Bernardo el al. • BLACK-FRONTED PIPING GUAN DENSITY ESTIMATES 
695 
The largest continuous mainland Atlantic 
Forest (Serra do Mar massif) had a low density; 
a similar pattern was found for the non-connected 
mainland forests (DE <0.5 groups/km 2 ) with no 
observations in two continuous forests and one 
non-connected area (Table 2). 
DISCUSSION 
We added to the knowledge of the global 
population status of Black-fronted Piping Guans. 
as we studied -36% of the currently known 
world occurrence sites of this species. Line- 
transect methodology was adequate for our 
surveys, and we highly recommend use of this 
method for other areas where the species is 
present, mainly in southern Brazil and Paraguay. 
However, this methodology requires great effort 
considering the total number of km walked 
(2,241 km walked) and low number of observa¬ 
tions (70). Pooling all observations in areas with 
few observations per study area was needed to 
obtain an effective strip width estimate. This 
allowed more precise density estimates based on 
>40 sightings, as recommended by Buekland et 
al. (2001). 
The probability detection from the transect line 
up to 4.6 m was 100% (Fig. 2) indicating 
observers delected all birds on the transect line 
which met an important assumption of the 
method. Probability of detection decreased with 
increasing distance, as expected, because the 
dense understory and canopy made bird detection 
difficult. The probability of detection was - 50% 
and was between 4.7 and 13 in. Black-fronted 
Piping Guans have discrete movements and calls, 
and it is likely that some individuals were not 
detected at distances >4.7 m. Thus, our estimates 
should be considered conservative. 
The differences in density values among areas 
are suggestive and not conclusive because we 
had insufficient sample sizes for statistical 
analysis. We had high density estimates in 
continuous forests of the Paranapiacaba massif 
and inshore islands. These densities were higher 
than in the continuous forests of the Serra do 
Mar massif, which is the largest remnant 
Atlantic rainforest. 
Density estimates of Black-fronted Piping 
Guans in the Serra do Mar massif were the lowest 
obtained in our study (<0.5 individuals/km 2 or 
<0.4 groups/km 2 . Table 2). and far below the 
average density estimates for other cracids in the 
Amazon and Andes regions (e.g., Silva and Strahl 
1991, Thiollay 1994, Rios et al. 2005, Londono et 
al. 2007, Hill ct al. 2008. Setina 2009). Densities 
in the Serra do Mar were higher than those 
obtained for other cracids in only two areas of the 
Amazon forest: Razor-billed Curassow (Mitu 
tuberosum) in an area of high hunting pressure 
(0.02 individua!s/km : ) and Spix's Guan (Penelope 
jacquacu) in an area of low hunting pressure (0.19 
individuals/km 2 ) (Begazo and Bodmer 1998, 
Haugaasen and Peres 2008). The conservation 
status of Black-fronted Piping Guans in the Serra 
do Mar region is of concern because local 
extinction can occur when population densities 
are low. This is a priority area for conducting 
more research and conservation action, e.g., 
population supplementation, if threats are elimi¬ 
nated. 
Sanchez-Alonso et al. (2002) surveyed the 
Paranapiacaba area in 1998 (Intervales, Carlos 
Botelho, and Alto Ribeira parks), using the line- 
transect method, and estimated a mean density of 
2.67 birds/knr. Our mean density estimates in 
Paranapiacaba massif are between 3.0 and 4.4 
individuals/km 2 (Tabic 2) and suggest Carlos 
Botelho is an important area for Black-fronted 
Piping Guan conservation. Immigration of the 
species from Paranapiacaba to surrounding patch¬ 
es may occur, e.g., Parque do Zizo (adjacent to 
Carlos Botelho), that apparently also have popu¬ 
lations (C. O. Gussoni, pers. comm.). 
Galetti et al. (1997) presented density 
estimates of Black-fronted Piping Guans in 
several areas of Atlantic rainforest, but our 
data are not comparable due to differences in 
methodologies. We recorded more observations 
in Ilhabela and Ilha do Cardoso, but lower 
numbers per group. The Black-fronted Piping 
Guan only flies short distances and the closest 
distance from Ilhabela to the mainland is 
>1 km; thus, we believe this population is 
isolated although the species can cross the 
narrow (—300 m) channel between Ilha do 
Cardoso and the mainland. Galetti et al. (1997) 
indicated the population of Black-fronted Piping 
Guans on Ilha do Cardoso had been extirpated 
based on no records between 1994 and 1995. 
Our study demonstrated the species is present 
in Ilha do Cardoso and the population density 
is higher than in some larger mainland regions. 
The absence of the Black-fronted Piping Guan 
records in Jurupara Park suggests movements 
among forests of Paranapiacaba and Serra do 
Mar may no longer occur (Fig. 3). 
