Mother-chick interactions are affected by chicks' sex and brood composition in Japanese quail

Sex is a trait which leads mothers to invest asymmetrically in their young, especially in species with a strong dimorphism. Authors usually consider that members of the largest sex require the most investment by mothers. In other cases, mothers care preferentially for members of the sex that increase their fitness, e.g. males, in numerous species. In quail, a precocial bird, mother seems to take more care of their males which are more sensitive to their separation. This study investigates the influence of chicks' sex and brood's sexual composition on the maternal behavior of quail. We evaluated three batches of mothers, composed of (a) unisex broods of males (MM), (b) unisex broods of females (FF), and (c) mixed sex broods (Mx). We recorded mother-chick interactions during 11 days of mothering. We found that MM mothers spent more time warming their chicks and FF mothers were more active. Moreover, females rejected more aggressively and earlier their female chicks than their male chicks. Finally, Mx chicks, whatever their sex, interacted more with their mothers. Our results highlight a greater quantity and quality of maternal care towards male. Mothers invest more in male chicks. We discussed results in terms of each sex's needs.