Spatial and begging behaviours of juvenile Tawny Owls (Strix aluco) from fledging to independence under contrasting food conditions

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The post-fledging dependency period (PFDP: from fledging to cessation of parental care) is a critical yet poorly studied life history transition phase during which juveniles mature and develop skills for independence. We studied the spatial and vocal behaviour of radio-tagged juvenile Tawny Owls in 41 broods from fledging to independence (56–84 days) in 6 years of contrasting food conditions. Dispersion and nocturnal movements increased during the first 20–30 days post-fledging, after which the young roamed the entire natal territory, indicating fully or almost fully developed flying skills. During the entire PFDP, siblings were strongly associated both during the day (mean inter-sibling distances decreased from 11 to 0.6 m from the first to the 30th day after fledging) and at night (mean distances decreased from 32 to 6 m during the same period), and rarely moved outside the borders of the parental home range. The probability of begging per 20-min nocturnal observation period increased from 21 % at fledging to 80 % at independence during years of good food supply, but remained high (>82 %) in years of poor food supply. No change was observed in nocturnal movement distances or begging rates during the last 5 days before juvenile independence. Hence, juvenile Tawny Owls old enough to survive on their own invested heavily in begging, with no noticeable signs of increased hunting or exploration of potential settling areas outside the natal range, until they were no longer fed by their parents.