SHORT COMMUNICATIONS 
617 
Mann and Carrion 1994). Marin and Stiles (1992) 
mentioned that a clutch size of two eggs seems to 
be characteristic in this genus, having been cited 
forS. zonaris (Rowley and Orr 1965. Stockton de 
Dod 1979. De la Pena 1982, Whitacre 1989, 
Mann and Carrion 1994. this study), S. biscuiata 
i Andrade and Freitas 1987). S. rutihi (Belcher and 
Smooker 1936. Collins 1968). and .V. phetpsi 
(Marin and Stiles 1992). However, single egg 
clutches have also been observed for all species ot 
this genus. 
The incubation period was 22 days for S. 
zonaris and apparently is the shortest within the 
genus (Table 2) and possibly for the Cvpseloidi- 
nae. Hatching at the end of November coincides 
with that reported by De la Pena (1982) in 
Cordoba; this author found eggs in advanced slate 
of incubation at the end of November, Develop¬ 
ment of nestlings was slow compared with other 
swifts, probably due to the wet and cold 
microclimates they select (Collins 1968. Marin 
and Stiles 1992, Marin 1997b). The age of 
fledglings leaving the nest within Slreptoprocne 
species is usually not less than 40 days (Table 2). 
All nestlings in my study Hedged in early to mid- 
January displaying the same behavior as S. 
biscuiata (Pichorim 2002) and S. ruiila (Marin 
and Stiles 1992). Departure may be based on 
acquisition of a given body mas.s and wing length 
(Marin and Stiles 1992. Marin 1997b. Pichorim 
2002 ). 
This study provides new information about the 
breeding biology of S. zonaris in Argentina, and 
the first reports of the incubation and nestling 
periods for the species in South America. 
ACKNOWLEDGMENTS 
I thank Manuel Marin. Martin Inotido. and Pablo 
Bolcaito for their continued, critical, and affectionate way 
to leach. This work was supported by CONtCET (Argen¬ 
tina! and benefited greatly from comments by anonymous 
reviewers. I thank Lucas Piladcs Ricci and family, and 
Aicolas Altamirano for allowing me to conduct research on 
the study site. I thank the Buleler and Saravia families and 
a ll who provided information: Centro de Investigaciones de 
(•*'■ Rcgiones Semiaridas (CIRSA). Centre lor Applied 
Zoology Cordoba. Ada Echevarria, Martin De la Pena, and 
TitoNarosky. I especially thank Federico Rios. Maria Julia 
CavalJero, Alberto Didicr. Carlos Passcggi. and Valeria 
Pena for helping me as field and logistic assistants. 
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