This study examined the social preferences and reactions to strangers in young White Leghorns and red jungle fowl. Chicks were tested in two runway tests. In the first test, the chicks could choose between familiar and unfamiliar breed members. In the second test, the chicks could choose between unfamiliar chicks of their own breed and the other breed. An open field test was used to assess spacing and agonistic interactions of 28 pairs of chicks per breed (in half the pairs, chicks were unfamiliar to each other). Leghorns showed preferences for familiar chicks and avoidance of unfamiliar social stimuli during the first runway test. During the second runway test, both breeds showed preferences for their own breed members, but this was more pronounced in Leghorns. During the open field test, the Leghorns were more involved in agonistic interactions than red jungle fowl chicks. The results of this study help explain why Leghorns are less able to cope with novel social and environmental stimuli. Therefore, their welfare might be compromised in situations where they encounter unfamiliar birds.