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

Abstract

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.

Landscapes without boundaries: wildlife and their environments in northern Australia

“…The first is loosely drawn for a seed-eating bird, the Gouldian finch, at the Yinberrie Hills near Katherine, with resource availability grossly simplified, but based loosely on known patterns (Woinarski and Tidemann 1991;Dostine et al 2001). For this example (Fig.…”

“…Gouldian finch (Erythrura gouldiae), water python (Liasis fuscus), dusky rat (Rattus colletti): Madsen and Shine 1996;Dostine et al 2001). …”

Effects of season, water and predation risk on patch use by birds on the African savannah

“…In tropical savannahs, grass seed abundance on ground surfaces varies seasonally, reaching its peak in the early dry season and gradually declining throughout the dry season, with minimum abundance at the beginning of the wet season (Dostine et al 2001). Later on in the wet season, birds may pluck mature seeds from standing grass stalks (Dostine et al 2001).…”

“…Later on in the wet season, birds may pluck mature seeds from standing grass stalks (Dostine et al 2001). We carried out field studies throughout the year and classified our study periods into four seasons according to food and water availability ( Table 1).…”

“…The period between the end of May and the end of June (early wet season) coincides with the first few rain showers, although temperatures are still generally high. During this period, most grass seeds that have dropped to the ground during the dry season start to germinate (Crowley and Garnett 1999;Dostine et al 2001) and thus become unavailable for the birds. In our study site, grasses started to set seed towards the end of June and only began to mature some weeks later (own observations).…”