Cestari et al. • COMMON POTOO NESTLING BEHAVIOR 
103 
TABLE 1. Recording sessions at a 
Common Potoo nest in southeastern Brazil. 
Date (sampling day) 
Estimated nestling age (days) 
Total recording time (hrs, min) 
Recording periods (hrs) 
8 Dec 
14 
2, 35 
1920-2210 
12 Dec 
18 
2, 57 
1832-2138 
13 Dec 
19 
2, 02 
1823-2028 
16 Dec 
22 
1, 31 
1844-2015 
or accompanied by one of the parents: (1) feeding 
bouts on passing insects, (2) defecations, (3) 
movements in the nest, (4) wing exercising, (5) 
plumage maintenance, and (6) calling. Feeding 
bouts to capture insects were used by the nestling 
and adults while they were perched on the nest (on 
the top of the fence post) and attacked flies that 
were passing. Defecation behavior was perceived 
when the nestling raised the tail and ejected feces 
from the nest. Movements on the nest were used 
by the nestling to move short distances (several 
centimeters) from border to border of the stump. 
Wing exercising was used by the nestling 
apparently to exercise without flying. Plumage 
maintenance with the beak was used by the 
nestling and adults. Calls were used in a parental 
interaction and included begging notes uttered by 
the nestling and advertisement calls uttered by 
adults. We quantified the frequency per hour of 
each of these categories. 
We verified the amount of time the nestling and 
each parent remained in alert posture, the 
frequency and times that each parent left the nest, 
and the number of times they alternated care and 
fed the nestling through regurgitation. The alert 
posture was adopted when nestling or adults 
raised their beak, compressed the plumage, and 
kept the neck outstretched (Fig. 1). 
Common Potoos do not show any sexual 
dimorphism (Cohn-Haft 1999). However, we 
noted a difference in the pattern of dark blotches 
°n the breast of the two adults (hereafter, 
indicated as individuals A and B) that enabled 
us to identify shared parental care. 
RESULTS 
Description of the Nest, Egg, Nestling, and 
Parents.— A Common Potoo responded to a 
Playback of its call by vocalizing during a 
nocturnal bird survey and perched on a fence 
post on 4 November 2008. The potoo could be 
closely approached and another visit to the site 
w as made 2 days later to confirm the existence of 
a nest. The simple and unlined nest contained a 
single dull white egg with lilac and brown spots 
(40.95 X 31.55 mm). It was directly placed on top 
of a 1.25-m tall abandoned fence post. The top of 
the post had an irregular surface that measured 
5 X 19 cm (Fig. 1). 
Presence of the nestling with an egg tooth and 
eggshell fragments in the nest indicated hatching 
occurred between 22 and 24 November. The 
nestling was covered by creamy-white down 
plumage marked with fine gray brown stripes on 
the first recording day (8 Dec). It was — one-third 
of the size of an adult at this time and could stay 
completely hidden among the ventral feathers of 
the parent (Fig. 1). The nestling was slightly more 
than half the size of an adult on the last day of 
recording (16 Dec), and remained almost com¬ 
pletely exposed even when among the ventral 
feathers of the adult. Adults had a buff plumage 
with light gray and black blotches. The same 
gray-brown stripes of the nestling were also 
apparent along the adult’s body. A visit to the 
nesting site on 21 December revealed the nestling 
had probably been predated and the adults were 
no longer present. 
Quantitative Aspect of Categories of Behav¬ 
ior .—Digital recordings (9 hrs and 6 min) were 
made when the nestling was —14—16 days until 
22-24 days of age (Table 1). Adults stayed with 
the nestling during nearly 5 hrs and 54 min 
(64.8% of total recording time) and the time the 
parents brooded the nestling decreased as it 
became older (Fig. 2). 
The adult present gradually relaxed to a less 
motionless posture and slowly opened its eyes at 
nightfall. It completely opened its eyes at -1854 
to 1908 hrs and initiated nocturnal activities, 
flying from the nest between 1904 to 1909 hrs. 
Generally, the nestling became active from the 
motionless posture similarly to the adult. 
The nestling engaged in feeding bouts on 
passing flies and flapped its wings only when 
alone after the first day of recording. Frequencies 
of short movements on the nest and plumage 
maintenance were also higher when the nestling 
