Avian responses to an extreme ice storm are determined by a combination of functional traits, behavioural adaptations and habitat modifications

Divergent ecological responses to typhoon disturbance revealed via landscape-scale acoustic monitoring

Climate change is increasing the frequency, intensity, and duration of extreme weather events across the globe. Understanding the capacity for ecological communities to withstand and recover from such events is critical. Typhoons are extreme weather events that are expected to broadly homogenize ecological dynamics through structural damage to vegetation and longer-term effects of salinization. Given their unpredictable nature, monitoring ecological responses to typhoons is challenging, particularly for mobile animals such as birds. Here, we report spatially variable ecological responses to typhoons across terrestrial landscapes. Using a high temporal resolution passive acoustic monitoring network across 24 sites on the subtropical island of Okinawa, Japan, we found that typhoons elicit divergent ecological responses among Okinawa's diverse terrestrial habitats, as indicated by increased spatial variability of biological sound production (biophony) and individual species detections. This suggests that soniferous communities are capable of a diversity of different responses to typhoons. That is, spatial insurance effects among local ecological communities provide resilience to typhoons at the landscape scale. Even though site-level typhoon impacts on soundscapes and bird detections were not particularly strong, monitoring at scale with high temporal resolution across a broad spatial extent nevertheless enabled detection of spatial heterogeneity in typhoon responses. Further, species-level responses mirrored those of acoustic indices, underscoring the utility of such indices for revealing insight into fundamental questions concerning disturbance and stability. Our findings demonstrate the significant potential of landscape-scale acoustic sensor networks to capture the understudied ecological impacts of unpredictable extreme weather events.

Consequences of arthropod community structure for an at-risk insectivorous bird

Global declines in bird and arthropod abundance highlights the importance of understanding the role of food limitation and arthropod community composition for the performance of insectivorous birds. In this study, we link data on nestling diet, arthropod availability and nesting performance for the Coastal Cactus Wren (Campylorhynchus brunneicapillus sandiegensis), an at-risk insectivorous bird native to coastal southern California and Baja Mexico. We used DNA metabarcoding to characterize nestling diets and monitored 8 bird territories over two years to assess the relationship between arthropod and vegetation community composition and bird reproductive success. We document a discordance between consumed prey and arthropod biomass within nesting territories, in which Diptera and Lepidoptera were the most frequently consumed prey taxa but were relatively rare in the environment. In contrast other Orders (e.g., Hemiptera, Hymenoptera)were abundant in the environment but were absent from nestling diets. Accordingly, variation in bird reproductive success among territories was positively related to the relative abundance of Lepidoptera (but not Diptera), which were most abundant on 2 shrub species (Eriogonum fasciculatum, Sambucus nigra) of the 9 habitat elements characterized (8 dominant plant species and bare ground). Bird reproductive success was in turn negatively related to two invasive arthropods whose abundance was not associated with preferred bird prey, but instead possibly acted through harassment (Linepithema humile; Argentine ants) and parasite transmission or low nutritional quality (Armadillidium vulgare; "pill-bug"). These results demonstrate how multiple aspects of arthropod community structure can influence bird performance through complementary mechanisms, and the importance of managing for arthropods in bird conservation efforts.

Mixed-species bird flocks re-assemble interspecific associations across an elevational gradient

Understanding how non-trophic social systems respond to environmental gradients is still a challenge in animal ecology, particularly in comparing changes in species composition to changes in interspecific interactions. Here, we combined long-term monitoring of mixed-species bird flocks, data on participating species' evolutionary history and traits, to test how elevation affected community assemblages and interspecific interactions in flock social networks. Elevation primarily affected flocks through reassembling interspecific associations rather than modifying community assemblages. Specifically, flock networks at higher elevations (compared to low elevations) had stronger interspecific associations (larger average weighted degree), network connectivity (enhanced network density) and fewer subnetworks. A phylogenetic and functional perspective revealed that associations between similar species weakened, whereas connections between dissimilar and/or random species were unchanged or strengthened with elevation. Likewise, network assortativity for the traits of vertical stratum and breeding period declined with elevation. The overall pattern is a change from modular networks in the lowlands, where species join flocks with other species that have matching traits, to a more open, random system at high elevations. Collectively, this rewiring of interspecific networks across elevational gradients imparts network stability and resiliency and makes mixed-species flocks less sensitive to local extinctions caused by harsh environments.

Small habitat matrix: How does it work?

We present herein our perspective of a novel Small Habitats Matrix (SHM) concept showing how small habitats on private lands are untapped but can be valuable for mitigating ecological degradation. Grounded by the realities in Sabah, Malaysian Borneo, we model a discontinuous "stepping stones" linkage that includes both terrestrial and aquatic habitats to illustrate exactly how the SHM can be deployed. Taken together, the SHM is expected to optimize the meta-population vitality in monoculture landscapes for aerial, arboreal, terrestrial and aquatic wildlife communities. We also provide the tangible cost estimates and discuss how such a concept is both economically affordable and plausible to complement global conservation initiatives. By proposing a practical approach to conservation in the rapidly developing tropics, we present a perspective from "ground zero" that reaches out to fellow scientists, funders, activists and pro-environmental land owners who often ask, "What more can we do?"

There's a storm a-coming: Ecological resilience and resistance to extreme weather events

Extreme weather events (EWEs) are expected to increase in stochasticity, frequency, and intensity due to climate change. Documented effects of EWEs, such as droughts, hurricanes, and temperature extremes, range from shifting community stable states to species extirpations. To date, little attention has been paid to how populations resist and/or recover from EWEs through compensatory (behavioral, demographic, or physiological) mechanisms; limiting the capacity to predict species responses to future changes in EWEs. Here, we systematically reviewed the global variation in species' demographic responses, resistance to, and recovery from EWEs across weather types, species, and biogeographic regions. Through a literature review and meta-analysis, we tested the prediction that population abundance and probability of persistence will decrease in populations after an EWE and how compensation affects that probability. Across 524 species population responses to EWEs reviewed (27 articles), we noted large variation in responses, such that, on average, the effect of EWEs on population demographics was not negative as predicted. The majority of species populations (80.4%) demonstrated compensatory mechanisms during events to reduce their deleterious effects. However, for populations that were negatively impacted, the demographic consequences were severe. Nearly 20% of the populations monitored experienced declines of over 50% after an EWE, and 6.8% of populations were extirpated. Population declines were reflected in a reduction in survival. Further, resilience was not common, as 80.0% of populations that declined did not recover to before EWE levels while monitored. However, average monitoring time was only two years with over a quarter of studies tracking recovery for less than the study species generation time. We conclude that EWEs have positive and negative impacts on species demography, and this varies by taxa. Species population recovery over short-time intervals is rare, but long-term studies are required to accurately assess species resilience to current and future events.

Trait-environment relationships differ between mixed-species flocking and nonflocking bird assemblages

Hypotheses about the mechanisms of community assembly suggest that biotic and abiotic filters constrain species establishment through selection on their functional traits. It is unclear how differences in traits influence the niche dimensions of closely related bird species when they coexist in spatiotemporally heterogeneous environments. Further, it is necessary to take into account their participation in mixed-species flocks, social systems that can include both competition and facilitation. For 6 yr, we conducted counts of forest bird species and took measurements of environmental variables along an elevational gradient in the Nanling Mountains, China. To disentangle different deterministic and historical/stochastic processes between flocking and nonflocking bird assemblages, we first compared phylogenetic and functional structure, and community-weighted mean trait values (CWM). We further assessed elevational variations in trait-environment relationships. We found that the flocking and nonflocking bird assemblages were structured by environmental gradients in contrasting ways. The nonflocking assemblage showed a strong change from over-dispersed to clustered community structure with increasing elevations, consistent with the strong selective pressures of a harsh environment (i.e., environmental filtering). The nonflocking assemblage also displayed significant trait-environment relationships in bivariate correlations and multivariate ordination space, including specific morphological and foraging traits that are linked to vegetation characteristics (e.g., short trees at high elevations). By contrast, flocking birds were more resilient to habitat change with elevation, with relatively consistent community membership, and showed fewer trait-environment associations. CWM of traits that are known to be associated with species' propensity to join mixed-species flocks, including small body size and broad habitat specificity, were linked to the flocking assemblage consistently across the elevational gradient. Collectively, our trait-based analyses provide strong evidence that trait-environment relationships differ between flocking and nonflocking bird assemblages. Besides serving as bellwethers of changing environments, emergent properties of flock systems may increase the resilience of animal communities undergoing environmental change. Mixed-species flocks present an ideal model with which to explore cooccurrence of closely related species, because habitat filtering may be buffered, and the patterns observed are therefore the outcomes of species interactions including both competition and facilitation.

Effects of ice storm on species richness and abundance of resident birds in subtropical forest in southern China

Between January and February 2008, a severe ice storm occurred in southern China. The storm damaged nearly 21 million hectares of forest lands with broken branch, trunk breakage, and stem bending of many trees. This natural disturbance provides a unique opportunity to study impacts of extreme climatic event on forest birds. Using hierarchical multi-species occupancy model (species richness; 27 species) and N-mixture model (abundance; 3 species), we investigated how the storm affected resident bird species in subtropical forest in southern China. We sampled birds at Chebaling National Nature Reserve in Guangdong Province, monthly for 1 year each before and after the storm by mist nets. To take into account variations in temperature between years and between months, we incorporated monthly mean temperature into the models as an additional covariate. Observed species richness was greater before the storm. Estimated species richness (from the hierarchical model) also tended to be greater before than after the storm although 95% Bayesian credible intervals of these estimates were overlapped. Temperature showed a negative effect on estimated species richness, indicating greater species richness during winter. Among three species captured the most, abundance of Chestnut Bulbul (Hemixos castanonotus) significantly decreased after the storm. Other two species, Grey Treepie (Dendrocitta formosae) and Huet's Fulvetta (Alcippe hueti) showed insignificant responses to the storm. Our study indicates that the 2008 ice storm may not have a significant impact on species richness of resident birds in subtropical forest; however, the effect can be species-specific and negative to some species' population.

Phylogenetic and Functional Structure of Wintering Waterbird Communities Associated with Ecological Differences

Ecological differences may be related to community component divisions between Oriental (west) and Sino-Japanese (east) realms, and such differences may result in weak geographical breaks in migratory species that are highly mobile. Here, we conducted comparative phylogenetic and functional structure analyses of wintering waterbird communities in southern China across two realms and subsequently examined possible climate drivers of the observed patterns. An analysis based on such highly migratory species is particularly telling because migration is bound to reduce or completely eliminate any divergence between communities. Phylogenetic and functional structure of eastern communities showed over-dispersion while western communities were clustered. Basal phylogenetic and functional turnover of western communities was significant lower than that of eastern communities. The break between eastern and western communities was masked by these two realms. Geographic patterns were related to mean temperature changes and temperature fluctuations, suggesting that temperature may filter waterbird lineages and traits, thus underlying geographical community divisions. These results suggest phylogenetic and functional divisions in southern China, coinciding with biogeography. This study shows that temperature fluctuations constitute an essential mechanism shaping geographical divisions that have largely gone undetected previously, even under climate change.