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1: Metapopulation types proposed by Harrison and Taylor (1997). Closed circles represent occupied habitat patches, open circles represent unoccupied habitat patches. Dashed circles represent the boundaries of local populations. Arrows represent dispersal. A: Classical model, B: Mainland-Island model, C: Patchy population, D: Mixed metapopulation combining types B and C.
Source publication
White-browed Babbler Pomatostomus superciliosus groups occupying linear strips of vegetation had breeding territories that were smaller in area and had longer linear dimensions than those occupying patches. A group's non-breeding home range was larger than its breeding territory. Groups occupying linear/patch home ranges expanded the linear extent...
Contexts in source publication
Context 1
... findings of this study indicate that the population of White-browed Babblers in the Kellerberrin landscape has a hierarchical structure (Fig 10.11). The basic unit of this system is the group, which in the Kellerberrin area represents a single breeding unit. ...
Context 2
... population of the White-browed Babbler in the Kellerberrin area was hierarchically structured with four levels of organisation: 1) group (basic breeding unit); 2) social neighbourhood; 3) local population; and 4) metapopulation ( Fig. 10.11). This population structure fits the broad definition of a metapopulation, in which a set of local populations are connected by a low level of dispersal (Hanski & Gilpin 1991). However, as with many empirical studies it does not reflect the definition of a metapopulation that has been used to generate most of Metapopulation Theory ...
Context 3
... reproductive success of individual babbler groups (group dynamics) was influenced primarily by differences in the shape and vegetation structure of habitat patches, which altered the level of nest predation and the survival of juveniles ( Fig. ...
Context 4
... pattern of male dispersal in White-browed Babblers was important to the reproductive success of groups by altering their group size ( Fig. 11.2). Male babblers tended to disperse from large to small groups (Chapter 9), because this increased their chances of obtaining a breeding position (Chapter 7). This pattern of male dispersal may have maintained larger groups, and so increased reproductive success, in habitat of lower reproductive quality. However, the process of male ...
Context 5
... the social dynamics and population structure of the White-browed Babbler in the Kellerberrin landscape. Parameters within the circle represent the social dynamics of babbler groups. Effects occurred in the direction of the arrows. dispersal directly through its effect on landscape connectivity and indirectly through its effect on group dynamics ( Fig. 11.2). The persistence of local populations of the White- browed Babbler was not assessed directly in this study. However, the size and shape of a local population are likely to be important to its persistence, because populations with more reproductive individuals are less likely to suffer from stochastic extinction (Caughley & Gunn 1996). ...
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Citations
... Larger babbler groups tend to occupy territories with intermediate (20–50%) woody cover and a mix of vegetation types and structure [42]. Similar relationships between habitat variables and group size and/or breeding success have also been found for other species of Australian babbler [43,44] . These inter-relationships among group size, breeding success and regional populations make group size a relevant metric for Grey-crowned Babbler conservation. ...
... The results suggest that widening existing roadside habitat through fencing buffers on the adjacent private land thus excluding livestock, together with additional replanting of native trees and shrubs is an effective way to increase babbler group size. As shown for other species of woodland fauna utilizing linear habitats in Australian woodlands [56], it is possible that habitat width may influence site selection by babblers because of the increased availability of habitat and food resources at the local scale and a reduced need to travel far from nests [43]. Yet restoration effectiveness also makes sense in the context of the species' preference for structurally-diverse, mature woodland habitat [38,47,57]. ...
... Habitat buffers containing active or passive restoration may also provide a complementary nesting resource as babblers tend to nest in large shrubs or small trees [57]. Thus, the effect of restoration works is likely related to improved breeding success at those sites [43], as the increases over 2008/09 suggest. However, these increases may also have been partly due to higher survival rates of group members, site fidelity and/or the immigration of individuals from other groups [31,42]. ...
Background:
Considerable resources are spent on habitat restoration across the globe to counter the impacts of habitat loss and degradation on wildlife populations. But, because of time and resourcing constraints on many conservation programs, the effectiveness of these habitat restoration programs in achieving their long-term goals of improving the population viability of particular wildlife species is rarely assessed and many restoration programs cannot demonstrate their effectiveness. Without such demonstration, and in particular demonstrating the causal relationships between habitat restoration actions and demographic responses of the target species, investments in restoration to achieve population outcomes are of uncertain value.
Approach:
Here, we describe an approach that builds on population data collected for a threatened Australian bird - the Grey-crowned Babbler Pomatostomus temporalis - to evaluate how effectively targeted habitat restoration work improves its viability. We built upon an extensive historical survey by conducting surveys 13 years later at 117 sites stratified by presence/absence of restoration works and by detection or not of birds in the first survey. Our performance metric was the number of individuals in a social group, which is both a measure of local abundance and directly related to breeding success. We employed an occupancy model to estimate the response of Grey-crowned Babbler social group size to the effects of time, restoration works, local habitat as measured by the density of large trees, and distance to the nearest other known group of babblers.
Results and implications:
Babbler group size decreased over the survey period at sites without restoration works, but restoration works were effective in stemming declines where they were done. Restoration was responsible for a difference of about one bird per group of 3-5 individuals; this is an important effect on the reproductive success of the social group. Effectiveness of restoration works targeted at the Grey-crowned Babbler was only demonstrable by sampling through time and including control sites without restoration works. This work demonstrates that while calls for better monitoring of restoration are valid, scope exists to recover a signal of effectiveness from opportunistic retrospective analyses.
... Breeding success is strongly associated with group size in chestnut-crowned babblers [73] and the number of male helpers in grey-crowned babblers [74], with greater helper retention likely to be associated with aridity in grey-crowned babblers [75]. Resource availability also appears to influence juvenile dispersal in chestnut-crowned babblers [76] and habitat configuration can influence the size and arrangement of breeding territories [77], [78]. Together these studies suggest complex interactions between environmental heterogeneity, social structure and dispersal that not only influence reproductive success in babblers, but lead to considerable variance in the degree of spatial and temporal connectivity between social groups. ...
... A sedentary, cooperative and sometimes plural breeder from southern Australia, it lives in social groups of up to 15 individuals [25] and defends breeding territories year-round [26]. Dispersal is female-biased, with males queuing to inherit the natal or neighbouring territory [27]. The presence of close relatives on the natal territory alters the potential for selection to occur [28] and may result in the over-representation of rare alleles within social groups [29]. ...
... The white-browed babbler, like its congeners, is a co-operatively breeding species that forms social groups and maintains discrete territories [26,27]. Cooperative breeding involves the presence of non-breeding helpers that delay dispersal and are often the offspring of the resident breeding pair. ...
Mitochondrial sequence data is often used to reconstruct the demographic history of Pleistocene populations in an effort to understand how species have responded to past climate change events. However, departures from neutral equilibrium conditions can confound evolutionary inference in species with structured populations or those that have experienced periods of population expansion or decline. Selection can affect patterns of mitochondrial DNA variation and variable mutation rates among mitochondrial genes can compromise inferences drawn from single markers. We investigated the contribution of these factors to patterns of mitochondrial variation and estimates of time to most recent common ancestor (TMRCA) for two clades in a co-operatively breeding avian species, the white-browed babbler Pomatostomus superciliosus. Both the protein-coding ND3 gene and hypervariable domain I control region sequences showed departures from neutral expectations within the superciliosus clade, and a two-fold difference in TMRCA estimates. Bayesian phylogenetic analysis provided evidence of departure from a strict clock model of molecular evolution in domain I, leading to an over-estimation of TMRCA for the superciliosus clade at this marker. Our results suggest mitochondrial studies that attempt to reconstruct Pleistocene demographic histories should rigorously evaluate data for departures from neutral equilibrium expectations, including variation in evolutionary rates across multiple markers. Failure to do so can lead to serious errors in the estimation of evolutionary parameters and subsequent demographic inferences concerning the role of climate as a driver of evolutionary change. These effects may be especially pronounced in species with complex social structures occupying heterogeneous environments. We propose that environmentally driven differences in social structure may explain observed differences in evolutionary rate of domain I sequences, resulting from longer than expected retention times for matriarchal lineages in the superciliosus clade.
... First, if corridors are to provide for gene flow by providing occupied habitat, then there may be costs to the populations involved, so a thorough weighing of the balance between benefits and costs is required. In particular, edge effects in narrow habitat strips may mean that population sinks may be created when corridors are occupied282930 . Such sinks could potentially decrease both the likelihood of dispersal between patches and the overall viability of the population, even though the corridor might appear to be a success because it is occupied . ...
Background: Habitat fragmentation and accompanying isolation effects are among the biggest threats to global biodiversity. The goal of restoring connectivity to offset these threats has gained even greater urgency under the looming spectre of climate change. While linear corridors have been the most commonly proposed solution to these issues, it has become increasingly recognised that structural connectivity exists in different forms with a variety of characteristics. We previously conducted a systematic review from 2008-2010 to collate and synthesise evidence regarding the relationship between these different types of structural connectivity and the actual movement of native Australian plants and animals (i.e., functional connectivity). Our previous review produced a number of management recommendations but also identified significant knowledge gaps. Given that empirical research into connectivity has become even more common since the original review and that it has been more than five years since the original literature searches, the time is ripe for an update of that review. Methods: We will update our previous systematic review by repeating a thorough search for both published and unpublished evidence on the effects of structural connectivity on animal and plant movement through heterogeneous landscapes. We will slightly broaden the scope of the original review by including data on semi-aquatic species as well as terrestrial ones. Studies will be included if they: 1) contain data on a terrestrial or semi-aquatic native Australian species; 2) have at least one study site that contains some form of structural connectivity between otherwise isolated patches of habitat; and 3) include data on movement of species through the connectivity or data that allow inference of movement (or the lack thereof). We will repeat the analyses carried out for the original review which used hierarchical linear modelling to assess the effects of numerous sources of heterogeneity (e.g., type of connectivity, width of connection, ecosystem type, taxonomic group, and many other characteristics of the species, habitat, and connectivity) on the amount of movement observed in a landscape. If increased sample sizes allow we will also carry out additional meta-analyses, which were not possible with the original dataset.
... In species that accumulate resources for egg production immediately before breeding, smaller females can accumulate resources faster, and replenish them sooner between breeding attempts (Downhower 1976). Such an explanation appears likely for babblers since they are multi-brooded (Brown et al. 1982; Cale 1999) and presumably accumulate resources for egg production immediately before each breeding attempt. Sexual size dimorphism in babblers also varies in extent among traits, which is common among birds (Szekely et al. 2007). ...
Sexual size dimorphism in birds is widely used by ornithologists to identify the sex of individuals using linear discriminant analysis of morphological measurements. The feasibility of using this approach for the sexually monochromatic Hall's Babbler Pomatostomus halli using 154 genetically-sexed individuals from a single population was investigated. In addition, geographic variation in size was examined using morphological measurements of museum specimens because this can reduce the accuracy of discriminant equations when applied to additional populations. Hall's Babbler exhibited clear sexual size dimorphism with males being 2-7 per cent larger than females in culmen, head-bill, wing, tail and tarsus lengths and body mass. The best performing discriminant equation, which used wing and head-bill lengths, correctly identifi ed the sex of 88 per cent of individuals. Geographic variation in body size of Hall's Babbler was not evident for any morphological trait; therefore, the accuracy of discriminant equations may be similar across populations. Like two of its congeners, sexual size dimorphism was proportionally greatest in culmen length. Such disproportionate dimorphism may be adaptive in reducing intersexual overlap in resource use, since babblers rely heavily on their bill to probe substrates. However, data on intersexual foraging differences in babblers are currently lacking to test this hypothesis.
... Among cooperative breeders, it is commonplace for one sex to disperse earlier, more frequently or further than the other. For example, in white-browed babblers (Pomatostomus superciliosus), sons are generally philopatric and, if they do disperse, travel no further than approximately one kilometre, whereas daughters disperse more frequently and travel greater distances (Cale 1999Cale , 2002). Grey-crowned babblers, however, show no obvious sex differences in dispersal: offspring of both sexes may remain on the natal territory for several years and there are no sex differences in the age structure of helpers (Blackmore & Heinsohn 2008). ...
... First, if corridors are to provide for gene flow by providing occupied habitat, then there may be costs to the populations involved, so a thorough weighing of the balance between benefits and costs is required. In particular, edge effects in narrow habitat strips may mean that population sinks may be created when corridors are occupied (Lynch et al. 1995; Cale 1999; Hess & Fischer 2001). Such sinks could potentially decrease both the likelihood of dispersal between patches and the overall viability of the population, even though the corridor might appear to be a success because it is occupied. ...
... Working in the central wheatbelt of Western Australia , Brooker and Lefroy (2004) used field data on species occurrence from previous studies (e.g. Storr, 1991; Brooker, 1997, 2002; Cale, 1999) and Australian national bird censuses (Bird Atlas I – Blakers et al., 1984 and Bird Atlas II – Barrett et al., 2003 ) to identify regional thresholds of fragmentation for 34 sedentary declining bird species. Using a hierarchical neighbourhood base model (see Brooker and Brooker, 2003; Cale, 2003) that they validated using existing data and new ground-truthing of previously unsurveyed areas, they developed statistical models to predict threshold amounts of habitat required for species occurrence and viability. ...
In the life and natural sciences, the concept of thresholds or points or zones of change from one state to another has been investigated since the late 18th century. Over the past three decades, ecologists and economists around the world have been examining the existence and use of ‘ecological thresholds’ in natural and modified systems, primarily as a conceptual basis for the development of tools to conserve and sustainably manage natural resources. In Australia, there has been a recent renewed interest in the definition and application of ecological thresholds in the conservation of threatened fauna and flora, modelling the impact of habitat loss, modification and fragmentation on terrestrial biota, management of pest plant and animal species, and development of natural resource management policies and plans. This paper reviews the threshold concept from an ecological perspective. It considers the definition, types and behaviour of this phenomenon. The theoretical and empirical evidence for their purported existence is reviewed and their potential utility in biodiversity conservation and natural resource management is discussed, along with key issues relating to their use.
... White-browed Babblers are medium-sized (37–50 g), predominantly insectivorous birds. The adults forage on the ground or under the bark of shrubs (Cale, 1994Cale, , 1999 ). They feed their young a wide range of invertebrates and occasionally small skinks (Cale, 1999). ...
... The adults forage on the ground or under the bark of shrubs (Cale, 1994Cale, , 1999 ). They feed their young a wide range of invertebrates and occasionally small skinks (Cale, 1999). There are no discernible differences in the plumage of male and female White-browed Babblers. ...
... There are no discernible differences in the plumage of male and female White-browed Babblers. However, the sexes do differ in size and can be reliably distinguished using the head-bill measurement (Rogers et al., 1986; Cale, 1999). The native vegetation within the Kellerberrin area is a diverse mosaic of communities including, heaths, shrublands, mallee and woodlands (McArthur, 1993). ...
White-browed Babblers Pomatostomus superciliosus lived in groups of up to 13 birds in the highly fragmented landscape of the WA wheatbelt. Contacts between these groups and sexual differences in dispersal behaviour interacted with the landscape mosaic at a number of spatial scales to produce a hierarchically structured population with four levels of organization: (1) groups, which were the basic breeding unit; (2) social neighbourhoods, where group interactions were frequent, and male dispersal and female post-natal and breeding dispersal occurred; (3) local population neighbourhoods, which contained social neighbourhoods between which female natal dispersal was frequent; and (4) metapopulations, which contained local population neighbourhoods between which dispersal was infrequent. The boundaries of these structural units, with the exception of the group, were not discrete and were influenced by the structure of the landscape they occupied.
... These size categories were given a weighting (i.e. small=1, medium=3, large=9) to represent the relationship between prey length and biomass (following Cale, 1999). Prey size was determined during playback of videotapes. ...
The rufous treecreeper (Climacteris rufa) has declined in abundance in the agricultural regions of southwestern Australia. The patterns of decline are well documented, but the processes that threaten population persistence are poorly understood. I compared the reproductive success and survival of the treecreeper between three sites in an unfragmented landscape and four remnant categories (large, small, grazed and ungrazed) in a fragmented, agricultural landscape. Nest success and annual productivity were significantly higher in the unfragmented landscape, but varied between sites and remnant categories within landscapes. Nest success was lowest in grazed remnants and annual productivity was positively associated with territory size in the fragmented landscape. Fledgling survival rates did not differ between landscapes, but there was a trend for juvenile survival rates to be higher in the unfragmented landscape. I used artificial nests to compare relative predation rates between landscapes, and provisioning rates and prey biomass brought to nestlings to assess differences in food availability. There were no landscape differences in predation rates, but provisioning rates to nestlings and total prey biomass were significantly lower in the fragmented landscape. Mean habitat quality was also lower in the fragmented landscape, although it differed between remnant categories. Reduced reproductive success, juvenile survival, food availability and habitat quality may threaten the viability of the rufous treecreeper population living in the fragmented landscape. Limiting the modification of remaining habitat (e.g. removing stock grazing) and improving habitat quality are required to assist in the conservation of this species.
... The White-browed Babbler Pomatostomus superciliosus is a co-operative breeder with an extensive distribution across southern Australia. In the central wheatbelt of Western Australia, a highly fragmented agricultural landscape, it lives in groups of 2 to 13 individuals, which support only one breeding pair (Cale 1999). These White-browed Babbler groups hold mutually exclusive territories during the breeding season, but during the non-breeding season have home ranges that frequently overlap (Cale 2002). ...
... In the same landscape, the quality of Whitebrowed Babbler home ranges for breeding was found to vary depending on their shape and the density of the foliage in the shrub layer (Cale 1999). Linear home ranges with low foliage density were considered the lowest habitat quality. ...
... Linear home ranges with low foliage density were considered the lowest habitat quality. Patch home ranges with low foliage density and linear home ranges with high foliage density were of similar quality, but were ranked 2 and 3 respectively, while patch home ranges with high foliage density were considered the highest quality for breeding (Cale 1999). Dispersal behaviour of White-browed Babblers in the central wheatbelt landscape indicated that this species was willing to cross relatively large gaps (at least 270 m) in the remnant vegetation (Brooker et al. 1999 ). ...
White-browed Babbler Pomatostomus superciliosus groups occupying linear strips of vegetation had breeding
territories that were smaller in area and had longer linear dimensions than those occupying patches. A group's nonbreeding home range was larger than its breeding territory. Groups occupying linear/patch home ranges expanded the linear extent and area of their home ranges more than those within other home range configurations.
Some groups moved during the non-breeding season and this was more likely to occur if the group occupied a
remnant with a low abundance of invertebrates during summer. Some groups that moved returned prior to the next
breeding season, but the majority were never seen again. New groups moved into the study sites and established in vacant home ranges. This suggests that those groups that left the study sites may have established new home ranges elsewhere. Breeding site fidelity was lower in groups that had failed in previous breeding attempts. Therefore, group movements were influenced by the feeding and breeding quality of the habitat. However, the configuration of the local population also influenced group movements with those groups on the edge of a local population being more likely to move than those in the interior.
New groups were formed by two processes; group dispersal, where groups generally filled a vacant home range,
and group budding, which involved the splitting of a large group. Group dispersal maintained group densities while
group budding increased the density of groups in a local populfliifli1 These two processes were common, producing localized fluctuations in the density of groups. Since babbler groups contain only one breeding pair, changes in group density represent changes in effective population size. Therefore, group dynamics may be important to the persistence of local populations of White-browed Babblers, especially in landscapes that have suffered from habitat loss and fragmentation.
