SHORT COMMUNICATIONS 
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A B C 
FIG. 1. Yellow-faced Parrot repertoire in Brasilia: (A) Bight call: (B) long-range alarm; (C) agonistic vocalization I; 
(D) agonistic vocalization II; (E) sentinel call; (F) the two notes of short-range alarm call. 
(Table 1). It may help maintain flight cohesion, 
indicating individual positions during flight. We 
also heard solitary individuals uttering this 
vocalization, possibly seeking other individuals 
in the area, indicating a contact message. The 
emission rate of the call was 0.69 ± 0.32 Hz (/» = 
34 calls from 8 individuals). This call also caused 
inter-specific responses, as we observed individ¬ 
uals of the Turquoise-fronted Amazon responding 
lo the call, leading to a mixed-flock formation. 
Long-range Alarm Call— This type of vocali¬ 
zation was common throughout the year 
(Fig. IB). It was heard during flight or while 
perched, as a response to the approach of 
predators such as Southern Crested Caracara 
(Caracara plancus), or even during the approach 
of the observer. It consists of a quick series of 
flight calls. The emission rate of this call is 2.61 
- 0.61 Hz (30 calls from 7 individuals), over 
three times higher than the flight call (U -test P < 
0 . 0001 ). 
Congregation Call .—The call is composed of 
the long-range alarm call uttered by several 
individuals with substantial overlap. This creates 
a noisy sound of great intensity, but with species 
recognition quality. Distant flocks were observed 
responding with the same vocalization. It was 
common to observe flocks congregating on a tree 
after a few repetitions, or even clustering during 
Oight. This response indicates a nock cohesion 
function by giving Hock location at great 
distances. We were able to visually locate feeding 
flocks on a map using visual clues as trees, fences. 
and crops. The maximum communication range 
was 800 m. However, distances were only 
registered when both flocks were heard and seen 
at ground level by the observer, and with medium 
size flocks. Thus, the communication range might 
be greater. 
Agonistic Vocalization l .—This vocalization 
was observed during feeding, when individuals 
perched close to each other (Fig. 1C). When a 
flying parrot perched too close to an already 
perched parrot, the perched parrot would open its 
wings and emit this highly modulated and 
harmonically rich call. The fundamental frequen¬ 
cy decreases from 4 to 1 kHz, and the call has a 
duration of 171 ms (Table l). The response to this 
call was to fly, usually together with agonistic 
vocalization II. The events could happen in 
inverse order, and agonistic vocalization I could 
be uttered only after agonistic vocalization II. We 
considered this call to be part of the long-range 
repertoire due to the high sound intensity, 
although the message recipient was at close range. 
Agonistic Vocalization II .—This call is closely 
associated with agonistic vocalization I, but its 
intensity is ~ll dB lower (Fig. ID). It seems to 
calm the parrot that uttered agonistic vocalization 
1. It consists of a six pseudo-pulse trill with 
fundamental frequency of 1 kHz and duration of 
-100 ms (Table 1). We also observed this 
vocalization being uttered before agonistic vocal¬ 
ization I. The perching individual possibly sought 
to avoid any discomfort caused by its proximity to 
the already perched parrot. 
