Simon J. Watson

In prey species, it is often the case that individuals give alarms when they are threatened. In birds, such signals are frequently vocal signals that alert conspecifics to the presence of a threat. The responses to these calls by receivers may include fleeing to cover or approaching to mob the predator. Although most birds do give alarm calls when threatened, not all species do. We used Australian arid-zone bird species (n = 171) to test the hypothesis that alarm calling behaviour is determined by ecological, behavioural, and morphological characteristics. Eighty-nine percent of birds analysed possessed an alarm call, highlighting the prevalence of this behaviour. Our study found three variables – number of food types eaten, mobility, and breeding system – that were associated with predicting alarm calling behaviour in these species. The correspondence of alarm calling with these key life history attributes provides insight into benefits of having alarm calls and the evolutionary processes that have given rise to this behaviour.

Aim: Climatic extremes and fire affect ecosystems across the globe, yet our understanding of how species are influenced by the interaction of these broadscale ecological drivers is poorly understood. Using a ten‐year dataset, we tested how extreme drought and rainfall interacted with time since fire (TSF) to shape bird species’ distributions.Location: Semi‐arid mallee woodlands of south‐eastern Australia.Methods: We quantified the effects of climatic extremes on bird species’ occurrence, species richness and incidence at 180 sites across three climatic periods—an El Niño‐associated drought (the “Big Dry”), immediately after La Niña drought‐breaking rainfall (“Big Wet”) and three years following the La Niña event (“Post‐Big Wet”). We then compared species’ responses with TSF across the three climatic periods using a chronosequence of sites from 1 to 117 years post‐fire.Results: La Niña rainfall had sustained impacts on species’ occurrence. Over half of species increased significantly during the Big Wet. Despite three intervening years of below‐average rainfall, three quarters of these species remained comparably high, Post‐Big Wet. By contrast, less than half of threatened and declining species benefited from high rainfall. Responses of species to TSF were found to differ contingent on climatic conditions: almost twice as many species responded to TSF during the Big Wet and almost three times as many Post‐Big Wet, compared with the Big Dry. Across climatic periods, a majority of species showed preference for mid to older post‐fire vegetation.Main conclusions: Variation in responses to TSF is likely due to the effect of climatic variation on resources. We suggest that, at sites of different post‐fire age, interactions between TSF and climate may differentially influence both the availability and longevity of resources. Given climatic extremes are predicted to become increasingly severe with climate change, accounting for their influence on fauna–fire dynamics will require careful management of fire.

In an era characterised by recurrent large wildfires in many parts of the globe, there is a critical need to understand how animal species respond to fires, the rates at which populations can recover, and the functional changes fires may cause. Using quantified changes in habitat parameters over a ~400 year post‐fire chronosequence in an obligate‐seeding Australian eucalypt woodland, we build and test predictions of how birds, as individual species and aggregated into functional groups according to their use of specific habitat resources, respond to time since fire. Individual bird species exhibited four generalised response types to time since fire: incline, decline, delayed and bell. All significant relationships between bird functional group richness or abundance and time since fire were consistent with predictions based on known time since fire‐associated changes in habitat features putatively important for these bird groups. Consequently, we argue that the bird community is responding to post‐fire successional changes in habitat as per the habitat accommodation model, rather than to time since fire per se, and that our functional framework will be of value in predicting bird responses to future disturbances in this and other obligate‐seeder forest and woodland ecosystems. Most bird species and functional groups that were affected by time since fire were associated with long‐unburnt woodlands. In the context of recent large, stand‐replacement wildfires that have affected a substantial proportion of obligate‐seeder eucalypt woodlands, and the multi‐century timescales over which post‐fire succession occurs, it would appear preferable from a bird conservation perspective if fires initiating loss of currently long‐unburnt woodlands were minimised. Once long‐unburnt woodlands are transformed by fire into recently‐burnt woodlands, there is limited scope for alternative management interventions to accelerate the rate of habitat development after fire, or supplement the resources formerly provided to birds by long‐unburnt woodlands, with the limited exception of augmenting hollow availability for key hollow‐nesting species.

Conservation managers regularly burn vegetation to regenerate habitat for fire‐dependent species. When determining the time since fire at which to burn, managers model change in a species’ occurrence over time, post‐fire (fire‐response curve) and identify the time since fire associated with decline in occurrence. However, where species exhibit variability in their fire response across space, using a single fire‐response curve to determine the timing of burns may lead to burning habitat at an inappropriate time since fire. We tested if elevation, local topography, soil properties, vegetation type or evapotranspiration affect the fire response of the endangered Mallee Emu‐wren Stipiturus mallee and its hummock‐grass habitat Triodia scariosa in southeastern Australia (n = 217). Previous work on the Mallee Emu‐wren found a unimodal fire response with decline in occurrence at ~30–50 yr since fire and a time window of occurrence of ~30 yr. We found that time since fire and elevation interact to affect the Mallee Emu‐wren fire response. At high elevations (55–98 m), Mallee Emu‐wrens declined in occurrence at ~50 yr since fire, with a time window of occurrence of 20–40 yr. However, at low elevations (28–55 m), Mallee Emu‐wrens showed no decline in occurrence with increasing time since fire with a time window of occurrence of up to 107 yr. Extent cover of Tall T. scariosa showed similar patterns to the Mallee Emu‐wren, indicating that vegetation structure is a likely driver of variability in the Mallee Emu‐wren fire response. We speculate that the effect of low elevation is mediated by increased soil nutrient and water availability for key plants. We used our findings to map the appropriate time since fire at which to burn to regenerate habitat for the Mallee Emu‐wren across the study region. We recommend no burning for regeneration across one‐third of potential habitat, because the Mallee Emu‐wren showed no decline in occurrence in these areas. We recommend managers model variability in species’ fire responses across space to improve the timing of burns for regeneration.

Context: After fire, immigration from outside burnt areas is important for the recovery of faunal communities. However, for recovery to occur, the matrix around the fire must support source populations of immigrants. Therefore, the landscape context of fires may be a critical determinant of the species pool available for (re)colonisation, hence post-fire community composition. Increasingly, fires occur in fragmented systems, and there is limited knowledge of how the surrounding landscape interacts with post-fire community recovery. Aim: The present study aimed to examine how landscape context influences faunal communities after large wildfires. Methods: Three reserves burnt by wildfire were examined ~18 months before the study in the Mallee region of south-eastern Australia. In all cases the burnt area consisted of natural mallee woodland. Two fires occurred within a matrix of extensive natural vegetation, while the third fire burnt >80% of a reserve situated within a highly fragmented, largely agricultural landscape. Birds, reptiles and mammals were surveyed at 90 sites inside and outside the fire boundaries, and relationships of species occurrence to reserve location, burnt versus unburnt status and distance from fire edge were all examined. Key results: Post-fire faunal communities reflected the species in the surrounding unburnt landscape. Notably, open habitat specialists, invasive species and species that can persist in small habitat patches were prominent within the fragmented system. Post-fire fauna communities were also influenced by variation of the natural vegetation surrounding the fire. The occurrence of species with low dispersal ability (i.e. reptiles) was influenced by local (patch scale) vegetation structure. 2Conclusions: The landscape context of fires is a major driver of the composition of post-fire faunal communities. Our results highlight the potential loss of species sensitive to fragmentation from fire-prone natural vegetation within modified landscapes, and that a reduced pool of potential immigrants leads to ‘attenuated succession’, compromising recovery of the pre-fire community. Implications: Post-fire colonists reflect the surrounding landscapes species pool, such that reserves surrounded by fragmented or otherwise low quality habitat are at risk of attenuated succession after fire. Landscape context should be incorporated into conservation planning in fire-prone ecosystems, including consideration of surrounding habitat quality and connectivity and protecting long unburnt vegetation.

Multiple-species (floristically diverse) plantings of trees and shrubs in former agricultural landscapes to offset (sequester) emissions of carbon dioxide are a recent component of Australian landscapes. Although their potential to mitigate biodiversity loss is recognised, this ecological function has not been investigated, in particular with respect to insect diversity. Over two summers, we used light trapping to sample Lepidoptera (moths) and Coleoptera (beetles) in multiple-species plantings in two distinct locations in Victoria (plantings of four ages per location) as well as in nearby remnant forest and in pasture. At both locations, we found that plantings had a greater abundance of Lepidoptera than remnants but that the abundance in plantings was comparable to the abundance in pasture. The species richness of Lepidoptera in plantings did not differ significantly from that in remnants but was significantly greater than that in pasture. The abundance and species richness of Coleoptera in plantings was lower than in remnant forests but higher than in pasture. The community composition of Lepidoptera and Coleoptera in plantings was intermediate between that of remnant forest and pasture, i.e. possibly transitional between the two vegetation types. Dissimilarity between all vegetation types was nevertheless high, reflecting that the abundance of individual taxa reflects the influence of temporally and spatially dependent factors, e.g. host plant size and suitability. Greater abundances of grass-feeding Lepidoptera in plantings explained much of the dissimilarity between plantings and remnant forests. Proximity to remnant forest was an important determinant of the community composition of Lepidoptera but not of Coleoptera. Moth forewing length (relevant to vagility which is an indicator of dispersal capacity) appeared less important to proximity relationships than larval host plant specificity, i.e. whether grass or dicot-feeding. The location of sequestration plantings relative to remnant forest as well as their composition (including the persistence of pasture grasses) will determine the attractiveness of the resources provided to insect herbivores and hence the rate at which they are colonised. Plantings near remnant native forest benefit insect diversity but adoption of novel silvicultural practices could hasten the rate at which they become functional mimics of native forests and support more comparable communities of insect. Potential trade-offs between increased establishment costs and more complex carbon accounting might need to be investigated to cost biodiversity credits associated with dual accreditation schemes.

The creation of supplementary habitats that effectively mimic the physical and thermal characteristics of natural tree hollows should be a key priority for landscape restoration and biodiversity offset programs. Here, we compare the thermal profiles of natural tree hollows with three types of artificial hollows designed for small marsupial gliders and tree-roosting insectivorous bats: (1) ‘chainsaw hollows’ carved directly into the trunks and branches of live trees, (2) ‘log hollows’, and (3) plywood nest boxes. Chainsaw hollows had thermal profiles that were similar to natural tree hollows: they were consistently warmer than ambient conditions at night, while remaining cooler than ambient during the day. In contrast, glider and bat boxes had the opposite pattern of heating and cooling, being slightly cooler than ambient at night and substantially hotter during the day. Glider log hollows had greater variation in internal temperatures compared to natural hollows and chainsaw hollows, but fluctuated less than glider boxes. Our results provide the first empirical evidence that artificial hollows carved directly into live trees can produce thermally stable supplementary habitats that could potentially buffer hollow-dependent fauna from weather extremes; whereas, poorly insulated plywood nest boxes produce lower-quality thermal environments. Together these findings provide positive impetus for stakeholders involved in conservation management and biodiversity offset programs to consider trialing chainsaw hollows in situations where target fauna require well-insulated supplementary habitats.

Many psyllids are manipulative herbivores that alter their hosts to provide shelter and ameliorate nutritional quality. Among eucalypt‐feeding psyllids, Cardiaspina have specialised to manipulate natural processes of foliar senescence and thereby host nutritional quality but not foliar morphology. Using a natural outbreak, we assessed the effects of feeding by nymphs of Cardiaspina densitexta Taylor, ultraviolet exposure and temperature on changes in nutritional quality and leaf abscission. Over 6 months, we followed the responses of tagged Eucalyptus fasciculosa F.Muell. leaves that, at the beginning of the study, were at one of three different stages of utilisation by psyllids (no psyllids, only eggs present, or leaves with late instar nymphs and red lesions). We measured foliar pigments, free amino acids and polyphenols every second month to characterise foliar nutritional quality. Psyllid feeding was briefly associated with chlorosis but lesions rapidly turned red (anthocyanic) and died after nymphs had matured. Red leaves had shortened longevities and their risk of abscission was positively correlated with the UV‐index rating of the preceding fortnight but not with psyllid abundance or area necrotic. Hence, psyllids altered the balance of chlorophylls and anthocyanin‐equivalents of green leaves and presumably therefore their ability to fully utilise incoming light energy. Green leaves had distinct free amino acids and polyphenol compositions compared to red leaves. In green leaves, changes in anthocyanin‐equivalents were negatively correlated with methionine while in red leaves psyllids were positively correlated with threonine and negatively correlated with leucine. Feeding by Cardiaspina densitexta nymphs is associated with the visible symptoms of photodamage which are associated with pronounced changes in nutritional quality. These changes are not analogous to foliar hypersensitive responses because they are expressed by old leaves, necrotic tissues are not abscised, they occur late in the development of nymphs and do not directly affect their survival. Specialisation of Cardiaspina on old eucalypt leaves may appear maladaptive if these modules are considered to be low in amino nitrogen and high in polyphenols. This perspective needs refining given the influence of photodamage on nutrient availability and because condensed tannins (weak pro‐oxidants) are more abundant than hydrolysable tannins in old leaves.