SHORT COMMUNICATIONS 
607 
parrot species also suggest that small feeding 
flocks may improve feeding efficiency (Chapman 
et al. 1989; Paranhos et al. 2007, 2009; Seixas 
2009; Tubelis 2009). Wc found that feeding Hocks 
were not as large as roosting Hocks. Hence, there 
has to be an efficient congregating mechanism, 
especially if we consider the high dispersive 
abilities of Yellow-faced Parrot (CBdeA, pers. 
obs.). The congregation system used by Yellow - 
faced Parrots is long-range acoustical communi¬ 
cation, through use of flight or higher range 
congregation calls. 
Conservation programs should consider the large 
areas used by parrots, as parrots could guarantee 
food throughout the year by use of large areas. 
These programs should also consider acoustical 
communication, as it is the mechanism that allows 
use of a wide area and still roost in a large Hock at 
night. Noisy environments may compromise long- 
range communication, and feeding efficiency of 
Yellow-faced Parrots. Noisy environments may not 
be suitable for species conservation, and care 
should be taken to avoid building roads for heavy 
traffic near conservation areas. 
Short-range calls allow information exchange 
at close range as their low intensity reduces 
detection. This feature seems to be advantageous, 
as Yellow-faced Parrots usually remain hidden 
while perched (Sick 2001). The presence of a 
large short-range repertoire (CBdeA, pers. obs.) 
indicates substantial information exchange during 
feeding. Unlike White-vented Violet-ear (Colihri 
1 ierrirostris ), where the song complexity could be 
responsible for male selection by females (Silva 
and Viclliard 2006). each note of Yellow-faced 
Parrots seems to have a precise meaning, and a 
precise behavioral response. Thus, the interpreta¬ 
tion of repertoire size should be different tor 
parrots. However, we were not able to describe its 
full short communication repertoire, as we 
depended on behavioral responses that are not 
always observed. 
foraging flocks split and congregated constant¬ 
ly- Long-range communication is essential to 
flocks congregation and tlighl coordination. The 
intensity of the call also has a major role, as it 
correlates to the range at which it is heard. There 
1S a great amount of intensity variation involved in 
*he repertoire of the Yellow-laced Parrot. The 
lung-range alarm call is 14 dB louder than sentinel 
calls. Flock cohesion is attained through long- 
range alarm call overlap, and may be 10 dB 
louder. As a consequence, the Hock cohesion call 
can be 24 dB louder than sentinel calls, corre¬ 
sponding to a range ~16 times greater (Backus 
1977), and a detectable area 256 times larger. 
Flock cohesion high intensity calls are achieved 
through individual long-range alarm call overlap 
and. the louder the congregation call, the larger 
the Hock size. Parrots, when in small Hocks, use 
low intensity sounds, maintaining communication 
while reducing detection. 
ACKNOWLEDGMENTS 
We thank Renato Caparmz and lubata Faria for help with 
field work; Milena Corbo at the Unicamp Bioacoustics 
laboratory; ASN (Neotropical Sound Archive) and Emas 
National Park for logistic support: C. E. Braun and two 
anonymous reviewers for providing constructive comments 
that helped improve the contents of this paper; and Faepex 
(Unicamp) and Katherine McLennan Brown Charitable 
Foundation for funding. 
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