This collection summarises the rich body of research on understanding the behaviour of chickens and using this knowledge to optimise welfare management of broilers and layers.Part 1 of this volume reviews advances in research on key aspects of poultry behaviour and welfare monitoring. Chapters include the genetics and epigenetics of poultry behaviour, sensory perception, pain and strass responses, leaning and cognition as well as social behaviour. The section also includes coverage of wearable, video and acoustic technologies to monitor chicken behaviour and welfare as well as developments in welfare protocols.Part 2 discusses particular welfare issues affecting broilers and layers. Topics covered include welfare in hatcheries and during rearing, housing and management, the role of enrichment as well as optimising welfare during catching, transport and slaughter. It also reviews advances in understanding specific welfare issues such as injurious pecking, bone and skin health.