Lr. Powers et al., NESTING AND FOOD-HABITS OF THE FLAMMULATED OWL (OTUS-FLAMMEOLUS) IN SOUTH-CENTRAL IDAHO, The Journal of raptor research, 30(1), 1996, pp. 15-20
Flammulated owls (Otus flammeolus) arrived at our 25-km(2) study area
in Idaho from mid- to late May 1991-94. Twenty-four nesting pairs util
ized 22 nesting cavities. Twenty (83%) of the nests were in dead trees
and four (17%) in live trees. Thirteen (54%) nests were in broken-top
Douglas-fir (Pseudotsuga menziesii) snags, and 11 (46%) were in tremb
ling aspen (Populus tremuloides). Mean diameter at breast height of 13
nest trees was 49.9 cm (SD = 18.9), while mean cavity height was 5.1
m (SD = 0.6). Mean entrance diameter for 11 nests was 6.8 cm (SD = 1.3
). Mean hatching date at 11 of the 24 nests was 26 June (range, 12 Jun
e through 11 July) and mean fledging date was 18 July (range, 7 July t
hrough 2 August). Mean brood size for nine nests was 2.3 (range, 2-3)
young per nest. Nightly food deliveries at nest sites peaked within th
e 2-hr period after dark and before daylight. Mean number of nest visi
ts by adults during the nesting stage was 93. Although lepidopterans c
omprised 79% and orthopterans 0.3% of the available prey within the st
udy area in 1992, 65 food deliveries at one nest revealed 43.1% orthop
teran and 9.2% lepidopteran prey. At other nest sites, lepidopterans w
ere the prominent prey. Four banded owls returned to the same territor
y for two, three, and four consecutive nesting seasons.