Frye and Jageman • NORTHERN PYGMY-OWL POST-FLEDGING ECOLOGY 
203 
Five radio-marked males (MT-1, MT-2, MT-3, 
MT-4, ID-4) returned to the nest stand (850- 
3,171 m distant) within 6-16 days (37-50 days 
alter Hedging; Table 2). All females with active 
transmitters (MT-1. MT-2, MT-4, ID-2) returned 
to the nest stand 31-35 days after departing family 
groups (40-57 days after fledging; Table 2). 
Females relumed to the nest stand 5-12 days 
later than males within territories (Table 2). Wc 
observed mated pairs together shortly after 
females returned to the nest stand at all but one 
of these territories. 
Five males that were eilher confirmed or 
suspected to be breeding (ID-1. ID-2, ID-5, ID- 
6. ID-7) exhibited a different movement pattern 
after the post-fledging dependency period. These 
males made relatively abrupt movements of 1.5- 
3.2 km to areas not previously used during the 
nesting season. We did not observe any of these 
males returning to the nest stand (or the 
concentrated-use area for the males suspected of 
breeding) following their departure, but they were 
only tracked for 1 to 16 days after leaving the 
breeding territory because of limited transmitter 
battery life. 
Post-fledging ranges varied in size, as did the 
maximum distance family groups were observed 
from nests (Table 2). One family group (ID-1) 
moved in a roughly circular pattern around the 
nest site, reaching a maximum distance of 
1.200 m. but returning to within 500 m. Another 
family group (MT-4) was a maximum of 943 m 
from the nest, but returned to within 200 m. 
Family groups, with these two exceptions, moved 
progressively farther from the nest during the 
post-fledging period. 
Independence and Dispersal. —Radio-marked 
young began to move farther from brood mates I 
to 8 days after males ceased associating with 
family groups. It was not possible to document 
complete disassociation of fledglings with certain¬ 
ty because of the limited number of young with 
transmitters. However, the highly vocal nature of 
young pygmy-owls reliably facilitated detection of 
unmarked young throughout the post-fledging 
period, even after males ceased attending young. 
Thus, w'hen observation periods failed to yield 
aural or visual evidence of additional owls, w'e 
assumed fledglings had ceased associating with 
one another. Radio-marked young remained within 
their natal territories for I to 10 days after departure 
of males (35-42 days after fledging; Table 2). 
At that point, either transmitter signals were lost 
(n = 2). or we documented young moving outside 
of adult home range boundaries (n = 3). 
Behavior and Development. —The earliest ob¬ 
servations of successful hunting by young occurred 
9 days after Hedging. Two of six (33%) hunting 
attempts during the observation period on that date 
resulted in successful capture of small unidentified 
Lepidoptera. Hunting attempts by young were 
observed during 59% of observation periods > I hr 
in duration after 12 days postfledging (n = 46). 
Young used exaggerated head movements while 
concentrating on potential prey and perches, at 
times turning Iheir heads nearly upside dowm. The 
first successful capture of vertebrate prey (a 
southern red-backed vole | Clethnonomys gap- 
peri |) by young was observed 14 days after 
Hedging. Fledglings were successful during 47% 
of observed hunting attempts (// = 75). 
Young were not observed to cache prey items, 
although they procured prey from adults they did 
not immediately consume during 6% of prey 
deliveries (n = 80). Adults cached prey during 
5% of prey deliveries (n = 80), apparently 
because fledglings did not respond to delivery 
calls. The young became highly vocal, excitedly 
converged on the adult, and rapidly consumed 
prey during 74% of prey deliveries (n = 80). 
Adults provisioned fledglings with arthropod, 
avian, and mammalian prey. 
The young were active during 90% of diurnal 
observation periods (n = 91). Activity was 
notably less intense from late morning through 
mid-afternoon than during early morning and 
evening hours, consisting primarily of intermittent 
vocalizations and short movements (< 100 m). 
Young were only observed to remain silent and 
inactive >1 hr during 11% of observation periods 
lasting SI hr (n = 72). Fledgling activity 
increased during crepuscular periods. Young 
made longer and more frequent movements within 
or among stands in the early morning and 
evening. Seventy-seven percent of hunting at¬ 
tempts by young In = 75) were observed during 
crepuscular periods. Observations during all 
nocturnal observation periods (n = 10) indicated 
that owls remained in the same tree until 
approximately dawn. 
Fledgling vocalizations were limited to the 
begging call (described by Holt and Peterson 
2000), which was given repeatedly during all 
observation periods in which young were active 
(// = 82). The vocalizations of one fledgling often 
caused others to vocalize. Periods of vocalization 
