Supplementary feeding of wild birds indirectly affects the local abundance of arthropod prey

Providing supplementary food for wild birds is a globally popular past-time; almost half of the households in many developed countries participate and billions of US dollars are spent annually. Although the direct influence of this additional resource on bird survivorship and fecundity has been studied, there is little understanding of the wider ecological consequences of this massive perturbation to (what are usually) urban ecosystems. We investigated the possible effects of wild bird feeding on the size and survivorship of colonies of a widespread arthropod prey species of many small passerine birds, the pea aphid [Acyrthosiphon pisum (Harris); Hemiptera: Aphididae], in suburban gardens in a large town in southern England. We found significantly fewer aphids and shorter colony survival times in colonies exposed to avian predation compared to protected controls in gardens with a bird feeder but no such differences between exposed and protected colonies in gardens that did not feed birds. Our work therefore suggests that supplementary feeding of wild birds in gardens may indirectly influence population sizes and survivorship of their arthropod prey and highlights the need for further research into the potential effects on other species.

An objective, niche-based approach to indicator species selection

1. Species-based indices are frequently employed as surrogates for wider biodiversity health and measures of environmental condition. Species selection is crucial in determining an indicators metric value and hence the validity of the interpretation of ecosystem condition and function it provides, yet an objective process to identify appropriate indicator species is frequently lacking. 2. An effective indicator needs to (i) be representative, reflecting the status of wider biodiversity; (ii) be reactive, acting as early-warning systems for detrimental changes in environmental conditions; (iii) respond to change in a predictable way. We present an objective, niche-based approach for species' selection, founded on a coarse categorisation of species' niche space and key resource requirements, which ensures the resultant indicator has these key attributes. 3. We use UK farmland birds as a case study to demonstrate this approach, identifying an optimal indicator set containing 12 species. In contrast to the 19 species included in the farmland bird index (FBI), a key UK biodiversity indicator that contributes to one of the UK Government's headline indicators of sustainability, the niche space occupied by these species fully encompasses that occupied by the wider community of 62 species. 4. We demonstrate that the response of these 12 species to land-use change is a strong correlate to that of the wider farmland bird community. Furthermore, the temporal dynamics of the index based on their population trends closely matches the population dynamics of the wider community. However, in both analyses, the magnitude of the change in our indicator was significantly greater, allowing this indicator to act as an early-warning system. 5. Ecological indicators are embedded in environmental management, sustainable development and biodiversity conservation policy and practice where they act as metrics against which progress towards national, regional and global targets can be measured. Adopting this niche-based approach for objective selection of indicator species will facilitate the development of sensitive and representative indices for a range of taxonomic groups, habitats and spatial scales.

Lyme borreliosis in the UK: ecology and risks to domestic animals and man

The different associations of Borrelia burgdorferi sensu lato spirochaetes with their natural reservoir hosts and tick vectors are slowly being unravelled. This review discusses the interactions of different genospecies of Lyme borreliosis spirochaetes and their differing tick vectors, vertebrate reservoirs and 'accidental hosts'. Particular reference is made to spirochaete-host interactions and occurrence of pathological consequences. Attention is focused on the unique prevalence of enzoonotic cycles in operation within the UK. Risk factors for acquiring Lyme borreliosis in man are discussed. (C) 2001 Lippincott Williams & Wilkins.

Beyond urban legends : an emerging framework of urban ecology, as illustrated by the Baltimore Ecosystem Study

The emerging discipline of urban ecology is shifting focus from ecological processes embedded within cities to integrative studies of large urban areas as biophysical-social complexes. Yet this discipline lacks a theory. Results from the Baltimore Ecosystem Study, part of the Long Term Ecological Research Network, expose new assumptions and test existing assumptions about urban ecosystems. The findings suggest a broader range of structural and functional relationships than is often assumed for urban ecological systems. We address the relationships between social status and awareness of environmental problems, and between race and environmental hazard. We present patterns of species diversity, riparian function, and stream nitrate loading. In addition, we probe the suitability of land-use models, the diversity of soils, and the potential for urban carbon sequestration. Finally, we illustrate lags between social patterns and vegetation, the biogeochemistry of lawns, ecosystem nutrient retention, and social-biophysical feedbacks. These results suggest a framework for a theory of urban ecosystems.

Anthropogenic natal environmental effects on life histories in a wild bird population

Recent work suggests that the environment experienced in early life can alter life histories in wild populations [1, 2, 3, 4 and 5], but our understanding of the processes involved remains limited [6 and 7]. Since anthropogenic environmental change is currently having a major impact on wild populations [8], this raises the possibility that life histories may be influenced by human activities that alter environmental conditions in early life. Whether this is the case and the processes involved remain unexplored in wild populations. Using 23 years of longitudinal data on the Mauritius kestrel (Falco punctatus), a tropical forest specialist, we found that females born in territories affected by anthropogenic habitat change shifted investment in reproduction to earlier in life at the expense of late life performance. They also had lower survival rates as young adults. This shift in life history strategy appears to be adaptive, because fitness was comparable to that of other females experiencing less anthropogenic modification in their natal environment. Our results suggest that human activities can leave a legacy on wild birds through natal environmental effects. Whether these legacies have a detrimental effect on populations will depend on life history responses and the extent to which these reduce individual fitness.