No abstract

Montane birds face significant threats from a warming climate, so determining the environmental factors that most strongly influence the composition of such assemblages is of critical conservation importance. Changes in temperature and other environmental conditions along elevational gradients are known to influence the species richness and abundance of bird assemblages occupying mountains. However, the role of speciesspecific traits in mediating the responses of bird species to changing conditions remains poorly understood. We aimed to determine whether different bird species responded differently to changing environmental conditions in a relatively understudied biodiversity hotspot in subtropical rainforest on the east coast of Australia. We examined patterns in avian species richness and abundance along two rainforest elevational gradients using monthly point counts between September 2015 and October 2016. Environmental data on temperature, wetness, canopy cover and canopy height were collected simultaneously, and trait information on body size and feeding guild membership for each bird species was obtained from the Handbook of Australian, New Zealand and Antarctic Birds. We used a generalized linear mixed modelling (GLMM) framework to determine the drivers of species richness and abundance and to quantify species' trait-environment interactions. GLMMs indicated that temperature alone was significantly positively correlated with species richness and abundance. Species richness declined with increasing elevation. When modelling abundance, we found that feeding guild membership did not significantly affect species' responses to environmental conditions. In contrast, the predicted abundance of a species was found to depend on its body size, due to significant positive interactions between this trait, temperature and canopy cover. Our findings indicate that large-bodied birds are likely to increase in abundance more rapidly than small-bodied birds with continued climatic warming. These results underline the importance of temperature as a driving factor of avian community assembly along environmental gradients.

Summary Assessment of habitat restoration requires baseline information on the communities present in both converted and intact forms of the focal ecosystem to enable comparisons with restored sites. Ants and beetles are commonly used in ecological monitoring programmes, as they display assemblage‐level responses to habitat change and can be a more direct measure of the recommencement of some ecosystem functions than the presence of more obvious biota such as plants. However, as these taxa differ substantially in ecological traits, their response patterns and utility as potential bioindicators may vary. Using pitfall traps, we compared assemblages of ant and beetle species between two reference habitats, pasture and remnant rainforest in subtropical eastern Australia. The assemblage composition of both groups differed significantly between rainforest and pasture but only beetles showed accompanying differences in species richness and abundance, which were both significantly lower in pasture. We identified ant and beetle species characteristic of either pasture or rainforest remnants, which may be used as bioindicators in future monitoring programmes. These species, however, displayed patchy distributions, suggesting that the use of individual species as bioindicators is likely to be unreliable. These findings support the use of ‘composite habitat indices’, which combine information from sets of indicator species. Given that patterns of change in species composition were similar between ants and beetles, either is an appropriate focal taxon for future monitoring programmes. Beetles, however, displayed some limitations as no species were indicative of the disturbed pasture habitat. Ants and beetles are likely to respond in different ways to different aspects of habitat change; thus, using both together could strengthen assessments of rainforest degradation or recovery.

Many montane avian communities are likely to be impacted negatively by future climate change. The ability to monitor these ecosystems effectively is therefore a priority. As species are expected to track their preferred climates by moving upwards in elevation, using indicator species of elevations has been suggested as a climate change monitoring strategy and has been explored for a variety of taxa in eastern Australia. Birds have great potential as vertebrate indicators due to their familiarity, detectability, and well known life histories. We used automated recording units (ARUs) and point counts to sample the avifauna along two elevational gradients in subtropical rainforest in north-eastern New South Wales, Australia. We used the indicator value protocol to identify avian indicators of elevation suitable for long-term monitoring. Pairs of species were more reliable than single species as indicators, and searching for indicators of elevational ranges (e.g. 300–500m) proved more effective than looking for indicators of single elevations (e.g. 300m). Point counts and ARUs were equally effective at determining indicators of elevations and ARUs performed particularly well in spring. We present avian indicator sets of lowland and highland sites, which provide a baseline for future monitoring of the effects of climate change on the region’s avifauna. The methodology employed here is broadly suitable for similar studies elsewhere. We propose that the use of ARUs to identify indicator species of elevations is an effective strategy for monitoring the effects of climate change on montane avian communities worldwide.

The Zoothera thrush complex is represented on the Australian mainland by the Bassian Thrush Z. lunulata and the Russet-tailed Thrush Z. heinei. These species are sympatric at several locations on the eastern coast. Often, these populations occupy different elevations, with the Bassian Thrush preferring higher elevations, though reasons for this are poorly understood. I present data from automated acoustic recordings made of these species in the Border Ranges and Mebbin National Parks of north-eastern New South Wales between ~300 m and 1100 m above sea-level over a 1-year period from June 2015 to May 2016. Bassian Thrushes were recorded most frequently in October, typically at or above 900 m. Russet-tailed Thrushes were recorded most frequently in August, at or below 700 m. Differences in elevational preference between the species may be driven by several factors including adaptation to cold, avoidance of interspecific competition and avoidance of hybridisation.