Seasonal use of savanna landscapes by the Gouldian finch, Erythrura gouldiae, in the Yinberrie Hills area, Northern Territory

2001 ◽  
Vol 28 (4) ◽  
pp. 445 ◽  
Author(s):  
P. L. Dostine ◽  
G. C. Johnson ◽  
D. C. Franklin ◽  
Y. Zhang ◽  
C. Hempel
Keyword(s):  
Full Range ◽  
Northern Territory ◽  
Dry Season ◽  
Perennial Grasses ◽  
Grass Species ◽  
Wet Season ◽  
Themeda Triandra ◽  
Annual Grasses ◽  
Gouldian Finch ◽  
Hills Area

The diet, attributes of feeding sites and patterns of seasonal movements of a population of the Gouldian finch, Erythrura gouldiae, were studied in the Yinberrie Hills area north of Katherine in the Northern Territory. In the dry season (April–November) Gouldian finches foraged mostly on burnt ground and fed on exposed seed of annual grasses, especially seed of spear-grass, Sorghum spp. In the wet season (December–March) Gouldian finches fed on seed of a sequence of perennial grass species, including Themeda triandra, Alloteropsis semialata, Chrysopogon fallax and Heteropogon triticeus. Gouldian finches undertake regular seasonal shifts in habitat, from breeding areas in hill woodland in the dry season to adjacent lowlands throughout much of the wet season, in response to seasonal changes in food availability. There is an annual pulse in abundance of fallen seed in the early dry season that is depleted to near zero levels by germination of annual grasses early in the wet season. Thereafter, finches depend on seed from other sources, principally ripe and ripening seed of perennial grasses. Observations over three successive wet seasons suggest that Gouldian finches track seed resources provided by seeding perennial grasses over an extensive area of lowland grassy woodland adjacent to the breeding area, favouring small patches of grassy woodland for brief periods until seed fall. There were subtle differences between years in the types of resources used. Management of Gouldian finch populations will entail protection and management of the full range of grassland habitats used throughout the annual cycle, and will require predictive knowledge of the causes of patterning of seed resources and probably an ability to exert control over the timing and extent of fires in fire-prone seasonal savanna landscapes.

Evaluation of management options for increasing the productivity of tropical savanna pastures. 3. Trees

1989 ◽  
Vol 29 (5) ◽  
pp. 631 ◽  
Author(s):  
WH Winter ◽  
JJ Mott ◽  
RW McLean
Keyword(s):  
Dry Season ◽  
Perennial Grasses ◽  
Fertility Level ◽  
Wet Season ◽  
Management Options ◽  
Themeda Triandra ◽  
Weight Losses ◽  
Nitrogen Concentrations ◽  
The Mean ◽  
Stocking Rates

The effect of killing trees upon the production and quality of native perennial grasses, Themeda triandra, Chrysopogon fallax, Sehima nervosum, and Sorghum plumosum, and oversown legumes from the genus Stylosanthes, was studied over 4 years at Katherine, in the semi-arid tropics of northwestern Australia. The pastures were either unfertilised or received low inputs of superphosphate, and for each fertility level were grazed at 3 stocking rates. At no time were legume yields affected by killing the trees but, in the first 3 years, the amount of grass was approximately twice as much when the trees were killed. During this period the mean grass yields declined 4-5 fold from about 2.2 t/ha. By the fourth year the advantage from tree killing upon grass yield was apparent only at the lowest stocking rates at each fertility level. Nitrogen concentrations of the grasses and legumes, with the exception of S. hamata, were increased 7 and 10% respectively above the mean annual values of 0.89 and 1.75% where the trees were killed, while the phosphorus and sulfur concentrations were not affected. Tree killing had no effect upon wet season liveweight gains during the last 2 years of the experiment. However, there were some benefits during the dry season when weight losses were lower for most treatments during the early dry season (June-September) and also lower for the lowest stocking rate treatment without fertiliser during the late dry season (October-November).

scholarly journals Causes of the decline of the Gouldian Finch Erythrura gouldiae

1996 ◽  
Vol 6 (1) ◽  
pp. 49-61 ◽  
Author(s):  
Sonia C. Tidemann
Keyword(s):  
Clutch Size ◽  
Nest Site ◽  
Northern Territory ◽  
Dry Season ◽  
Northern Australia ◽  
Wet Season ◽  
Breeding Sites ◽  
Low Intensity ◽  
Tree Hollows ◽  
Gouldian Finch

SummaryPopulations of Gouldian Finch Erythrura gouldiae, an estrildid endemic to northern Australia, declined markedly during the last two or three decades. A survey revealed the species in two areas of Northern Territory, with an estimated 2,000 individuals, including juveniles. Recaptures were low either because of mortality or dispersal. Gouldian Finches eat predominantly Sorghum spp. seeds, but consume other seeds before Sorghum ripens. Other finches declined as cattle increased. Gouldian Finches breed in tree hollows of predominantly two species of eucalypts that grow on rocky slopes. They require water within about 4 km of the nest site. There was no shortage of nesting hollows at the known breeding sites. Fires in the early to mid-dry season allow birds access to seed without damaging trees, but later fires can destroy trees with nest hollows and remove shade. Average clutch-size is 5.2. About 72% of eggs laid, and 63% of nests, fledged young. Pairs lay up to three clutches in a season (February-August), the length of which may depend on rainfall during the preceding wet season. Air-sac mite (Sternostoma tracheacolum), found in 62% of Gouldian Finches sampled, may be preventing the species recovering to former numbers. New colonies of Gouldian Finches should be identified, populations monitored, and habitat managed by effecting patchy burns by low-intensity fires early in the dry season.

Effects of moisture supply in the dry season and subsequent defoliation on persistence of the savanna grasses Themeda triandra, Heteropogon contortus and Panicum maximum

1992 ◽  
Vol 43 (2) ◽  
pp. 241 ◽  
Author(s):  
JJ Mott ◽  
MM Ludlow ◽  
JH Richards ◽  
AD Parsons
Keyword(s):  
Growing Season ◽  
Close Correlation ◽  
Dry Season ◽  
Carbon Gain ◽  
Panicum Maximum ◽  
Wet Season ◽  
Themeda Triandra ◽  
Heteropogon Contortus ◽  
Moisture Conditions ◽  
Sheath Material

The close correlation between grazing-induced mortality and major climatic patterns in Australian savannas, led us to the hypothesis that moisture conditions during the dry, non-growing season could affect sensitivity to grazing in the subsequent growing season. Using three widespread savanna species (Themeda triandra, Heteropogon contortus and Panicum maximum), this hypothesis was tested experimentally and the mechanisms controlling this response examined and quantified. In T. triandra drought during the dry season led to major mortality in defoliated plants in the next growing season. This mortality was caused by a synchrony of tillering at the commencement of the wet season, leaving few buds for replacement once parent tillers were killed by defoliation. T. triandra was also the most sensitive species to defoliation. This sensitivity was due to the poor ability of the plant to maintain positive carbon gain after defoliation. Several factors contributed to this poor ability, including: low total photosynthetic rate, low specific leaf area, and a large proportion of sheath material with poor photosynthetic capacity remaining after cutting. Both H. contortus and P. maximum growing under irrigated and fertilized conditions did not display any effects of previous moisture treatments when defoliated during the next wet season and were much less sensitive to defoliation than T. triandra.

Thinking honeyeater: nectar maps for the Northern Territory, Australia

2000 ◽  
Vol 6 (1) ◽  
pp. 61 ◽  
Author(s):  
John C. Z. Woinarski ◽  
Greg Connors ◽  
Don C. Franklin
Keyword(s):  
Northern Territory ◽  
Dry Season ◽  
Spatial And Temporal Variation ◽  
Wet Season ◽  
Nectar Production ◽  
The World ◽  
Eucalypt Forests ◽  
The Times ◽  
Species Specific ◽  
Nectar Availability

We create monthly maps of nectar availability for the 1.4 x 106 km2 jurisdiction of the Northern Territory, Australia. These are based on a combination of vegetation mapping and a series of indices of plant species specific nectar scoring. The maps reveal complex spatial and temporal variation in nectar availability, but most notably a greater nectar resource in the monsoon-influenced north than in the arid south, and a peak in nectar availability in the dry season. The latter is associated with the extensive tropical eucalypt forests (especially those co-dominated by Eucalyptus miniata and E. tetrodonta). In contrast, wet season nectar availability in these forests is limited, but riparian and swampland forests, typically dominated by Melaleuca species, provide rich but spatially restricted nectar resources. The extensive and rich nectar resources available in eucalypt forests in the dry season supplement the diets of many species which are not primarily nectarivorous. This resource helps shape the singularity of northern Australian eucalypt forests relative to other extensive forests elsewhere in the world. Nectarivores remain in the system through a combination of movements across a number of scales, habitat shifting, and diet shifting. The latter is aided by the peaking of invertebrate and fruit resources at the times of minimum nectar production; a shuffling in resource availability brought about by the extreme climatic seasonality.

Diet determination of cattle grazing in the Sanyati communal areas in Zimbabwe

2006 ◽  
Vol 34 ◽  
pp. 35-40
Author(s):  
Hanne H. Hansen ◽  
Jørgen Madsen
Keyword(s):  
Plant Species ◽  
Cattle Grazing ◽  
Dry Season ◽  
Particle Identification ◽  
Grass Species ◽  
Wet Season ◽  
Communal Area ◽  
Communal Areas

SummaryThe diet of cattle grazing in the Sanyati communal area, Zimbabwe was determined using plant particle identification from faeces from intact animals, and faeces and oesophageal extrusa from fistulated animals. A total of 130 plant genus, species and types were identified. The twenty most frequently occurring species in the samples comprised between 76 and 90% of the identifiable diet. The most frequent grass species were more than half of the identified diet in the dry season while they were half or less of the identified diet in the wet season. There were more plant species identified in the wet season than in the dry season. Significant differences were found when comparing the plant species identified in faeces to those in oesophageal extrusa from fistulated animals. This may be due to incomplete recovery of ingesta in the bags, or to the loss of identifiable particles in the faeces when compared to oesophageal extrusa because of digestibility. More research is needed to validate the use of oesophageal extrusa for diet botanical determination.

Correlations between environmental factors, the biomass of exotic annual grasses and the frequency of native perennial grasses

2006 ◽  
Vol 54 (7) ◽  
pp. 655 ◽  
Author(s):  
Tanja I. Lenz ◽  
José M. Facelli
Keyword(s):  
Species Composition ◽  
Soil Fertility ◽  
Perennial Grass ◽  
Perennial Grasses ◽  
Annual Rainfall ◽  
Grass Species ◽  
Soil Factors ◽  
Annual Grasses ◽  
Exotic Annual Grasses ◽  
Native Perennial Grass

The species composition of temperate grasslands in the mid-north of South Australia has been radically altered from a system dominated by native perennial grasses to a system dominated by Mediterranean annual grasses. This study investigated the importance of chemical and physical soil characteristics, topographical features and climatic variables on the abundance of native and exotic grass species in nine ungrazed grasslands. Overall, climatic and other abiotic factors were highly variable. In addition, past management practices and original species composition are generally unknown, leading to further unexplained variation in the data. On a large spatial scale (among sites), the abundance of exotic annual grasses was positively correlated with mean annual rainfall, and on any scale, with finer soil textures and higher soil organic carbon levels. The most abundant annual grass, Avena barbata (Pott ex Link), was generally associated with soil factors denoting higher soil fertility. The abundance of native perennial grass species was not correlated with any environmental variables at any scale. The various native perennial grass species did not show clear associations with soil factors, although they tended to be associated with factors denoting lower soil fertility. However, at small spatial scales (within some sites) and among sites, the abundances of exotic annual and native perennial grasses were strongly negatively correlated. The results suggest that at the present time, rainfall and soil properties are important variables determining the abundance of annual grasses. The driving variables for the abundance of perennial grasses are less clear. They may be controlled by other factors or extreme rainfall events, which were not surveyed. In addition, they are likely to be controlled by competitive interactions with the annual grasses.

Distribution and Abundance of Ducks in the Alligator Rivers Region, Northern Territory

1990 ◽  
Vol 17 (6) ◽  
pp. 573 ◽  
Author(s):  
SR Morton ◽  
KG Brennan ◽  
MD Armstrong
Keyword(s):  
Northern Territory ◽  
Dry Season ◽  
Correction Factors ◽  
The South ◽  
Wet Season ◽  
Aerial Surveys ◽  
Black Duck

Aerial surveys between 1981 and 1984 were used to identify monthly trends in the abundance of wandering whistling-duck Dendrocygna arcuata, plumed whistling-duck D. eytoni, radjah shelduck Tadorna radjah, Pacific black duck Anas superciliosa, and grey teal A. gibberifrons on five floodplains of the Alligator Rivers region, 250 km east of Darwin in the monsoonal north of the Northern Territory. Ground surveys were conducted during the same period on one of the floodplains, the Magela plain, to provide more detailed information. The Magela floodplain was inhabited by few ducks during the wet season (November to March), but numbers then increased to dramatic peaks in the late dry season. The Nourlangie floodplain and Boggy Plain (a large backswamp of the South Alligator floodplain) showed similar patterns, but the numbers of ducks were usually fewer. Ducks were uncommon on the shallower East Alligator and Cooper floodplains except for relatively brief periods in the wet season. The ground surveys suggested that ducks sought out the persistent swamps that characterise the Magela floodplain in the dry season. Ground surveys also indicated that aerial surveys underestimated densities; on the basis of correction factors calculated from the ground surveys, peak numbers on the five floodplains were roughly estimated to be 400 000 wandering whistling-ducks, 70 000 plumed whistling-ducks, 20 000 radjah shelducks, 50 000 Pacific black ducks, and 50 000 grey teal. Pink-eared ducks Malacorhynchus membranaceus and hardhead Aythya australis were recorded sporadically in low numbers. The Alligator Rivers region acted as a dry season refuge for large concentrations of ducks because of the atypical persistence of freshwaters on the Magela and Nourlangie floodplains and some of the backswamps of the South Alligator, such as Boggy Plain. The large aggregations appear to be unique in Australia.

VECTOR AND HOST RELATIONS OF NORTH AMERICAN WHEAT STRIATE MOSAIC VIRUS

1963 ◽  
Vol 41 (8) ◽  
pp. 1171-1185 ◽  
Author(s):  
J. T. Slykhuis
Keyword(s):  
Mosaic Virus ◽  
Lolium Multiflorum ◽  
Perennial Grass ◽  
Perennial Grasses ◽  
Grass Species ◽  
Wheat Varieties ◽  
Wheat Seedlings ◽  
Annual Grasses ◽  
Chloris Gayana ◽  
Test Plants

Wheat striate mosaic virus from wheat in southeastern Saskatchewan was acquired and transmitted by both nymphs and adults of the leafhopper Endria inimica (Say) collected in Ontario. The preinfective period of leafhoppers varied from 4–6 to 22–24 days after they first fed on diseased plants. Records of serial transmission by individual insects varied greatly. Some insects infected most test plants on which they were given 2-day feeds during 20 to 30 days after the preinfective period, but subsequently they transmitted irregularly. Some transmitted virus for only a few days. Others transmitted intermittently for several weeks. None of the insects infected any plants on which they fed later than 72 days after feeding on diseased plants even though some lived another 10 to 20 days. Two of 25 insects became infective after feeds as short as 30 seconds on diseased plants, but the percentages of infective insects increased to more than 90% as acquisition access times were increased to 2 or more days. All insects from some inbred lines became infective after 3 days on diseased plants, but 45% of the descendants of one non-transmitting female failed to become infective. The inoculation threshold period on Ramsey wheat test plants was 15 minutes, but the percentage of test plants infected increased from 15% to 88.8% as the test access times were increased to 4 days. The incubation period of the virus in Ramsey wheat seedlings varied from 6 to more than 28 days.In tests of host reactions, all durum wheat varieties were highly susceptible to the virus. Several of the hard red spring and winter wheat varieties were highly susceptible and a few others were highly resistant or immune, but most were mildly to moderately susceptible. Most varieties of oats and barley and 10 species of wild annual grasses were moderately susceptible. Mild to moderate symptoms also developed on some of the plants in one or more varieties of Zea mays L., Lolium multiflorum Lam., L. perenne L., and Bromus inermis Leyss. Four varieties of rye tested did not develop symptoms, nor did any plants in 13 species of perennial grasses, including Chloris gayana Kunth, which is susceptible to the Australian wheat striate mosaic virus. E. inimica multiplied on wheat and 14 other annual and 21 perennial grass species, many of which are common on the prairies. There was considerable variation in the reactions to the virus of different plants in the variety Ramsey, but there were no inherent variations detected between the virus isolates used for the experiments. The wheat varieties Cappelle-Desprez and Rescue which are highly susceptible to the European type of wheat striate mosaic virus did not become infected with the Canadian isolates tested.Attempts to transmit the European type of wheat striate mosaic virus with E. inimica failed.

Fire, growth and survivorship in a Neotropical savanna grass Andropogon semiberbis in Venezuela

1989 ◽  
Vol 5 (4) ◽  
pp. 387-400 ◽  
Author(s):  
Juan F. Silva ◽  
Fernando Castro
Keyword(s):  
Seedling Growth ◽  
Canopy Structure ◽  
Structural Complexity ◽  
Dry Season ◽  
Root Competition ◽  
Annual Rainfall ◽  
Grass Species ◽  
Mortality Factors ◽  
Wet Season ◽  
Adult Plants

ABSTRACTThis study was conducted in a woodland savanna in western Venezuela exclosed from grazing and burnt once a year towards the end of the dry season. Mean annual rainfall is 1500 mm, with a strong seasonality.Two cohorts of seedlings of Andropogon semiberbis were tagged and monitored for up to three years. Several variables such as survivorship, plant size, seedling density, fire damage and distance to the nearest adult were measured or estimated. Two burning experiments to measure survivorship before and after fire, and two seedling-growth experiments to assess competitive interference from adult plants of three grass species were performed.The highest mortality takes place during the dry season and is due to fire. This decreases as the plants get bigger due to increasing structural complexity of the clump by growth which gives added protection to the meristems. Other mortality factors such as desiccation, uprooting and shading seem to be important during the wet season, when mortality rate is relatively constant. Survivorship during the first year and after three years is strongly correlated to the size attained by the end of the first growing season.Seedling densities are rather low and do not seem to play any role in survivorship in this population. Adult interference with seedling growth decreases with distance and seems to be due to root competition, although there is a tendency toward increased foliage interference related to the canopy structure of adult plants.

The effect of a phosphorus supplement on the performance of steers grazing Townsville stylo-based pasture in north Queensland

1977 ◽  
Vol 17 (86) ◽  
pp. 357 ◽  
Author(s):  
L Winks ◽  
FC Lamberth ◽  
PK O'Rourke
Keyword(s):  
Dry Season ◽  
Wet Season ◽  
Dry Tropics ◽  
Stylosanthes Humilis ◽  
Native Pasture ◽  
Weight Gains ◽  
Annual Grasses ◽  
Townsville Stylo

The effect of phosphorus supplementation on the performance of steeres grazing unfertilized native pasture and Townsville stylo (Stylosanthes humilis) with andwithout superphosphate fertilizer on the subcoastal spear grass region of the dry tropics of north Queensland was studied over a period of 40 months. Liveweight gains in the absence of supplementation on fertilized Townsville stylo pastures were greater than on unfertilized Townsville stylo, where performance was similar to that recorded on untreated native pasture. Phosphorus supplementation increased weight gains during the wet season on both unfertilized Townsville stylo and native pasture but had no significant effect on dry season performance or performance on fertilized Townsville stylo. Fertilized areas became dominated by annual grasses, Digitaria ciliaris and Brachiaria milliiformis, and legume yields were higher on unfertilized than on fertilized areas. Fertilizer improved the quality of available pastures.

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