Paolo Becciu , Kim Schalcher, Estelle Milliet, James L. Savage, Andrea Romano, Bettina Almasi, Alexandre Roulin

Parental cooperation in offspring care is essential for offspring survival in species with extended biparental care. Yet, the mechanisms through which each parent’s foraging skills and performance shape both their own and their partner’s contributions to offspring rearing, particularly in natural conditions, remain poorly understood. Using high-resolution GPS and accelerometer data, we simultaneously tracked male and female barn owls (Tyto alba) during chick-rearing to investigate parental roles in unprecedented detail. Our results reveal a spectrum of parental contributions, ranging from uniparental male care to balanced biparental effort, with individual hunting efficiency and environmental conditions considerably influencing each parent’s provisioning behaviour. Notably, we found low repeatability of biparental cooperation (biparentality) within pairs across nights, indicating that investment is dynamically adjusted in response to the partner’s
contribution and environmental factors. Females increased their foraging effort when male hunting performance declined, or resources were likely scarce. Higher biparentality across pairs was associated with enhanced growth outcomes for the
youngest chicks, underscoring the fitness benefits of cooperative parental investment. Using cutting-edge high-resolution tracking technology, this study reveals previously inaccessible insights into the flexible, context-dependent dynamics of biparental care. We demonstrate how parental roles adjust to partner contribution and behaviour under natural conditions, showcasing the potential of biologging tools to deepen our understanding of the complex and often synergistic behavioural and ecological influences on parental care.