Neighbourhood models reveal Common cuckoo parasitism decisions depend on social information

1. Individuals inadvertently provide a rich source of information about the local environment, influencing resource acquisition and breeding decisions, as well as how selection operates within and between species.2. In theory, the availability and utility of this social information should depend on proximity in time and space, as well as variation in traits between the information source and potential users. However, it remains challenging to combine these data and model how ‘neighbourhood information’ affects behavioural decisions.3. Here we adopt a common approach from plant ecology, neighbourhood models with maximum likelihood approach, to evaluate whether laying decisions of brood-parasitic Common cuckoos are influenced by variation in the availability and quality of the local host environment.4. We used a georeferenced 9-year dataset to model parasitism probability of redstart hosts depending on the characteristics of surrounding nests (neighbourhood density and variation in clutch size as a proxy for quality) and found that neighbourhoods were more informative of parasitism risk than attributes of the nest where the cuckoo deposited her egg. Although hosts of higher quality were slightly more likely to be parasitised, any given nest was less likely to be parasitised if neighbours were closer, and/or of higher quality.5. Our results therefore reveal that cuckoos gain information from patrolling host neighbourhoods beyond just monitoring for egg-laying opportunities and may make strategic decisions based on host quality. This highlights the potential for neighbourhood models to improve understanding more broadly of systems where risk or decision-making may be influenced by the social environment.