SHORT COMMUNICATIONS 
623 
temperature (37° C) was lower than average bird 
body temperature (40 C) (Gill 2007). Dunn (1975) 
suggested that altricial nestlings became endother¬ 
mic w hen nestling body mass was 60-70% of their 
parents body mass. However. Ricklefs and Hains- 
worth (1968) suggested endothermy in nestling 
birds is not influenced by body mass. They 
suggested endothermy is proportional to the length 
of the nestling period, where nestlings of species 
with shorter nestling periods will become endo¬ 
thermic faster than species with longer nestling 
periods. Our study suggests thermoregulation 
occurs when the feathers are completely devel¬ 
oped. However, further studies of other species are 
necessary to evaluate if endothermy correlates with 
completion of feather development. 
Nest attentiveness was 64%. which is similar to 
other neotropical passerine species (Tielcmun et 
al. 2004, Auer et al. 2007, Martin et al. 2007). 
However, unlike previously documented increases 
in nest attentiveness throughout the incubation 
period in neotropical passerines (Martin et al. 
2007, Londono 2009), R. fulvipectus decreased 
time on the nest as incubation period progressed. 
This reduction resulted from a small change in the 
number of trips (17%). Time on the nest 
decreased a few days prior to egg hatching for 
heth nests, but the behavior used by the two 
individuals to decrease lime on the nest differed. 
The female al the first nest increased the number 
°f trips, but the female at the second nest 
increased length of foraging bouts. This suggests 
tropical birds have multiple ways to regulate egg 
temperature during incubation to successfully 
reach egg hatching within and between species. 
Intrinsic factors may have an important role on 
behavioral decisions during incubation. 
Our study reinforces the specificity of the genus 
Rynehocyclus for nesting sites along creeks, and 
indicates R. fulvipectus has longer incubation and 
nestling periods compared to other tropical 
species (Tieleman 2004. Auer et al. 2007, Marlin 
et al. 2007). 
ACKNOWLEDGMENTS 
We (hank Julio Bemuidez. Manuel Siinchez, Rachel 
Hanauer. Adam Carter, and Alex Nina for help in the field. 
Daniel Blanco allowed us to work at Cock of the Rock 
Field Station and provided climatological data. Rachel 
Hanauer and Judit Ungvari-Martin provided valuable 
comments and corrections of an early version of this 
manuscript. H. F. Greeney, C. E. Braun, and two anonymous 
reviewers provided insightful comments that improved this 
manuscript. Our animal use was approved by the University 
of Florida IACUC. Financial support was provided by the 
Katherine Ordwuy Foundation, the Dexter Fellowships in 
Tropical Conservation, and a Louis Agassiz Fuertes Award 
(Wilson Ornithological Society). DOR thanks Universidad 
de Antioquia (COD1) for financial support. 
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