season, but protein levels of males were lower in winter. Females undergoing rapid
follicle development before laying were fatter than non-breeding birds in the same months. Before
laying, females stored fat but not protein for egg production. They used 44% of their pre-laying fat
while laying, and a further 47% of the body fat present at the beginning of incubation was used
during it. Laying and incubating maned ducks, and ducks with young, were less fat than non-breeding
birds in the same months. Body condition of maned ducks was related to food availability, whether
breeding or not, to the stage of breeding, and in females to pair status.

The results of six annual surveys of waterfowl hunters in New South Wales by mail card are reported.
The aims of the survey were to ascertain reported distribution of hunting effort, size and composition of
hunters' bags, and state of hunter origin. Hunting effort and waterfowl harvests were highest in southern
inland New South Wales. Seasonal bag sizes varied between 15.8 and 27.2 ducks per hunter. Pacific black
duck, grey teal and maned duck made up 88.6% of hunters' bags. About half the hunters in New South
Wales originated from Victoria. Bag size and species composition, effect of reducing bag size on total harvest,
regional bias in hunting effort and harvest, and annual variation in licence sales are discussed.

Most food studies of Australian waterfowl have relied on gizzard analyses. This introduces bias because of differential digestion rates. Oesophageal and gizzard contents collected from feeding grey teal (Anas gibberifrons) and pink-eared duck (Malacorhynchus membranaceus) at 2 sites in south-western New South Wales were determined. Pink-eared duck ate 99.6% animal food (mainly chironomid larvae and ostracods); grey teal ate 74.2% animal food (mainly corixids and dipteran larvae) at one site but 63.9% plant food (mainly grass seeds) at the other. Both species contained higher proportions of animal material in their oesophagi than in their gizzards. Rank correlation analyses showed no significant relationships between oesophageal and gizzard contents in the 2 species in this study, nor in other Australian and overseas waterfowl reported in the literature. It is suggested that gizzard analysis has led to overestimation of the importance of seeds in the diet of Australian waterfowl and underestimation of the importance of invertebrates. It is recommended that future food habits studies of waterfowl use oesophageal contents from feeding birds, and results from previous gizzard studies be treated with caution.

'Monthly waterbird counts from February 1974 to June 1977 at six wetlands in the Richmond River valley in northern coastal New South Wales were analysed to investigate relationships between numbers of each species, and season and water variables. Black swan, Pacific black duck, purple swamphen, dusky moorhen, cattle egret, comb-crested jacana and sharp-tailed sandpiper were strongly influenced by season. Grey teal, straw-necked ibis, little black cormorant, Pacific heron and black-winged stilt numbers were related to Murray River discharge, an index of inland wetland availability in New South Wales, northern Victoria and parts of southern Queensland. Numbers of most waterbirds were highest on the coast from late summer to the end of winter. Their seasonal abundance patterns conform with the results of some previous studies but differ somewhat from others.

Duck hunters have been surveyed on the opening morning of duck seasons since 1972 at Lake Cowal
and Barrenbox Swamp in southern inland New South Wales. Mean numbers of ducks shot per hunter
on opening morning reflected the numbers of ducks at the sites two to three weeks previously. At
Barrenbox Swamp, but not at Lake Cowal, mean bag sizes were inversely related to recent local rainfall.
Mean bag sizes on opening morning at Lake Cowal and Barrenbox Swamp did not diminish following
reduction of the opening-day bag limit from 20 to 10 ducks per day in 1988. Generally, numbers of
ducks and mean bag sizes at Lake Cowal and Barrenbox Swamp have not declined or increased since
1972 (exceptions are increased numbers but decreased bag sizes of Pacific black duck at Barrenbox
Swamp, and increased bag sizes of maned duck at Lake Cowal). At neither hunting site were numbers
of ducks related to mean bag sizes in the previous year. In summary, hunting does not appear to
be adversely affecting numbers of major species of game ducks at either Lake Cowal or Barrenbox
Swamp.

Populations of waterfowl of three game species, the Pacific black duck Anus superciliosa, grey teal
A. gibberifrons, and maned duck Chenonetta jubata, were assessed by aerial survey in October 1983
within a survey region of 2 697 000 km2 of eastern Australia. The numbers of each species were
assessed on all surface waters of over 1 ha, and on a sample of smaller surface waters within 10 survey
bands each 30 km wide and spaced at intervals of 2� latitude from 20�30' to 38�30'S. The area within
the survey bands was 324 120 km2, which gave a sampling intensity of 12.0% of the land surface area.
The area of features shown as wetlands or water impoundments within the survey bands on 1 : 2 500 000
topographic maps was 19 200 km2 or 11.2% of the total area of these features in the survey region.
The area of surface waters surveyed was assessed at 465 300 ha. Assessments of populations of each species
were tallied for wetlands by grid cells of 6 min of 1� longitude along the survey bands (258-309 km2
depending on latitude). Distributions were then mapped, with log*10 indices of populations in each cell.
Distributions of the black duck and grey teal showed a pattern of intense aggregation in limited numbers
of cells, that of the maned duck was more evenly distributed. The major concentrations of the Pacific black
duck were recorded in northern New South Wales and the south-eastern, western, central eastern and
central coastal regions of Queensland; those of the grey teal were in south-western, western and northern
New South Wales and central-eastern Queensland; the maned duck was broadly distributed over inland
New South Wales with the exception of the far west, inland southern Queensland, and central northern
Victoria.

Mortality of maned duck and grey teal due to hunting at Barrenbox Swamp in New South Wales in 1982
was estimated from band returns. Birds were marked a short while before the open season commenced.
The mortality rates were 33.0% in maned duck and 10.9% in grey teal on opening morning, and 41.0%
and 14.3% for the season. The validity of the estimates is discussed. Barrenbox Swamp is a popular
hunting site and a permanent wetland. Hunting mortality at the level recorded for maned duck in this
study could be detrimental to waterfowl during droughts, when populations concentrate on such
permanent waters.