Unexpected diversity in socially synchronized rhythms of shorebirds

The behavioural rhythms of organisms are thought to be under strong selection, influenced by the rhythmicity of the environment. Such behavioural rhythms are well studied in isolated individuals under laboratory conditions, but free-living individuals have to temporally synchronize their activities with those of others, including potential mates, competitors, prey and predators. Individuals can temporally segregate their daily activities (for example, prey avoiding predators, subordinates avoiding dominants) or synchronize their activities (for example, group foraging, communal defence, pairs reproducing or caring for offspring). The behavioural rhythms that emerge from such social synchronization and the underlying evolutionary and ecological drivers that shape them remain poorly understood. Here we investigate these rhythms in the context of biparental care, a particularly sensitive phase of social synchronization where pair members potentially compromise their individual rhythms. Using data from 729 nests of 91 populations of 32 biparentally incubating shorebird species, where parents synchronize to achieve continuous coverage of developing eggs, we report remarkable within-and between-species diversity in incubation rhythms. Between species, the median length of one parent's incubation bout varied from 1-19 h, whereas period length-the time in which a parent's probability to incubate cycles once between its highest and lowest value-varied from 6-43 h. The length of incubation bouts was unrelated to variables reflecting energetic demands, but species relying on crypsis (the ability to avoid detection by other animals) had longer incubation bouts than those that are readily visible or who actively protect their nest against predators. Rhythms entrainable to the 24-h light-dark cycle were less prevalent at high latitudes and absent in 18 species. Our results indicate that even under similar environmental conditions and despite 24-h environmental cues, social synchronization can generate far more diverse behavioural rhythms than expected from studies of individuals in captivity. The risk of predation, not the risk of starvation, may be a key factor underlying the diversity in these rhythms.</p

Unexpected diversity in socially synchronized rhythms of shorebirds

The behavioural rhythms of organisms are thought to be under strong selection, influenced by the rhythmicity of the environment1, 2, 3, 4. Such behavioural rhythms are well studied in isolated individuals under laboratory conditions1, 5, but free-living individuals have to temporally synchronize their activities with those of others, including potential mates, competitors, prey and predators6, 7, 8, 9, 10. Individuals can temporally segregate their daily activities (for example, prey avoiding predators, subordinates avoiding dominants) or synchronize their activities (for example, group foraging, communal defence, pairs reproducing or caring for offspring)6, 7, 8, 9, 11. The behavioural rhythms that emerge from such social synchronization and the underlying evolutionary and ecological drivers that shape them remain poorly understood5, 6, 7, 9. Here we investigate these rhythms in the context of biparental care, a particularly sensitive phase of social synchronization12 where pair members potentially compromise their individual rhythms. Using data from 729 nests of 91 populations of 32 biparentally incubating shorebird species, where parents synchronize to achieve continuous coverage of developing eggs, we report remarkable within- and between-species diversity in incubation rhythms. Between species, the median length of one parent’s incubation bout varied from 1–19 h, whereas period length—the time in which a parent’s probability to incubate cycles once between its highest and lowest value—varied from 6–43 h. The length of incubation bouts was unrelated to variables reflecting energetic demands, but species relying on crypsis (the ability to avoid detection by other animals) had longer incubation bouts than those that are readily visible or who actively protect their nest against predators. Rhythms entrainable to the 24-h light–dark cycle were less prevalent at high latitudes and absent in 18 species. Our results indicate that even under similar environmental conditions and despite 24-h environmental cues, social synchronization can generate far more diverse behavioural rhythms than expected from studies of individuals in captivity5, 6, 7, 9. The risk of predation, not the risk of starvation, may be a key factor underlying the diversity in these rhythms

Capillary isotachophoresis for separation of silver nanoparticles according to size

Capillary isotachophoresis (ITP) was used for the separation of Ag nanoparticles according to their size. For this purpose, ethanol–water dispersions of Ag nanoparticles stabilized by gelatin were prepared. The ITP separations were performed in a column-coupling system filled with two electrolytes with a pH of leading electrolytes of 7.1 (system I – LE: 10 mM HNO3, ε-aminocaproic acid, TE: 10 mM caproic acid) and 4.5 (system II – LE: 10 mM HNO3, imidazole, TE: 5 mM 2-(N-morpholino)ethanesulfonic acid). In both electrolyte systems the four main peak-mode zones of Ag nanoparticles migrating at zone boundaries were identified, however, the better separation was achieved by the system II. The Ag nanoparticle dispersions were also examined by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The zeta potential and thickness of gelatin double layers adsorbed on the nanoparticles were found to depend on pH. The TEM analysis revealed four size fractions of 4 nm, 10 nm, 16 nm and 22 nm, which correspond to the zones separated by ITP. Other migration zones of the electrolyte systems, such as impurities and/or products of the nanoparticle synthesis, served as spacers and separated the peak zones of the Ag nanoparticles.Web of Science573591365913

Predators and predation rates of skylark Alauda arvensis and woodlark Lullula arborea nests in a semi-natural area in the Netherlands

Predation is a major cause of breeding failure in bird species with open nests. Although many studies have investigated nest predation rates, direct identification of nest predators is sporadic, especially in (semi-)natural habitats. We quantified nest success and identified nest predators in a population of Skylarks Alauda arvensis and Woodlarks Lullula arborea breeding in a protected semi-natural area dominated by heathland and different succession states of grassland on nutrient-poor soil in The Netherlands. We monitored 54 nests by means of continuous video surveillance to determine survival times and predators, and monitored another 44 nests without a camera. Fates of the 58 (40) Skylark (Woodlark) nests were: fledging 41(27), depredation 13 (12), egg desertion 1 (0) and nestling death 3 (1). The overall nest success of all monitored nests (58 (40), Mayfield estimate) was 33% (22%; all mortality factors considered) or 43% (25%; only depredation). Predators of Skylark nests were Red Fox Vulpes vulpes (5), Carrion Crow Corvus corone (1) and European Adder Vipera berus (1). Woodlark nests were depredated by Carrion Crow (2), Eurasian Jay Garrulus glandadus (1) and Red Fox (1). Results suggest that the main nest predators might differ between the two co-occurring lark species; Skylark nests located in more open sites were preyed upon mainly by Red Fox, while the main predators of Woodlark nests, located generally closer to trees, are corvids

Predators and predation rates of skylark <em>Alauda arvensis</em> and woodlark <em>Lullula arborea</em> nests in a semi-natural area in the Netherlands

Predation is a major cause of breeding failure in bird species with open nests. Although many studies have investigated nest predation rates, direct identification of nest predators is sporadic, especially in (semi-)natural habitats. We quantified nest success and identified nest predators in a population of Skylarks Alauda arvensis and Woodlarks Lullula arborea breeding in a protected semi-natural area dominated by heathland and different succession states of grassland on nutrient-poor soil in The Netherlands. We monitored 54 nests by means of continuous video surveillance to determine survival times and predators, and monitored another 44 nests without a camera. Fates of the 58 (40) Skylark (Woodlark) nests were: fledging 41(27), depredation 13 (12), egg desertion 1 (0) and nestling death 3 (1). The overall nest success of all monitored nests (58 (40), Mayfield estimate) was 33% (22%; all mortality factors considered) or 43% (25%; only depredation). Predators of Skylark nests were Red Fox Vulpes vulpes (5), Carrion Crow Corvus corone (1) and European Adder Vipera berus (1). Woodlark nests were depredated by Carrion Crow (2), Eurasian Jay Garrulus glandadus (1) and Red Fox (1). Results suggest that the main nest predators might differ between the two co-occurring lark species; Skylark nests located in more open sites were preyed upon mainly by Red Fox, while the main predators of Woodlark nests, located generally closer to trees, are corvids.</p

Nanocomposite of montmorillonite and silver nanoparticles: Characterization and application in catalytic reduction of 4-nitrophenol

Silver ions previously intercalated into a montmorillonite (MMT) interlayer were reduced by sodium borohydride forming a nanocomposite of MMT and silver nanoparticles (Ag–MMT) with no other stabilizing additives. Within 360 min no coagulation of an aqueous Ag–MMT dispersion was observed. However, after 24 h the coagulation was indicated by a red shift of absorption maximum from 408 nm to 434 nm and by broadening of the absorbance band. The nanocomposite was characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and measurements of specific surface area (SSA). It contained 4.94 wt. % of silver. Ag nanoparticles with an average size of 6.9 nm were located on the external MMT surface, mostly in its pores. Ag–MMT was used as a catalyst for reduction of 4-nitrophenol with sodium borohydride forming 4-aminophenol. After 30 s the reaction kinetics changed from zero order to first order, which was explained by means of the Langmuir–Hinshelwood model. The whole reduction was completed after 290 s. During this time min. 95 wt. % of Ag nanoparticles stayed fixed on the MMT support.Web of Science1402-349849

ZnS/MMT nanocomposites : the effect of ZnS loading in MMT on the photocatalytic reduction of carbon dioxide

Different weight loadings (2–4.2 wt.%) of ZnS nanoparticles stabilized by cetyltrimethylammonium bromide (CTAB) were deposited on montmorillonite (MMT) in order to investigate the performance of ZnS/MMT nanocomposites in the CO2 photocatalytic reduction. Physicochemical properties of prepared nanocomposites were comprehensively characterized by using nitrogen physisorption, XRD, TEM, DR UV–vis spectroscopy and contact potential difference measurements. The main reaction products in a gas phase were hydrogen and methane. According to the blank test the pristine montmorillonite did not possess any photocatalytic performance. The order in photocatalytic performance of individual ZnS/MMT nanocomposites in CO2 reduction depending on the ZnS loading was following: 3.1 wt.% ZnS > 4.2 wt.% ZnS > 2.0 wt.% ZnS. This trend was explained based on UV–vis, TEM and contact potential difference measurements as follows. The increasing loading of ZnS nanoparticles affects the degree of ZnS nanoparticles agglomeration on MMT and this agglomeration finally influences the properties/behavior within electronic structure of ZnS, correlating with the photocatalytic performance of ZnS/MMT nanocomposites in the CO2 reduction.Web of Science15841741