Chronic stress in superb fairy‐wrens occupying remnant woodlands: Are noisy miners to blame?

Abstract

Interactions between competing species may be intensified when they are restricted to small patches of remnant habitat, potentially increasing physiological stress in individuals. The effects of interspecific competition on stress in wildlife remain largely unexplored. In Australia, remnant woodlands are often dominated by aggressive honeyeaters, especially the noisy miner (Manorina melanocephala). Harassment of smaller birds by miners may result in their exclusion from suitable woodland habitat. We tested whether the presence of noisy miners is also associated with elevated stress in a model species of small passerine bird, the superb fairy-wren (Malurus cyaneus). We sampled wrens from six sites, three remnant woodlands with noisy miners and three larger fragments of reserved habitat without noisy miners. Differential white blood cell counts were used to infer levels of chronic stress. We also assessed variation in body condition and the prevalence of blood parasites (Haemoproteus spp.) to test for associations between stress and parasitemia. The mean heterophil-to-lymphocyte (H:L) ratio was 1.8 9 higher among superb fairy-wrens living in miner-dominated woodlands, suggesting higher levels of chronic stress. Individuals with higher stress appeared to be in poorer condition, as indicated by fat scores and residual body mass. Prevalence of blood parasites was generally high and was highest in reserved habitat (59%) where miners were absent. Birds with blood parasites living in these habitats had higher H:L ratios but the intensity of infection and H:L ratio was inversely related. Our results suggest that birds persisting in the presence of noisy miners might experience chronic stress, but further study is necessary to separate the relative importance of noisy miner aggression from other potential stressors in small patches of degraded woodland. Stress induced by interspecific aggression should be considered in future studies of wildlife living in remnant vegetation.

Research supporting restoration aiming to make a fragmented landscape ‘functional’ for native wildlife

“…Our research on Midlands avifauna provides the first insight into physiological stress as one of the mechanisms by which Noisy Miners impact small native birds (Bain et al 2019). This is a challenging area of research, in part because small birds are rapidly displaced by invading Miners leaving a small window of opportunity for studying process, and because stress levels are influenced also by other factors (Baker et al 2013).…”

Including random effects in statistical models in ecology: fewer than five levels?

“…Often researchers (sometimes nudged by peer-reviewers) cite this guideline of needing 5 levels before random effects inclusion as a reason why they were unable to use a mixed-effects model (Bain, Johnson & Jones, 2019;Bussmann & Burkhardt-Holm, 2020;Evans & Gawlik, 2020; . CC-BY 4.0 International license available under a was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.…”

New approaches for revegetating agricultural landscapes to provide connectivity for wildlife: The example of the Tasmanian Midlands, Australia

“…In most cases, vegetation islets achieved the objective of creating dense thickets of vegetation, which have been shown to be used by a suite of woodland birds (Kittipalawattanapol et al 2021). These thickets have the potential to provide suitable habitat in which woodland birds can hide from hyper-aggressive Noisy Miners (a native-invasive honeyeater) (Bain et al 2019;Jones et al 2021, this issue) and in which small marsupials can shelter to evade predation by cats (Hamer et al 2020;Jones et al 2021, this issue). The concept was successful, but the size of islets and species mix could be improved.…”

“…Further, the species mix used to create vegetation islets only comprised tree and shrub species. Recent animal studies emphasise the importance of a dense ground cover of native grasses and sedges in the provision of native animal habitat (Gardiner et al 2019;Jones et al 2021, this issue), in conjunction with dense copses of tall shrubs to provide sanctuary for woodland birds, which face aggression from noisy miners (Bain et al 2019;Jones et al 2021, this issue).…”