Sex allocation theory predicts that whenever the relative fitness of sons and daughters differ, females should invest more
in the sex with the greatest fitness return. In this study, we evaluated the influence of various ecological factors on the
brood sex ratio (BSR) of Savi’s warblers (Locustella luscinioides) across several breeding seasons. There was a slight but significant female production bias at the population level, which
is consistent with the ‘local resource competition’ hypothesis, as the breeding density is very high and females are more
prone to disperse. We found that there was a significant decline in BSR during the breeding season, but no influence of male
size, female size, social status nor extra-pair paternity were detected. The seasonal decline in BSR was further evaluated
by assessing the within- and between-female effects, which indicated that multiple factors were operating simultaneously in
our study population. First, there was a significant within-female decline in BSR, which was consistent with the decline in
female condition due to the reproductive effort associated with multiple brooding (supporting the Trivers and Willard hypothesis).
Second, a significant decline in BSR with the laying date of first clutches of different pairs indicated that male and/or
female qualities are also associated with the seasonal variation in BSR. Finally, a comparison between the sex of the youngest
nestling with the remaining ones did not suggest any bias, indicating that females do not compensate for the increased mortality
of the last nestling (caused by asynchronous hatching) by producing a male from the last laid egg. 相似文献
There is a need to reduce the amount of fossil energy used for transport, both because of the easily available fossil fuel is becoming sparser and because of climate concerns. In this article, the concept of “peak oil” is briefly presented. Second, a practical approach to reduction of fossil fuel use for transport elaborated by two British commissions is presented. A key feature is the introduction of electric cars. This raises the third issue covered in this article: namely, how battery technology is going to meet the increasing needs posed by the transport sector. 相似文献
Relevant and understandable environmental information about production and products is needed in any attempt to mitigate environmental impact from production, products, and consumption. This paper introduces an analytical framework for studying the drivers, barriers and enablers of corporate environmental information collection, management and communication. The framework is built up by two main parts. In the first, we sort out what corporate environmental information is and how to spot gaps in information collection, management and communication. The second part examines the stakeholders and company features that could constitute important influencing factors. The framework is intended to support qualitative and quantitative studies which aim to increase understanding of what shapes the flow of environmental information in companies and product chains. 相似文献
Life-cycle assessments are normally made without quantitative estimations of their uncertainty. More interest has been focused on sensitivity analysis. In ISO 14040, LCA standard and SETAC's ‘code of practice’ sensitivity and uncertainty analysis are recommended or even requested. In the EPS system, an analysis of significance and sensitivity has been carried out for several years. The article describes this procedure in ISO terms and generalises it for other types of life-cycle assessments. 相似文献
Many cities today face challenges related to urban growth. This is also the case in Oslo, currently one of the fastest growing capitals in Europe. In order to prepare for the population growth, a new municipal master plan has been prepared. In this, sustainable development is a prominent concept, and the urban district is going to be densified as part of the strategy. This paper examines some obstacles of turning planning theory into practice. There is a lack of coherence between municipal goals and the actual outcome. The analysis indicates that the official strategy is not able to cater for social sustainability partly due to institutional constraints. Moreover, there is no concise understanding of what sustainability means, which in turn hampers the ability to operationalise the concept in urban planning. 相似文献
Summary Tengmalm's owl Aegolius funereus is a hole-nesting polygynous species in which female nomadism is a reaction to cyclic lows of staple prey. For 2 years during a peak in vole abundance, I examined recruitment of mates and male singing behavior in a local population. Females and about half of the breeding males seemed to arrive successively throughout the breeding period of the first year. In contrast, a majority of the breeding males and likely also females were already on the breeding grounds at the beginning of the breeding season in the second year. Before breeding in the first peak year, males were singing at up to five different nest holes. All early breeding males (67% of total number) continued to sing at secondary nest holes after attracting and installing primary females. Secondary singing locations were never closer than 300 m from primary females' nest holes, although closer locations were used for singing before mating. All bigynous males with nests within the study area were also singing at tertiary nest holes, but none successfully attracted a third female. Polyterritoriality was confirmed by a late male settling between primary and secondary nest holes of a bigynous male. Polyterritorial behavior and reduced breeding success of secondary females are in line with the deception model. Females apparently could not discriminate between paired and unpaired singing males. Females made short visits to different males before mating. During courtship, the number and quality of nest holes defended by males may have been of particular importance to female choice. 相似文献
The multi-scale approach to conserving forest biodiversity has been used in Sweden since the 1980s, a period defined by increased reserve area and conservation actions within production forests. However, two thousand forest-associated species remain on Sweden’s red-list, and Sweden’s 2020 goals for sustainable forests are not being met. We argue that ongoing changes in the production forest matrix require more consideration, and that multi-scale conservation must be adapted to, and integrated with, production forest development. To make this case, we summarize trends in habitat provision by Sweden’s protected and production forests, and the variety of ways silviculture can affect biodiversity. We discuss how different forestry trajectories affect the type and extent of conservation approaches needed to secure biodiversity, and suggest leverage points for aiding the adoption of diversified silviculture. Sweden’s long-term experience with multi-scale conservation and intensive forestry provides insights for other countries trying to conserve species within production landscapes.