Flexible Resource Use but Consistent Parental Care across Populations in a Nocturnal Raptor

Gian Luigi Bucciolini , Patrik Karell, Jon Brommer, Pietro Semprebon, Marie Delmas, Peter Ericsson, Lars-Ove Nilsson, Chiara Morosinotto

Parental investment is often quantified by how much food offspring receive, yet parental behaviour throughout the breeding phase and the timing and composition of resource delivery may be equally important. We tested this by integrating behaviour, diet and activity rhythms in two populations of tawny owl (Strix aluco) in northern Europe. Parental behaviour followed conserved temporal patterns across populations, shifting from nest attendance before hatching to increased provisioning activity as chicks developed. In contrast, diet composition (the identity and relative abundance of prey types) varied geographically despite similar diet diversity and prey biomass, indicating flexible resource use while maintaining comparable overall dietary breadth and energy intake. Provisioning activity was strongly nocturnal and highly consistent between populations, although prey-specific timing reflected differences in prey ecology. Different components of parental investment were associated with different reproductive outcomes: diet diversity increased fledgling success, while provisioning effort was associated with earlier fledgling.
Together, these results show that behavioural and temporal patterns are conserved but diet composition remains flexible. This combination between flexibility and conserved traits allows consistent reproductive performance across environments and highlights that multiple, interacting components of parental investment underlie fitness variation.