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THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 124. No. 2. June 2012 
within a brood at times exceeded 1 hr in duration, 
punctuated only by brief intervals of silence. 
Adults used the ‘chitter call’, primary song (Toot 
song’), and Trill calf (described by Holt and 
Peterson 2000) when in the vicinity of fledglings. 
An alarm call (described by Frye 2005) was also 
observed on five occasions in association with 
avian predators near young. A two-note call 
composed of notes resembling those of the 
primary song, but the second note often slightly 
higher in pitch than the first, was used by males 
preceding prey deliveries. Spacing between the 
two notes was similar to that between notes of the 
primary song, but repeated calls were spaced by at 
least 8-10 sec and at times 1 min or more. These 
two-note vocalizations were often given repeat¬ 
edly for several minutes, at limes accompanied by 
trill calls, before males began using the chitter 
call. The chitter call was used by both adults 
during prey deliveries. We observed increased 
male vocal activity (the primary song and trill 
call) after return to the nest vicinity (37-50 days 
after fledging; Table 2). 
DISCUSSION 
Synchronous or nearly synchronous Hedging 
appears to be typical of Northern Pygmy-Owls. 
Giese and Forsman (2003) observed all young 
exiting nest cavities within a 6-hr period at four 
nests on the Olympic Peninsula, Washington. Holt 
and Norton (1986) observed a brood of six owls 
fledge over a 2-day period in Montana. Rashid 
(1999) reported a brood of three owls leaving the 
nest within a 2-day period in Colorado. Fledging 
was directly observed at only one nest during our 
study, but observations prior to and following 
fledging indicated that all successful nests for 
which fledging duration was known (n = 14) were 
\acated within 1-2 days of the first ow l leaving the 
cavity. Nesting phenology was more advanced in 
Idaho than in Montana. The Idaho study area had 
milder climate with less snow cover than the 
Montana site. The influence of these differences on 
prey availability may explain the observed differ¬ 
ences in nesting phenology, as birds are thought to 
time nesting to coincide with seasonal peaks in 
r“ lity (LaCk l954) ' Fled S in S ‘>“urred 
rj en Junc and 17 July in Washington (n ~ 9; 
G.ese and Forsman 2003), 5 and 6 June in western 
and m '* H0lt and Norton l986 >’ u "d 12 
d 13 July in Colorado (n - I; Rashid 1999) 
and S r S h ° Ciat, ‘. ln Individuals within family groups 
and the role of breeding adults in attending 
dependent young vary among species of forest 
owls. Both adults attend Ferruginous Pygmy-Owl 
broods during the post-fledging period (Proudfoot 
and Johnson 2000). Flammulalcd Owls (Otto 
Jlcwimeolus) exhibit brood partitioning, the young 
separating into two groups, each of which is 
attended by one adult (Linkhart 1984. Goggans 
1986, Linkhart and Reynolds 1987). Northern 
Saw-whet Owl (Aegolius acadicus) broods remain 
loosely associated as a family group after fledging 
and are provisioned primarily by the male and 
occasionally by the female (Cannings 1993). 
Female Eurasian Pygmy Ow ls (Glaucidium pas- 
serinum) care for young alone for the first week 
after fledging, after which the male returns and 
assists in provisioning young. Eventually, the 
female departs, leaving the male to attend young 
alone for the remainder of the post-fledging 
dependency period (Konig et al. 1995, 1999). 
The attendance strategy of adults that we 
observed most closely resembles that of the 
Eurasian Pygmy Owl, the difference being that 
both Northern Pygmy-Owl adults attended broods 
prior to female departure. We observed this 
strategy in all family groups for which the role 
ol the female was known (n — 6). However, it is 
possible that both adults attend some broods 
throughout the post-fledging period. For example, 
some Spotted Owl (Sirix occidentalis) broods are 
attended by both adults and some by a single adult 
during the post-fledging period (Gutierrez et al. 
1995). The variation that we observed in duration 
o! female attendance supports this possibility. One 
female attended a brood for -88% (30 days) of 
the post-fledging dependency period, whereas 
another attended a brood for only -21% (9 days). 
Previous information on family group proxim¬ 
ity to nests during the post-fledging period is 
limited. Holt and Peterson (2000) reported a brood 
ol six young roosting 75 m from the nest 8 days 
after fledging. Rashid (1999) observed two of 
three fledglings from a brood in Colorado -270 in 
Irom the nest 18 days after fledging. Post-fledging 
movements Irom the nest varied greatly among 
family groups in our study. All family groups 
were substantially farther than 75 m from the nest 
8 days after fledging (300-670 m). Proximity to 
nests after 18 days was more varied (200- 
2,400 m). 
No previous information is available on inde¬ 
pendence and dispersal timing for Northern 
Pygmy-Ow'ls. Our observations of provisioning 
and attendance by males indicate young achieve 
