Academic literature on the topic 'Noisy scrub-bird'

The Noisy Scrub-bird is a small, semi-flightless insectivore which forages in leaf litter and the lower stratum of dense vegetation. More widespread when discovered last century the species declined rapidly after European settlement of Westem Australia due to habitat clearing and large scale, uncontrolled wildfires. A small, remnant population survived in dense low forest and thickets on Mt Gardner at Two Peoples Bay. Exclusion of fire from scrub-bird habitat allowed the population at Two Peoples Bay to increase through natural breeding. Translocations to new sites, where successful, have provided more habitat for the scrub-bird resulting in seven sub-populations in the area between Oyster Harbour and Cheyne Beach east of Albany. Rapid increases in numbers have occurred in the Mt Manypeaks area in recent years. The whole population has now increased to 10.5 times its size at rediscovery. This paper reviews Noisy Scrub-bird conservation efforts during the 35 years since its rediscovery and focuses on recent progress, population trends, and the current status of the species. Successful conservation management has been based on research into the scrub-bird's biology and ecology and has involved habitat reservation and protection, fire management, population monitoring, and translocation. Scrub-bird conservation has also provided benefits for other threatened species.

SummaryAfter European settlement, the range of the Noisy Scrub-bird Atrichornis clamosus contracted and only the population at Two Peoples Bay survived. Management policy at Two Peoples Bay Nature Reserve has been one of wildfire prevention, which has created increased areas of suitable habitat for the species. Territories rose from 45 in 1970 to 189 in 1994. Habitat use was assessed by grouping the dominant vegetation associations in each territory in five categories, in descending order of suitability (assessed on breeding and feeding resources): low eucalypt forest, Agonis forest, tall thicket, low thicket and heath. Turnover rates in territory use gave the same habitat rankings. A range of values of Ne (effective population size) was calculated using assumptions about breeding potential of each habitat category. There may be insufficient habitat at Two Peoples Bay for the population to reach an Ne of 500. Successful translocation to Mt Manypeaks, and the establishment of three small populations by birds dispersing from Two Peoples Bay, suggest that an integrated regional population can develop with an Ne well in excess of 500. The management of areas with populations and the corridors linking them must include minimizing the incidence and extent of wildfires.

The noisy scrub-bird is endangered and confined to one natural population on Mount Gardner and several translocated populations east of Albany, Western Australia. Annual monitoring of the number of singing males at Mount Gardner since 1966 indicates a steady rise in numbers, peaking at 179 birds in 1994 followed by a less regular decline to 19 by 2017. The Lakes, an adjacent location, had a similar pattern of increase from the early 1970s then irregular decline from the mid-1980s. Broken stick regression models confirmed that both apparent patterns represented significant increase then decline in the number of singing males. Territory size estimates from 1994, 2005 and 2014 suggest an increase in size of territories over time but that pattern was not significant when only common territories were compared. Variance in bird numbers was not correlated with annual rainfall, which has broadly declined over the study period, or with number of rain days. We discuss five possible causes of decline: (1) inbreeding, (2) control of exotic predators and associated impact on non-target, natural predators, (3) resource/food availability (which may interact with rainfall), (4) removal of birds for introduction programs, and (5) the absence of wildfire and associated changes (senescence) in vegetation. None are compelling, single explanations for decline but their collective impact may be high. Survival of the noisy scrub-bird may be increasingly dependent on the introduced, managed populations of this species at Mount Manypeaks and on Bald Island.

The noisy scrub-bird Atrichornis clamosus at Two Peoples Bay was censused, the number of singing males being used as the population index. Incomplete data from 1962 to 1968 suggest that the number of males varied from 40 to 50 during this period. The first rigorous census found 45 males in 1970 and this number increased to 138 in 1983. The most likely reason for this increase is the absence of fire from the area since 1970. Since 1975 the population has expanded out of its headland stronghold to the south-west of Two Peoples Bay to form a subpopulation around Lake Gardner that is well separated from the headland population by roads, firebreaks and a strip of control burnt blocks. The growth of this subpopulation has added a further safeguard to the population. Observations on the vegetation formations (heath, thicket, low forest A and low forest B) used by male noisy scrub-birds on the headland indicate that most of the best habitat (low forest B) is occupied and that an increasing number of males are occupying suboptimal habitat (heath and thicket). There is sufficiently good habitat to the west of Lake Gardner to allow at least 30 additional males to live in the area.

The Endangered Noisy Scrub-bird is a small passerine that is seldom seen but often heard in its range on the south coast of Western Australia. The difficulties in observing this cryptic bird mean that little is known about its social system. The loud, conspicuous territorial song of the male provides a convenient, non-intrusive means by which to study this species. The aim of this project was to investigate the patterns of song sharing and repertoire change in the Noisy Scrub-bird to provide indications of the social structure. It was found that groups of up to ten territorial males shared the same set of about five song types. Song groups were discrete, with members of a song group sharing most, if not all, of their song types. Males from different song groups had no song types in common. Repertoire change was rapid and, with the exception of one individual, was found in every territorial male studied in the Mt Gardner population. It occurred simultaneously in all members of a song group, with males making the same changes to their shared songs. The source of repertoire change was mainly modification of existing song types with occasional divergence of a single song type into two distinct song types, as well as some innovation providing new song types. The average life of a song type was approximately 6 months. Although some song types persisted for the entire 16 month sampling period, they were continually modified and a year later could no longer be recognised as the same type. Translocation of eight male scrub-birds to the Porongurup National Park provided an opportunity to combine individuals that initially did not share any songs. This allowed the process of song group formation to be studied. Within a one to two month period these males altered their songs so that they shared with their new neighbours. There was some evidence that the songs of dominant males were copied. Observation of the population established on Bald Island by translocation confirmed that there were no appreciable long-term effects on the songs of translocated Noisy Scrub-birds. Song group size, repertoire size and levels of song sharing were very similar to those found in the Mt Gardner population. The striking feature of Noisy Scrub-bird song groupings was their discreteness and cohesiveness even in the presence of continual repertoire change. It is suggested that each song group consists of a dominant male whose songs are more attractive to females and/or effective in territory defence. This dominant male is surrounded by subordinate males that copy his effective songs. Repertoire change can be explained by the dominant male continually making changes to his songs, with the other males copying these changes to retain their mimicked effectiveness. Each song group may in fact represent a dispersed lek. The scenario suggested to explain Noisy Scrub-bird song groupings bears striking similarities to the hotshot hypothesis to explain lek formation whereby males cluster around a successful male. This study demonstrates the potential of using song to investigate aspects of the social system of a species which is otherwise very difficult to observe. Management of an Endangered species such as the Noisy Scrub-bird will always benefit from increased knowledge about their social system. For example, this study showed that taking males from different song groups for translocation probably has little impact on their success at the new site because of their ability to rapidly alter their songs to form new song groups. An additional benefit of regularly monitoring the songs of translocated males was that it allowed ongoing identification of individuals, even though their songs were continually changing.

The Endangered Noisy Scrub-bird is a small passerine that is seldom seen but often heard in its range on the south coast of Western Australia. The difficulties in observing this cryptic bird mean that little is known about its social system. The loud, conspicuous territorial song of the male provides a convenient, non-intrusive means by which to study this species. The aim of this project was to investigate the patterns of song sharing and repertoire change in the Noisy Scrub-bird to provide indications of the social structure. It was found that groups of up to ten territorial males shared the same set of about five song types. Song groups were discrete, with members of a song group sharing most, if not all, of their song types. Males from different song groups had no song types in common. Repertoire change was rapid and, with the exception of one individual, was found in every territorial male studied in the Mt Gardner population. It occurred simultaneously in all members of a song group, with males making the same changes to their shared songs. The source of repertoire change was mainly modification of existing song types with occasional divergence of a single song type into two distinct song types, as well as some innovation providing new song types. The average life of a song type was approximately 6 months. Although some song types persisted for the entire 16 month sampling period, they were continually modified and a year later could no longer be recognised as the same type. Translocation of eight male scrub-birds to the Porongurup National Park provided an opportunity to combine individuals that initially did not share any songs. This allowed the process of song group formation to be studied. Within a one to two month period these males altered their songs so that they shared with their new neighbours. There was some evidence that the songs of dominant males were copied. Observation of the population established on Bald Island by translocation confirmed that there were no appreciable long-term effects on the songs of translocated Noisy Scrub-birds. Song group size, repertoire size and levels of song sharing were very similar to those found in the Mt Gardner population. The striking feature of Noisy Scrub-bird song groupings was their discreteness and cohesiveness even in the presence of continual repertoire change. It is suggested that each song group consists of a dominant male whose songs are more attractive to females and/or effective in territory defence. This dominant male is surrounded by subordinate males that copy his effective songs. Repertoire change can be explained by the dominant male continually making changes to his songs, with the other males copying these changes to retain their mimicked effectiveness. Each song group may in fact represent a dispersed lek. The scenario suggested to explain Noisy Scrub-bird song groupings bears striking similarities to the hotshot hypothesis to explain lek formation whereby males cluster around a successful male. This study demonstrates the potential of using song to investigate aspects of the social system of a species which is otherwise very difficult to observe. Management of an Endangered species such as the Noisy Scrub-bird will always benefit from increased knowledge about their social system. For example, this study showed that taking males from different song groups for translocation probably has little impact on their success at the new site because of their ability to rapidly alter their songs to form new song groups. An additional benefit of regularly monitoring the songs of translocated males was that it allowed ongoing identification of individuals, even though their songs were continually changing.