Distribution and abundance of grebes, pelicans, darters, cormorants, rails and terns in the Alligator Rivers Region, Northern Territory

1993 ◽  
Vol 20 (2) ◽  
pp. 203 ◽  
Author(s):  
SR Morton ◽  
KG Brennan ◽  
MD Armstrong
Keyword(s):  
Northern Territory ◽  
Dry Season ◽  
Correction Factors ◽  
Phalacrocorax Carbo ◽  
Wet Season ◽  
Aerial Surveys ◽  
Fulica Atra ◽  
Chlidonias Hybrida ◽  
Great Cormorants ◽  
Porphyrio Porphyrio

Aerial surveys between 1981 and 1984 were used to identify monthly trends in the abundance of Australian pelicans (Pelecanus conspicillatus), darters (Anhinga melanogaster), little pied cormorants (Phalacrocorax melanoleucos), and whiskered terns (Chlidonias hybrida) on five floodplains of the Alligator Rivers region, 250 km east of Darwin in the monsoonal Northern Territory. Ground surveys were conducted during the same period on one of the floodplains, the Magela plain. The aerial surveys indicated that the Magela floodplain was inhabited by few of these birds during the wet season (November-March), but that numbers then increased substantially in the dry season. The Nourlangie floodplain showed similar patterns, but the numbers of birds tended to be lower. Birds were generally uncommon on the shallower East Alligator and Cooper floodplains. Ground surveys suggested that the birds 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 ground surveys, peak numbers on the five floodplains were roughly estimated to be about 2000 darters, 9000 little pied cormorants, 55 000 Australian pelicans and 50 000 whiskered terns. Little black cormorants (Phalacrocorax sulcirostrus) were sometimes abundant, but their sporadic occurrence prevented analysis of seasonal trends. Australasian grebes (Tachybaptus novaehollandiae), great cormorants (Phalacrocorax carbo), pied cormorants (Phalacrocorax varius), buff-banded rails (Rallus philippensis), Baillon's crakes (Porzana pusilla), white-browed crakes (Poliolimnas cinereus), purple swamphens (Porphyrio porphyrio), Eurasian coots (Fulica atra), silver gulls (Larus novaehollandiae), white-winged terns (Chlidonias leucoptera), gull-billed terns (Gelochelidon nilotica) and Caspian terns (Hydroprogne caspia) were recorded in low numbers. The Alligator Rivers region acted as an important dry season refuge because of the unusually persistent fresh waters of the Magela and Nourlangie floodplains and some of the backswamps of the South Alligator, such as Boggy Plain.

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.

Distribution and abundance of herons, egrets, ibises and spoonbills in the Alligator Rivers Region, Northern Territory

1993 ◽  
Vol 20 (1) ◽  
pp. 23 ◽  
Author(s):  
SR Morton ◽  
KG Brennan ◽  
MD Armstrong
Keyword(s):  
Northern Territory ◽  
Dry Season ◽  
Correction Factors ◽  
The South ◽  
Wet Season ◽  
Fresh Waters ◽  
Aerial Surveys ◽  
Sacred Ibis ◽  
Egretta Garzetta

Aerial surveys between 1981 and 1984 were used to identify monthly trends in the abundance of Pacific herons (Ardea pacifica), pied herons (Ardea picata), cattle egrets (Ardeola ibis), great egrets (Egretta alba), little egrets (Egretta garzetta), intermediate egrets (Egretta intermedia), glossy ibis (Plegadis falcinellus), sacred ibis (Threskiornis aethiopica), straw-necked ibis (Threskiornis spinicollis) and royal spoonbills (Platalea regia) on five floodplains of the Alligator Rivers region, 250 km east of Darwin in the monsoonal Northern Territory. Ground surveys were conducted during the same period on one of the floodplains, the Magela. The aerial surveys indicated that the Magela floodplain was inhabited by few of these birds during the wet season (November-March), but that numbers then increased substantially in the dry season. The Nourlangie floodplain and Boggy Plain (a large backswamp of the South Alligator floodplain) showed similar patterns, but the numbers of birds tended to be lower. Birds were generally uncommon on the shallower East Alligator and Cooper floodplains, except for egrets in the wet season. Ground surveys suggested that the birds sought out the persistent swamps that characterise the Magela foodplain in the dry season. Ground surveys also indicated that aerial surveys underestimated densities. On the basis of correction factors calculated from ground surveys, peak numbers on the five floodplains were roughly estimated to be about 4000 pacific herons, 50 000 pied herons, 300 000 egrets (primarily intermediate egrets), 60 000 glossy ibis, 16 000 sacred ibis, 80 000 straw-necked ibis and 35 000 royal spoonbills. Great-billed herons (Ardea sumatrana), white-faced herons (Ardea novaehollandiae), striated herons (Butorides striata), rufous night herons (Nycticorax caledonicus), black bitterns (Dupetor flavicollis) and yellow-billed spoonbills (Platalea flavipes) were recorded sporadically in low numbers. The Alligator Rivers region acted as a dry-season refuge for herons, egrets, ibises and spoonbills because of the unusually persistent fresh waters of the Magela and Nourlangie floodplains and some of the backswamps of the South Alligator, such as Boggy Plain.

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.

Seasonal Distribution and Abundance of Dugongs in the Western-Gulf-of-Carpentaria

1989 ◽  
Vol 16 (2) ◽  
pp. 141 ◽  
Author(s):  
P Bayliss ◽  
WJ Freeland
Keyword(s):  
Relative Density ◽  
Relative Abundance ◽  
Coastal Waters ◽  
Seasonal Changes ◽  
Aboriginal People ◽  
Dry Season ◽  
Seasonal Distribution ◽  
Wet Season ◽  
Aerial Surveys ◽  
The 1960S

Aerial surveys of coastal waters (27 216 km2) in the western Gulf of Carpentaria during the dry season of 1984 and wet season of 1985 indicated no major seasonal changes in distribution and relative abundance of dugongs. Minimum population size in the dry season was estimated as 16 816 � 2946 (standard error), with a relative density of 0.62 k 0.11 km-2, and that for the wet season 16 846 + 3257, with a relative density of 0.62 � 0.12 km-2. The estimates exclude 5% of observations which could have been either dugongs or Irrawaddy dolphins, and were corrected for submerged dugongs and those missed on the surface. Dugongs were unevenly distributed over the study area, and neither mean group size nor proportion of calves varied between seasons. Dugong abundance was correlated with area of available seagrass. The catch rate of dugongs by Aboriginal people off Numbulwar decreased six-fold between the 1960s and 1985 (60 to 10 p.a.), possibly due to excessive hunting.

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.

Germination and establishment of the weeds Sida acuta and Pennisetum pedicellatum in the Northern Territory

1980 ◽  
Vol 20 (105) ◽  
pp. 463 ◽  
Author(s):  
JJ Mott
Keyword(s):  
Northern Territory ◽  
Dry Season ◽  
Dormant Seed ◽  
Weed Species ◽  
Wet Season ◽  
Perennial Weed ◽  
Hard Seed ◽  
Sida Acuta ◽  
Seed Fall ◽  
Almost All

Two serious weed species in the Northern Territory are Sida acuta, a perennial weed of improved pastures, and Pennisetum pedicellatum, an annual grass that infests grain sorghum crops. In P. pedicellatum the customary successive ploughing carried out to kill seedlings in the early wet season may not give satisfactory control of the weed, while with S. acuta there appears to be a long-term dormant seed pool which can give rise to new generations of seedlings, Investigation into the germination requirements of the 2 species showed that both are dormant at seed fall and require high alternating temperatures to remove an after-ripening requirement. In addition S. acuta needs a further period at high temperature to fracture its impermeable seed coat. Almost all P. pedicellatum seed is non-dormant at the end of the dry season, but that of S. acuta still retains 30% hard seed after one dry season. In the field P. pedicellatum germinated faster than S. acuta, with 80% of the total wet season germination occurring with the first rain. In S. acuta germination was spread over the first 2 months of the season. Ploughing immediately after the break of the wet season killed seedlings of P. pedicellatum, but could bury viable dormant seed. Once buried, this store of dormant seed could remain viable and germinate when disturbed at crop planting. At the end of the wet season no viable seed of P. pedicellatum remained in the soil, but there could be a considerable amount of hard S. acuta seed. The results suggest that control of P. pedicellatum could be best accomplished by the use of minimum tillage procedures, with little ground disturbance to bury the seed, while oversowing with a vigorous perennial pasture species such as calopo (Calopognium mucunoides) could lead to suppression of S. acuta.

Seasonal variations in the macroinvertebrate fauna of billabongs along Magela Creek, Northern Territory

1982 ◽  
Vol 33 (2) ◽  
pp. 329 ◽  
Author(s):  
R Marchant
Keyword(s):  
Seasonal Variations ◽  
Littoral Zone ◽  
Northern Territory ◽  
Dry Season ◽  
Wet Season ◽  
The Mean ◽  
Macroinvertebrate Fauna

The littoral zone of five permanent billabongs along Magela Creek was sampled monthly over 1 year for macroinvertebrates. In three shallow billabongs, greatest numbers of taxa (about 45) and of individuals (about 1000 individuals per minute) were caught in the late wet season and early dry season (April-July); by the end of the dry season (December) these values had decreased to about 18 taxa and about 200 individuals per minute. Fluctuations were not so marked in two deep (or channel) billabongs: rarely were there fewer than 30 taxa and 400 individuals per minute present, and maximal values were similar to those in the shallow billabongs. These changes appeared to be associated with the growth of macrophytes, which occurred during the wet season in all billabongs. There was little variation between billabongs in the mean composition of the fauna.

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.

Limnological survey of eight billabongs in the Magela Creek catchment, Northern Territory

1980 ◽  
Vol 31 (5) ◽  
pp. 611 ◽  
Author(s):  
BT Hart ◽  
RJ McGregor
Keyword(s):  
Dissolved Oxygen ◽  
Chlorophyll A ◽  
Bottom Water ◽  
Northern Territory ◽  
Dry Season ◽  
Wet Season ◽  
Sodium Potassium ◽  
Phosphate Nitrate ◽  
Bottom Waters ◽  
Limnological Survey

A 6-week survey of the physicochemical limnology of eight billabongs in the Magela Creek catchment of the Northern Territory was conducted between December 1977 and January 1978. This covered the important period corresponding to the end of the dry season and the commencement of the wet season. Each billabong was sampled approximately weekly. At the end of the dry season. the billabongs' waters had elevated conductivity and turbidity, and generally higher sodium, potassium. chloride, phosphate, nitrate and chlorophyll a concentrations. They were generally slightly acidic and. in some. the bottom water was anaerobic. With the commencement of the wet season. the billabongs were flushed and a significant improvement in water quality was noted. Temperature. dissolved oxygen and redox potential data were used to tentatively classify these billabongs as polymictic. Under certain circumstances mixing did not occur for several days. during which time the bottom waters became significantly depleted in dissolved oxygen. On the basis of limited nutrient and chlorophyll a data, the billabongs at the end of the dry season appear to be mesotrophic.

Intake of lick block supplements by cattle grazing native monsoonal tallgrass pastures in the Northern Territory.

1990 ◽  
Vol 12 (1) ◽  
pp. 7 ◽  
Author(s):  
AR Eggington ◽  
TH McCosker ◽  
CA Graham
Keyword(s):  
Northern Territory ◽  
Dry Season ◽  
Wet Season ◽  
Mineral Supplement ◽  
Protein Nitrogen ◽  
Lactating Cows ◽  
Native Pasture ◽  
Pure Salt ◽  
Dry Seasons ◽  
True Protein

Four supplementation treatments to investigate wet seasons responses were imposed on eight Brahman/Shorthom cross herds totalling 870 animals of all classes (cows and calves, bulls, heifers and steers). They grazed 12,300 ha of native pasture in the Darwin district of the Northern Territory. The treatments were: (i) control (no wet season supplement), (ii) Mineral (Ultraphos - supplementation with 13 minerals during the wet season), (iii) +Protein (Ultrapro-50 - the same 13 minerals plus non-protein nitrogen (WN) and true protein over the wet season), and (iv) Strategic (strategic use of salt, mineral and hTN supplements over the early wet, mid wet and late wet seasons respectively). All treatments received an hTN plus mineral supplement (Uramol) during the dry season. Supplement intakes by the herds were measured monthly for three years. Intake of Salt, Ultraphos and Ultrapro-50 supplements averaged 43, 124 and 149 g/animal/day respectively during the three wet seasons. Losses of the molasses-based block formulations due to rain were small (7%) during the wet season. However, up to one third of each pure salt block was eroded. Intake of Uramol during the three dry seasons averaged 182 g/animal/day across all herds. No urea toxicity problems were noticed over the three years of the supplement programme, despite high intakes during the dry season. All animals consumed some supplement. However, levels of supplement intake: (i) increased with the seasonal decrease in native pasture quality, (ii) decreased with an increase in proportion of paddock burnt, (iii) varied between animal classes, with lactating cows consuming 64% more supplement than non-lactating cows in two of the three years, and (iv) varied between individuals within classes. Individual intake varied widely (from 10 to 835 glanirnallday for lactating cows) with no significant correlation between individual intake and the pregnancy rate or average daily liveweight gain.

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