Rearing group size in young ravens: stress load or social opportunity?

Understanding how variations in early social environments generate different experiences for offspring (affecting their behaviour and the way others behave towards them) is crucial for uncovering mechanisms underlying the development of social behaviour. However, little is known about how subtle variations in rearing conditions—such as sibling numbers—affect the social experiences individuals undergo during development. Ravens exhibit diverse social strategies to access and secure food. Here, we investigated whether and how family size affects ravens’ early-life experiences, notably their competition and tolerance at food. Over three years, we manipulated offspring numbers in 15 captive families and tracked 35 offspring raised in small (F−; one or two chicks) or large families (F+; three or four chicks) exposed post-fledging to varying food distribution (one or two pieces). Offspring accessed food more easily in the two-piece condition and showed increased co-feeding and aggression as they aged. However, family size shaped sex differences: F− females, mostly from single-sex broods, exhibited better food access, higher co-feeding rates and more parental provisioning than F− males and F+ offspring. These findings highlight family size as a key determinant of early social experiences in ravens. Future studies should investigate how these experiences relate to socio-cognitive skills later in life.