Experimental manipulation of the dawn and dusk chorus in the blackbird Turdus merula

Summary We present experimental and correlational data that demonstrate that both the nutritional state of the male and his mate's fertility affect the timing and intensity of dawn and dusk song in the blackbird (Turdus merula). Food supplementation leads to paired males singing earlier, for longer, and at higher peak rate at both dusk and dawn succeeding the treatment. We argue that the timing, not just the intensity, of song conveys information about the male's phenotypic condition. Both dawn and dusk song start earlier and have longer duration as a male's mate reaches peak fertility indicating that, in agreement with literature on the great tit (Parus major), song at this time has particular significance in mate guarding for paired males of monogamous species. We discuss the relative importance of these factors as functional explanations for the dawn chorus. Offprint requests to: I.C. Cuthill     

Development and application of a GIS-based sediment budget model

Accelerated erosion and increased sediment yields resulting from changes in land use are a critical environmental problem. Resource managers and decision makers need spatially explicit tools to help them predict the changes in sediment production and delivery due to unpaved roads and other types of land disturbance. This is a particularly important issue in much of the Caribbean because of the rapid pace of development and potential damage to nearshore coral reef communities. The specific objectives of this study were to: (1) develop a GIS-based sediment budget model; (2) use the model to evaluate the effects of unpaved roads on sediment delivery rates in three watersheds on St. John in the US Virgin Islands; and (3) compare the predicted sediment yields to pre-existing data. The St. John Erosion Model (STJ-EROS) is an ArcInfo-based program that uses empirical sediment production functions and delivery ratios to quantify watershed-scale sediment yields. The program consists of six input routines and five routines to calculate sediment production and delivery. The input routines have interfaces that allow the user to adjust the key variables that control sediment production and delivery. The other five routines use pre-set erosion rate constants, user-defined variables, and values from nine data layers to calculate watershed-scale sediment yields from unpaved road travelways, road cutslopes, streambanks, treethrow, and undisturbed hillslopes. STJ-EROS was applied to three basins on St. John with varying levels of development. Predicted sediment yields under natural conditions ranged from 2 to 7Mgkm(-2)yr(-1), while yield rates for current conditions ranged from 8 to 46Mgkm(-2)yr(-1). Unpaved roads are estimated to be increasing sediment delivery rates by 3-6 times for Lameshur Bay, 5-9 times for Fish Bay, and 4-8 times for Cinnamon Bay. Predicted basin-scale sediment yields for both undisturbed and current conditions are within the range of measured sediment yields and bay sedimentation rates. The structure and user interfaces in STJ-EROS mean that the model can be readily adapted to other areas and used to assess the impact of unpaved roads and other land uses sediment production and delivery.     

The influence of the age and sex distributions of drivers on the reduction of impaired crashes: Ontario, 1974-1999

Legislative changes and public media campaigns to prevent impaired driving are often cited as explanations for the reduction in the rate of impaired crashes over the past 25 years in most of the industrialized world. Other factors may have contributed to these reductions, such as changes in the age and sex distribution of the driver population. The primary purpose of this article is to assess the extent to which the reduction in impaired crashes in Ontario, Canada, may be attributable to the changing age and sex distribution of drivers. In Ontario, the rate of impaired crashes declined by 78.1% from 1974 to 1999. During this time period, the average age of drivers increased from 39.4 years in 1974 to 43.2 in 1999. Similarly, from 1974 to 1999 the percentage of all drivers that were women increased from 39.6% to 46.8%. Since statistics show the likelihood of impaired crashes is lower for both older drivers and women, the reduction of impaired crashes is partially due to these demographic changes. Using indirect standardization, the aging population accounted for an 8.6% decline in the rate of impaired crashes. The changing sex distribution of drivers accounted for a 9.4% decline in impaired crashes. Other global factors may also help to explain the reduction of impaired crashes, such as general road safety improvements and reductions in per adult consumption of alcohol.     

Concentrations and hazard assessment of PCBs,organochlorine pesticides and mercury in fish species from the Upper Thames: river pollution and its potential effects on top predators

Aquatic environmental contamination levels of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and heavy metals in the Upper Thames catchment area, UK were assessed on the basis of fish muscle analysis in wet weight, and their effects on top predators were assessed. The contamination levels of lead, cadmium, dichloro-diphenyl-trichloroethane (DDT) and its metabolites were found to be low (undetectable) in the area. Average mercury contamination level varied between 55 and 342 microg/kg, dieldrin between less than 0.09 and 36.8, lindane between < 0.08 and 4.94, and PCBs between < 0.77 and 3.32. Eels (Anguilla anguilla) had always much higher concentration of OCPs compared to the other fishes from the same monitoring sites. The environmental contamination level of PCBs may be partly associated with industrial and human activities, however, it was difficult to find such associations for mercury level. The hazard indices (HI) of both dieldrin and PCBs were below 1 for mink (Mustela vison). However, the HI of mercury of the all fish species from all monitoring sites are above 1 for mink. These contamination levels may be less harmful to polecats (Mustela putorius), but more so to otters (Lutra lutra) as their diets are dominated by aquatic prey.     

对英国水獭(Lutra lutra)种群生长的长期监测

欧洲水獭自50年代来明显减少,正在从许多河流消失.本研究基于对英国西部3个自然建群的集水区和英国东部2个通过人工投放加速建群的集水区的长期监测(从1977年以来)结果.到2002年,在每条河流至少收集了16年的数据,在每条研究河上设置一系列研究点,记录水獭出现点的百分率、痕迹点的痕迹数,并通过结合以上2个参数计算年种群指数.在一条自然建群的西部河流,头5年水獭种群生长快速增长,接着生长缓慢.但在2个研究开始就已经有水獭的集水区,其生长比较稳定.东部河流水獭建群的速度缓慢,随时间有巨大的波动.年种群生长率约为1%～7%,在早期较高.对水獭的年度监测计划提出了建议.     

Growth in otter (Lutra lutra) populations in the UK as shown by long-term monitoring

European otters declined dramatically from the 1950s, disappearing from many rivers. We report here on longterm monitoring (from 1977) in 3 catchments in western Britain that were recolonized naturally and in 2 catchments in eastern England that were reinforced by captive-bred otters. A minimum of 16-years data was collected on each river until 2002. At a series of sites in each study river, the percentages which were positive for otters and the number of spraints per sprainting site were recorded and combined to produce an annual index of population. One western river, naturally recolonized, showed rapid early population growth for 5 years, followed by slower growth, while growth was steadier in 2 catchments which already held some otters at the beginning of the study. Colonization on the eastern rivers was slower, with greater fluctuations over time. Annual population growth rates were estimated at 1-7%, higher in the earlier years. A strategy for annual monitoring of otters is recommended.     

<Emphasis Type="Italic">Acropora austera</Emphasis> connectivity in the south-western Indian Ocean assessed using nuclear intron sequence data

The hypervariable carbonic anhydrase 3/550 intron marker was sequenced in order to ascertain the levels of genetic variability and connectivity within and between reefal populations of the hard coral, Acropora austera, on the south-east African coastline. Populations were sampled from (north to south) Bazaruto and Inhaca islands (Mozambique), Rabbit Rock, Two-mile and Red Sands Reefs and Leadsman Shoal (Maputaland, South Africa). Populations at Inhaca Island contained two private alleles, part of the only monophyletic clade with fixed differences between populations in this study. Haplotype and nucleotide diversity were higher in the north of the study area. Indices of migration and haplotype sharing supported significant connectivity between populations in South Africa and Mozambique, which may be important in sustaining genetic diversity in the down-current South African A. austera populations. Measures of population subdivision indicated a significant amount of fixation of allele frequencies amongst populations. Although fine, such differentiation in a marker from the nuclear genome of a hard coral is consistent with some demographic isolation between A. austera populations in southern Mozambique and South Africa. Populations at Rabbit Rock and Inhaca Island were found to be significantly isolated from, and thus less connected to, A. austera populations at other reefs.     

The effects of organotin on female gastropods

Female masculinisation (FM) in gastropods (imposex, intersex and ovo-testis) has been documented in > 260 species globally. Biomonitoring studies use FM to indirectly assess the presence of tributyltin (TBT), a once popular biocide in antifouling paint, which has since been regulated. Laboratory studies confirm that FM in gastropods can be induced not only by TBT, but other tin (Sn) compounds, Sn "cocktails", steroids, and other contaminants such as Aroclor 1260. Even though FM in gastropods in the field has been attributed to TBT from boating activity, there is evidence that imposex occurred prior to the advent use of TBT in the 1960s, and for some species imposex occurs naturally. There are roughly 42 species that do not elicit a FM response even if they are exposed to TBT under laboratory conditions, collected sympatrically with other species displaying FM, and/or have TBT in their tissues. A geographic analysis of field studies in four regions indicates that the bulk of studies were conducted in Europe > Asia and Oceania > North America > Latin America. More data are needed regarding FM in Africa, the Middle East, and Latin America since data regarding the masculinisation of female gastropods in these areas are lacking. The most studied gastropod species used in TBT biomonitoring studies is the dogwhelk, Nucella lapillus. This review summarizes the progression of the literature from 1962 to 2009 outlining how the terminology, science, and theories have evolved over time.     

Scale-dependent analysis of an otter–crustacean system in Argentinean Patagonia

The Southern river otter or ‘huillin’, Lontra provocax, is an endangered species endemic of the Andean Patagonian region of Argentina and Chile. It feeds almost exclusively on the genera of macro-crustacea: Aegla and Sammastacus. The aim of this study was to analyse the role of food availability on the huillin’s distribution using a scale-dependent analysis of crustacean and otter distributions. We compared the distributions of otters and macro-crustaceans along a north–south regional gradient, between river basins of northern Patagonia, in an altitudinal gradient within a river basin, and between habitat types within a lake. We investigated the distribution of otters by sign surveys along lake shores, river banks and marine coasts, and of crustaceans using surveys in the water, undigested remains in mink (Mustela vison) scats, presence of external skeletons at the waterside and through interviews with local people. Our results show that there were heterogeneities in the distributions of macro-crustaceans at four scales and these were generally reflected in the distributions of freshwater otters. We conclude that the main factor limiting the distributions of L. provocax in freshwater environments is the availability of macro-crustaceans. This paper shows how scale-dependent type analyses of population distribution serves as a method for identifying key environmental factors for species for which the use of long-term demographies is unfeasible.