Daniel J. Rogers

Repertoire size, song sharing and type matching in the Rufous Bristlebird (Dasyornis broadbenti)

Abstract A strong pattern has emerged between sedentary behaviour and song sharing between territorial neighbours for avian species that possess song repertoires. This paper investigates song-repertoire size, and rates of song sharing and type matching, in the Rufous Bristlebird (Dasyornis broadbenti), a southern Australian species for which there is strong evidence for sedentary and territorial behaviour. For 12 focal individuals (6 male, 6 female), estimated mean repertoire size was 31 song types for male birds, and 14 song types for females, recorded at the start of the breeding season. While the female song was similar in structure to the final phase of the male song, there was no sharing of song types between the sexes. A high degree of song sharing was exhibited in both sexes, with males sharing an average of 65% of song types, and females sharing 59% of song types, with immediate territorial neighbours. These rates of song sharing between neighbours were significantly greater than rates of song sharing between non-neighbouring individuals, although common song types between non-neighbours were encountered. Furthermore, bristlebirds used these common song types significantly more often than song types that were unique to their repertoires. While male neighbours preferentially matched song types, there was no evidence for repertoire matching. The degree of song sharing in neighbouring Rufous Bristlebirds is therefore consistent with the observed relationship between sedentary behaviour and high levels of song sharing.

Acoustic identification of individual Rufous Bristlebirds, a threatened species with complex song repertoires

Abstract Rufous Bristlebirds (Dasyornis broadbenti), possess song repertoires of between 12 and 30 different song-types, only a proportion of which are shared between different individuals. As a result, the comparison of songs among individuals is complicated by the use of multiple song-types. Using both discriminant function analysis (DFA) and spectrographic cross-correlation analysis (SPCC), those song-types that were shared among individuals demonstrated high levels of vocal individuality. DFA correctly classified an average of 98.3 ± 1.2% of male songs, whereas SPCC correctly classified an average of 87.4 ± 2.8% of songs. However, common song features among song-types showed limited value for individual identification. The information provided by the SPCC analyses was then used to discriminate among individuals over a distance of 7.8 km, the results of which supported those of previous studies with regard to the sedentary nature of Bristlebirds. Although the results of the present study show promise, the issue of song comparisons among multiple song-types remains a significant challenge for the development of acoustic identification systems for this species.

The conservation status of the Rufous Bristlebird, Dasyornis broadbenti, in South Australia

Abstract Using a combination of field study, published records covering the period 1984–2003 and vegetation data, the extent of occurrence of Dasyornis broadbenti broadbenti was estimated at 620 km2 the area of occupancy at 205–245 km2. By mapping the location of calling birds the mean home range of paired adults in the Coorong National Park was estimated to be 2.3 ha. The total South Australian population was estimated to be at least 17800. Trapping and radio-tracking studies confirmed that paired adult Rufous Bristlebirds are sedentary, with individual adults being recaptured within 95 m of their initial capture location, over periods of up to 3 years. Immature birds dispersed distances of at least 740 m. The results confirm that the conservation status of this taxon is Least Concern. While this classification can now be accepted with greater confidence, some aspects of the ecology of D. b. broadbenti require further investigation, particularly with regard to population trends and degree of fragmentation.

Understanding ecosystem dynamics in South Australia’s arid lands: a framework to assist biodiversity conservation

Determining what level of investment is required, and where and how it is used, to maintain biodiversity across vast areas is difficult. In response to this challenge, the South Australian Department of Environment, Water and Natural Resources has developed an information framework known as the ‘Aridlands Landscape Assessment Framework’ (ALAF) to provide a systematic basis for identifying landscape-specific, coarse-filter priorities for conservation investment across the arid zone. The ALAF is an analytical and conceptual framework that seeks to define ecosystem components and ecological processes operating at a landscape level, and understand where these processes are not meeting the requirements of extant biodiversity. This requires a systematic process to identify plant communities that occur in distinct biophysical settings. The next step is to document the dynamic processes that drive change within these communities in space and time. When coupled with knowledge of the requirements of indicator flora and fauna, this understanding will allow identification of those components that are at greatest risk, where, and for what reasons. This paper provides an overview of each step in the ALAF process and outlines how the framework has been used thus far to inform conservation planning across Witjira National Park.