James Brazill-Boast

Nest-site utilisation and niche overlap in two sympatric, cavity-nesting finches

Abstract Determining the relative access of a species to critical limiting resources requires knowledge of the spectrum of their resource utilisation (niche space) and that of potential competitors, and the frequency distribution of resources in the environment. We used this theoretical framework to assess the relative access to nesting sites and the potential for interspecific competition between two sympatric cavity-nesting finches. Gouldian (Erythrura gouldiae) and Long-tailed (Poephila acuticauda) Finches are both estrildid finches with similar ecological requirements, gross morphology and geographical ranges. By measuring the characteristics of all tree-cavities in an area of breeding habitat, and identifying those used by each of the two species, we were able to quantify the relationship between total available variation and variation in use by Gouldian and Long-tailed Finches. Using a likelihood-based method, we found that Long-tailed Finches exhibited a broader niche than Gouldian Finches with respect to available variation, and that these niches overlapped. Using these data we estimated that the effective availability of suitable nesting sites for Long-tailed Finches was 38% greater than for Gouldian Finches. Their relatively specialised niche and overlap with a more generalist competitor has the potential to constrain reproduction for Gouldian Finches, and will have implications for the conservation of remaining populations of this endangered species.

Interference from long-tailed finches constrains reproduction in the endangered Gouldian finch

1. Interspecific interference competition for nest-sites among cavity-nesting birds can have important effects on reproductive fitness and the distribution of competing species. 2. We observed interference at nest-sites in free-living populations of the endangered Gouldian finch (Erythrura gouldiae) and sympatric long-tailed finch (Poephila acuticauda), and also experimentally tested the relative strength and effect of interference at nest-sites in captive populations. 3. Levels of competitive interference at nest-sites in the wild were high for Gouldian, but not long-tailed finches, and interference frequency was inversely related to Gouldian finch reproductive success. High levels of interference conferred reduced fledging success but did not affect offspring condition. 4. Captive experiments corroborated the field data, also demonstrating fitness costs of interspecific competition, and that long-tailed finches dominated resources under standardized conditions. 5. Such asymmetrical competition dynamics are likely to constrain reproduction in Gouldian finch populations, potentially affecting recruitment and hindering the recovery of remaining populations of this endangered species.

Morph-dependent resource acquisition and fitness in a polymorphic bird

Understanding genetic colour polymorphism has proved a major challenge, both in terms of the underlying genetic mechanisms and the evolutionarily forces maintaining such genetic variation. In this context, genetic differences in aggression or competitive-related traits may covary with the expression of alternative phenotypes, and affect the evolutionary stability and maintenance of colour polymorphisms. Genetic red and black head-colour morphs of the Gouldian finch (Erythrura gouldiae) co-occur in temporally and geographically stable frequencies in sympatric populations. Gouldian finches are obligate cavity-nesters with highly specific preferences for nest-site morphometry that directly affect reproductive success. Because intra- and interspecific competition for high quality nest-sites is prevalent, and fitness is directly related to nest-site quality, we investigated the relative access (and consequences for reproductive success) of alternative morphs to this critical limiting resource in the wild. Red males defended higher quality nest-sites, and overcame greater levels of nest-site competition against conspecifics and superior heterospecific competitors than black males. Red-headed males also produced more fledglings (especially with red-headed females) than black-headed males, independent of nest-site quality. Finally, the independent (positive) effect of nest-site quality on reproductive success was confirmed. Such competitive asymmetries are important to relative selection among coexisting morphs, and are likely to contribute to the maintenance of alternative sympatric colour-morphs in wild populations.

Selection of breeding habitat by the endangered Gouldian Finch (Erythrura gouldiae) at two spatial scales

Abstract The Gouldian Finch (Erythrura gouldiae) has experienced significant decline in population and the extent of its range over the past 40 years, which has generally been attributed to the availability of suitable foraging habitat. Less research, however, has investigated the suitability or availability of breeding habitat of the species. Gouldian Finches are obligate cavity nesters, and a recent study has shown that they select nest-sites non-randomly based on structural characteristics of the cavity. Here we investigated the relative effects of different environmental factors on the spatial distribution of Gouldian Finch nests at two different scales. At the broader, landscape scale (over∼60 km2), the strongest predictor of nesting density at a site was the abundance of suitable nest-sites. At the finer scale (∼1 km2), no single factor explained the variation in location of nest-sites. Gouldian Finches require areas of habitat characterised by high densities of suitable nest-sites (tree-cavities). Within these patches, individuals are potentially selecting nest-sites based on the morphometry of cavities rather than landscape features such as topography, vegetation or proximity to water. Our findings should be integrated with studies of feeding and habitat requirements in the non-breeding season, with the aim of constructing holistic and predictive habitat-suitability models for this endangered species.

Spending limited resources on de-extinction could lead to net biodiversity loss

There is contentious debate surrounding the merits of de-extinction as a biodiversity conservation tool. Here, we use extant analogues to predict conservation actions for potential de-extinction candidate species from New Zealand and the Australian state of New South Wales, and use a prioritization protocol to predict the impacts of reintroducing and maintaining populations of these species on conservation of extant threatened species. Even using the optimistic assumptions that resurrection of species is externally sponsored, and that actions for resurrected species can share costs with extant analogue species, public funding for conservation of resurrected species would lead to fewer extant species that could be conserved, suggesting net biodiversity loss. If full costs of establishment and maintenance for resurrected species populations were publicly funded, there could be substantial sacrifices in extant species conservation. If conservation of resurrected species populations could be fully externally sponsored, there could be benefits to extant threatened species. However, such benefits would be outweighed by opportunity costs, assuming such discretionary money could directly fund conservation of extant species. Potential sacrifices in conservation of extant species should be a crucial consideration in deciding whether to invest in de-extinction or focus our efforts on extant species.

Three molecular markers show no evidence of population genetic structure in the Gouldian finch (Erythrura gouldiae)

Assessment of genetic diversity and connectivity between regions can inform conservation managers about risk of inbreeding, potential for adaptation and where population boundaries lie. The Gouldian finch (Erythrura gouldiae) is a threatened species in northern Australia, occupying the savannah woodlands of the biogeographically complex monsoon tropics. We present the most comprehensive population genetic analysis of diversity and structure the Gouldian finch using 16 microsatellite markers, mitochondrial control region and 3,389 SNPs from genotyping-by-sequencing. Mitochondrial diversity is compared across three related, co-distributed finches with different conservation threat-statuses. There was no evidence of genetic differentiation across the western part of the range in any of the molecular markers, and haplotype diversity but not richness was lower than a common co-distributed species. Individuals within the panmictic population in the west may be highly dispersive within this wide area, and we urge caution when interpreting anecdotal observations of changes to the distribution and/or flock sizes of Gouldian finch populations as evidence of overall changes to the population size of this species.

The colour of paternity: extra-pair paternity in the wild Gouldian finch does not appear to be driven by genetic incompatibility between morphs.

In socially monogamous species, individuals can use extra‐pair paternity and offspring sex allocation as adaptive strategies to ameliorate costs of genetic incompatibility with their partner. Previous studies on domesticated Gouldian finches (Erythrura gouldiae) demonstrated a genetic incompatibility between head colour morphs, the effects of which are more severe in female offspring. Domesticated females use differential sex allocation, and extra‐pair paternity with males of compatible head colour, to reduce fitness costs associated with incompatibility in mixed‐morph pairings. However, laboratory studies are an oversimplification of the complex ecological factors experienced in the wild and may only reflect the biology of a domesticated species. This study aimed to examine the patterns of parentage and sex ratio bias with respect to colour pairing combinations in a wild population of the Gouldian finch. We utilized a novel PCR assay that allowed us to genotype the morph of offspring before the morph phenotype develops and to explore bias in morph paternity and selection at the nest. Contrary to previous findings in the laboratory, we found no effect of pairing combinations on patterns of extra‐pair paternity, offspring sex ratio or selection on morphs in nestlings. In the wild, the effect of morph incompatibility is likely much smaller, or absent, than was observed in the domesticated birds. Furthermore, the previously studied domesticated population is genetically differentiated from the wild population, consistent with the effects of domestication. It is possible that the domestication process fostered the emergence (or enhancement) of incompatibility between colour morphs previously demonstrated in the laboratory.

A large-scale application of project prioritization to threatened species investment by a government agency

In a global environment of increasing species extinctions and decreasing availability of funds with which to combat the causes of biodiversity loss, maximising the efficiency of conservation efforts is crucial. The only way to ensure maximum return on conservation investment is to incorporate the cost, benefit and likelihood of success of conservation actions into decision-making in a systematic and objective way. Here we report on the application of a Project Prioritization Protocol (PPP), first implemented by the New Zealand Government, to target and prioritize investment in threatened species in New South Wales, Australia, under the state’s new Saving our Species program. Detailed management prescriptions for 368 threatened species were developed via an expert elicitation process, and were then prioritized using quantitative data on benefit, likelihood of success and implementation cost, and a simple cost-efficiency equation. We discuss the outcomes that have been realized even in the early stages of the program; including the efficient development of planning resources made available to all potential threatened species investors and the demonstration of a transparent and objective approach to threatened species management that will significantly increase the probability of meeting an objective to secure the greatest number of threatened species from extinction.

Endangered species recovery: A resource allocation problem

Explicit articulation of values and objectives is critical Many nations have laws to identify and protect imperiled species and their ecosystems. In the United States, actions taken under the Endangered Species Act (ESA) have prevented many extinctions, but few listed species have recovered to the point where they can have the ESA protections removed (1, 2). One reason for this [among many (3)] is a shortfall in funding, raising a conundrum for agencies responsible for species recovery: Should resources be allocated toward species facing imminent extinction or species whose long-term survival can most benefit from investment? Some argue that the latter strategy is ethically unsound because it may abandon species with little hope of long-term recovery [for example, (4)], even when science suggests that the former strategy may miss opportunities to prevent species from ever experiencing the risk of imminent extinction (2). We suggest that framing recovery prioritization as a resource allocation problem provides a structure to facilitate constructive debate about such important questions. We discuss here the merits of an explicit resource allocation framework and introduce a prototype decision tool [(5); see supplementary materials for details] that we developed with the U.S. Fish and Wildlife Service (USFWS) to facilitate transparent and efficient recovery allocation decisions.

Genetic diversity through time and space: diversity and demographic history from natural history specimens and serially sampled contemporary populations of the threatened Gouldian finch (Erythrura gouldiae)

Declines in population size can compromise the viability of populations by reducing the effective population size (Ne), which may result in loss of genetic diversity and inbreeding. Temporal population genetic data can be a powerful tool for testing the presence and severity of reductions in Ne. The Gouldian finch (Erythrura gouldiae) is a flagship for conservation of Australian monsoonal savanna species. This species underwent severe population declines in the twentieth century due to land use changes associated with European colonization. Microsatellite and mitochondrial genetic data from Gouldian finch samples sourced from natural history collections prior to land use changes were compared with contemporary samples to estimate the severity of decline in effective population size and to detect changes in gene flow. These data show that Gouldian finch decline was not as severe as some sources suggest, and that population genetic connectivity has not changed following land use changes in the twentieth century. Multiple estimators of current Ne using genetic data from consecutive years suggest the Gouldian finch Ne is likely between a few hundred and a few thousand individuals, with some estimates within the range considered of conservation concern. This work has identified the need to genetically characterize populations in Queensland, and to understand critical demographic parameters (e.g. lifespan) in the Gouldian finch. Understanding these factors is vital to further improve genetic estimates of population size, key to the formation of appropriate conservation management of this species.