Using citizen science to measure recolonisation of birds after the Australian 2019–2020 mega-fires

Large and severe fires (‘mega-fires’) are increasing in frequency across the globe, often pushing into ecosystems that have previously had very long fire return intervals. The 2019–2020 Australian bushfire season was one of the most catastrophic fire events on record. Almost 19 million hectares were burnt across the continent displacing and killing unprecedented numbers of native fauna, including bird species. Some bird species are known to thrive in post-fire environments, while others may be absent for an extended period from the firegrounds until there is sufficient ecosystem recovery. To test for systematic patterns in species use of the post-fire environment, we combined citizen science data from eBird with data on sedentism, body size, range size and the specialisation of diet and habitat. Using generalised additive models, we modelled the responses of 76 bird species to the 2019–2020 Australian mega-fires. Twenty-two species decreased in occurrence after the fire; 30 species increased; and no significant effect was found for the remaining 24 species. Furthermore, diet specialists, and birds with smaller body sizes and range sizes were less likely to be found in burnt areas after the fire event compared to before, a result which generates testable hypotheses for recovery from other mega-fires across the globe. Being displaced from the firegrounds for an event of this geographic magnitude may have severe consequences for population dynamics and thus warrant considerable conservation attention in pre-fire planning and in the post-fire aftermath.     

How might recruitment research on coral-reef fishes help manage tropical reef fisheries?

Abstract ‘Ecologic’ reef fishes (basic research subjects) and ‘Economic’ reef fishes (exploited by humans) share fundamental early life-history attributes of small, widely dispersed planktonic eggs, larvae, and (for some species in both groups) pelagic juveniles. These attributes predispose the open populations of species in both groups to limitation resulting from environmentally induced fluctuations in recruitment from planktonic/pelagic to benthic stages. Rates of movement within and among reefs, one of several postrecruitment processes likely to be subject to density-dependent regulation, may differ between Ecologies (mostly small-bodied) and Economics (generally larger-bodied). This is because of differences between species in the two groups in size-related differences in the home ranges of individuals. Existing data, however, neither support the notion that natural growth and mortality rates basically differ between the adults of Ecological and Economic species, nor that the generally larger home ranges of larger-bodied adult Economics are more subject to density-dependent control. Further, the small-bodied young-of-year juveniles of both groups on average probably have similar growth and mortality rates and small individual home ranges that are equivalently affected by density dependence. In conclusion I argue that, because of fundamental similarities in the sizes and durations of planktonic propagules and spawning periodicities, certain Ecologies and Economics may comprise a single recruitment guild. Coefficients of growth and mortality for postsettlement Ecologies also may resemble, and be applied as preliminary proxies for, analogous coefficients for Economic species. The efficacy of management strategies such as harvest refugia may differ for Ecological and Economic species, however, depending on whether the refugia are used to counter growth or recruitment overfishing.