Status, Habitat and Social Organisation of the Hooded Robin Melanodryas Cucullata in the New England Region of New South Wales
Total Page:16
File Type:pdf, Size:1020Kb
AUSTRALIAN 142 BIRD WATCHER AUSTRALIAN BIRD WATCHER 1997, 17, 142-155 Status, Habitat and Social Organisation of the Hooded Robin Melanodryas cucullata in the New England Region of New South Wales by LULU L. FITRP and HUGH A. FORD Department of Zoology, University of New England, Armidale, N.S.W. 2351 1(Present address: Laboratoire de Psychophysiologie et d'Ethologie, Universite'Paris X, 200, Avenue de la Re'publique, 92001 Nanterre Cedex, France) Summary Hooded Robins Me/anodryas cucul/ata inhabit woodland across most of Australia, including eucalypt woodland in New England. Although Hooded Robins are still found in this habitat, they are apparently declining in southern Australia and disappearing from a number of sites. In New England, they are sparsely distributed west of the Great Dividing Range and occur locally east of it. On the eastern fringe of their distribution, populations consist of one or a few pairs or groups, and at least four of these have disappeared in recent years. We found 19 groups (12 pairs, six trios and a single male) at 12 sites in spring 1991, typically in eucalypt woodland alongside cleared farmland. Home ranges through the year were from 8. 3 to 25.5 ha (mean 18 ha) and breeding territories were from 4.5 to 9.5 ha (mean 6 ha). The Robins extended their foraging ranges in autumn and winter, often into cleared land. Robins could not be found in 1996 at one site where they occurred in 1990 and 1991, indicating that the species' decline and contraction of range is continuing. The reasons for the species' apparent decline are unclear, but HAF intends to continue monitoring populations. Although such a widespread species cannot currently be regarded as threatened, the Hooded Robin is representative of many ground feeding insectivorous birds that are declining in eucalypt woodland. It is important that scientific studies of these species be carried out now to understand why they are declining and to suggest management that can arrest any further decline. Introduction Although Australian species of birds have survived better than mammals in the two centuries since European settlement (Morton 1990), there are indications that many species are in decline. This has led to dire predictions of a major loss of bird species from the more intensive agricultural and pastoral regions (Recher & Lim 1990, Robinson & Trailll996). Such declines and extinctions have already been described or predicted for the Western Australian Wheatbelt (Saunders 1989, Saunders & Hobbs 1989, Saunders & Curry 1990), the Mount Lofty Ranges in South Australia (Ford & Howe 1980, Paton et al. 1994), rural parts of Victoria (Robinson 1991) and the Northern Tablelands of New South Wales (Ford & Bell 1981, Barrett et al. 1994). Several observers have noted that woodland birds that feed and/or nest on the ground seem to be particularly at risk (Recher & Lim 1990, Robinson 1991, Garnett 1992, Paton et al. 1994). The reasons for this are unclear but may include: increased predation on adults, young, or nests by native and introduced predators; reduced food abundance due to habitat degradation by grazing livestock; and poor dispersal due to habitat fragmentation (Saunders 1989; Cale 1990, 1994; Recher & Lim 1990). Most attention has, understandably, been given to species that are currently threatened (e.g. Brouwer & Garnett 1990, Garnett 1992). However, conservationists are increasingly expressing concern for a second group of species that could become threatened next century. Recher & Lim (1990) and Robinson (1991, 1993), for instance, gave lists of species that have become locally rare in New South Wales and Victoria. Prudent research and management at this stage could arrest or even reverse VOL. 17 (3) SEPTEMBER 1997 Ecology of Hooded Robin in New England 143 the decline of these species, and would prove more successful and economical than waiting until the species are really in trouble in future decades (Ford et al. 1995, 1996a). The Hooded Robin Melanodryas cucullata, although widely distributed and apparently quite generalised in its habitat, is a good example of a species that is declining in woodlands and agricultural areas (Lord 1956; Brooker et al. 1978; Graham 1990; Recher & Lim 1990; Robinson 1991, 1993; Robinson & Traill 1996). It is a ground feeder (Gilmore 1985) and open nester (Beruldsen 1980, Boles 1988), making it vulnerable to predation on adults, young and eggs. The species has become extinct in the Kellerberrin district of the Wheatbelt in Western Australia (Saunders & Curry 1990) and is regarded as potentially threatened in Victoria (Bennett 1993). It has also been reported to have declined near Orange (Heron 1973) and Inverell (Baldwin 1975) in New South Wales, and in the Australian Capital Territory (Graham 1990, 1995). Indeed the Canberra Ornithologists Group has proposed that the Hooded Robin be declared a vulnerable species in the A.C. T. (B. Lindenmayer pers. comm.). In contrast, it is one of the most abundant and characteristic birds of Lancewood Acacia shirleyi woodlands in the Northern Territory (Woinarski & Fisher 1995a), a habitat largely unaffected by agriculture. Despite concerns about its declining status in southern Australia, the Hooded Robin has so far received only casual studies. Rogan (1964) found that two females may brood eggs in the same nest, and Bell (1984) demonstrated co-operative breeding, with non-breeding helpers. Graham (1990) described the habitat occupied by Hooded Robins and Sullivan (1993) the breeding behaviour, both in the A.C.T. The social organisation of several other Australian robins has been described in the non-breeding (Huddy 1979, Fleming 1980, Boles 1988, Robinson 1992) and breeding seasons (Marchant 1985, 1987; Robinson 1990, 1992). In this paper we describe the status, habitat and social organisation of Hooded Robins at a number of sites within 50 km of Armidale, in New England. In subsequent papers we shall describe the aggressive interactions among Hooded Robins and with other bird species, and the species' vocalisations, foraging behaviour and breeding biology. Study sites Hooded Robins were studied at three main study sites during 1991 and 1992 (Figure 1). Two were along the Armidale-Grafton Road: (i) Gara Crown Reserve, located in the middle catchment of the Gara River and including part of the 'Silverton' property, 15 km east of Armidale (30°32 'S , 151°47 'E); (ii) the properties 'Strathaven' and 'Brookside', spanning the Armidale-Grafton Road, with an adjoining travelling stock route (TSR), 10 km east of Armidale (30°33'S, 151 °46 'E) , and the third was in Torryburn Crown Reserve, a travelling stock route alongside the Yarrowyck to Kingstown road, 45 km west of Armidale (30°27'S, 151 °!6'E). An additional eight sites, within 50 km of Armidale (see Figure 1), were visited less frequently. Methods From April 1991 to April 1992, LLF noted the composition of groups during the breeding and non-breeding seasons. Groups of Hooded Robins were defined as those birds that were usually seen together over a period of time within one home range. The size of the group and the number of birds of each sex and age were recorded. Adult Hooded Robins are strongly sexually dimorphic, the male being black and white, the female greyish brown and white. Juvenile males are similar to females , though more mottled beneath. They progressively become dark grey and then gain the black plumage of the adult male. Even though most birds were not colour-banded, individual Hooded Robins could be followed on foot quite easily once found. Their locations were first noted by marking trees with surveyors' tape and then plotted onto a topographic map ( 1:25 000, published by the Central Mapping Authority of New South Wales). Home ranges were all areas that they used through the year, excluding occasional AUSTRALIAN 144 FITRI & FORD BIRD WATCHER Bundarra Kingstown Wollomombi "--..-..2.----+-;e- ·---+ Grafton + 2 4 L___..j Bendemeer 10 km Dividing Range Figure 1. Map of sites near Armidale where Hooded Robins were found in 1991-92. Lines are main roads. 1 Gara Crown Reserve; 2 'Strathaven'; 3 Millgrove Creek State Forest; 4 'Baguna'; 5 'Oakview' and 'Hillcrest'; 6 Booroolong Creek; 7 Church Gully and 'Tarraminda'; 8 Torryburn Crown Reserve; 9 Gwydir Park Crown Reserve; 10 Two Mile Creek; 11 Abington. + indicates sites where Hooded Robins formerly occurred but have apparently become extinct. Dotted line is Great Dividing Range. roaming far beyond their usual boundaries. When the breeding season started, pairs or groups of Hooded Robins defended their breeding territories, which were much smaller than their home ranges. Territories included all areas where aggressive interactions were recorded and the areas where breeding activity occurred. Home-range and breeding-territory sizes were calculated as the areas included within lines linking the outermost points (i .e. minimum polygon). Owing to the greater activity and especially aggression during breeding, the territories of most males were estimated more accurately than were home ranges. Attempts were made to capture and colour-band Robins at the three main sites, where more than one group occurred. It was difficult to mist-net Hooded Robins because of their small populations, large home ranges, and open habitat occupied. During the 1991 breeding season, four fledglings were colour-banded: two in Gwydir Park Crown Reserve and two in Church Gully. Three females, one adult male, and one subadult male were colour-banded at Gara in autumn 1992, and a single female bird was banded at Torryburn in spring 1992. Despite our attempts, no Hooded Robins were caught at 'Strathaven' . Each bird was banded with a numbered aluminium band supplied by the Australian Bird and Bat Banding Scheme and with two colour-bands. Tree and shrub density and ground cover were measured at ten points in each home range in each habitat (forest, woodland, open) at the three main sites.