Macro-scale relationship between body mass and timing of bird migration.

Clarifying migration timing and its link with underlying drivers is fundamental to understanding the evolution of bird migration. However, previous studies have focused mainly on environmental drivers such as the latitudes of seasonal distributions and migration distance, while the effect of intrinsic biological traits remains unclear. Here, we compile a global dataset on the annual cycle of migratory birds obtained by tracking 1531 individuals and 177 populations from 186 species, and investigate how body mass, a key intrinsic biological trait, influenced timings of the annual cycle using Bayesian structural equation models. We find that body mass has a strong direct effect on departure date from non-breeding and breeding sites, and indirect effects on arrival date at breeding and non-breeding sites, mainly through its effects on migration distance and a carry-over effect. Our results suggest that environmental factors strongly affect the timing of spring migration, while body mass affects the timing of both spring and autumn migration. Our study provides a new foundation for future research on the causes of species distribution and movement.

Effects of aquaculture on the maintenance of waterbird populations.

The global aquaculture industry has expanded rapidly and is increasingly important for maintaining food security while also providing alternative artificial habitats for many waterbirds. Clarifying how waterbirds use aquafarms and how aquafarm use affects waterbird population maintenance can be useful for improving management of the artificial landscape that can also provide waterbird habitat. Here, we investigated aquafarm use by waterbirds in China, the world's largest producer of aquaculture products, supported by literature review and questionnaire survey. We used Bayesian phylogenetic generalized linear mixed models to analyze the relationship between the degree of aquafarm use and population trends of waterbirds. The results showed that 69% of waterbird species in China have been recorded at aquafarms. Approximately one-quarter of all waterbird species and about the same proportion of threatened species were found to forage at aquafarms, consuming either cultured aquatic products or other food types. In general, species with a high degree of aquafarm use were unlikely to exhibit a population decline over the past two decades, when rapid loss of natural habitats occurred in China. This relationship was not detected in threatened species, despite there being no significant difference in the degree of aquafarm use between threatened and non-threatened species. Our study suggests that the large and expanding aquaculture industry is important for maintaining waterbird populations in China. However, aquafarms are not a replacement for natural habitats, because threatened species benefit less from aquafarm use. Given that aquafarms often come at the expense of natural wetlands, the degree to which aquafarms compensate for natural habitat loss probably depends on the quality of aquafarm habitat. We recommend an integrated ecological and economic analysis for formulating management policies that help conserve wildlife within the constraints and opportunities associated with maintaining human livelihoods. This article is protected by copyright. All rights reserved.

Far eastern curlew and whimbrel prefer flying low - wind support and good visibility appear only secondary factors in determining migratory flight altitude.

BACKGROUND: In-flight conditions are hypothesized to influence the timing and success of long-distance migration. Wind assistance and thermal uplift are thought to reduce the energetic costs of flight, humidity, air pressure and temperature may affect the migrants' water balance, and clouds may impede navigation. Recent advances in animal-borne long-distance tracking enable evaluating the importance of these factors in determining animals' flight altitude. METHODS: Here we determine the effects of wind, humidity, temperature, cloud cover, and altitude (as proxy for climbing costs and air pressure) on flight altitude selection of two long-distance migratory shorebirds, far eastern curlew (Numenius madagascariensis) and whimbrel (Numenius phaeopus). To reveal the predominant drivers of flight altitude selection during migration we compared the atmospheric conditions at the altitude the birds were found flying with conditions elsewhere in the air column using conditional logistic mixed effect models. RESULTS: Our results demonstrate that despite occasional high-altitude migrations (up to 5550 m above ground level), our study species typically forego flying at high altitudes, limiting climbing costs and potentially alleviating water loss and facilitating navigation. While mainly preferring migrating at low altitude, notably in combination with low air temperature, the birds also preferred flying with wind support to likely reduce flight costs. They avoided clouds, perhaps to help navigation or to reduce the risks from adverse weather. CONCLUSIONS: We conclude that the primary determinant of avian migrant's flight altitude selection is a preference for low altitude, with wind support as an important secondary factor. Our approach and findings can assist in predicting climate change effects on migration and in mitigating bird strikes with air traffic, wind farms, power lines, and other human-made structures.

The Agility of a Neuron: Phase Shift Between Sinusoidal Current Input and Firing Rate Curve.

The response of a neuron when receiving a periodic input current signal is a periodic spike firing rate signal. The frequency of an input sinusoidal current and the surrounding environment such as background noises are two important factors that affect the firing rate output signal of a neuron model. This study focuses on the phase shift between input and output signals, and here we present a new concept: the agility of a neuron, to describe how fast a neuron can respond to a periodic input signal. In this study, we derived three agility score functions for the balanced leaky integrate-and-fire model, the Hodgkin-Huxley model, and the Connor-Stevens neuron model. By applying the score of agility, we are capable of characterizing the surrounding environment; once the frequency of the periodic input signal is given, the actual angle of phase shift can then be determined and, therefore, different neuron models can be normalized and compared with each other.

Synthesis of a Class of Chiral-Bridged Phosphoramidite Ligands and Their Applications in the First Iridium-Catalyzed Asymmetric Addition of Arylboronic Acids to Isatins.

A series of novel chiral phosphoramidite ligands based on chiral-bridged biphenyl backbones have been prepared conveniently and characterized. The ligands complexed with [IrCodCl]2 provided the first iridium catalyst system for the asymmetric addition of arylboronic acids to N-protected isatins with high efficiency. When performed in THF/H2O at 80 °C with 2 equiv of the arylboronic acids, the transformations acquired good to excellent results (up to 98% yield and 95% ee).

Highly enantioselective synthesis of 2,3-dihydro-1H-imidazo[2,1-a]isoindol-5(9bH)-ones via catalytic asymmetric intramolecular cascade imidization-nucleophilic addition-lactamization.

Highly enantioselective catalytic asymmetric intramolecular cascade imidization-nucleophilic addition-lactamization of N(1)-alkylethane-1,2-diamine with methyl 2-formylbenzoate catalyzed by a chiral phosphoric acid represents the first efficient method for the preparation of medicinally interesting chiral 2,3-dihydro-1H-imidazo[2,1-a]isoindol-5(9bH)-ones with high yields and excellent enantioselectivities. This strategy has been shown to be quite general toward various methyl 2-formylbenzoates.