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1.
Warke  G. M. A.  Day  K. R.  Greer  J. E.  Davidson  R. D. 《Hydrobiologia》1994,(1):91-100
Breeding cormorants, Phalacrocorax carbo, in Northern Ireland remain seasonally dependent on a coastal environment where they can be censused with accuracy, but numbers in other habitats and at other times of the year are less certain. This study establishes the long term and regional patterns of abundance at breeding and feeding localities, which might in turn be related to diet.Birds were regularly observed and counted at a variety of feeding sites, and some aspects of their breeding success and fledgling diet evaluated at the largest N.Ireland breeding colony.Numbers of breeding birds increased dramatically over a period of eight years but recently show signs of declining. There is likely to be a dynamic relationship between populations of a tapeworm (Ligula intestinalis L.), the numbers of roach (Rutilus rutilus [L.]) and cormorant populations feeding at Lough Neagh, the largest lake in the British Isles. While roach are not a major component in the diet of fledglings, the large numbers of cormorants feeding at the perimeter of L. Neagh suggest that changes in roach populations will affect birds most acutely during or following the winter. We suggest that this might result in a reduction in the proportion of the population volunteering to breed in the subsequent season, but require further data. The longer term effects of one fish species on cormorant populations are unlikely to be critical, since these birds are highly opportunist.In other habitats cormorant numbers are either very stable (estuary) or variable (river) depending on the seasonal and annual availability of their prey. There is no evidence for a systematic seasonal shift in habitat, as suggested by other studies.  相似文献   

2.
LATE MESOZOIC FISH FAUNA FROM WESTERN LIAONING, CHINA   总被引:3,自引:2,他引:1  
Thelycopteridsarecharacterizedbythefollowingcombinationoffeatures:na-salstube-like,andseparatedbymesethmoid;temporalfenestrapresentonposterola-teralregionofcranium;hyomandibularwithadistinctanteroventralprocess;ant-orbitalsemicircularinshape,4-5infraorbitalbones,nosupraorbital;innermarginofpectoralfinwithalargeunbranchedray;afullneuralspinepresentonfirstpreuralcentrum,nomorethanoneepural,6-7hypurals,3-5uroneurals;cycloidscaleswithfineconcentriccirculiandwithbasalradii.Amongthenominatedgenerawhi…  相似文献   

3.
We studied Great Reed Warblers Acrocephalus arundinaceus at two localities in Ghana during the winter. In the north (Tono), the birds arrived from late September and conducted a rapid moult soon after arrival. Towards the end of moult, birds accumulated fat and disappeared from the site. In the south (Tafo), birds arrived from mid-November in fresh plumage. This seemed to be the final wintering area as birds stayed there during the winter. In March-April they again accumulated fat, although only small amounts, before spring migration back to breeding areas.  相似文献   

4.
Examination of the diet of Lates calcarifer , based on 3684 specimens of 4–1200 mm total length (T.L.), from two localities in north Australia showed it is an opportunistic predator with an ontogenetic progression in its diet from microcrustacea to macrocrustacea to fish. The increasing importance of fish in the diet of L. calcarifer in salt water (up to 87% of food consumed) involved a dietary shift from feeding on bottom-dwelling forms to pelagic forms. There were few differences in the diet of L. calcarifer between the two localities. Cannibalism was rarely encountered in the Gulf of Carpentaria although it was significant (11–4% of the diet of L. calcarifer of 1001–1200 mm T.L.) in Van Diemen Gulf. A significant correlation between predator and prey length was found for Ariidae, Dorosomidae, Engraulidae, L. calcarifer , Mugilidae and Polynemidae. The maximum prey/predator length ratio observed was 0–61 for the dorosomid, Nematolosa erebi.  相似文献   

5.
6.
简要回顾了内蒙古二连盆地古近系研究的历史,介绍了最新的研究进展,同时对主要地点的位置以及地层发育情况进行了讨论,并针对不同地点或地区分析了二连盆地古近系划分对比中存在的问题,对化石产地的地名和岩石地层单位名称的使用提出了建议。  相似文献   

7.
Two inshore and four shore localitites of Ligusticum scoticum in C Norway were studied regarding the growth and reproductive characteristics of the L. scoticum individuals, and the vegetation and ecology of the sites. L. scoticum showed a similar growth and reproductive characteristics at the inshore and the shore localities. The inshore localities were judged as relatively persistent on their basis of growth and reproductive characteristics and population size, and one of the inshore localities has with certainty maintained itself for at least 20 years. We suggest the inshore populations have established from seeds dispersed from the shore by birds. There were large differences in vegetation and ecological variables and cover between the inshore and the shore localities. At the inshore localities vegetation contained a large number of dwarf shrub and moss species which were almost entirely absent from the shore. Due to various physiological properties L. scoticum has a relatively better competitive ability and is better adapted to grow on inshore localities in the northern part of its distribution area. At the inshore localities L. scoticum occurred at two types of localitites: summits and rocky walls. The absence of inshore localitites in areas where conditions for further dispersal would appear to be ideal, indicate that specific conditions are required for successful establishment of L. scoticum at inshore localities. We suggest that the occurrence of L. scoticum at the summits depends to some extent promoted by the influence of birds, e.g. by nutrients in the excrements. However in the case of rocky walls this is an unlikely explanation, because individuals are often scattered over many hundreds of metres.  相似文献   

8.
The closely related species of leafhoppers, Oncopsis flavicollis (L.) and 0. subangulata (Sahl.), are restricted to birches, Betula pendula Roth and B. pubescens Ehrh., as host plants. Morphometric discriminant analyses of adult insects from S Wales showed O. flavicollis populations from the two Betula species to be significantly different. The best discrimination was provided by characters of the male dorsal abdominal apodemes. Analyses of such apodeme morphology in populations more widely from S Britain showed three distinct types: in western localities type 1 dominantly on B. pubescens , type 2 dominantly on B. pendula and type 3 absent; in eastern localities type 3 only on B. pendula , type 2 on both species of Betula and type 1 only on B. pubescens. Acoustic calling and courtship signals of males showed clear differences between the three apodeme types of 0. flavicollis. It is concluded that the three 0. flavicollis types, together with 0. subangulata , are distinct but very closely related biological species. Contrary to earlier suggestions, this example provides no evidence for host plant utilization polymorphisms.  相似文献   

9.
Three species of birds and 5 species of mammals were captured in the wild from 2 plots in which mortality from naturally occurring nucleopolyhedrosis virus (NPV) among gypsy moth,Lymantria dispar (L.), larvae was 15% and 70%. Bioassays of intestinal contents showed that blue jays,Cyanocitta cristata (L.), towhees,Pipilo erythrophthalmus (L.), white-footed mice,Peromyscus leucopus (Rafinesque), redback voles,Clethrionomys gapperi (Vigers), raccoons,Procyon lotor (L.), and a chipmunk,Tamias striatus (L.), contained infectious (L.), and masked shrews,Sorex cinereus (Kerr), did not. Comparisons among mice and voles indicated that those collected from the plot in which the NPV mortality was greatest (70%) contained the most virus. We concluded that birds and mammals can passively transport infectious gypsy moth NPV in the wild.
Résumé Trois espèces d'oiseaux et 5 espèces de mammifères ont été capturées en 2 endroits où la mortalité due à la présence naturelle du virus de la nucléopolyhédrose (VNP) chez les larves deLymantria dispar (L.), était de 15% et de 70%. Le système digestif des geais bleux,Cyanocitta cristata (L.), guiraca à poitrine rose,Pipilo erythrophthalmus (L.), souris-au-pied-blanc,Peromyscus leucopus (Rafinesque), campagnols-au-dos-rouge,Clethrionomys gapperi (Vigers), ratons laveurs,Procyon lotor (L.) et d'un tamia,Tamias striatus (L.), était infecté par le virus alors que celui des rouges-gorges,Turdus migratorius (L.) et des musaraignes,Sorex cinereus (Kerr), ne l'état pas. Une comparaison entre les campagnols et les souris a indiqué que les animaux provenant de l'endroit où la mortalité par virose était la plus forte (70%) contenaient le plus de virus. Nous concluons que les oiseaux et les mammifères peuvent transporter passivement dans la nature les polyèdres nucléaires deL. dispar.


The work reported was funded in part by a U.S. Department of Agriculture sponsored program entitled, “The Expanded Gypsy Moth Research, Development and Applications Program”.  相似文献   

10.
In the Solent estuarine system on the central south coast of England, Zostera marina L. occurs both in mainly sublittoral beds on firm substrate around the low-water mark of spring tides, and in large eulittoral beds on mudflats between the low-water mark of neap tides and the uppermost level of the shore. Zostera noltii Hornem. occurs with eulittoral Z. marina on uppershore mudflats and also on exposed sandy shores near the low-water mark of spring tides. Since 1960 the eulittoral Zostera beds have spread widely on mudflats in Portsmouth, Langstone and Chichester Harbours, where they now occupy 430–450 ha. The Zostera beds at the bottom of the shore remain winter-green, but the mudflat Zostera beds shed most of their leaves between November and January. Comparisons are made with localities further east, which show earlier and greater leaf loss.The uppershore Zostera beds in the three harbours comprise an important and favoured autumn and early winter food for Dark-bellied Brent Geese, (Branta bernicla bernicla (L.)) and Wigeon (Anas penelope L.), which consume the leaves and rhizomes, and Teal (Anas crecca L.) which consume the seed. The pattern of occurrence of these three species of birds is, to some extent, related to the availability of Zostera.  相似文献   

11.
Appreciation of the true species diversity of the genus Ulva in Australian waters has been blinkered by the unproved assumption that its representatives there are largely cosmopolitan. As species of Ulva are some of the longest‐standing and most widely reported taxa of macroalgae, the presumption that they are worldwide in distribution has led to most Australian members being equated with species originally described from extra‐Australian type localities. Ulva species can be notoriously difficult to identify due to the few and often variable characters on which classical taxonomic studies focus so that names of specimens in hand, as well as names appearing in historical distribution records, are frequently difficult or impossible to verify. The combination of morphological and molecular analyses, the latter involving both nuclear (internal transcribed spacer [ITS]) and plastid (rbcL) markers, is critically important in taxonomic studies of the genus and has here been applied to selected Ulva populations from mostly cool‐temperate southern Australian localities. It has been determined that habit‐ and anatomy‐based keys of standard taxonomic literature are largely adequate for assigning species names based on classical concepts, but they often obscure a number of cryptic and pseudocryptic species that do not conform to extra‐Australian populations of the same designation, as indicated by the corresponding molecular data. Here, we present six species (Ulva australis Aresch., U. compressa Forssk., U. fasciata Delile, U. intestinalis L., U. laetevirens Aresch., U. tanneri H. S. Hayden et J. R. Waaland) for which anatomical and molecular data were congruent with both classical concepts and GenBank accession data and confirm these as cosmopolitan taxa in Australia. We also present six putative species designations based on anatomy [U. clathrata (Roth) C. Agardh, U. flexuosa Wulfen, U. linza L., U. prolifera O. F. Müll., U. stenophylla Setch. et N. L. Gardner, U. brisbanensis sp. nov.] that are inconsistent with molecular data, suggesting novel or cryptic taxa not represented in GenBank.  相似文献   

12.
Summary The bilberry (Vaccinium myrtillus L.), is the dominant plant in the field layer of many boreal forests in northern Sweden. It is utilized by several herbivorous insect larvae as food (i.e. Lepidoptera: Geometridae, Tortricidae and Hymenoptera: Symphyta). Total density of insect larvae was 63% lower where birds had access to larvae compared to exclosures. Larvae with a feeding behaviour which exposes them to birds (geometrids and sawflies) showed a pronounced reduction in density when exposed to bird predators. Density of larvae with a concealed feeding behaviour (tortricids) was unaffected by birds. The frequency of larval damage to bilberry annual shoots was significantly higher in areas where larval density was high due to exclusion of birds. I concluded that birds have the potential to heavily modify the interaction between bilberry and insect larvae.  相似文献   

13.
Three species of the arcto-boreal, large gastropod Neptunea , described by Linnaeus in 1758 and 1771, occur in large numbers over wide areas of the inshore North Atlantic and adjacent Arctic seas and are conspicuous among Pliocene and Pleistocene molluscs in the Icelandic, North Sea, and western Mediterranean basins. Selections of lectotypes for these species from shells in the collection of the Linnean Society of London, and designations of their type localities, establish the identity of Linnaeus' neptunes and more accurately determine their geographic and geologic distribution. The geographic range of Neptunea (Neptunea) antiqua (L.), the type species, now extends from southern Norway to the northern Biscay coast of France and from the westernmost Baltic Sea to southwestern Ireland; this species also occurs in Pliocene-Holocene marine deposits in West and East Germany, Sweden, the Netherlands, England and France. Its type locality is determined to be the North Sea. N. (Neptunea) despecta (L.) lives in the eastern Canadian Arctic, off southern Greenland, the Barents Sea, and North Atlantic as far south as Massachusetts and Portugal; it also occurs in Pliocene-Holocene strata of eastern Canada, east-central Greenland, Norway (including Svalbard), the Soviet Union, Sweden and England. Its type locality is determined to be the postglacial deposits at Uddevalla in southwestern Sweden. N. (Sulcosipho) contraria (L.) now extends from the southern Biscay coast of France to Cape Spartel, Morocco; this species also occurs in Pleistocene and lower Holocene sequences of the western Mediterranean. Its type locality is determined to be Vigo Bay, Spain. A closely related fossil species, N. (S.) angulata (S. V. Wood), occurs in Pliocene and Pleistocene deposits of the North Sea basin.  相似文献   

14.
Nine new species of ascophoran cheilostome Bryozoa are described from Antarctic localities. Five species are considered to be new to science ( Smittina favulosa, Smittina diffidentia, Smittoidea pugiuncula, Escharella mamillata, Fenestrulina antarctica ), while four others have been previously recorded under other names ( Smittoidea malleata, Escharella watersi, Lacerna watersi, Hippothoa belgica ). Escharella crozetensis Waters, formerly recorded from Antarctica, is considered to be limited to the Kerguelen region of the South Indian Ocean.  相似文献   

15.
Large-scale habitat use of some declining British birds   总被引:8,自引:1,他引:7  
1. Large-scale habitat use of eight species of breeding birds was considered using data collected across Britain. The species were skylark Alauda arvensis (L.), dunnock Prunella modularis (L.), blackbird Turdus merula (L.), song thrush Turdus philomelos (L.), starling Sturnus vulgaris (L.), linnet Carduelis cannabina (L.), bullfinch Pyrrhula pyrrhula (L.) and reed bunting Emberiza schoeniclus (L.). All are linked by roughly synchronous population declines over the last 25 years in southern Britain (and mostly in farmland landscapes). Discussion is limited to the conservation status of these species.
2. Breeding densities were estimated for broad habitat types and these were used to estimate population sizes within habitat types. Confidence limits on the estimates were derived using a bootstrap procedure.
3. For most species considered, farmland holds a high proportion of their population (in excess of 50% for four species), reflecting the predominance of this land use across Britain. This suggests that sympathetic changes in farming practices are likely to provide the best mechanism for improving the status of these species.
4. Substantial proportions of particular species occur outside farmland, but different species occur in different habitats. A considerable proportion of skylarks occur on upland moor, bullfinches in wooded habitats, and reed buntings in riparian habitats. Conservation of this group of species thus requires appropriate management of the wider countryside, including their main habitats.
5. Habitats associated with human habitation hold > 20% of the British populations of blackbird, song thrush and starling, and considerable numbers of other species. The management of parks, gardens and other 'green space' may have an important impact on their populations and should not be neglected by conservationists.  相似文献   

16.
浙江临海小菜蛾成虫数量季节消长规律   总被引:2,自引:0,他引:2  
汪恩国  郑永利 《昆虫知识》2007,44(2):271-274
在浙江临海相隔60km的2个十字花科蔬菜种植区,于2002~2005年利用性诱剂诱捕器每日对小菜蛾Plutella xylostella(L.)雄成虫进行诱集并计数。对两地成虫数量季节消长与种群基数、气温、雨量和日照等因子的相关性做了统计分析,建立了5个预测模型。应用这些模型可预测全年36个旬期的雄成虫数量变化,从而可预测春季高峰期并对全年的发生量和为害程度进行预警,这对提高当地小菜蛾监测预警与综合防治水平具有实践意义。  相似文献   

17.
Several anatomical parameters of the reproductive system have been used to distinguish Lymnaea cubensis from L. viatrix, the snail hosts of fascioliasis in South America and the Caribbean area. Three samples have been collected in the type localities of L. cubensis (Cuba), L. viatrix var. A ventricosa (Argentina, Río Negro Lower Valley), and L. viatrix var. B elongata (Peru, Lima), respectively. Only one parameter, the relative lengths of the penis sheath and preputium, showed significant differences between L. viatrix var. ventricosa and the two other taxa. None of the studied parameters separated L. cubensis from L. viatrix var. elongata.  相似文献   

18.
There is a lack of information concerning the prevalence of Toxoplasma gondii infection in wild birds in Mexico. In the present study, serum samples and tissues from 653 birds from Durango State, Mexico, were evaluated for T. gondii infection. Antibodies to T. gondii (modified agglutination test, titer 1∶25 or higher) were found in 17 (2.6%) of the 653 birds, including 1 of 2 curve-billed thrashers (Toxostoma curvirostre), 2 (1 Anas platyrhynchos, 1 Anas diazi) of 4 ducks, 1 of 2 eagles (Aquila sp.), 5 (27.8%) of 18 great-tailed grackles (Quiscalus mexicanus), 7 (1.3%) of 521 rock pigeons (Columba livia), and 1 (14.3%) of 7 quail (Coturnix coturnix). The seroprevalence of T. gondii infection in birds captured in a park outside the city zoo (11.6%, 8/69) was significantly higher than that found in birds from other regions (1.5%, 9/584, OR = 8.38; 95% CI: 2.82-24.77; P = 0.0001). Brains and hearts of 23 birds (17 seropositive, 6 seronegative) were bioassayed in mice for the isolation of T. gondii . Viable T. gondii was isolated from 1 of 7 seropositive pigeons. The DNA obtained from the T. gondii isolate from the pigeon was genotyped using the PCR-RFLP typing using 11 markers (B1, SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico) and revealed an atypical genotype. This is the first report of T. gondii infection in great-tailed grackles, the Mexican duck, and curved-billed thrashers and the first survey of wild birds in Mexico.  相似文献   

19.
Among the Pleistocene localities of the Sierra de Atapuerca, the site called Sima del Elefante is famous for having delivered in its lower level (TE-LRU) some hominid remains currently considered the oldest in Western Europe (about 1.2 Ma). In its upper part (TE-URU), this site has fossiliferous levels pertaining to the late Middle Pleistocene (350-250 ka). Here we describe for the first time the amphibians and reptiles of these upper levels (TE18 and TE19), which have proved to be one of the richest assemblages of all the localities of the Sierra de Atapuerca. The faunal list is composed of 18 taxa made up of urodeles (Salamandra salamandra and Lissotriton helveticus), anurans (Discoglossus sp., Alytes sp. Pelobates cultripes, Pelodytes punctatus, Bufo bufo, Bufo calamita, Hyla arborea and cf. Rana sp.), a terrestrial tortoise (Testudo s.l.), lizards (Lacerta s.l., Podarcis sp. and Anguis fragilis) and snakes (Natrix natrix, Natrix maura, Coronella cf. girondica and Vipera latasti). For the first time, the genera Lissotriton, Discoglossus and Podarcis are mentioned in the Pleistocene localities of the Sierra de Atapuerca. TE19 also corresponds to the earliest mention for L. helveticus in the Iberian Peninsula. With the exception of tortoises, all these species are currently present in the province of Burgos, and thus suggests that the herpetofauna has a modern aspect since the Middle Pleistocene. This association of amphibians and reptiles suggests a slightly warmer climate than the current one, but may correspond to a “cold and dry” period if compared with other Pleistocene localities of the Sierra de Atapuerca. The landscape was probably composed of a gallery forest along a quiet water river within a Mediterranean environment alternating laterally between dry meadows, rocky or stony areas and open scrubland.  相似文献   

20.
Stomach contents were examined from guillemots Uria aalge (Pont.), Razorbills Alca torda Linnaeus and Little auks Alle alle (Linnaeus) killed by oil in the Skagerrak in January 1981. The range of prey species was small; the commonest fish found in the stomachs were Gobiusculus flavescens (Fabricius), Crystallogobius linearis (Düben), Sprattus sprattus (L.), Trisopterus minutus (L.) and Ammodytes sp. The relative importance of these fish depended on bird species and locality. Guillemots contained gadoids more frequently and sandeels less frequently than razorbills, and the composition of guillemot samples from Oslo Fjord differed from that of samples from Sweden. Invertebrate remains were uncommon in all bird species; the commonest items recorded were polychaete jaws. The frequency of occurrence of items in the diet of guillemots from Oslo Fjord was apparently influenced by the extent of oiling suffered by the birds.  相似文献   

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