256 
THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 123. No. 2. June 2011 
fruits (e.g., Ocotea spp.) in their beak, (2) 
vocalized from a tree perch but did not meet 
simultaneously at the nest, and (3) perched in 
other trees when older nestlings vocalized con¬ 
stantly. Some of these behaviors have been 
observed in other birds (Breitwisch 1986. Hall 
and Karubian 1996, White et al. 2006). and served 
to diminish attraction of predators to the nest site. 
I did not measure size of the food items carried 
by parents to the nestlings, because parents 
usually regurgitated directly to the young. How¬ 
ever, the provisioning rate shows the relative 
parental effort, which was verified when the rate 
increased with nestling age. Both parents allocat¬ 
ed equal and substantial provisioning to nestlings, 
which is different from fruiteaters and fruitcrows 
where principally males fed nestlings and only 
females brooded (Amaya-Espinel 1997, Gelis et 
al. 2006). Increased provisioning rates for older 
nestlings characterizes many tropical birds (e.g.. 
Wheelwright 1983, Dyrcz 2000, Dobbs et al. 
2001) including cotingas (Amaya-Espinel 1997, 
Willis and Oniki 1998, Karubian et al. 2003, Muir 
et al. 2008) and is elicited mostly by posture and 
nestling calls (Kilner and Johnstone 1997, Roulin 
2001). Conversely, brooding time which requires 
a lower energetic investment than provisioning 
young (Williams 1996), decreased. These behav¬ 
iors illustrate the relation between growth of 
nestlings and parental investment. 
My research confirms that nestling care by 
Bolivian Swallow-tailed Cotingas is biparental 
and the pair is monogamous. This differs from the 
behavior commonly found in the Cotingidae, where 
females care for nestlings (Snow 2004). These 
differences are presumably associated with frugiv- 
ory or predation (Beehlcr and Foster 1988, Stutch- 
buiy and Morton 2001. Cockbum 2006). Willis and 
Omki (1998) suggested high levels of predation in 
tropical closed forests might influence females to 
care for the nestlings by themselves. Nesting habitat 
may also influence monogamous behavior, as 
Bolivian Swallow-tailed Cotingas nest in open 
areas, which may have lower predation rates than 
closed forests (Skutch 1985). 
Nesting success during incubation was lower 
than success during the nestling period. Me/.quida 
and Marone (2001) suggested for other bird 
species that parents might defend nestlings more 
than eggs, or those nests under high predation 
pressure were likely of being destroyed by 
predators. Nests that survived at the nestling stage 
were those difficult for predators to locate. The 
nestling period was successful, but combined 
nesting success was low (20%), primarily because 
of predation (72%). Low nesting success and high 
nest predation appears to be common patterns 
among neotropical birds (Martin et al. 2000, 
Stutchbury and Morton 2001). especially among 
understory birds (Robinson et al. 2000)and Cock- 
of-the-rock (Snow 2004). The high number and 
diversity of nest predators in the Neotropics may 
have resulted in this pattern (Stutchbury and 
Morton 2001). Tayras. birds of prey, cuckoos, 
snakes, rodents, and weasels are nest predators 
(Skutch 1985. Roper and Goldstein 1997. Eisen- 
berg and Bedford 1999, Dobbs et al. 2001, Patrick 
et al. 2004, Auer et al. 2007) that occur in savanna 
habitat and forest fragments. Predators may have 
also increased because of habitat modification 
(Martin 1996). More detailed studies of predation 
during the nesting period of Bolivian Swallow¬ 
tailed Cotingas are needed. Climate may also 
influence nesting success of birds (Robinson et ul. 
2000) and less concealed nests of the cotinga 
failed after heavy rains; long-term studies maybe 
useful for evaluating the influence of climate, and 
climate change on the population. Increased rain 
or adverse weather conditions might influence the 
success rate of the species. This work provides the 
first behavioral and ecological information on 
nesting of the Bolivian Swallow-tailed Cotinga 
and can serve as a baseline for future research on 
nesting success in this species and its conservation. 
ACKNOWLEDGMENTS 
1 thank the Aten community for permitting me to 
undertake this research, especially the Cespedes family. I 
am grutclul to Kazuya Naoki for helping with data analysis 
and comments on a prior draft of the manusenpt I 
appreciate the improvements in English by Daniel Brooks 
through the Association of Field Ornithologists’ program of 
editorial assistance. I also thank N. T. Wheelwright, an 
anonymous reviewer, and C. E. Braun for helpful comments 
and assistance on the manuscript. Institute dc ecology 
provided financial support for this research and Asociacion 
Armonfa also supported the fieldwork. 
LITERATURE CITED 
Amaya-Espinel. J. d. 1997. Biologfa reproductive y 
aspcctos de la historia natural de Querula purpurm 
(Aves: Cotingidae) en un bosque humedo tropical del 
P.N.N. Tinigua (Meta. Colombia). Thesis. Universidad 
dc Los Andes. Bogota. Colombia. 
Auer. S. K„ r. d. Bassar. J. j. Fontaine, and T. E- 
Martin. 2007. Breeding biology of passerines in a 
subtropical montane forest in northwestern Argentina. 
Condor 109:321-323. 
