Cognitive abilities bring together all of the mental processes such as attention, memory, and reasoning skills that allow an animal to understand and to adapt to its environment. They are the basis of many behaviours. In this review, in a synthetic way, we will first make an inventory of current knowledge on the cognitive capacities of domestic birds, such as hens or chickens. We will show that these birds have a diverse sensory universe, are capable of rich social interactions and of learning, among other capacities. Even if there is still research to be carried out, these birds probably have a repertoire of cognitive abilities much more extensive than what is though. In a second part, we will illustrate that this knowledge brings a new vision of our understanding of certain behaviours observed in farming systems, such as range exploration of free-range chickens, or injurious pecking in laying hens. This knowledge and this research theme, which are currently developing more and more at the international level, will contribute to a better understanding of the biology of these animals and could, in the long term, provide original avenues for promoting the adaptation of these birds to their rearing system and their welfare.