Frye and Jageman • NORTHERN PYGMY-OWL POST-FLEDGING ECOLOGY 
201 
TABLE 1. Reproductive data and post-fledging observation effort for Northern Pygmy-Owl family groups in the 
Rocky 1 Mountains of Montana and Idaho. 
Family group" 
Year 
Observation (hrs) 
Radiomarked owls 
Breeding status 
Fledging date 
Brood size 
MT-I 
2004 
26.5 
Male, female, two young 
Breeding 
28 Jun 
7 
MT-2 
2003 
45.6 
Male, female, two young 
Breeding 
8 Jul 
4 
MT-3 
2006 
46.7 
Male, female, one young 
Breeding 
15 Jul 
3 
MT-4 
2005 
38.1 
Male, female 
Breeding 
5 Aug 
5 
MT-5 
2005 
0 
None 
Breeding 
8 Jul 
4 
MT-6 
2005 
0 
None 
Breeding 
18 Jul 
4 
MT-7 
2002 
0 
None 
Breeding 
10 Jul 
3 
MT-8 
2003 
0 
None 
Breeding 
25 Jul 
6 
MT-9 
2006 
0 
None 
Breeding 
5 Jul 
6 
MT-10 
2002 
0 
None 
Breeding 
23 Jul 
3 
MT-I 1 
2005 
0 
None 
Breeding 
28 Jul 
5 
ID-1 
2008 
14.4 
Male 
Breeding 
1 Jul h 
3 
ID-2 
2008 
4.9 
Male, female 
Breeding 
24 Jun 
4 
ID-3 
2009 
7.5 
None 
Breeding 
28 Jun 
5 
ID-4 
2008 
0.9 
Male 
Breeding 
1 Jul b 
3 
ID-5 
2007 
0 
Male 
Breeding 
18 Jun 
2 
ID-6 
2007 
0 
Male 
Suspected 
Unknown 
Unknown 
ID-7 
2007 
0 
Male 
Suspected 
Unknown 
Unknown 
a MT = Montana. ID = Idaho. 
Fledging date estimate based on developmental stage of young when first observed. 
distinct breeding territories in Montana (MT-1, 
MT-2, MT-3, MT-4; Table I). One fledgling was 
radiomarked in one of these family groups (MT-3; 
Table 1) and two fledglings were radiomarked in 
each of two family groups (MT I and MT-2; 
Table I). Both adults were radiomarked in one 
family group in Idaho (ID-2; Table I). The adult 
male from three additional family groups (ID I, 
ID-4. ID-5; Table 1) and two adult males 
suspected of breeding (ID-6. ID-7; Table 1 1 were 
also radiomarked. We assigned ‘suspected breed¬ 
ing’ status to ID-6 and ID-7 based on the spatio- 
temporal location patterns of these owls. Both of 
these owls began concentrating their space use at 
approximately the same time as locations of pre¬ 
nesting owls in Idaho were concentrated near nest 
areas. The timing and duration of use for these 
areas (hereafter 'concentrated-use areas’), which 
were similar in size to the breeding season home 
ranges of ow ls known to be nesting (HRJ. unpubl. 
data), coincided with the timing and duration of 
the nesting/post-fledging periods for owls known 
to have nested. We did not radiomark fledglings 
in Idaho. Fledglings that were not radiomarked 
were located by listening for vocalizations. 
Family groups were randomly selected for this 
investigation, but previously monitored individu¬ 
als and territories were excluded from the 
selection process. Each radio-marked family 
group was tracked for one breeding season 
between 2003 and 2009 (Table 1). 
We captured owls with mist nets, balcha-tri 
traps, bow nets, or by hand at nest cavities. Adults 
were captured and radiomarked during or prior 
to nesting. Young were radiomarked within 6 days 
after fledging. Very High Frequency (VHF) trans¬ 
mitters weighing 1.4-2.2 g (<3% body mass; 
Holohil Systems Ltd.. Carp, ON. Canada and 
Wildlife Materials Inc., Carbondale, IL, USA) were 
affixed using back pack-style harnesses constructed 
of braided Dacron cordage. All owls studied in 
Montana were also marked with color bands to aid 
in individual identification. 
We regularly observed five family groups (MT- 
1. MT-2, MT-3. MT-4, ID-1) for periods ranging 
from 0.25 to 5.25 hrs (x = 2.03 hrs, n = 91) 
during at least three visits per week from date of 
fledging until young began to disperse from their 
natal territory'. Observation periods were stratified 
so that morning (30 min before sunrise to 1000 
hrs), mid-day (1001 to 1600 hrs), and afternoon/ 
evening (1601 hrs to dark) were approximately 
evenly sampled. Additional behavioral data were 
gathered opportunistically from three family 
groups (ID-2, ID-3. ID-4: Table 1). Behavioral 
data were obtained by observing owls through 
binoculars (from -10-80 m distant) and record¬ 
ing descriptions, times , and durations of activities 
