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THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 123. No. 3. September 2011 
one egg; the second egg was laid the following 
day. The first egg hatched on 19 November and 
the second the following day. for an incubation 
period of 24 days. The nestlings died 15 days after 
hatch as a result of a landslide that knocked down 
the nesting tree. The other nest with eggs that was 
studied successfully hatched on 15 November, 
and the nestling was still in the nest on 13 
December when we left the station; thus, the 
nestling period was at least 29 days. 
Nest and Eggs. —AH nests were hanging and 
attached to the end of tree branches above small 
creeks. The nest was a dome structure with a side 
entrance opening towards the ground. Nests had 
extra nesting material above the dome, changing 
the general shape of the nest to resemble the shape 
of a pear. 
Nests were composed of two layers. The 
external layer, which included extra material 
attached mainly to the upper part of the nest, 
weighed (X ± SD) 100.1 ± 38.7 g (n = 3) and 
was composed mainly of long bamboo ( Guadua 
spp.) fibers (60%) as well as mosses, fern leaves, 
and dry roots with pieces of bark (40%). The inner 
layer weighed 26.5 ± 16.3 g (n = 3) and was 
mainly composed of dry bamboo leaves (95%) 
and fine white roots (5%). 
The average (± SD) height of the nest above 
water was 2.1 ± 0.4 m (n = 7). The external 
measurements of the nest were 147.5 ± 55.8 mm 
X 156.9 ± 43.0 mm X 179.6 ± 6.7 mm (length, 
width, and height, respectively; n = 5). The nest 
entrance was 44.4 ± 10.8 x 39.0 ± 10.5 mm 
(length and width, respectively; n = 5), average 
nest thickness was 23.6 ±5.5 mm, and distance 
from the entrance of the vertical tunnel to the roof 
was 81.5 mm (n = 1). The length of the cup was 
122.5 ± 19.3 mm (n = 5) and cup depth was 49.8 
± 8.2 mm. The extra nest material above the 
dome nest measured 206.6 ± 89.7 mm in length 
X 94.1 ± 20.1 mm in width. 
Most eggs were white with small reddish dots 
at the larger end, but the eggs were entirely white 
in two clutches. The eggs measured 24.4 ± 0.6 X 
16.8 ± 0.5 mm (n = 13) and fresh weight was 3.5 
± 0.3 g (n = 6). 
Incubation Patterns. —The average nest tem¬ 
perature was 34.4 C (22.1-41.7° C) when the 
female was on the nest, and decreased to 29. S' C 
(20.1-38.9° C) during foraging bouts. We ob¬ 
served daily incubation patterns for 21 days at 
three nests. Generally, the incubating birds made 
their first daily foraging trip a few minutes after 
sunrise (between 0515 and 0639 hrs) and returned 
to the nest for continuous night incubation 
between 1609 and 1825 hrs. 
We only observed one parent incubating the 
eggs (presumably the female, based on the low 
nest attentiveness, <85%; Deeming 2002); it 
made on average 12.6 trips/day (min-max = 10- 
15 trips/day, n = 21). Incubation bouts at one nest 
lasted on average 33.6 min (5-82 min. n = 265) 
and foraging bouts averaged 22.4 min (9- 
104 min). The number of trips increased at the 
first nest through time from II to 13 trips/day 
during the first 5 days to 12-15 trips/day during 
the last 10 days. The average duration of 
incubation bouts was similar during the 16 days 
the nest was monitored (34.2 ± 4.7 min) with a 
small decrease during the last 3 days (28,3 ± 
3.2 min). The average duration of foraging trips 
varied little during the 16 days, but longer trips 
(up to 74 min) were recorded during the last few 
days, especially during the last 3 days (Fig. 1A- 
C ), The number of trips per day for the second 
nest during the last 3 days of the incubation period 
was 12, incubation bouts lasted on average 
29.7 min (28-32 min), and foraging bouts lasted 
on average 29.9 min (11-104 min) (Fig. ID). We 
observed 11.5 trips/day for the third nest with an 
average duration of incubation bouts of 34.7 (31- 
38 min) with foraging bouts lasting on average 
17.6 min (10-30 min). 
Average daily nest attentiveness was 64% and 
varied between 51 and 75% (n - 21). Nest 
attentiveness for the nest for which we had 
incubation data between days 7 and 22 of the 
incubation period was higher (66%; 65-68%' 
during the first 5 days and decreased during the 
last 10 days (63%; 57-67%). We documented low 
nest attentiveness for the second nest during the 
last 3 days of the incubation period; 55% (51- 
61%). The third nest had a nest attentiveness of 
74-75% during 3 days before it was predated. 
Nestlings. —The nestlings weighed 3.1 ± 0.4 g 
(n - 3) on day of hatch, the skin was pink-orange, 
the eyes were closed, and there was gray down on 
the back and wings. Pin feathers started to emerge 
from the skin 5 days after hatching and. 13 days 
after hatching, leathers started to emerge from the 
pins; leathers were yellow on the flanks and olive 
over the rest ol the body. The feathers completely 
emerged by day 27, except around the bill and the 
tail feathers. Nestlings gained mass (.v ± SD) at a 
rate of 1.5 ± 0.1 g/day (n = 3) during the first 
17 days, reaching a mass of 30.45 g (Fig. 2A). 
