Flight initiation distance (FID) is a metric often used to study an individual's perceptions of risk when facing a predatory threat. Longer FID indicates lower risk‐taking, while shorter FID identifies bolder individuals who tolerate greater risk. Until now, no studies have tested the potential effect of the observer's sex on the escape behaviour of wild birds. Given observed differences in how laboratory animals may respond to the sex of humans interacting with them, the lack of reports in the field is surprising. In five European countries, we tested whether urban birds perceived the risk posed by approaching female versus male observers differently, using FID as a response variable. First, we matched the female and male observers according to their height and clothing. Then, we fitted Bayesian regression models, controlling for the phylogenetic relatedness of bird species, to test for the effect of human observer sex after controlling for a variety of other important factors known to explain variation in FID (starting distance, flock size, sex of the target bird, land use characteristics and vegetation cover). We found that male birds were more risk‐tolerant than females and – unexpectedly—birds in general escaped sooner when approached by women than by men. The escape difference associated with the observer's sex (~1 m longer when approached by women than by men) was consistent in populations across all five examined European countries. We discussed various hypotheses to explain birds' escape responses related to the observer's sex; however, further research is necessary to fully understand this phenomenon. Read the free Plain Language Summary for this article on the Journal blog.
Insects are the most diverse terrestrial organisms, yet they are underrepresented in large‐scale conservation assessments. To address this gap, the California Insect Barcoding Initiative is developing a publicly accessible, statewide DNA‐barcode reference library for California insects to support scalable surveys, establish baseline biodiversity measurements, and generate potential distribution maps that inform conservation planning. Specimens are collected with a hybrid strategy that combines standardized Malaise trapping, to enable replicable sampling, and opportunistic collecting, to maximize taxonomic coverage. Using samples collected primarily from 2022–2024 at 72 longer‐term Malaise trap sites, coupled with collecting using varied methods at 454 additional locations across California, we have barcoded over one million specimens. Preliminary completeness analyses suggest that current sampling captures roughly 65–69% of the fauna, implying a conservative minimum of circa 61 000 insect species in California, as delimited by their DNA barcode sequence. Using all sequenced specimen records, we generated rule‐based spatial range interpolations constrained by ecoregion and vegetation type, and used these to infer spatial patterns in insect species richness across the state. We identify areas of both high and low potential species richness, with current peaks in the Southern California Mountains ecoregion and the Mojave Basin and Range ecoregion. Our species richness estimates and spatial patterns are explicitly provisional and are expected to evolve as sampling gaps are addressed. Finally, we make all sequence data, specimen images, and occurrence records publicly available via the Barcode of Life Datasystem. This ongoing effort constitutes the first large‐scale DNA barcode‐based survey for California insects, providing an expandable foundation for tracking temporal change, testing drivers of insect diversity, and prioritizing regions for conservation and targeted inventory.
Caribbean coral reefs face rising pressure from coastal development, yet the pathways by which urban pollution reaches these endangered ecosystems remain poorly understood. Bays act as dynamic channels, trapping, transforming, and releasing matter that can impact adjacent reef systems. We investigated the temporal and spatial variability of suspended particulate matter (SPM), a key vector for pollutants and nutrients, derived from an urbanized bay in Curaçao and determined their effect on surrounding coral reefs. Using sediment traps deployed across spatial gradients (bay mouth to nearby reefs in the East and West) during the dry (April–May) and wet (October–November) seasons in 2023, we measured mass, carbon, and nitrogen fluxes and associated grain-size and geochemical particle composition. Results were compared to environmental conditions (e.g. rainfall, current speed) and revealed a clear spatial gradient of bay influence: the bay mouth showed the strongest terrestrial signal with highest mass fluxes, followed by the eastern reef (sheltered from currents) with elevated SPM and carbon fluxes of fine particles enriched in terrigenous elements (Si, Fe, Al, and Mn), while the western reef (exposed to open-ocean flow) exhibited lower fluxes of coarser particles with elevated Ca/Fe, Pb, Cu and Ni. This indicates a diminished bay effect and stronger marine influence mixed with localized pollution. During the dry season, differences in SPM fluxes and composition between reef sites were minimal, but wet season conditions amplified spatial patterns, with rainfall-driven runoff locally increasing dissolved and particulate matter delivery. This implies that reef vulnerability to bay-derived pollution locally depends on both proximity to source waters and seasonal hydrodynamic variability, with sheltered reefs experiencing the greatest impacts during periods of enhanced terrestrial runoff.
Response surface designs are usually described as being run under complete randomization of the treatment combinations to the experimental units. In practice, however, it is often necessary or beneficial to run them under some kind of restriction to the randomization, leading to multi-stratum designs. In particular, some factors are often hard to set, so they cannot have their levels reset for each experimental unit. This article presents a general solution to designing response surface experiments in any multi-stratum structure made up of crossing and/or nesting of unit factors. A stratum-by-stratum approach to constructing designs using compound optimal design criteria is used and illustrated. It is shown that good designs can be found even for large experiments in complex structures. A general strategy for construction is presented, which allows designs with arbitrary complexity to be constructed, thus giving the most complete solution to date of how to design response surface experiments.
Spectral shaping is a technique to spectrally focus the broadband solar spectrum for diverse energy conversion applications from luminescent solar concentrators to horticulture. Fluorescent dyes have been used as optically active components due to their high photoluminescence quantum yield (PLQY), but their absorption range is limited. Nanocrystals offer broadband absorption but are typically limited in spectral shifting, causing photon recycling. Here, we investigate radiative energy transfer from CsPbBr3 nanocrystals to Nile Red dye, combining the nanocrystals' broadband absorption with the dye's targeted emission. We use experimental transmittance and (time-resolved) photoluminescence (PL) spectroscopy together with photon random walk simulations to show that indeed radiative energy transfer occurs and that the resulting extended absorption range due to the nanocrystals can significantly enhance the spectral conversion efficiency. Experimentally, the energy transfer manifests in PL excitation spectra as strongly enhanced absorption and in time-resolved PL as a prolonged rise and decay time, reflecting the delay due to the extra absorption and emission processes. The photon random walk simulations account for the observed spectra quantitatively and allow prediction of conversion spectra for a wide range of nanocrystal and dye concentrations as well as their material parameters such as the PLQYs of the components. Specifically, we highlight the role of competitive absorption and the importance of taking the spectral intensity profile of excitation light into account when quantifying broadband energy transfer. These results open the door to tuning of absorption and emission spectra via the design of optimized compound mixtures for targeted spectral shaping applications.
