In 2008, SBS commissioned the Centre for Agri-Environmental Research (CAER) at the University of Reading to carry out a comprehensive review of all predation research carried out in the UK to date. The aim of the review was to:

  • Clearly describe the state of current knowledge on predation.
  • Critically evaluate the existing evidence linking changes in predator populations with changes in the numbers of their avian prey.
  • Identify key issues requiring future research.

The project was conducted by Dr. Malcolm Nicoll, a post-doctoral Research Fellow within the centre under the supervision of Professor Ken Norris, Director of CAER. It took approximately two years to complete.

Read the full research report here.


Summary of Findings

  • The probability of a study detecting an impact on prey abundance was strongly, positively related to the quality and quantity of data upon which the gradient in predation rates was inferred

  • The assessment of the quality of the evidence presented by studies which found no impact of predation on songbird abundance, typically graded this evidence as low or very low quality

  • Findings from studies which use opportunistic data, for a limited number of predator species, should be treated with caution

  • Future studies should employ bespoke census techniques to monitor predator abundance for an appropriate suite of predators

  • Future studies should consider including all appropriate widespread and local predators (i.e. a suite of predators where appropriate) in order to maximize the potential of detecting a predator impact if it exists

The study reviewed 32 published studies and called into question the validity of existing approaches which have failed consider all appropriate widespread and local predators (i.e. a suite of predators where appropriate). The re-establishment of a community of predators across the UK, has potentially resulted in prey populations experiencing a cumulative predation impact by multiple predator species rather than a single predator species in isolation.

The quality of evidence used in research which found no impact of predation on songbird abundance, was found to be low or very low, raising the issue of whether or not a null result is believable based on the evidence presented. This is particularly relevant to studies such as the SBS-funded research into avian and grey squirrel predation.

Citation: Nicoll, M.A.C. and Norris, K. (2010). Detecting an impact of predation on bird populations depends on the methods used to assess the predators. Methods in Ecology & Evolution 1: 300–310.

Researcher profiles

Dr Malcolm Nicoll
Dr Nicoll was Senior Research Fellow at the Centre for Agri-Environmental Research (CAER) at the University of Reading when he undertook this research commissioned by SBS. His research experience centres on understanding the ecology and dynamics of threatened species populations in a rapidly changing environment. His interests also lie in the implementation and refinement of management techniques applied to remnant wild and reintroduced populations.

Professor Ken Norris
Professor Norris was Director of the Centre for Agri-Environmental Research (CAER) at the University of Reading when he supervised this SBS-funded research project. His research interests span a range of individual, population, community and ecosystem approaches to understanding how biodiversity responds to environmental change. This work has included a long-term interest in basic and applied avian ecology.