Individual roosting strategies in a flock-living bird: movement and social cohesion of hooded crows (Corvus corone cornix) from pre-roost gatherings to roost sites

The function of the conspicuous pre-roost gathering in communally roosting birds is poorly known. We studied movement and social cohesion of radio-tagged hooded crows (Corvus corone cornix) from their daytime location via pre-roost to roost in autumn and winter. With increasing snowfall the previous 24 h, the crows attended pre-roosts farther from the territory, and moved longer from pre-roost to roost. The crows became more likely to roost communally as distance to their territory increased. Attending a pre-roost on average almost doubled the travel distance to a communal roost. Crows were much more likely to join the same roost when they had attended the same pre-roost than otherwise. Breeding mates were more likely to keep together from pre-roost to roost than were other assigned pairs of a territorial male and female. For assigned pairs of non-mates, cohesion from pre-roost to roost decreased with increasing distance to roost, and was higher when both crows roosted communally compared to when at least one of them roosted in its territory. When both roosted communally, cohesion decreased with increasing snowfall and increasing number of crows attending the pre-roost, increased with increasing snow depth, and became higher among two females, compared to other combinations of two crows, with increasing number of crows attending the pre-roost. These patterns may be interpreted as supporting several of the current hypotheses on the function of pre-roost gathering. Electronic Publication     

Which regional features of Danish agriculture favour the corn bunting in the contemporary farming landscape?

Corn buntings Miliaria calandra were abundant throughout arable agricultural landscapes in Europe, but have catastrophically declined since the mid 1970s with changes in farming practice and now give serious conservation cause for concern. Corn buntings declined in Denmark during 1976–1993, but (almost unique in Europe) have since increased (by up to 11% per annum) in some areas without specific conservation recovery actions. Based on breeding bird surveys in the mid 1990s, highest corn bunting densities occurred on mixed agriculture in west Denmark (Jylland); the species was rarer or absent in regions of highest arable land cover. Corn bunting density and extent of rotational and permanent grassland were correlated, but not with spring sown barley (all known to constitute important corn bunting winter habitat). The extent of spring barley rapidly declined in Denmark during the 1980s, but since 1990, most counties have since shown 2–3% annual increases in this crop, except in Nordjylland, where high densities of corn buntings have remained stable. Elsewhere in Jylland, corn buntings have increased in counties supporting highest densities during the mid 1990s, contrasting stable or declining trends in south and east Denmark where densities were originally lower. After dramatic decreases everywhere in Denmark, corn buntings retain highest breeding densities associated with mixed agriculture, especially where grassland and spring sown barley remained in greatest extent. Although purely based on land use correlation and bird surveillance, these results show an association between mixed farming and favourable conservation status of a species now red-listed throughout much of Europe. Further investigations of habitat use at small spatial scales and throughout the annual cycle are urgently required to better enlighten specific recommendations for wider applicability of guidelines for corn bunting recovery actions elsewhere.     

Using advanced surface complexation models for modelling soil chemistry under forests: Solling forest, Germany

Various dynamic soil chemistry models have been developed to gain insight into impacts of atmospheric deposition of sulphur, nitrogen and other elements on soil and soil solution chemistry. Sorption parameters for anions and cations are generally calibrated for each site, which hampers extrapolation in space and time. On the other hand, recently developed surface complexation models (SCMs) have been successful in predicting ion sorption for static systems using generic parameter sets. This study reports the inclusion of an assemblage of these SCMs in the dynamic soil chemistry model SMARTml and applies this model to a spruce forest site in Solling Germany. Parameters for SCMs were taken from generic datasets and not calibrated. Nevertheless, modelling results for major elements matched observations well. Further, trace metals were included in the model, also using the existing framework of SCMs. The model predicted sorption for most trace elements well.     

Black carbon-dominated PCDD/Fs sorption to soils at a former wood impregnation site

The influence of black carbon (BC) on the sorption of 17 native polychlorinated-p-dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) was studied in five soil samples from a sawmill site where wood used to be impregnated with chlorophenol preservatives. The presence of BC caused measured total organic carbon (TOC)-water distribution ratios (K(TOC)) to be a median factor of 51 (interquartile range 18-68, n=85) higher than modeled amorphous organic carbon (AOC)-water distribution ratios (K(AOC)). K(TOC) was a factor of 73+/-27 above K(AOC) for PCDFs (n=10) and a factor of 20+/-13 (n=7) for PCDDs. The reason for this difference is probably that attaining a planar configuration after sorption to BC is less thermodynamically favorable for PCDDs than for PCDFs. BC-water distribution ratios were calculated from K(TOC), K(AOC) and BC contents, and ranged from 10(9.9) (2,3,7,8-Tetra-CDD) to 10(11.5) l kg(-1) (Octa-CDF). More than 90% of the PCDD/Fs in the soil was calculated to be BC-sorbed. Dissolved organic carbon (DOC)-water distribution ratios were measured to be in the same order of magnitude as K(AOC). This study shows that strong sorption to BC should be included when assessing ecotoxicological risk or modeling transport to groundwater of PCDD/Fs in soil.     

Occurrence of orthophosphate monoesters in lake sediments: significance of myo- and scyllo-inositol hexakisphosphate

Orthophosphate monoesters often constitute a significant fraction of total phosphorus in lake sediments. The knowledge on the specific composition and recalcitrance of these compounds is however limited. The main aim was therefore to identify and quantify specific orthophosphate monoesters in sediment from 15 Danish lakes by solution (31)P NMR spectroscopy. The four most quantitatively important orthophosphate monoesters were myo-inositol hexakisphosphate (myo-IP(6)), scyllo-inositol hexakisphosphate (scyllo-IP(6)) α-glycerophosphate (α-GP) and β-glycerophosphate (β-GP). The compounds were identified in 9, 4, 8 and in all 15 lakes, respectively. In total these four components made up 46-100% of the orthophosphate monoester pool. The glycerophosphates (GPs) are most likely degradation products of phospholipids, created as an artifact by the alkaline extraction procedure used for (31)P NMR spectroscopy, while the inositol hexakisphosphates (IPs) are naturally occurring compounds. There was a significant positive correlation between myo-IP(6) and total aluminium in the sediment and a negative correlation between myo-IP(6) and lake water pH, suggesting that myo-IP(6) is stabilized in the sediment by adsorption at slightly acidic or neutral conditions. In three lakes, the depth distribution of the orthophosphate monoesters was investigated. The content of scyllo-IP(6) and myo-IP(6) was constant with sediment depth in two of the lakes while the content of myo-IP(6) decreased with depth in one of the lakes. In all cases the IPs seem to be preserved with sediment depth to a higher extent than the orthophosphate diesters and especially the GPs suggesting that IPs can be a sink for phosphorus in the lake ecosystem or at least delay P-recycling for years.     

Modelling of geochemical and isotopic changes in a column experiment for degradation of TCE by zero-valent iron

Zero-valent iron (ZVI) permeable-reactive barriers have become an increasingly used remediation option for the in situ removal of various organic and inorganic chemicals from contaminated groundwater. In the present study a process-based numerical model for the transport and reactions of chlorinated hydrocarbon in the presence of ZVI has been developed and applied to analyse a comprehensive data set from laboratory-scale flow-through experiments. The model formulation includes a reaction network for the individual sequential and/or parallel transformation of chlorinated hydrocarbons by ZVI, for the resulting geochemical changes such as mineral precipitation, and for the carbon isotope fractionation that occurs during each of the transformation reactions of the organic compounds. The isotopic fractionation was modelled by formulating separate reaction networks for lighter ((12)C) and heavier ((13)C) isotopes. The simulation of a column experiment involving the parallel degradation of TCE by hydrogenolysis and beta-elimination can conclusively reproduce the observed concentration profiles of all collected organic and inorganic data as well as the observed carbon isotope ratios of TCE and its daughter products.     

Status and trends of terrestrial arthropod abundance and diversity in the North Atlantic region of the Arctic

Ambio - The Circumpolar Biodiversity Monitoring Programme (CBMP) provides an opportunity to improve our knowledge of Arctic arthropod diversity, but initial baseline studies are required to...     

Long-term declines of European insectivorous bird populations and potential causes

Evidence of declines in insect populations has recently received considerable scientific and societal attention. However, the lack of long-term insect monitoring makes it difficult to assess whether declines are geographically widespread. By contrast, bird populations are well monitored and often used as indicators of environmental change. We compared the population trends of European insectivorous birds with those of other birds to assess whether patterns in bird population trends were consistent with declines of insects. We further examined whether declines were evident for insectivores with different habitats, foraging strata, and other ecological preferences. Bird population trends were estimated for Europe (1990–2015) and Denmark (1990–2016). On average, insectivores declined over the study period (13% across Europe and 28% in Denmark), whereas omnivores had stable populations. Seedeaters also declined (28% across Europe; 34% in Denmark), but this assessment was based on fewer species than for other groups. The effects of insectivory were stronger for farmland species (especially grassland species), for ground feeders, and for cold-adapted species. Insectivory was associated with long-distance migration, which was also linked to population declines. However, many insectivores had stable populations, especially habitat generalists. Our findings suggest that the decline of insectivores is primarily associated with agricultural intensification and loss of grassland habitat. The loss of both seed and insect specialists indicates an overall trend toward bird communities dominated by diet generalists.     

Buchbesprechungen

Ohne Zusammenfassung