Birds of woodlands and grasslands
Current or emerging issues paper
Penny Olsen, Andrew Silcocks, Michael Weston and Chris Tzaros - Birds Australia
prepared for the 2006 Australian State of the Environment Committee, 2006
This document was commissioned for the 2006 Australian State of the Environment Committee. This and other commissioned documents support the Committee's Report but are not part of it.
Olsen P, Silcocks A, Weston M and Tzaros C 2006 'Birds of woodlands and grasslands' paper for the 2006 Australian State of the Environment Committee, Department of Environment and Heritage, Canberra.
Woodlands and grassland cloak about three-quarters of the Australian continent, so it is hardly surprising that they provide habitat for the majority of Australian land bird species. These habitats, especially temperate and tropical woodlands and grasslands, also provide much of the country's agricultural land, which has greatly modified them. About one-third of the major woodland type, eucalypt woodlands, and 80 per cent of temperate woodlands have been cleared (McIntyre et al 2002, Lindenmayer et al 2005). Much of the remainder is thinned, degraded and deteriorating, and often in poorer country—steep, rocky, wet or with less fertile soils. Little grassland has been formally cleared, but ploughing, grazing, introduced pastures and weeds, changed burning regimes, and other disturbances have caused major, widespread change (NLWRA 2002a).
For at least a decade there has been growing recognition that birds of temperate woodlands are among the most threatened in the country (Saunders & Ingram 1995, Robinson & Traill 1996, Reid 1999). Concern has also been raised for the birds of northern savanna woodlands (Woinarski 1993).
Birds Australia has conducted two nationwide Atlases (1977–1981 and 1998 onwards), during which thousands of volunteers monitored birds (Barrett et al 2003). Comparing Atlases, there was a general trend towards increase in reporting rate during the second Atlas, apparently associated with wetter conditions (Table 1). About half of the species monitored showed no change between Atlases, one-third increased and 15 per cent decreased. Overall, woodland birds mirrored this trend, with 13 per cent of species decreasing nationally.
|Habitat/feeding niche2||No. of species3||Decrease||No change||Increase|
|All grassland species||71||37%||38%||25%|
|All woodland species||196||13%||38%||48%|
|Grassland ground feeders||59||36%||36%||29%|
|Woodland ground feeders||71||24%||41%||35%|
|All ground feeders||130||29%||38%||32%|
|Grassland non-ground feeders||8||12.5%||75%||12.5%|
|Woodland non-ground feeders||95||4%||35%||61%|
|All non-ground feeders||103||5%||38%||57%|
1 Reporting rate is an estimate of abundance—in this case statistically adjusted for variation in survey effort and seasonal effects (see Barrett et al 2003 for methodology)
2 Categorised according to Silcocks et al (2005). Some species were classed as both woodland and grassland species, and the feeding categories exclude species that feed both on and off the ground, hence the totals may differ.
3 Species for which sufficient data were available for robust analysis.
However, when woodland birds are categorised according to their main feeding niche, it is apparent that ground feeders fared worse than non-ground feeders: 24 per cent of ground feeders declined between Atlases. This group has previously been identified as at risk because of loss of understorey and general habitat complexity, due to overgrazing, inappropriate fire regimes, weed invasion, clearing and firewood removal (e.g., Woinarski 1993, Freudenberger 1999, Reid 1999).
Several woodland bird species, particularly the ground feeders, also use grasslands, and most grassland birds are ground feeders. How have grassland birds fared? Over one-third of grassland species declined nationally between Atlases, despite the generally better climatic conditions (Table 1).
These decreasing woodland and grassland ground feeders occur mainly in the agricultural areas of the south-west and south-east, and in pastoral country of Cape York and the Top End, particularly in the Top End and south-west wheatbelt (Figure 1). Although it appears that bird diversity has not changed in some long-cleared south-eastern regions, the expectation is that they would have increased due to the wetter conditions.
Figure 1. Change in species richness in each IBRA region between two five-year Atlas periods, 1977–1981 and 1999–2004: woodland non-ground feeders (a) and grassland species (b). Large decrease in number of species = >-10%; small decrease = -10% to -3 %; no change = -3% to 3%; small increase = 3% to 10%; large increase = >10%.
Trends in the last eight years suggest that at least some ground feeders are continuing to decline (Figure 2). Two individual examples show clearly that regions of greatest change are the agricultural areas of the south-east, south-west and northern Australia (Figure 3).
Figure 2. Change in annual reporting rate, an estimate of abundance, based on repeated surveys in 2 ha plots (reporting rate = no. records/no. surveys): ground feeders and non-ground feeders. The White-fronted Chat is a grassland species, Jacky Winter, Crested Shrike-tit and Dusky Woodswallow typically occur in woodlands, and Zebra Finch and White-throated Needletail use both habitats. All these species showed significant decreases in reporting rate between Atlases (Barrett et al 2003).
Are these declines reflected in threatened species lists? Thirty-nine woodland and grassland taxa are listed as threatened nationally; six of those are extinct (Table 2). A nationwide, expert-reviewed assessment The Action Plan for Australian Birds (Garnett & Crowley 2000) identified eight additional taxa as threatened: the Victorian Pied Currawong as Critically Endangered, and the Tasmanian Owlet-Nightjar, Tiwi Island Hooded Robin, Cape York Star Finch, Flinders Ranges Chestnut-rumped Heathwren and King Island Green Rosella, Yellow Wattlebird, and Black Currawong as Vulnerable. It also identified a number of Near Threatened woodland and grassland birds; together these threatened and near-threatened species are concentrated in the agricultural-pastoral zone (Figure 4) and on offshore islands.
|Kangaroo Island Emu||Ex|
|King Island Emu||Ex|
|Emu (Tasmanian subspecies)||Ex|
|Cape Barren Goose (south-western subspecies)||V|
|Buff-banded Rail (Macquarie Island subspecies)||Ex|
|Partridge Pigeon (western subspecies)||V|
|Partridge Pigeon (eastern subspecies)||V|
|Squatter Pigeon (southern subspecies)||V|
|Red-tailed Black-Cockatoo (south-eastern subspecies)||E|
|Glossy Black-Cockatoo (Kangaroo Island subspecies)||E|
|Baudin's (Long-billed) Black-Cockatoo||V|
|Western Long-billed (Muir's) Corella||V|
|Regent Parrot (eastern subspecies)||V|
|Red-crowned Parakeet (Macquarie Island subspecies)||Ex|
|Masked Owl (Tiwi Island subspecies)||V|
|Masked Owl (northern subspecies)||V|
|Purple-crowned Fairy-wren (western subspecies)||V|
|Grey Grasswren (Bulloo subspecies)||V|
|Chestnut-rumped Heathwren (Mt Lofty Ranges subspecies)||E|
|Brown Thornbill (King Island subspecies)||E|
|Yellow Chat (Dawson subspecies)||CE|
|Spotted Quail-thrush (Mt Lofty Ranges subspecies)||CE|
|Crested Shrike-tit (northern subspecies)||V|
|Black-throated Finch (southern subspecies)||E|
|Star Finch (southern subspecies)||E|
This is a very poor record, and with intensification of agriculture and continued inadequate management for biodiversity, more species are likely to be lost. With the cessation of broadscale clearing by the end of 2006 the challenge will be to limit small scale removal, repair remnants and revegetate appropriately. If the diversity of birds is to be maintained in Australia, structural diversity must be restored to woodlands and grasslands by better management of grazing, fire and weeds. It is significant that where woodland is revegetated or allowed to regenerate, decreases in some species have been reversed at a local level (e.g., Lindenmayer 2003, Tzaros 2005). Woodlands and grasslands are high priorities for further addition to the protected areas system (NLWRA 2002b), but as the majority of these lands are privately owned, their management and the fate of their birds will depend on private landholders.
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