Duca and Marini • BREEDING OF THE SHRIKE-LIKE TANAGER 
263 
(MAM, unpubl. data), but apparently shorter than 
that reported for the White-rumped Tanager 
(16 days) (Santos and Marini 2010), Wedge-tailed 
Grass Finch (Emberizoides herbicola) (16 days) 
(MAM, unpubl. data), and the 15.2 days estimated 
for both the Suiriri Flycatcher (Suiriri affinis) and 
the Chapada Flycatcher ( S. islerorum) (Lopes and 
Marini 2005a). Several studies have shown high 
nest predation rates in Cerrado (Lopes and Marini 
2005b, Gressler 2008, Santos and Marini 2010) 
and other neotropical biomes (Pinho et al. 2006, 
Duca and Marini 2008, Nobrega and Pinho 2010), 
and a few more days of nest exposure can be 
expressive in an environment with high predation 
rate. Shorter incubation periods decrease the time 
the nest is exposed to predators (Martin 1987). 
However, these small differences in the incuba¬ 
tion period may change temporally and in 
response to changes in environmental conditions 
and food availability (Murphy 1986, Rotenbery 
and Wiens 1991). 
The Shrike-like Tanager nestling period 
(11.7 days) was ~20% longer than that (9.5 days; 
n ~ 4) estimated by Alves and Cavalcanti (1990). 
Random variation in nestling period among the 
few nests they studied may account for this 
difference. This short nestling period is similar to 
that reported for the White-rumped Tanager 
(12,1 days) (Santos and Marini 2010) and 
Wedge-tailed Grass Finch (11.3 days; MAM. 
unpubl. data) at the same study site. It is much 
shorter than reported for the Black-throated 
Saltator (14 days) (MAM, unpubl. data) or several 
flycatchers (15 to 18.9 days) in the same study 
area (Lopes and Marini 2005a; Medeiros and 
Marini 2007; Marini et al. 2009a, b). The short 
nestling period for the Shrike-like Tanager and 
other species may be related to high nestling 
mortality rates that could be a selective factor 
favoring high growth rates and a short nestling 
period (Ricklefs 1976, Alves and Cavalcanti 
'990), Some species leave the nest earlier than 
others (Willis 1961), which may be related to 
ground feeding habits (Alves and Cavalcanti 
1990). 
Only females built nests and incubated eggs. 
Both males and females, and probably helpers. 
Provisioned nestlings as reported by Manica 
(2008). These behaviors are similar to those of 
bother population of Shrike-like Tanager (Alves 
*990. Alves and Cavalcanti 1990) and the White- 
otmped Tanager in the same study area (Santos 
and Marini 2010). 
Clutch Size .—The clutch size (~2) for the 
Shrike-like Tanager is similar to that for tanagers 
in South America (Alves and Cavalcanti 1990, 
Yom-Tov et al. 1994). Explanations for small 
clutch size of tropical species arc possibly related 
to cost of egg production and raising young, as 
well as climatic variation in temperature, air 
humidity, and photopetiod (reviewed by Ricklefs 
2000a, b; Stutchbury and Morton 2001). 
The larger clutch size (2-3 eggs) for 2003 
compared to the other years is apparently atypical 
for the species. It also differs from that recorded by 
Alves and Cavalcanti (1990). Larger clutch size in 
2003 occurred in the same year as the earliest onset 
of rain (INMET 2006). Early rainfall may cause an 
increase in food resources (i.e., fruits and arthro¬ 
pods) in the Cerrado (Diniz and Morais 1997, 
Batalha and Mantovani 2000, Pinheiro et al. 2002, 
Batalha and Martins 2004) as elsewhere (Wolda 
1978. Dantas et al, 2002). The Shrike-like Tanager 
may have responded to better conditions by starting 
breeding activities earlier and laying more eggs, 
revealing flexibility and ability to adapt to changes 
in temporal climatic patterns. 
The Shrike-like Tanager had breeding flexibility 
and ability to adapt to changes in precipitation 
patterns. Clutch size variation among years and 
flexibility in nest initiation timing is probably 
related to climatic unpredictability. This suggests 
clutch size may be the first response to climate 
change. 
ACKNOWLEDGMENTS 
This study was funded by CNPq and the Funda<;ao O 
BoticSrio de Protean A Natureza. Charles Duca was 
supported by a fellowship from CAPES/CNPq, and M. A. 
Marini was supported by a research fellowship from CNPq. 
We thank ESECAE/SEMARH for authorization to conduct 
this study. Institutional support was provided by PEQUI - 
Pcsquisa e Conservopio do Cerrado. We thank all friends 
from Laboratdrio de Ecologia c Conserva^ao de Aves at 
Universidade de Brasilia for field support We also thank R. 
B. Cavalcanti. R. H. F Macedo. M. A. S. Alves, and R. J. 
Young for suggestions to improve the manuscript. We also 
thank anonymous reviewers that kindly made suggestions 
on the manuscript. 
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