Brood size affects maternal behaviour and chick’s social development in a precocial bird

International audienceThe size of a brood can be costly for the mother, which in turn can influence the level of her investment in each offspring. This factor can lead to a change in the development of offspring. Here we investigated the influence of brood size on maternal and chicks’ behaviour during the mothering period and on offspring development in the Japanese quail. We compared two sizes of brood: small broods of three chicks (N=9) and large broods of six chicks (N=9). We observed mothers’ and chicks’ behaviour during the mothering period and we assessed chicks’ social and emotional traits with behavioural tests. Our results show that mothers of large broods emitted more maternal vocalisations at the beginning of mothering period but, at the end, they were more negligent with their chicks than mothers of small broods. Furthermore, chicks of large brood huddled up more whereas chicks of small broods rested alone more frequently. Finally, these chicks developed a higher level of social motivation than that of small brood chicks, although their emotional reactivity levels were no different. We evidence the importance of brood size and the brood’s influence on the chicks’ interactions with their siblings which both impact on the chicks’ social development