Parent-offspring conflict over the decision on the length and termination of parental care in a bird of prey

Abstract Background Parent-offspring conflict is a fundamental concept in evolutionary biology that explains the discrepancy between parents’ and offspring’s optimal strategies for allocating parental investments. Two alternative evolutionary strategies were proposed to explain the timing of termination of the post-fledging dependence period (PFDP). The age-of-independence hypothesis (H1) predicts that offspring will receive parental care for as long as possible, as determined by parents. The early-dispersal hypothesis (H2) states that young attain independence as soon as possible once reaching ontogenetic maturity, as determined by offspring. Results We radio-tracked 91 Tengmalm’s owl ( Aegolius funereus ) fledglings from 31 nests over six years in Czechia and Finland until independence. The mean, minimum and maximum recorded PFDP durations were longer in Czechia [49.4 ± 6.4 days (mean ± SD; range: 34–61 days)] than in Finland [38.3 ± 6.5 days (28–54 days)]. In both areas, the PFDP duration was relatively short (44.5 ± 4.9 vs. 36.6 ± 4.8 days, respectively) during the rich, but much longer (56.7 ± 3.4 vs. 50.5 ± 2.5 days, respectively) during the poor season of food abundance. The PFDP was shorter across sites with delayed hatching dates, probably reflecting the higher quality of early-nesting parents and their ability to invest more in offspring, as well as the need for all parents to recover from parental effort before winter onsets. The longer PFDPs during food shortage, and in Czechia compared to Finland, as well as the shorter PFDP duration with delayed offspring hatching dates, supported the age-of-independence hypothesis (H1), but were inconsistent with the early-dispersal hypothesis (H2). Therefore, we suggest that parents primarily decide on the length and termination of PFDP. Conclusions We suggest that maintaining prolonged PFDP parental care is important for Tengmalm’s owl offspring’s prospects, enabling the development of flight skills that directly impact hunting success after reaching independence, the critical period for their future survival. Finally, our results demonstrate, for the first time, that differing environmental conditions across distant study sites (Central versus North Europe) are crucial in determining PFDP duration, an important life-history trait of altricial birds.