Distribution of trace elements in subcellular fractions of three aquatic birds

This study investigated the subcellular distribution of Cu, Zn, Cd and Ag in liver of mallard (Anas platyrhynchos), spot-billed duck (A. poecilorhyncha) and great cormorant (Phalacrocorax carbo) to better understand metal fractionation and dynamics in avian liver. Most of the total Cu, Zn, Cd and Ag were present in hepatocytosol, and their concentrations increased with total hepatic levels in all the three avian species. Copper, Zn and Cd in hepatocytosol were present mostly in metallothionein fractions (MTs), and Cu and Cd contents in this fraction were positively correlated with hepatocytosol levels in all the species. Silver was observed mostly in both high-molecular weight and MT fractions in hepatocytosol in mallard and great cormorant, whereas it was present in both low-molecular weight and MT fractions in spot-billed duck, suggesting that distribution of Ag in the hepatocytosol was species-specific. The elution profile of metals in MT fractions revealed six metallic peaks in mallard and spot-billed duck, and three peaks in great cormorant, implying the presence of multiple MT isoforms in the liver of these avian species. The present study demonstrated that MTs are closely associated with metal regulation, especially Cu and Cd, in these three aquatic birds.     

Seasonal changes in the feeding ecology of guillemots (Uria aalge) off north and east Scotland

Stomach contents were examined from 750 guillemots collected at several sites in the northern North Sea. The dietary composition was compared between months and between localities in order to assess seasonal and geographical trends in feeding strategy.From March to August sandeels dominated the diet, but in September a changeover period occurred when clupeid and gadoid remains became increasingly frequent in the stomach contents. This situation persisted over the winter period, but the importance of the two fish families varied with area, clupeids being more important in more southerly samples and gadoids in the north. Dietary data were considered in relation to available fisheries information and to known guillemot distribution patterns.     

A re-analysis of the marine bird Asiahesperornis from northern Kazakhstan

Fossil bird material is exceptionally rare in the Mesozoic of western Asia. With the notable exception of the Upper Cretaceous foot-propelled diving bird Asiahesperornis bazhanovi from northern Kazakhstan, the only bird fossils described from this region have been bone fragments from the Upper Cretaceous of Uzbekistan. In this paper, all material referred to date to the hesperornithiform Asiahesperornis is reviewed and re-described. New postcranial elements of this taxon from the holotype Kushmurun locality (Maastrichtian Zhuravlovskaya Svita) are presented, and the taxonomic history and likely affinities of this ocean-going bird are discussed.     

南大港湿地保护研究

笔者根据对南大港湿地的考察和调研 ,阐述南大港湿地的变迁和现状植被及鸟类资源状况 ,提出了保护南大港湿地的措施。     

Desertification and animal biodiversity in the desert grasslands of North America

Studies of breeding birds and small mammals were conducted at a series of sites that form a gradient of severity of desertification. Desert grassland sites represented the least changed landscape units and mesquite coppice dunes represented the most severe degradation, an irreversibly degraded landscape unit. The hypothesis that desertification reduces species diversity was not supported by the data. Species richness and diversities (Shannon-Weaver H′) of breeding birds were higher in the desertified areas than in the grassland with one exception. Data from a site dominated by the exotic African grass,Eragrostis lehmanniana, in south-eastern Arizona showed that breeding bird diversity was lower at that site than at a site in the same region that was dominated by native grasses. Species richness, diversity (H′), and abundance of small mammals were also higher in desertified areas than in desert grassland. Most grassland species of birds and mammals persist in the desertified habitats and species that are characteristic of shrublands colonize desertified desert grasslands. This accounts for the increases in species richness. However some species such as the banner-tailed kangaroo rat,Dipodomys spectabilis, are eliminated when grassland degrades to mesquite coppice dune or eroded creosotebush communities. These data suggest that other measures of faunal biodiversity such askeystone speciesmay be better measures of the impact of desertification on animal biodiversity.     

青岛胶州湾湿地水鸟资源现状及保护对策

胶州湾是山东半岛面积最大的河口海湾型湿地,湿地总面积约3.7万hm2,由于其特殊的地理位置和丰富的湿地生物资源,成为亚太地区水鸟迁徙的重要停歇地和越冬地。目前胶州湾湿地鸟类有12目26科156种,其中包括许多全球濒危和国家级重点保护种类。鉴于目前胶州湾的不断萎缩及湿地生物多样性和生态环境的不断破坏现状,为保护湿地水鸟资源,恢复胶州湾良好的生态环境,应尽早建立湿地自然保护区,开展水鸟资源的保护和湿地环境生态改造,为亚太地区候鸟的顺利迁徙提供良好的栖息地,推动青岛市自然保护区建设事业。     

A polar dinosaur feather assemblage from Australia

Exceptionally preserved Mesozoic feathered dinosaur fossils (including birds) are famous, but recognized from only very few localities worldwide, and are especially rare in the Southern Hemisphere. Here we report an assemblage of non-avian and avian dinosaur feathers from an Early Cretaceous polar (around 70°S) environment in what is now southeastern Australia. The recovered remains incorporate small (10–30 mm long) basal paravian-like tufted body feathers, open-vaned contour feathers, and asymmetrical bird-like wing feathers that possess high-angled barbs with possible remnants of barbicels — amongst the geologically oldest observed to date. Such morphological diversity augments scant skeletal evidence for a range of insulated non-avian theropods and birds inhabiting extreme southern high-latitude settings during the Mesozoic. Although some of these fossil feathers exhibit what may be residual patterning, most are uniformly toned and preserve rod-shaped microbodies, as well as densely-packed microbody imprints on the barbules that are structurally consistent with eumelanosomes. Geochemical analysis detected no identifiable residual biomolecules, which we suspect were lost via hydrolysis and oxidization during diagenesis and weathering. Nevertheless, an originally dark pigmentation can be reasonably inferred from these melanic traces, which like the coloured feathers of modern birds, might have facilitated crypsis, visual communication and/or thermoregulation in a cold polar habitat.     

Palaeoecology of Holocene peat deposits from Nordvestø, north-west Greenland

Two extensive peat deposits on Nordvestø, between Greenland and Canada, were examined for macroscopic remains of plants and animals. One of the peat deposits accumulated during the period from c. 7,100 to 5,100 cal. years BP. This peat is guanogenic and completely dominated by the coprophilous bryophyte Aplodon wormskioldii, and also contains frequent remains of feathers. The peat formed close to a large former sea bird colony, probably a puffin (Fratercula arctica) colony. Puffins are now rare in the region, but the population may have been larger during the mid Holocene, when the sea was ice-free for a longer period than at present. The other peat deposit is dated to c. 9,300–7,400 cal. years BP, it is minerogenic and the macrofossils reflect deposition in a shallow, richly vegetated pond. This peat formed during warmer summers than at present.     

Methane levels in shallow subtropical lake sediments: Dependence on the trophic status of the lake and allochthonous input

The vertical sediment profiles (10 cm) of the margins of three shallow subtropical lakes (Rio Grande, Brazil) with different trophic states and surrounding areas were evaluated to identify the effects of the allochthonous input on the methane concentration in the sediment. Sediment cores were collected to quantify the organic matter content (OM) and total carbon (TC), total nitrogen (TN), total phosphorous (TP) and methane (CH₄) concentrations.The three lakes were distinguished according to the trophic status and classified as oligotrophic, dystrophic and eutrophic. The natural characteristics of the dystrophic and eutrophic lakes have been changed due to the allochthonous input of leaves and twigs (Eucalyptus sp.) and the excreta of birds, respectively. In the eutrophic lake, the allochthonous input contributed to high autochthonous production. The highest values of OM, TC, TN and TP were found in the superficial sediments of the dystrophic and eutrophic lakes. The accumulation of allochthonous organic matter in the littoral zone promoted changes in the vertical sediment profiles and contributed to increases in the CH₄ concentrations in the sediment.     

Variation in the mobilization of mercury into Black-winged Stilt Himantopus himantopus chicks in coastal saltpans,as revealed by stable isotopes

Causes of variation in mobilization of mercury into Black-winged Stilt Himantopus himantopus chicks were studied through analysis of stable isotope ratios of carbon and nitrogen. Blood and breast feathers were collected from chicks in coastal saltpans during successive breeding seasons. Detritus samples and potential prey (macroinvertebrates) were also collected. Total mercury concentrations and stable isotope signatures were measured using atomic absorption spectroscopy and isotope ratio mass spectrometry respectively. Mercury levels in Chironomidae, Corixidae and Hydrophilidae correlated with mercury levels in chick feathers. Differences of δ¹⁵N signatures between macroinvertebrate groups indicated that they belong to different trophic levels. δ¹⁵N signatures of invertebrates correlated with mercury levels in invertebrates and chicks, but not with δ¹⁵N signatures in chicks. Between-group and between-site differences of δ¹⁵N signatures and mercury levels in invertebrates suggested that they contribute differently to mercury mobilization into chicks, and their relative contribution depends on prey availability in each site. Inter-site differences in the biomagnification factor reinforced that idea. δ¹³C signatures in invertebrates marked a larger range of carbon sources than just detritus. Variation of water inflow regime and prey availability may cause between-group and between-site differences of δ¹³C signatures in prey. Discrepancies between feather and blood for δ¹³C signatures in Praias-Sado and Vaia suggested that temporal variation of prey availability may be the main factor affecting mercury mobilization into chicks in both those cases, since their water inflow regimes are the same. The lowest levels of δ¹³C signatures in Vau suggested that water inflow regime may be the main factor in this case, since no discrepancy existed in δ¹³C signatures between blood and feather.