Добірка наукової літератури з теми "Stagonopleura guttata"

Biotic invasions are among the main drivers of ecosystem change and contribute to species declines. In the southern hemisphere, perennial native understorey plants have been largely outcompeted by fast-growing annual crop grasses and herbs. This significant compositional change has altered patterns of seed production. Granivores such as the diamond firetail (Stagonopleura guttata) are likely to be affected by such alterations. This species has been declining nationally since large-scale land-clearance prior to 1980. Focussed, species-specific research is required to identify the threats and their interactions that contribute to ongoing declines. This thesis examined an isolated meta-population in the Mount Lofty Ranges (MLR), South Australia, subsisting in heavily degraded grassy woodland dominated by exotic annual grasses. The hypothesis that changes in grass seed phenology associated with invasion by exotic annual species has resulted in seasonal food shortages was tested. An assessment of the seed resources available to ground-foragers in the southern MLR confirmed that introduced, annual species dominate the understorey. Total seed biomass was over seven times greater in spring (4.08 g m-2) than in autumn, when biomass was just 0.53 g m-2. High spring seed biomass was predominantly produced by annual grasses. The subsequent drop in biomass coincided with breaking autumn rains, implicating mass-germination as the cause. Variation in seed biomass was attributed to seasonal changes in the seed abundance of annual weedy grasses and forbs. Diet analyses found that S. guttata diets mirrored the abundance and diversity of seasonal resources. However, during winter, when grass seed biomass was scarce, S. guttata relied heavily on the seeds of the drooping sheoak (Allocasuarina verticillata). A mark-resight study determined that S. guttata populations were affected by seasonal resource fluctuations. Stagonopleura guttata encounters were strongly correlated with seed abundance and S. guttata densities reflected seed biomasses. To further explore the reason for low numbers of S. guttata in autumn and winter, an in-field food supplementation experiment was conducted. The food-supplemented population had significantly higher survival than the non-supplemented population, indicating that food is limiting for S. guttata. Juveniles were less efficient foragers than adults, highlighting their vulnerability during times of seed scarcity. However, food supplementation appeared to increase the proportion of juveniles that survived their first winter. The transition of independent fledglings from spring/summer breeding into young breeding adults is critical for recruitment and is likely to be hampered by winter food shortages. Overall densities of S. guttata in the southern MLR were 0.023–0.062 birds/ha, lower than the minimum viable population estimate of 0.069 birds/ha. As such, this meta-population is not sustainable at current densities. To improve the persistence of S. guttata, it is essential that the grassy woodlands of the region are managed to create consistent, year-round food resources, particularly during winter. This requires the restoration of perennial native grasses in the understorey that seed more consistently and over longer time periods than annuals. In addition, rehabilitation of A. verticillata, a key resource, will improve food availability during times of scarcity.
Thesis (Ph.D.) -- University of Adelaide, School of Biological Sciences, 2020

It is not surprising that Australian grassfinches are highly popular with ornithologists and aviculturists, for included among the species are one of the most beautiful of all birds – the Gouldian Finch Erythrura gouldiae – and one of the most familiar cagebirds – the Zebra Finch Taeniopygia guttata. Despite a scarcity in published works on finches, interest in the species is growing, leading to a dramatic advancement in our knowledge of many species. For example, we have gained new information from field observations carried out on little-known species, including the Blue-faced Parrot-Finch Erythrura trichroa and the Red-eared Firetail Stagonopleura oculata. Significant advances in taxonomic research, largely as a consequence of the development and refinement of biochemical analyses, often involving DNA-DNA hybridisation, have given us a new insight into relationships among species, with some unexpected alliances being determined. Additionally, dramatic changes have taken place in avicultural practices, and in virtually all countries aviculture has taken on a new professional approach, with the most notable results being increased productivity and success with a wider variety of species. After a lapse of almost half a century since publication of Klaus Immelmann’s eminent work on finches, based on extensive field studies, the time has come for a new examination of Australian grassfinches. In Grassfinches in Australia, Joseph Forshaw, Mark Shephard and Anthony Pridham have summarised our present knowledge of each species, and have given readers a visual appreciation of the birds in their natural habitats and in aviculture. The resulting combination of superb artwork and scientifically accurate text ensures that this volume will become the standard reference work on Australian grassfinches. In addition to enabling aviculturists to know more about these finches in the wild as a guide to their own husbandry techniques, detailed information on current management practices for all species in captivity is provided. The book also includes colour plates depicting some of the more common mutations held in Australian and overseas collections. 2013 Whitley Award Commendation for Illustrated Zoology.