Leader: Dr Stephen Garnett, Queensland Environmental Protection Agency, Cairns

Project 2.2.1

Summary | Research results | Outputs | Future directions | 

Summary

This project examined the ecology of the gouldian finch and the partridge pigeon — granivorous birds of the savannas. These birds depend on an essential feature of savannas, the seed-producing annual and perennial grasses that also support grazing, one of the savannas' major production activities. The central aim of the project was to use the birds as a model to explore interactions between savanna wildlife and land use dependent on the health of the same resource, and so develop principles for land management capable of sustaining both natural and production systems.

This project is now complete and has shown that many granivorous birds have declined markedly in range and abundance. To understand the factors affecting their status requires an examination of fundamental processes in grassland dynamics, and how those dynamics change with different land-use intensity or with the application of management tools such as fire.

Research results

Since this research project began in 1996, a draft management program for the gouldian finch has been prepared and accepted by the Northern Territory Government. Geographic Information System (GIS) coverages of relevant habitat features at Yinberrie Hills is complete, and well advanced at Newry Station in the Northern Territory.

A methodology was established for data collection and analysis. Linkages to models of grassland dynamics were developed.

This project has important links to other TS-CRC projects, especially Fire and Savanna Landscapes . Logistical and cost-sharing links with that project include complementary purchases of satellite imagery for the provision of relevant fire histories, and collection of data on fire extent and intensity for ground-truthing satellite imagery. Interpretation of patterning of grassland resources are being assisted by the long-term analysis of vegetation response to fire being gathered in a variety of savanna types under that project.

In addition, the land condition studies underpinning the project Indicators of Landscape Health will provide data on density of perennial grasses in pastoral landscapes. These data will provide an additional perspective on the availability of favourable high-density patches in landscapes of different types and the effects of grazing on those patches.

Other work completed includes:

• A comprehensive, savanna-wide review of the conservation status of all species of birds that are substantially dependent on seeds for at least part of the year. An analysis of change in reporting rates through time showed that 29 per cent are now much less commonly encountered than previously, and that the total area of the savannas from which they were reported had also contracted.
• Ecological attributes were identified that are common to those birds that have clearly declined in range and abundance. Researchers examined behaviour such as where birds build nests, the size of clutches, feeding mode and diet, but found the only characteristic closely associated with decline was the habit of feeding on the ground.
• Description, at a range of spatial scales, of grassland and woody species patterning in sites used by gouldian finches for wet-season feeding. Preliminary results indicate that foraging areas support relatively higher densities of these plants than the wider landscape, often clumped into patches exceeding 50 metres wide.
• Field studies were completed of home range and features of habitat used by the partridge pigeon throughout the year.
• Completion of experimental field studies of depredation of artificial ground nests and observations of patterns of loss of genuine partridge pigeon nests. Observations and evidence of predators taking nests suggests that losses were primarily due to native predators and that disturbances associated with roads, tracks or firebreaks are unlikely to cause increased rates of nest failure.

A database was assembled of more than 60,000 historical and contemporary records of bird distributions. Associated outcomes include studies of biogeographic patterns at the national scale, confirming the existence of a distinct 'savanna' community of granivorous birds. The robust identification of those species that have undergone decline has facilitated the design of new projects that take advantage of the geographic variation in status. Collaborative studies with the Queensland Environmental Protection Agency will allow researchers to more rigorously explore changes implicated in loss of species. This should permit a robust identification of characteristics of 'healthy' savannas and the potential to develop corrective management responses.

Outputs

The project fed outputs into the Information Clearinghouse , the Graduate Diploma and Master of Tropical Environmental Management and modules of the extension project.

Future directions

The demonstration of a widespread decline of many savanna birds that feed on the ground provides a context for design and interpretation of other studies. Complementary work on the gouldian finch reveals three important patterns that may be related to this wider problem. The range of foraging options contracts in the wet season, the sites that attract the birds occupy a small proportion of the landscape, and important grass species are spatially clumped within those sites.

The project is therefore switching from description of savanna-wide patterns of granivore decline and studies of the natural history of declining species to an examination of the factors influencing distribution of critical resources. Work to date has erected a platform from which more detailed studies of grassland patterning and avifaunal responses can be launched, with the aim of identifying important patch types and developing management regimes that maintain their suitability for birds. This will be the ongoing future emphasis.