KEVIN J GASTON

Bonnington, C., Gaston, K.J. & Evans, K.L. 2013. Fearing the feline: domestic cats reduce avian fecundity through trait-mediated indirect effects that increase nest predation by other species. Journal of Applied Ecology 50, 15-24.

Urban areas contain high densities of non-native species, which in the UK include the domestic cat and the grey squirrel. The direct predation effects of domestic cats on prey populations attract intense debate, and such influences of the nest-predatory grey squirrel are receiving increasing attention. In contrast, theory predicts that sublethal and indirect effects are more important, but empirical evidence is currently lacking. We conducted controlled model presentation experiments at active urban blackbird nests to provide the first empirical evidence that quantifies the potential sublethal and indirect effects of predators (domestic cat and grey squirrel) on avian reproductive success. Domestic cat models reduced subsequent parental provisioning rates, a strong indicator of sublethal effects, by one-third relative to a nonpredatory rabbit control. There was no compensatory increase in food load size. Previous experiments demonstrate that this magnitude of reduced food delivery will reduce nestling growth rates by c. 40%. The grey squirrel model induced similar but weaker effects. Following the brief presence of the domestic cat model, subsequent daily nest predation rates, chiefly by magpies and carrion crows, increased by an order of magnitude relative to the squirrel and rabbit models. The intensity of parental nest defence elicited in response to model presentations predicts the probability of such third-party predator predation events, and the domestic cat model generated significant increases in nest defence behaviour. It is imperative that future assessments of the impact of predatory species on avian prey species take lethal trait-mediated indirect effects into account, as so doing will prevent biased estimates of predator effects and facilitate the design of more effective management strategies.

Dornelas, M., Magurran, A.E., Buckland, S.T., Chao, A., Chazdon, R.L., Colwell, R.K., Curtis, T. Gaston, K.J., Gotelli, N.J., Kosnik, M.A., McGill, B., McCune, J.L., Morlon, H., Mumby, P.J., Øvreås, L., Studeny, A. & Vellend, M. 2013. Quantifying temporal change in biodiversity: challenges and opportunities. Proceedings of the Royal Society, B 280, 20121931.

Growing concern about biodiversity loss underscores the need to quantify and understand temporal change. Here, we review the opportunities presented by biodiversity time series, and address three related issues: (i) recognizing the characteristics of temporal data; (ii) selecting appropriate statistical procedures for analysing temporal data; and (iii) inferring and forecasting biodiversity change. With regard to the first issue, we draw attention to defining characteristics of biodiversity time series – lack of physical boundaries, uni-dimensionality, autocorrelation and directionality – that inform the choice of analytic methods. Second, we explore methods of quantifying change in biodiversity at different timescales, noting that autocorrelation can be viewed as a feature that sheds light on the underlying structure of temporal change. Finally, we address the transition from inferring to forecasting biodiversity change, highlighting potential pitfalls associated with phase-shifts and novel conditions.

Edmondson, J.L., Davies, Z.G., McHugh, N., Gaston, K.J. & Leake, J.R. 2012. Organic carbon hidden in urban ecosystems. Scientific Reports 2, 963.

Urbanization is widely presumed to degrade ecosystem services, but empirical evidence is now challenging these assumptions. We report the first city-wide organic carbon (OC) budget for vegetation and soils, including under impervious surfaces. Urban soil OC storage was significantly greater than in regional agricultural land at equivalent soil depths, however there was no significant difference in storage between soils sampled beneath urban greenspaces and impervious surfaces, at equivalent depths. For a typical U.K. city, total OC storage was 17.6 kg m-2 across the entire urban area (assuming 0 kg m-2 under 15% of land covered by buildings). The majority of OC (82%) was held in soils, with 13% found under impervious surfaces, and 18% stored in vegetation.Wereveal that assumptions underpinning current national estimates of ecosystem OC stocks, as required by Kyoto Protocol signatories, are not robust and are likely to have seriously underestimated the contributions of urban areas.

A warm welcome to James Duffy, who joins the research group as a technician, providing analytical support for a range of projects. We look forward to keeping him very busy!

Fuller, R.A., Irvine, K.N., Davies, Z.G., Armsworth, P.R. & Gaston, K.J. 2012. Interactions between people and birds in urban landscapes. Studies in Avian Biology 45, 249-266.

A large body of work over the past few decades has revealed the manifestly dramatic impacts of urbanization on species’ distributions and ecologies, many of which result from gross changes in land use and configuration. Less well understood are the rather more direct interactions between people and biodiversity in the urban arena. While there is a general concern that urbanization impoverishes human contact with nature, daily interaction with biodiversity in urban greenspaces and the widespread provision of food and nesting resources for wildlife form a part of many city-dwellers’ experience. Using data from the UK, we show that supplementary resource provision aimed explicitly at enhancing avian populations can result in high levels of additional foraging and nesting opportunities, particularly in urban areas. However, our data also indicate that levels of such resource provision are strongly positively correlated with human population density at a regional scale, and within a large city. The proportion of households participating in bird feeding depends on social and economic features of the human population, suggesting that strong covariation between human and ecological communities will result. Indeed, we demonstrate that the abundances of some urban-adapted bird species are positively related to the density of feeding stations across the urban landscape, although such relationships were not apparent for other species that commonly use garden feeding stations. It has been suggested that interactions with nature, such as feeding birds, could have beneficial consequences for human health. A better understanding of this potential feedback is required.

Webb, T.J., Freckleton, R.P. & Gaston, K.J. 2012. Characterising abundance-occupancy relationships: there is no artefact. Global Ecology & Biogeography 21, 952-957.

A short piece logically and empirically refuting a recent suggestion that interspecific relationships between local abundance and regional occupancy are often artefactual. Rather, these patterns remain fundamentally important descriptors of the structure of species assemblages.

Canard, E., Mouquet, N., Marescot, L., Gaston, K.J., Gravel, D. & Mouillot, D. 2012. Emergence of structural patterns in neutral trophic networks. PLoS One 7, e38295.

Networks of interactions between species are central elements of ecological systems and have very complex structures. Historically, much effort has focused on niche-mediated processes to explain these structures, while an emerging consensus posits that both niche and neutral mechanisms simultaneously shape many features of ecological communities. However, the study of interaction networks still lacks a comprehensive neutral theory. Here we present a neutral model of predator-prey interactions and analyze the structural characteristics of the simulated networks. We find that connectance values (complexity) and complexity-diversity relationships of neutral networks are close to those observed in empirical bipartite networks. High nestedness and low modularity values observed in neutral networks fall in the range of those from empirical antagonist bipartite networks. Our results suggest that, as an alternative to niche-mediated processes that induce incompatibility between species (‘‘niche forbidden links’’), neutral processes create ‘‘neutral forbidden links’’ due to uneven species abundance distributions and the low probability of interaction between rare species. Neutral trophic networks must be seen as the missing endpoint of a continuum from niche to purely stochastic approaches of community organization.

Davies, Z.G., Fuller, R.A., Dallimer, M., Loram, A. & Gaston, K.J. 2012. Household factors influencing participation in bird feeding activity: a national scale analysis. PLoS One 7, e39692.

In highly urbanized nations, domestic gardens can play a significant role in maintaining biodiversity and facilitating human-wildlife interactions, which benefit personal and societal health and wellbeing. The extent to which sociodemographic and socioeconomic factors are associated with engagement in wildlife gardening activities remain largely unresolved. Using two household-level survey datasets gathered from across Britain, we determine whether and how the socioeconomic background of a household influences participation in food provision for wild birds, the most popular and widespread form of human-wildlife interaction. A majority of households feed birds. House type, household size and the age of the head of the household were all important predictors of bird feeding, whereas gross annual household income, the occupation of the head of the household, and whether the house is owned or rented were not. In both surveys, the prevalence of bird feeding rose as house type became more detached and as the age of the head of the household increased. A clear, consistent pattern between households of varying size was less evident. When regularity of food provision was examined in the study cities, just 29% of households provided food at least once a week. The proportion of households regularly feeding birds was positively related to the age of the head of the household, but declined with gross annual income. As concerns grow about the lack of engagement between people and the natural environment, such findings are important if conservation organizations are successfully to promote public participation in wildlife gardening specifically and environmentally beneficial behaviour in society more generally. [Image: M.J. Gaston]