SHORT COMMUNICATIONS 
637 
from a previous nesting attempt was within the 
second egg chamber (Fig. 1). which suggests, at 
least in this nest, that two eggs may have been 
laid. We found no evidence of egg shells inside 
the other two nest cups and their size was smaller 
than the fourth. The nests were collected and 
deposited in Museo de Zoologfa. Universidad de 
Costa Rica. 
DISCUSSION 
Nest reuse in birds could be related to nesting 
success, nest site fidelity, or habitat limitation 
(Haney et al. 1979, Vergara et al. 2()0(>. Aguilar 
and Marini 2007). The first two causes would be 
more likely if previous nesting attempts were 
successful (Beheler et al. 2003. Hoover 2003). 
Nest choice in hummingbirds and other species 
that nest during the rainy season, such as the 
Scintillant Hummingbird (Stiles and Skuteh 
1989), may be limited to locations with adequate 
nest cover. Nests with better shelter from the 
environmental elements (e.g., less direct rain) 
may reduce thermoregulatory costs (Calder 1971). 
Sheltered nests may allow the female to spend 
more time foraging, because eggs and chicks are 
relatively protected. The Scintillant Hummingbird 
nest that we observed was completely sheltered 
and the benefits of shelter may be the main reason 
this nest was reused on multiple occasions. Also, 
if the light bulh was on during part of the day, it 
might have reduced thermoregulatory costs. 
We do not know if all nest attempts were 
successful, but our data suggest the only success¬ 
ful nest was the fourth. We based this upon it 
having a larger egg chamber size, a characteristic 
observed in several hatchling hummingbird nests 
(Calder 1973. Baltosser 1986). It is possible that 
nesting success was not the main cause of nest 
reuse. Most hummingbird females are territorial 
ngainst conspecifics (Stiles and Skuteh 1989). 
which suggests the nest was built by only one 
female, as occurs for Costa's (Calypte costae) and 
Black-chinned (Archilocus ate.xamlri) humming¬ 
birds (Gault 1885, Baltosser and Scott 199b. 
Baltosser and Russell 2000). However, we are not 
certain if all nests were built by the same female, 
m which case nesting success may have nothing to 
do with the nest reuse. 
Nest reuse may have also occurred because it 
was structurally solid, and was a good foundation 
for a second nest (Bergin 1997). Generally, this 
condition is rare in the tropics, where decompo¬ 
sition rate for vegetal material is high (Sandoval 
and Barrantes 2009). We believe the reuse of this 
Scintillant Hummingbird nest was most likely due 
to the ideal nest location below a covered 
structure. 
ACKNOWLEDGMENTS 
We thank Daniel Hanley. C. E. Braun. W. H. Baltosser, 
and an anonymous reviewer lor the useful comments on an 
early version of this manuscript, and Guiselte Sanchez for 
collecting the nest. LS was supported by the Ministers de 
Ciencia y Tecnologia (M1CIT) and the Consejo Nacional 
para Investigation's Cientificas y Tecnologicas (CONICIT) 
during the writing phase of this manuscript. 
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