Malurus Cyaneus Research Articles

Maternal in‐nest call structure reduces habituation risk in songbird embryos

Repetition of the same vocal stimulus during vocal learning may result in habituation. Therefore, selection may favor vocal tutors that produce vocal stimuli with characteristics that reduce the risk of habituation. Superb fairywren Malurus cyaneus mothers produce a two‐element (A and signature B) call to embryos, but embryos only produce one element type (B) after hatching. Why do mothers use the A element to embryos? We broadcast calls with one (B) or two (AB) element types and measured embryo response. Embryos habituated to calls with one element type and remained responsive to calls with both. We conclude that signal characteristics in tutors may guide learning to retain pupil attention during learning.

Social restructuring during harsh environmental conditions promotes cooperative behaviour in a songbird.

Cooperation may emerge from intrinsic factors such as social structure and extrinsic factors such as environmental conditions. Although these factors might reinforce or counteract each other, their interaction remains unexplored in animal populations. Studies on multilevel societies suggest a link between social structure, environmental conditions and individual investment in cooperative behaviours. These societies exhibit flexible social configurations, with stable groups that overlap and associate hierarchically. Structure can be seasonal, with upper-level units appearing only during specific seasons, and lower-level units persisting year-round. This offers an opportunity to investigate how cooperation relates to social structure and environmental conditions. Here, we study the seasonal multilevel society of superb fairy-wrens (Malurus cyaneus), observing individual responses to experimental playback of conspecific distress calls. Individuals engaged more in helping behaviour and less in aggressive/territorial song during the harsher non-breeding season compared to the breeding season. The increase in cooperation was greater for breeding group members than for members of the same community, the upper social unit, comprised of distinct breeding groups in association. Results suggest that the interaction between social structure and environmental conditions drives the seasonal switch in cooperation, supporting the hypothesis that multilevel societies can emerge to increase cooperation during harsh environmental conditions.

No effect of testosterone or sexual ornamentation on telomere dynamics: A case study and meta-analyses.

Life-history theory predicts that reproductive investments are traded-off against self-maintenance. Telomeres, the protective caps on the ends of chromosomes, offer a promising avenue for assessing life-history trade-offs, as they shorten in response to stressors and are predictive of the remaining lifespan. In males, testosterone frequently mediates life-history trade-offs, in part, through its effects on sexual ornamentation, which is an important aspect of reproductive investment. However, studies of within-individual associations between telomere dynamics and sexual ornamentation are limited in number and have produced mixed results. Furthermore, most such studies have been observational, making it difficult to discern the nature of any causal relationship. To address this, we used short-acting testosterone implants in free-living male superb fairy-wrens (Malurus cyaneus) to stimulate the production of a sexual ornament: early moult into a costly blue breeding plumage. We found no evidence that elevated testosterone, and the consequent earlier moult into breeding plumage, accelerated telomere shortening. We therefore followed up with a systematic review and two meta-analyses (28 studies, 54 effect sizes) exploring the associations between telomeres and (1) testosterone and (2) sexual ornamentation. In line with our experimental findings, neither meta-analysis showed an overall correlation of testosterone or sexual ornamentation with telomere length or telomere dynamics. However, meta-regression showed that experimental, compared to observational, studies reported greater evidence of trade-offs. Our meta-analyses highlight the need for further experimental studies to better understand potential responses of telomere length or telomere dynamics to testosterone or sexual ornamentation.

Noise constrains heterospecific eavesdropping more than conspecific reception of alarm calls.

Many vertebrates eavesdrop on alarm calls of other species, as well as responding to their own species' calls, but eavesdropping on heterospecific alarm calls might be harder than conspecific reception when environmental conditions make perception or recognition of calls difficult. This could occur because individuals lack hearing specializations for heterospecific calls, have less familiarity with them, or require more details of call structure to identify calls they have learned to recognize. We used a field playback experiment to provide a direct test of whether noise, as an environmental perceptual challenge, reduces response to heterospecific compared to conspecific alarm calls. We broadcast superb fairy-wren (Malurus cyaneus) and white-browed scrubwren (Sericornis frontalis) flee alarm calls to each species with or without simultaneous broadcast of ambient noise. Using two species allows isolation of the challenge of heterospecific eavesdropping independently of any effect of call structure on acoustic masking. As predicted, birds were less likely to flee to heterospecific than conspecific alarm calls during noise. We conclude that eavesdropping was harder in noise, which means that noise could disrupt information on danger in natural eavesdropping webs and so compromise survival. This is particularly significant in a world with increasing anthropogenic noise.

Thermoregulatory strategies of songbird nestlings reveal limited capacity for cooling and high risk of dehydration

How the accelerating pace of global warming will affect animal populations depends on the effects of increasing temperature across the life cycle. Developing young are sensitive to environmental challenges, often with life-long consequences, but the risks of climate warming during this period are insufficiently understood. This may be due to limited insight into physiological sensitivity and the temperatures that represent a thermal challenge for young. Here we examined the physiological and behavioural effects of increasing temperatures by measuring metabolic rate, water loss, and heat dissipation behaviours between 25–45 °C in nestlings of a small free-living songbird of temperate SE-Australia, the superb fairy-wren. We found a high and relatively narrow thermoneutral zone from 33.1 to 42.3 °C, with metabolic rate increasing and all nestlings panting above this range. Evaporative water loss sharply increased above 33.5 °C; at the same temperature, nestlings changed their posture (extended their wings) to facilitate passive heat loss. However, at all temperatures measured, water loss was insufficient to dissipate metabolically produced heat, indicating poor cooling capabilities, which persisted even when individuals were panting. While nestlings are relatively tolerant to higher temperatures, with no evidence for hyperthermia at temperatures below 42 °C, they are at a high risk of dehydration even at lower temperatures, with limited ability to mitigate this. Thus, climate warming is likely to elevate the risk dehydration, which is concerning, since it is accompanied by drier conditions.

Cool, dry nights and short heatwaves during growth result in longer telomeres in temperate songbird nestlings.

Exposure to rising sublethal temperatures can affect development and somatic condition, and thereby Darwinian fitness. In the context of climate warming, these changes could have implications for population viability, but they can be subtle and consequently difficult to quantify. Using telomere length (TL) as a known biomarker of somatic condition in early life, we investigated the impact of pre-hatching and nestling climate on six cohorts of wild nestling superb fairy wrens (Malurus cyaneus) in temperate south-eastern Australia. Models incorporating only climate information from the nestling phase were best supported compared to those including the (pre-)laying to incubation phase (previously shown to affect mass) or both phases combined. This implies that nestling TL is most sensitive to ambient climate in the nestling phase. The top model showed a negative relationship between early-life TL and nestling mean daily minimum temperature when rainfall was low which gradually became positive with increasing rainfall. In addition, there was a positive relationship between TL and the frequency of hot days (daily maximum temperature ≥35°C), although these temperatures were rare and short-term. Including other pre-hatching and nestling period, climate variables (e.g., mean daily maximum temperature and mean diurnal temperature variability) did not improve the prediction of nestling TL. Overall, our results suggest that cooler nights when conditions are dry and short-term temperature spikes above 35°C during development are conducive for somatic maintenance. While these findings indicate a potential pathway for climate warming to impact wildlife fitness, they emphasize the need to elucidate the mechanisms underlying these complex associations.

From nestling to adult: personality traits are consistent within but not across life stages in a wild songbird

Abstract Personality traits can remain consistent throughout adult life, but it is less clear when these behavioural differences first arise and whether they are maintained across ontogenetic stages. We measured personality across three life stages (nestling, fledgling, and adult) in a wild population of superb fairy-wrens (Malurus cyaneus). We assessed (1) boldness (response to human handling, at all three stages), (2) exploration (response to a novel environment, in fledglings and adults) and (3) aggressiveness (response to mirror-image stimulation, in fledglings and adults). Personality differences were often consistent within life stages but never across them: specifically, aggressiveness was repeatable in fledglings and all three traits were repeatable in adults. We had insufficient statistical evidence for the presence of behavioural syndromes between any of our three personality traits, either at the fledgling or adult stages. Our results suggest that long-term personality traits may not become entrenched until adulthood in this species.

Use of Airborne Laser Scanning to assess effects of understorey vegetation structure on nest‐site selection and breeding performance in an Australian passerine bird

AbstractIn wild bird populations, the structure of vegetation around nest‐sites can influence the risk of predation of dependent offspring, generating selection for nest‐sites with vegetation characteristics associated with lower predation rates. However, vegetation structure can be difficult to quantify objectively in the field, which might explain why there remains a general lack of understanding of which characteristics are most important in determining predation rates. Airborne laser scanning (ALS) offers a powerful means of measuring vegetation structure at unprecedented resolution. Here, we combined ALS with 11 years of breeding data from a wild population of superb fairy‐wrens Malurus cyaneus in southeastern Australia, a species which nests relatively close to the ground and has high rates of nest and fledgling predation. We derived structural measurements of understorey (0–8 m) vegetation from a contiguous grid of 30 × 30 m resolution cells across our c. 65 hectares study area. We found that cells with nests (nest‐cells) differed in their understorey vegetation structure characteristics compared to unused cells, primarily in having denser vegetation in the lowest layer of the understorey (0–2 m; the ‘groundstorey’ layer). The average height of understorey vegetation was also lower in cells with nests than in those without nests. However, relationships between understorey vegetation structure characteristics and breeding performance were mixed. Nest success rates decreased with higher volumes of groundstorey vegetation, as did fledgling survival rates, though only in nest‐cells with lower height vegetation. Our results indicate that ALS can identify vegetation characteristics relevant for superb fairy‐wren nest‐site selection, but that nesting preferences are not beneficial under current predation pressures. The study illustrates the potential for using ALS to investigate how ecological conditions affect behaviour and life‐histories in wild animal populations.

Ecogeography of group size suggests differences in drivers of sociality among cooperatively breeding fairywrens.

Cooperatively breeding species exhibit a range of social behaviours associated with different costs and benefits to group living, often in association with different environmental conditions. For example, recent phylogenetic studies have collectively shown that the evolution and distribution of cooperative breeding behaviour is related to the environment. However, little is known about how environmental variation may drive differences in social systems across populations within species, and how the relationship between environmental conditions and sociality may differ across species. Here, we examine variation in social group size along a steep environmental gradient for two congeneric cooperatively breeding species of fairywrens (Maluridae) and show that they exhibit opposing ecogeographic patterns. Purple-backed fairywrens, a species in which helpers increase group productivity, have larger groups in hot, dry environments and smaller groups in cool, wet environments. By contrast, superb fairywrens, a species with helpers that do not increase group productivity despite the presence of alloparental care, exhibit the opposite trend. We suggest differences in the costs and benefits of sociality contribute to these opposing ecogeographical patterns and demonstrate that comparisons of intraspecific patterns of social variation across species can provide insight into how ecology shapes social systems.

Multilevel social structure predicts individual helping responses in a songbird

Multilevel societies are formed when stable groups of individuals spatially overlap and associate preferentially with other groups, producing a hierarchical social structure.1 Once thought to be exclusive to humans and large mammals, these complex societies have recently been described in birds.2,3 However, it remains largely unclear what benefits individuals gain by forming multilevel societies.1 One hypothesis-based on food sharing in hunter-gatherers4-is that multilevel societies facilitate access to a range of cooperative relationships, with individual investment varying across the hierarchical levels of the society. We tested experimentally whether such graded cooperation occurs in the multilevel society of a songbird, the superb fairy-wren (Malurus cyaneus). Specifically, we measured whether responses to playbacks of distress calls-used to recruit help when in extreme danger-varied according to the social level at which the focal individual is connected with the caller. We predicted that anti-predator responses should be highest within breeding groups (the core social unit), intermediate between groups from the same community, and lowest across groups from different communities. Our results confirm that birds exhibit the predicted hierarchical pattern of helping and that, within breeding groups, this pattern is independent of kinship. This pattern of graded helping responses supports the hypothesis that multilevel social structures can sustain stratified cooperative relationships and reveals similarity in cooperation in qualitatively different behaviors-anti-predator behavior and food sharing-in the multilevel societies of songbirds and humans.

When does early-life telomere length predict survival? A case study and meta-analysis.

Suboptimal conditions during development can shorten telomeres, the protective DNA caps on the end of chromosomes. Shorter early-life telomere length (TL) can indicate reduced somatic maintenance, leading to lower survival and shorter lifespan. However, despite some clear evidence, not all studies show a relationship between early-life TL and survival or lifespan, which may be due to differences in biology or study design (e.g., survival period measured). In superb fairy-wrens (Malurus cyaneus), we assessed whether early-life TL predicts mortality across different life-history stages (fledgling, juvenile, adult). However, in contrast to a similar study on a congener, early-life TL did not predict mortality across any life stage in this species. We then performed a meta-analysis including 32 effect sizes from 23 studies (15 birds and three mammals) to quantify the effect of early-life TL on mortality whilst taking into consideration potential sources of biological and methodological variation. Overall, the effect of early-life TL on mortality was significant, corresponding to a 15% reduction in mortality risk with each standard deviation increase in TL. However, the effect became weaker when correcting for publication bias. Contrary to our predictions, there was no evidence that effects of early-life TL on mortality varied with species lifespan or the period over which survival was measured. However, negative effects of early-life TL on mortality risk were pervasive throughout life. These results imply that effects of early-life TL on mortality are more likely to be context-dependent than age-dependent, although substantial power and publication bias issues highlight the need for more research.

Winter mortality of a passerine bird increases following hotter summers and during winters with higher maximum temperatures.

Climate change may influence animal population dynamics through reproduction and mortality. However, attributing changes in mortality to specific climate variables is challenging because the exact time of death is usually unknown in the wild. Here, we investigated climate effects on adult mortality in Australian superb fairy-wrens (Malurus cyaneus). Over a 27-year period, mortality outside the breeding season nearly doubled. This nonbreeding season mortality increased with lower minimum (night-time) and higher maximum (day-time) winter temperatures and with higher summer heat wave intensity. Fine-scale analysis showed that higher mortality in a given week was associated with higher maxima 2 weeks prior and lower minima in the current fortnight, indicating costs of temperature drops. Increases in summer heat waves and in winter maximum temperatures collectively explained 62.6% of the increase in mortality over the study period. Our results suggest that warming climate in both summer and winter can adversely affect survival, with potentially substantial population consequences.

Intraspecific fledgling adoption by a pair of Superb Fairy-wrens Malurus cyaneus

Adoption is a form of alloparenting in which an individual raises an unrelated offspring, although it is sometimes unclear whether this behaviour is adaptive or the product of reproductive error. Here, we report an observation of intraspecific adoption in a cooperatively breeding songbird, the Superb Fairy-wren Malurus cyaneus. In a colour-banded population at Cleland Conservation Park, South Australia, a breeding pair with three nutritionally dependent fledglings adopted an additional male fledgling from an adjacent territory. The adoptee was first observed with the new group about 2 weeks after fledging and was regularly fed by his adoptive parents. The fledgling continued to associate with his adoptive group for at least 7 months, even though his natal group remained intact in the adjacent territory. Genetic analyses confirmed that the adopted fledgling was the product of within-pair mating and was not closely related to its adoptive parents. There is some evidence that adult fairy-wrens may discriminate against offspring based on the acoustic structure of their begging calls; however, begging calls recorded at the adoptee’s nest were equally similar to incubation calls from both the genetic and adoptive mother. Finally, we discuss similar instances in the literature of intraspecific and interspecific adoption by Superb Fairy-wrens and suggest possible explanations for this behaviour.

Superb fairy-wrens with extreme exploration phenotypes respond more strongly to simulated territory intrusions

Individuals can exhibit strong consistencies in behaviours across time and contexts, referred to as animal personalities. Yet studies linking personality differences measured in captivity to ecologically relevant social behaviours in the wild are sparse and contradictory. Here, we used wild superb fairy-wrens, Malurus cyaneus , to investigate whether two personality traits measured in short-term captivity (exploration and aggressiveness) predicted aggressiveness in the wild (measured as territory defence). We first identified behavioural phenotypes within our study population by temporarily capturing adult birds to measure their (1) emergence, activity and sector visits in a novel environment (exploration) and (2) aggression in response to mirror image stimulation (aggressiveness). We later simulated two conspecific intrusions within their territory using playback of vocalizations (female or male chatter song) within their territory, in a pairwise design. Both exploration and breeding status (breeder/dominant versus helper/subordinate) influenced the birds’ response to the simulated intrusions. Dominant individuals and individuals with extreme exploration phenotypes (i.e. fast or slow explorers) responded more strongly to playback compared to helpers or those with intermediate exploration phenotypes, respectively. However, aggressiveness measured in short-term captivity (mirror response) did not correlate with our measure of aggressiveness in the wild (playback response during territory defence). The personality matching of breeding pairs (whether their partner had a matching or mismatching exploration phenotype) also influenced playback response, as pairs with mismatching exploration phenotypes responded more strongly to conspecific intruders than pairs with similar phenotypes. Our results support a growing number of studies showing the importance of animal personalities for response strategies and social behaviours. • We explored associations between personality traits in wild superb fairy-wrens. • Birds with extreme exploration phenotypes were more aggressive against conspecifics. • Aggressiveness in captivity did not correlate with aggressiveness in the wild. • Pairs with mismatching exploration phenotypes responded more strongly to intruders. • Our results support the validity of personality in fitness-related contexts.

When aggressiveness could be too risky: linking personality traits and predator response in superb fairy-wrens.

Personality syndromes in animals may have adaptive benefits for survival. For example, while engaging in predator deterrence, reactive individuals tend to prioritise their own survival, while proactive individuals engage in riskier behaviours. Studies linking animal personality measured in captivity with individual fitness or behaviours in the wild are sparse, which is a gap in knowledge this study aims to address. We used playback experiments in superb fairy-wrens (Malurus cyaneus), a common Australian songbird with a cooperative breeding system, to assess whether three personality traits measured during short-term captivity correlated with behavioural responses in the wild to a perceived nest and adult predator, the grey currawong (Strepera versicolor). We used three standard measures of personality in birds: struggle responses to human handling (boldness), exploration during a novel environment test, and aggressiveness during a mirror presentation. Superb fairy-wrens showed a significantly stronger response to the predator playback than to the control (willie wagtail, Rhipidura leucophrys) playback, suggesting that they recognised the predator playback as a threat without any accompanying visual stimulus. Birds that attacked their mirror image during the mirror presentation and those that spent a moderate amount of time close to the mirror responded more strongly to predator playback (by approaching the speaker faster and closer, spending more time near the speaker, and being more likely to alarm call) compared to those with low aggressiveness or those that spent very short or long durations close to the mirror. Neither boldness nor exploration in the novel environment test predicted playback response. Our results align with a growing number of studies across species showing the importance of animal personalities as factors for fitness and survival.

Projecting biodiversity benefits of conservation behavior-change programs.

Biodiversity loss is driven by human behavior, but there is uncertainty about the effectiveness of behavior-change programs in delivering benefits to biodiversity. To demonstrate their value, the biodiversity benefits and cost-effectiveness of behavior changes that directly or indirectly affect biodiversity need to be quantified. We adapted a structured decision-making prioritization tool to determine the potential biodiversity benefits of behavior changes. As a case study, we examined two hypothetical behavior-change programs--wildlife gardening and cat containment--by asking experts to consider the behaviors associated with these programs that directly and indirectly affect biodiversity. We assessed benefits to southern brown bandicoot (Isoodon obesulus) and superb fairy-wren (Malurus cyaneus) by eliciting from experts estimates of the probability of each species persisting in the landscape given a range of behavior-change scenarios in which uptake of the behaviors varied. We then compared these estimates to a business-as-usual scenario to determine the relative biodiversity benefit and cost-effectiveness of each scenario. Experts projected that the behavior-change programs would benefit biodiversity and that benefits would rise with increasing uptake of the target behaviors. Biodiversity benefits were also predicted to accrue through indirect behaviors, although experts disagreed about the magnitude of additional benefit provided. Scenarios that combined the two behavior-change programs were estimated to provide the greatest benefits to species and be most cost-effective. Our method could be used in other contexts and potentially at different scales and advances the use of prioritization tools to guide conservation behavior-change programs.

Behaviour of probable hybrid Red-backed x Superb Fairy-wrens at Gladstone, Queensland

This note describes observations of the behaviour of two hybrid male fairy-wrens (most likely resulting from crosses between Red-backed Malurus melanocephalus and Superb Fairy-wrens M. cyaneus) at Gladstone, Queensland, and their pairing with two female Red-backed Fairy-wrens.

First recorded evidence of ejection of a cuckoo egg in a fairy-wren species

Brood-parasitic cuckoos lay their eggs in the nests of other birds, abandoning parental care to their hosts. Many host species have evolved defences to escape or reduce the costs associated with cuckoo parasitism. Superb Fairy-wrens Malurus cyaneus, which are a host to several cuckoo species in Australia, can distinguish cuckoo eggs based on their size or shape, or by using indirect cues such as the timing of egg laying or the presence of an adult cuckoo near the nest. They have previously been shown to reject cuckoo eggs by methods of egg burial or abandonment. These methods are likely to be costlier than ejecting the cuckoo egg from the nest (as seen in some other host species), because of the complete failure of the reproductive attempt, in addition to the costs associated with renesting. In this study, we document with photograph and video footage an incident of a Fan-tailed Cuckoo Cacomantis flabelliformis parasitising a nest of a Superb Fairy-wren in the Australian National Botanic Gardens, Canberra. Shortly after the parasitism event occurred, we recorded the female Fairywren returning to the nest and ejecting the single Cuckoo egg. To our knowledge, this footage represents the first evidence of ejection of a cuckoo egg in this species.

Complex effects of helper relatedness on female extrapair reproduction in a cooperative breeder

AbstractIn cooperatively breeding species, the presence of male helpers in a group often reduces the breeding female’s fidelity to her social partner, possibly because there is more than one potential sire in the group. Using a long-term study of cooperatively breeding superb fairy-wrens (Malurus cyaneus) and records of paternity in 1936 broods, we show that the effect of helpers on rates of extrapair paternity varied according to the helpers’ relatedness to the breeding female. The presence of unrelated male helpers in a group increased average rates of extrapair paternity, from 57% for groups with no unrelated helpers, to 74% with one unrelated helper, to 86% with 2+ unrelated helpers. However, this increase was due in equal part to helpers within the group and males in other groups achieving increased paternity. In contrast, helpers who were sons of the breeding female did not gain paternity, nor did they affect the level of extra-group paternity (which occurred at rates of 60%, 58%, 61% in the presence of 0, 1, 2+ helper sons, respectively). There was no evidence of effects of helpers’ relatedness to the female on nest productivity or nestling performance. Because the presence of helpers per se did not elevate extrapair reproduction rates, our results undermine the “constrained female hypothesis” explanation for an increase in extrapair paternity with helper number in cooperative breeders. However, they indicate that dominant males are disadvantaged by breeding in “cooperative” groups. The reasons why the presence of unrelated helpers, but not of helper-sons, results in higher rates of extra-group reproduction are not clear.

Hiphop: Improved paternity assignment among close relatives using a simple exclusion method for biallelic markers.

Assignment of parentage with molecular markers is most difficult when the true parents have close relatives in the adult population. Here, we present an efficient solution to that problem by extending simple exclusion approaches to parentage analysis with single nucleotide polymorphic markers (SNPs). We augmented the previously published homozygote opposite test (hot), which counts mismatches due to the offspring and candidate parent having different homozygous genotypes, with an additional test. In this case, parents homozygous for the same SNP are incompatible with heterozygous offspring (i.e., "Homozygous Identical Parents, Heterozygous Offspring are Precluded": hiphop). We tested this approach in a cooperatively breeding bird, the superb fairy-wren, Malurus cyaneus, where rates of extra-pair paternity are exceptionally high, and where paternity assignment is challenging because breeding males typically have first-order adult relatives in their neighbourhood. Combining the tests and conditioning on the maternal genotype with a set of 1376 autosomal SNPs always allowed us to distinguish a single most likely sire from his relatives, and also to identify cases where the true sire must have been unsampled. In contrast, if just the hot test was used, we failed to identify a single most-likely sire in 2.5% of cases. Resampling enabled us to create guidelines for the number of SNPs required when first-order relatives coexist in the mating pool. Our method, implemented in the R package hiphop, therefore provides unambiguous parentage assignments even in systems with complex social organisation. We also identified a suite of Z- and W-linked SNPs that always identified sex correctly.