Dispersal patterns can dictate genetic population structure and, ultimately, population resilience, through maintaining gene flow and genetic diversity. However, geographical landforms, such as peninsulas, can impact dispersal patterns and thus be a barrier to gene flow. Here, we use 13 375 genome‐wide single‐nucleotide polymorphisms (SNPs) to evaluate genetic population structure and infer dispersal patterns of the Western Grasswren Amytornis textilis textilis (WGW, n = 140) in the Shark Bay region of Western Australia. We found high levels of genetic divergence between subpopulations on the mainland (Hamelin) and narrow peninsula (Peron). In addition, we found evidence of further genetic sub‐structuring within the Hamelin subpopulation, with individuals collected from the western and eastern regions of a conservation reserve forming separate genetic clusters. Spatial autocorrelation analysis within each subpopulation revealed significant local‐scale genetic structure up to 35 km at Hamelin and 20 km at Peron. In addition, there was evidence of male philopatry in both subpopulations. Our results suggest a narrow strip of land may be acting as a geographical barrier in the WGW, limiting dispersal between a peninsula and mainland subpopulation. In addition, heterogeneous habitat within Hamelin may be restricting dispersal at the local scale. Furthermore, there is evidence to suggest that the limited gene flow is asymmetrical, with directional dispersal occurring from the bounded peninsula subpopulation to the mainland. This study highlights the genetic structure existing within and between some of the few remaining WGW subpopulations, and shows a need to place equal importance on conservation efforts to maintain them in the future.

Vocal production learning (the capacity to learn to produce vocalizations) is a multidimensional trait that involves different learning mechanisms during different temporal and socioecological contexts. Key outstanding questions are whether vocal production learning begins during the embryonic stage and whether mothers play an active role in this through pupil-directed vocalization behaviors. We examined variation in vocal copy similarity (an indicator of learning) in eight species from the songbird family Maluridae, using comparative and experimental approaches. We found that (1) incubating females from all species vocalized inside the nest and produced call types including a signature "B element" that was structurally similar to their nestlings' begging call; (2) in a prenatal playback experiment using superb fairy wrens (Malurus cyaneus), embryos showed a stronger heart rate response to playbacks of the B element than to another call element (A); and (3) mothers that produced slower calls had offspring with greater similarity between their begging call and the mother's B element vocalization. We conclude that malurid mothers display behaviors concordant with pupil-directed vocalizations and may actively influence their offspring's early life through sound learning shaped by maternal call tempo.

Dispersal patterns dictate genetic population structure, and ultimately population resilience, through maintaining critical ecological processes and genetic diversity. Direct observation of dispersal events is not often possible, but genetic methods offer an alternative method of indirectly measuring dispersal. Here, we use 7 652 genome-wide single-nucleotide polymorphisms (SNPs) to evaluate genetic population structure and infer dispersal capabilities of the Western Grasswren (Amytornis textilis textilis; WGW) in Western Australia ( n = 118), utilising a sister species, the Thick-billed Grasswren (Amytornis modestus; TBGW) as a comparison dataset ( n = 80). We found genetic divergence and low genetic diversity between two populations (Hamelin and Peron) in the WGW, despite evidence of long dispersal distances within populations by females. In addition, the two WGW populations were found to be more genetically divergent than two described subspecies of TBGW, despite the WGW occurring over a smaller spatial scale. By comparing these two grasswren species, our data suggest a narrow strip of land may be acting as a geographic barrier in the WGW, limiting dispersal between a peninsula population to the mainland. We investigate if morphology aligns with genetic divergence, with some estimates of divergence between WGW populations greater than those between subspecies of TBGW. However, confidence intervals were large, preventing definitive conclusions. Our results support the hypothesis that peninsula populations of small, ground-dwelling birds are genetically isolated from adjacent mainland populations. Furthermore, there is evidence to suggest that the limited gene flow is asymmetrical, with directional dispersal occurring from the bounded peninsula population to the mainland. Our study also highlights how substantial genetic divergence does not necessarily coincide with phenotypic differences.

Context In the era of the Anthropocene, habitat loss and environmental change threaten the persistence of many species. Genotyping-By-Sequencing (GBS) is a useful molecular tool for understanding how patterns of gene flow are associated with contemporary habitat distributions that may be affected by environmental change. Two parapatric subspecies of the threatened thick-billed grasswren (TBGW; Amytornis modestus ) more frequently occur in different plant communities. As such, a preference for plant community type could reduce subspecific introgression and increase genetic diversity at the parapatric boundary. Aims We aimed to measure gene flow within and among two TBGW subspecies and tested whether divergent genomic markers were associated with plant community type. Methods We sequenced 118 individuals from either of the two TBGW subspecies or in the region of parapatry and identified 7583 SNPs through ddRADseq. Key results We found evidence of asymmetric gene flow and a genomic pattern of isolation-by-distance. There were sixteen genomic outliers correlated with plant community type (regardless of location). Conclusions These findings show that plant community type does not prevent introgression in one subspecies ( A. m. raglessi ), but low dispersal and habitat heterogeneity could contribute to the maintenance of distinct subspecific morphotypes. Local adaptation in different plant community types could also provide a mechanism for future divergence. Implications We suggest subspecific introgression could increase genetic variation and the adaptive potential of the species, facilitating species persistence under conditions of climate change. Introgression between grasswren subspecies Characterising gene flow facilitates conservation management. This study used genomic markers to measure gene flow between thick-billed grasswren subspecies and found results that support taxonomic identification of the two subspecies and suggests grasswrens have low dispersal and may benefit from increased genetic diversity. Recognition of models of divergence with gene flow will be necessary for future conservation management.

Nest cavities are a limited resource, given the extensive land clearance that has occurred in Australia. Some obligate cavity-nesting birds are vulnerable to extinction and experience risk from heterospecific species that compete for limited nest cavities. The aim of this study was to identify intruder bird species at nest cavities of a threatened eastern subspecies of Regent Parrot (Polytelis anthopeplus monarchoides), and to measure the impact of intruder birds on parental care (parental time budgets) and nesting outcome (nest usurpation). We observed 25 eastern Regent Parrot nests using a combination of 608 h of video recording and 67 h of binocular observation. In total, we observed 16 heterospecific bird species at the nest entrance of the eastern Regent Parrot. Two of these species were examined for their impact on parental care behaviour. The presence of Noisy Miners (Manorina melanocephala) near the nest cavity increased the time that Regent Parrots spent at the nest cavity entrance. The number of Yellow Rosella (Platycercus elegans flaveolus) visits to the nest cavity predicted nest usurpation. Nest usurpation of a Regent Parrot nest occurred in 6/25 cases (24%), of which 5/6 nests were usurped by Yellow Rosellas. Understanding heterospecific competition for nest cavities in eastern Regent Parrots should inform targeted conservation measures.

The relationship between nest site characteristics and nest success is likely to be important in the conservation management of threatened cavity-nesting birds. The vulnerable eastern Regent Parrot (Polytelis anthopeplus monarchoides) is declining in South Australia, but there is little information on the behavioural ecology of its cavity-nesting habits. The aim of this study was to quantify parental nest visitation behaviour and measure nest site attributes in relation to nesting outcome. We collected data from 25 nests along the Murray River in South Australia, and analysed 608 h of video recording and 67 h of binocular observations. This study provides the first quantitative data on parental care behaviour of the eastern Regent Parrot. The results show (1) parent birds had similar to 0.5 visits per hour during incubation and similar to 2 visits per hour during feeding; (2) 16% of nesting cavities were abandoned, 24% usurped, 4% depredated (by lace monitor, Varanus varius), 4% unknown outcome; and (3) canopy cover was 58% at successful nests versus 34% at failed nests. Behavioural monitoring in the field should span at least two hours to capture parental activity at the nest, nesting success was correlated with canopy cover, and nesting failure was mostly explained by usurpation and abandonment.

Passerine song has many functions including mate attraction and territory defence. When songs across populations diverge, this can lead to changes in conspecific recognition and barriers to gene flow, which affect evolutionary processes that could lead to speciation. Two subspecies of thick-billed grasswren (Amytornis modestus) have a parapatric distribution characterised as a narrow region of high genetic admixture where the two subspecies meet. Outside the region of parapatry, the subspecies are genetically and morphologically diverged and weak inter-subspecific gene flow is asymmetric from A. m. indulkanna to A. m. raglessi. We examined the differences between song of A. m. indulkanna and A. m. raglessi and experimentally broadcast each subspecies song to compare territory-holder response in relation to intruder subspecies type. Our aim was to determine if territory owners have a different response to intruders based on the subspecific song type. The song of each subspecies contained unique vocal elements that were absent in the other subspecies. A. m. raglessi responded similarly to con-subspecific and hetero-subspecific intruder song, and A. m. indulkanna responded more often and with greater intensity to hetero- compared to consubspecific intruder song. The stronger response by A. m. indulkanna towards hetero-subspecific intruders provides a plausible behavioural explanation for the observed patterns of asymmetrical gene flow.

Habitat heterogeneity can have considerable effects on gene flow and migration across a region of parapatry. Describing habitat across a region of parapatry is important for the development of eco-evolutionary theory. Two subspecies of thick-billed grasswren (Amytornis modestus) share a region of parapatry between the South Australian salt lakes, Lake Eyre and Lake Torrens. While the two subspecies remain morphologically diverged outside the region of parapatry, it is not known what factors within the region of parapatry may affect migration and gene flow. In this study, we test associations between habitat differences and subspecies distributions and discuss whether ecological barriers could play a role in mitigating gene flow between the subspecies. We compare dominant plant species (1) between the allopatric ranges of the subspecies and within their region of parapatry, and (2) in relation to presence or absence of grasswrens within their region of parapatry. We found that the dominant plant species differed between grasswren subspecies in their allopatric range and in their region of parapatry, and also differed in the region of parapatry at sites with or without grasswrens. Specifically, grasswrens were absent in vegetation that is typical of sand dunes. These findings are discussed in light of evidence for secondary contact and hybridisation between A. m. indulkanna and A. m. raglessi, and susceptibility to introgression.

Summary Oxidative damage, caused by reactive oxygen species during aerobic respiration, is thought to be an important mediator of life‐history trade‐offs. To mitigate oxidative damage, antioxidant defence mechanisms are deployed, often at the cost of resource allocation to other body functions. Both reduced resource allocation to body functions and direct oxidative damage may decrease individual fitness, through reducing survival and/or reproductive output. The oxidative costs of reproduction have gained much attention recently, but few studies have investigated the long‐term consequences of oxidative damage on survival and (future) reproductive output under natural conditions. Using a wild population of the cooperatively breeding Seychelles warbler ( Acrocephalus sechellensis ), we tested the prediction that high levels of reactive oxygen species, or high antioxidant investments to avoid oxidative damage, have fitness consequences because they reduce survival and/or reproductive output. We found that individuals with higher circulating non‐enzymatic antioxidant capacity had a lower probability of surviving until the next year. However, neither current reproductive output, nor future reproductive output in the surviving individuals, was associated with circulating non‐enzymatic antioxidant capacity or oxidative damage. The negative relationship between antioxidant capacity and survival that we observed concurs with the findings of an extensive comparative study on birds, however the mechanisms underlying this association remain to be resolved. A lay summary is available for this article.

Divergence is the first phase of speciation and is commonly thought to occur more readily in allopatric populations. Subspecies are populations that are divergent but generally retain the capacity to interbreed should they come into contact. Two subspecies of the Thick-billed Grasswren (Amytornis modestus) are divergent by 1.7% at the mitochondrial ND2 gene and were previously considered to be allopatric. In this study, we discovered that the subspecies were parapatric. We use a larger sample size than previous studies to examine variation in morphology and mitochondrial haplotype across the distribution of each subspecies and within the region of parapatry. The subspecies occurring to the west, Amytornis modestus indulkanna, had larger body size and longer and narrower bill than the subspecies occurring to the east, A. m. raglessi. Within the region of parapatry, females were morphologically similar to A. m. indulkanna but had eastern mitochondrial haplotypes while males had intermediate morphology and either eastern or western haplotypes. Additionally, haplotypes from the western mitochondrial clade were found in A. m. raglessi. These patterns of morphology and mitochondrial diversity reveal discordance within the region of parapatry and to the east. We suggest that the subspecies have undergone asymmetric expansion from west to east, made secondary contact, and are currently hybridising.

Extra‐pair paternity (EPP), where offspring are sired by a male other than the social male, varies enormously both within and among species. Trying to explain this variation has proved difficult because the majority of the interspecific variation is phylogenetically based. Ideally, variation in EPP should be investigated in closely related species, but clades with sufficient variation are rare. We present a comprehensive multifactorial test to explain variation in EPP among individuals in 20 populations of nine species over 89 years from a single bird family (Maluridae). Females had higher EPP in the presence of more helpers, more neighbours or if paired incestuously. Furthermore, higher EPP occurred in years with many incestuous pairs, populations with many helpers and species with high male density or in which males provide less care. Altogether, these variables accounted for 48% of the total and 89% of the interspecific and interpopulation variation in EPP. These findings indicate why consistent patterns in EPP have been so challenging to detect and suggest that a single predictor is unlikely to account for the enormous variation in EPP across levels of analysis. Nevertheless, it also shows that existing hypotheses can explain the variation in EPP well and that the density of males in particular is a good predictor to explain variation in EPP among species when a large part of the confounding effect of phylogeny is excluded.

Despite its importance for the evolution of cooperative breeding, it has proven difficult to determine whether helpers improve their recipients' fitness. Helpers affect fitness in multiple ways, both positive and negative, but their effects can also be concealed through reduced maternal investment. Furthermore, determining the direction of causation is difficult, as helper presence may indicate a productive territory, rather than high productivity indicating an effect of help. In cooperatively breeding red-winged fairy-wrens (Malurus elegans) groups reduce care when they have male helpers, but groups with female helpers do not, so nestlings receive more food. Thus our predictions vary with helper sex rather than helper number, and by studying within-group changes with regard to group composition we separate phenotypically plastic responses from among-group correlations. Females did not reduce egg size in response to an increasing number of female helpers. However, more male or female helpers allowed females to lay larger clutches and more female helpers reduced re-nesting intervals. There was mixed support for a benefit of load lightening: Helpers, but not breeders, gained survival benefits with increasing number of male helpers. However, helper survival decreased with the number of female helpers, suggesting that increased competition counterbalanced these male helper benefits. We also found consistent among-group differences, which would have erroneously been interpreted as helper effects had we not disentangled the within-group changes with regard to group composition. This study highlights the importance of assessing carers' benefits in relation to both group composition and size, and of investigating the within-individual plastic response of helper effects.

The insect order of Hymenoptera (ants, bees, sawflies, and wasps) consists almost entirely of haplodiploid species. Under haplodiploidy, males develop from unfertilized eggs and are haploid, whereas females develop from fertilized eggs and are diploid. Although diploid males commonly occur, haploid females have never been reported. In analyzing the phenomenon of gynandromorphism in the parasitoid wasp Nasonia vitripennis, we found a line that generates complete phenotypic females from unfertilized eggs. These females have ovaries, can lay eggs, and are haploid, as shown by cytological and flow cytometric analyses. The data show that diploidy is not necessary for female development.