Testing territorial behaviour
Krebs’s doctoral research examined great-tit populations and territories. Building on long-term monitoring, he compared interventions such as adding food and removing territorial birds. Rapid reoccupation of favourable sites showed how territorial behaviour can influence where different individuals breed.
Benefits and costs of foraging
Working in Canada, Krebs explored with colleagues how animals distribute themselves among patches of food. A central question was when a bird should leave a patch as its resources decline. Travel time, energetic costs and uncertainty about the next patch could be represented in models and compared with experimental behaviour.
References: [1]
Quantitative thinking and observation
In a 2013 interview, Krebs recalled the influence of his supervisor Mike Cullen’s quantitative approach. His research combined statistical analysis of long-term population records with manipulation of food and territorial conditions, moving from descriptions of behaviour toward testable predictions.
References: [1]
Research administration and public affairs
Krebs became head of the Natural Environment Research Council in 1994 and took a leadership role in the new Food Standards Agency in 2000. Reflecting on these roles, he emphasised communicating evidence, uncertainty and further investigation separately, carrying an experimental outlook into public science.
References: [1]