We investigated the post-fledging ecology of the Northern Pygmy-Owl (Glaucidium gnoma) at two study areas in the Rocky Mountains of Montana and Idaho from 2002 to 2009. We observed 16 successful nesting attempts that fledged from two to seven young. Fledging dates ranged from 18 June to 5 August and all nests were vacated within a 2-day period. Post-fledging behavioral data were collected regularly from fledging through initiation of natal dispersal from five radiomarked family groups and opportunistically from three additional family groups. Post-fledging movement data were collected from eight family groups and two males that were suspected of nesting. Adults attended broods for 9 to 30 days (females) and 31 to 34 days (males) postfledging, after which they were not observed associating with their young. Young remained within the natal territory for 1 to 10 days following departure of adult males, after which they abruptly initiated natal dispersal. Areas used by family groups during the post-fledging dependency period ranged from 34.6 to 94.5 ha. Family groups were active throughout the day, but activity was notably more intense during crepuscular periods. Our earliest observations of young hunting occurred 9 days after fledging and 47% of all fledgling hunting attempts observed (n = 75) were successful. Adults and fledglings used vocalizations in contexts consistent with previous descriptions with the exception of an undescribed two-note vocalization that appeared to function as a contact call preceding prey deliveries.
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Vol. 124 • No. 2