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THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 123, No. 2, June 2011 
TABLE 2. Duration of parental care of nestlings (min/bout) by male and female Bolivian Swallow-tailed Cotingas 
(Phibalura f. boliviano) at five nests. Values = mean ± SD. 
Categories 
Nest number 
6* 
7 
8* 
9* 
10 
Total hours observed 
69.6 
57.4 
49.7 
49 
38.25 
Brooding time 
Male 
18.6 ± 16.7 
21.5 ± 15.1 
12.2 ± 10.0 
20.7 ±11.8 
22.0 + 16.7 
Female 
18.5 ± 16.7 
23.1 ± 22.0 
27.6 ± 19.6 
24.6 ± 16.8 
19.0 ± 11.5 
Perching time near nest 
Male 
7.8 ± 8.4 
8.5 ± 8.3 
4.0 ± 5.3 
13.3 ± 12.0 
12.4 ± 13.8 
Female 
5.2 ± 5.4 
9.7 ± 8.5 
3.5 ± 5.3 
12.3 ± 12.6 
8.9 ± 9.7 
Perching time in trees 
Male 
4.7 ± 5.6 
3.6 ± 4.3 
4.5 ± 5.1 
5.1 + 7.1 
7.5 - 5.7 
Female 
5.2 ± 5.6 
3.3 ± 4.4 
4.9 ± 6.3 
7.3 ± 7.6 
4.9 ± 75 
Foraging trip time 
17.8 ± 10.7 
11.0 ± 11.4 
13.3 ± 1.5 
12.9 ± 8.5 
16.5 ± 15.6 
Nest with fledglings. 
P < 0.001, n — 5; Figs. 1-2), but was not 
significantly different between parents (paired t- 
test = 1.5, df = 24, P = 0.15; Table 2). Brooding 
time was lower for 18 to 22-day-old nestlings than 
for those 2 to 5 days of age ( post-hoc test, P < 
0.002; Figs. 1-2). The mean time that each parent 
spent brooding nestlings 18 to 22 days of age was 
2.7 ± 2.0 min/hr versus 33.7 ±17.1 min/hr for 
small nestlings (Fig. 2). Brooding ceased at 22 days 
(Fig. 1), except during adverse climatic conditions. 
Brooding decreased once nestlings were 10 days 
of age and parents increased the time they spent 
perching near the nest. The mean amount of time 
parents spent perching near the nest increased by 
age categories (F = 11.2. df = 4 . P < 0.001). 
This behavior was higher for nestlings beginning 
" G - 2 : ^ ean ± SD time of brooding per hour of 
Bolivian Swallow-tailed Cotinga young by age groups. 
at 18 days of age than at 10 days of age (post-hoc 
tests, P < 0.023). Males perched near the nest 
longer than females (males: 8.8 ± 7.1 min/hr; 
females: 5.8 ± 7.9 min/hr; paired f-test = 2.264, 
df = 18, P = 0.036). Parental care from a distant 
tree perch did not differ significantly between 
parents (Z = 1.5, P = 0.12). but varied with 
nestling age (Friedman test = 19.7, df = 4, P - 
0.001). Parents perched in trees when nestlings 
were small for 1.2 ± 0.9 min/hr and when the 
nestlings were older for 6.4 ± 8.6 min/hr. 
Parental visits to the nest combined were at 
least twice per hour (2.4 ± 2.8 visits/hr, n = 5 
nests). The provisioning rate to nestlings did not 
differ significantly between males and females 
(paired r-test = 0.4, df = 26, P = 0.67), but did 
vary among age categories of nestlings (F = 18.8, 
df = 5, P < 0.001). The provisioning rate by 
parent was higher for 14-day-old nestlings than 
for 2-5 day-old nestlings ( post-hoc test P < 0.03: 
Fig. 3). Males and females did not differ signif¬ 
icantly in mean lengths of foraging trips (paired r- 
test = 3.4, df =28, P = 0.074). but varied among 
nestling age categories (F = 3.4, df - 5. P = 
0.01). Foraging trips were longer for 23-27 day- 
old nestlings than for those 18-22 days, and 2- 
5 days of age (P < 0.036). 
Nesting Success .—I located 48 active nests o! 
Bolivian Swallow-tailed Cotingas in the vicinity 
of Aten. The probability of daily survival during 
incubation was 0.9455 (/i = 44, total egg exposure 
days = 444, SD = 0.0045). The probability of 
daily survival during the nestling period was 
