The Anti-Viral and Anti-Inflammatory Properties of Edible Bird's Nest in Influenza and Coronavirus Infections: From Pre-Clinical to Potential Clinical Application

Edible bird's nest (BN) is a Chinese traditional medicine with innumerable health benefits, including anti-viral, anti-inflammatory, neuroprotective, and immunomodulatory effects. A small number of studies have reported the anti-viral effects of EBN against influenza infections using in vitro and in vivo models, highlighting the importance of sialic acid and thymol derivatives in their therapeutic effects. At present, studies have reported that EBN suppresses the replicated virus from exiting the host cells, reduces the viral replication, endosomal trafficking of the virus, intracellular viral autophagy process, secretion of pro-inflammatory cytokines, reorient the actin cytoskeleton of the infected cells, and increase the lysosomal degradation of viral materials. In other models of disease, EBN attenuates oxidative stress-induced cellular apoptosis, enhances proliferation and activation of B-cells and their antibody secretion. Given the sum of its therapeutic actions, EBN appears to be a candidate that is worth further exploring for its protective effects against diseases transmitted through air droplets. At present, anti-viral drugs are employed as the first-line defense against respiratory viral infections, unless vaccines are available for the specific pathogens. In patients with severe symptoms due to exacerbated cytokine secretion, anti-inflammatory agents are applied. Treatment efficacy varies across the patients, and in times of a pandemic like COVID-19, many of the drugs are still at the experimental stage. In this review, we present a comprehensive overview of anti-viral and anti-inflammatory effects of EBN, chemical constituents from various EBN preparation techniques, and drugs currently used to treat influenza and novel coronavirus infections. We also aim to review the pathogenesis of influenza A and coronavirus, and the potential of EBN in their clinical application. We also describe the current literature in human consumption of EBN, known allergenic or contaminant presence, and the focus of future direction on how these can be addressed to further improve EBN for potential clinical application.

Avian mud nest architecture by self-secreted saliva

We provide a biomechanical explanation of how swallows and phoebes can construct strong nests of incohesive mud granules using saliva as a paste. The analysis leads to a hypothesis for why only 57 small light-weighted bird species (of approximately 10,000 species worldwide) can build mud nests on walls by utilizing their saliva. Our comprehensive study, combining experiments on natural and artificial mud nests and mathematical models on granular cohesion, not only elucidates the physical mechanism of this extraordinary animal architecture, but also provides inspiration to three-dimensional printing technology based on environmentally benign granular materials.

Mud nests built by swallows (Hirundinidae) and phoebes (Sayornis) are stable granular piles attached to cliffs, walls, or ceilings. Although these birds have been observed to mix saliva with incohesive mud granules, how such biopolymer solutions provide the nest with sufficient strength to support the weight of the residents as well as its own remains elusive. Here, we elucidate the mechanism of strong granular cohesion by the viscoelastic paste of bird saliva through a combination of theoretical analysis and experimental measurements in both natural and artificial nests. Our mathematical model considering the mechanics of mud nest construction allows us to explain the biological observation that all mud-nesting bird species should be lightweight.

Factors Affecting Thermal Insulation of Songbird Nests as Measured Using Temperature Loggers

AbstractBird nests represent an extended phenotype that is variable among and within species in terms of nest location and construction materials. It has also been suggested that nests indicate niche construction, although empirical evidence to support this is lacking. The nest wall is often considered to confer some insulation because this would help minimize the energetic expenditure by the incubating adult. However, it has been previously suggested that nests are constructed primarily for their structural role rather than for insulation, but to date, studies have used a variety of techniques to investigate the insulation of nest walls but only for relatively few species. This study used temperature loggers to determine insulatory values of nests for 16 previously undescribed species and to replicate values for eight previously described species. In addition, data for nest wall insulation that were determined using temperature loggers have been collated for a total of 32 different passerine species. The effects of nest dimensions, mass, and composition on these values were examined. Base thickness, but not wall thickness, and nest mass significantly positively affected insulatory values. This study found that the proportions of feathers and moss in the nest wall significantly positively correlated with insulatory values. This suggests that there is a key role for nest materials in determining insulation, which provides empirical evidence that nest building constitutes niche construction. The data will also help us interpret data from future studies of the thermal properties of nests. Ultimately, we need to develop our understanding of the role of insulatory values in the evolution of nest function.

Conflict between biotic and climatic selective pressures acting on an extended phenotype in a subarctic, but not temperate, environment

Climatic selective pressures are thought to dominate biotic selective pressures at higher latitudes. However, few studies have experimentally tested how these selective pressures differentially act on traits across latitudes because traits can rarely be manipulated independently of the organism in nature. We overcame this challenge by using an extended phenotype-active bird nests-and conducted reciprocal transplant experiments between a subarctic and temperate site, separated by 14° of latitude. At the subarctic site, biotic selective pressures (nest predation) favoured smaller, non-local temperate nests, whereas climatic selective pressures (temperature) favoured larger local nests, particularly at colder temperatures. By contrast, at the temperate site, climatic and biotic selective pressures acted similarly on temperate and subarctic nests. Our results illustrate a functional trade-off in the subarctic between nest morphologies favoured by biotic versus climatic selective pressures, with climate favouring local nest morphologies. At our temperate site, however, allocative trade-offs in the time and effort devoted to nest construction favour smaller, local nests. Our findings illustrate a conflict between biotic and climatic selective pressures at the northern extremes of a species geographical range, and suggest that trade-offs between trait function and trait elaboration act differentially across latitude to create broad geographic variation in traits.