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SummaryIt has been found possible to identify plants and to estimate their relative proportions by volume in the stomachs of sheep and kangaroos (both the red and the grey species). The method involves grinding stomach contents to a fine powder and isolation of particles of a given size range by differential sieving.It is shown that kangaroos are reasonably sedentary so that comparison of the botanical composition of the stomach of free-roving kangaroos with those of sheep restricted to one area, is valid.The three species of herbivore, during the study period of 1 yr and under the conditions described, were found to have food preferences. These preferences were specific enough to justify the conclusion that the plants of the habitat and the three species of animals constitute an ecosystem.There is no evidence, pound for pound body weight, that kangaroos eat more than sheep.Large numbers of kangaroos could have a detrimental effect on wool production since they eat considerable quantities of dicotyledons which are rich in protein and which constitute about 50 % of the sheep's intake.Kangaroos, although ostensibly adapted for browsing, never ate mulga or berrigan. Sheep, however, browsed both these trees.

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This book lists the stomach contents of Australian songbirds collected by the CSIRO Wildlife and Ecology from 1963 to 1980.

In 8 periods between February 1967 and June 1968, covering a severe drought and subsequent rain, samples of 66 species of dicotyledons and 50 species of monocotyledons were collected from a large paddock in semiarid 'mulga-box' country in south-western Queensland. The mean N content of the dicotyledons ranged from 1.51 to 2.85 g/100 g DM, and that of the monocotyledons from 0.70 to 1.86 g/100 g DM.Stomach or faecal samples were analysed for plant parts. When known plant mixtures were given to 2 grey kangaroos (Macropus giganteus) and two sheep there was no species difference in the digestibility of the different plants or in the size distribution of faecal particles. Comparison of stomach and rectal samples from 5 shot kangaroos and 7 shot sheep showed quite good agreement. Samples of the faeces of sheep, grey kangaroo and a few red kangaroo (Megaleia rufa) were collected from the ground at the same intervals as the plant samples, dried and analysed for N and for plant parts. Detailed results are given. The grey kangaroos consistently ate more grasses than the sheep. The N content of sheep faeces was higher than that of kangaroo faeces, reflecting the higher protein intake of the sheep. The results confirm those of an earlier study (NAR 38, 1829) made in 1963–4 in a period of average rainfall. The authors conclude that competition between sheep and kangaroos is small.

A commonly used technique of herbivore diet analysis consists of grinding ingested material to homogenise the size of particles, extracting a sub-set of these by sieving, and then reconstructing the diet by counting the particles referable to various plant species. A set of experiments revealed that this technique is inaccurate because of variation between species in the number of particles produced per unit dry weight, in the proportion of these retained by the sieve, and in the proportion that could be identified. Thus the technique is badly flawed even without the added complication of differential digestibility, which in itself is shown to be considerable. Certain correction factors derived to cope with these effects are shown to be only partly successful.

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Crop contents of pigeons were studied near Griffith, NSW. For 740 crested pigeons (Ocyphaps lophotes) in pastoral country, food was 85.5% seeds, 13.5% green leaf and 0.7% insects and other animals, by volume. The most important were seeds of introduced weeds and pasture plants. In drought the pigeons survived mainly on seeds of the introduced weed Paterson's Curse (Echium lycopsis) and during high rainfall they fed mainly on the abundant herbage. On roadsides, during a 6-month period, spilled wheat was 46.9% of food and the rest was introduced weed seed.Common bronzewings (Phaps chalcoptera) ate mainly seeds, 98.8% of food; 79% of food was from cultivated plants and introduced weeds. The most important single source was waste wheat seed, but in late winter and spring, native seeds were important. Both species are secure for the present; further development of agriculture might favour the crested pigeon and affect adversely the bronzewing.