Breeding behavior of northern saw-whet owls in Oregon

We know little about the breeding behavior of most nocturnal raptors. Nest attendance and prey delivery rates can be used as indices of relative habitat quality or extent of parental care. We used video cameras to document and observe prey delivery rates, nest attendance and bout durations at two northern saw-whet owl (Aegolius acadicus) nests in two artificial nest boxes in north-central Oregon. We collected 858 hours of video surveillance between 21 March and 01 June 2014. The number of prey deliveries per night increased as the nesting season progressed: 1.25 during laying, 1.33 during incubation, and 4.0 during the nestling phase. Prey was delivered most often between 2100 and 2200. Nest attendance by females was high during pre-laying (97.8%), laying (97.9%) and incubation (98.2%), but decreased during the nestling phase (55.7%). Nest attendance was higher during diurnal hours than nocturnal hours across all nesting phases. Duration of off bouts (recesses) was similar during pre-laying and laying (26 min), decreased during incubation (19 min), then increased during the nestling phase (55 min). One of the nesting attempts was successful and the female abandoned the other clutch 22 days after initiation. The incubation and nestling periods were 30 days each.