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THE WILSON JOURNAL OF ORNITHOLOGY . Vol. 123, No. 3, September 2011 
TABLE 2. Breeding chronology and timing of reproductive stages of Streptoprocne spp. swifts. I = early in month, M 
= middle of month. F = end of month, (-) = no available data, and (**) = calculated from date of hatch. 
S. zonuris * 
S. hisruhiia' 
S. semicullaris 
S. niila * 
' 
2 and 4 3 
9 
6 
5 
1 7 and 8 
Latitude 
10" N 
16= N 31° S 
31° S 
25' S 
18 : N 
10° N 10 c N 
(Country) 
(Costa 
Rica) 
(Mexico) (Argentina) 
(Argentina) 
(Brazil) 
(Mexico) 
(Costa (Trinidad 
Rica) and Tobago) 
Egg laying 
F, Apr 
F, Apr; I, 
May 
I, Nov 
I, Nov 
F, May 
F. May; I, Jun 
M, Jun 
Hatching 
F, May F, Nov 
(Prob.) 
F, Nov 
F, Nov 
M, Jun 
(Prob.) 
M, Jul F, Jun 
Fledging 
M, Jul 
' 
I, Jan 
I, Jan 
- 
F, Aug I, Aug 
Approx. Approx. 
Incubation 
30-35 
days 
(est) 
23-25 
days 
Approx. 
20-25 
days 
24 days 
(Average) 
' 
24-26 22-23 
days days 
Age of 
nestlings 
at fledging 
(**) 
45-55 
days 
40-48 
days 
40-48 
days 
40_42 37-43 
days days 
Sources: ! Marin and Stiles 1992. 2 - Whitacre 1989, 3 = Dc la Pefia 1982.4 = Rowley and Orr 1965. 5 = Rowley and Orr 1962.6 = Pichorim2002. T = 
Snow 1962, 8 = Collins 1968, and 9 = this study. 
24 November and in nest S3 on ~ 11 December, a 
period of 18 days (Fig. I). At least one adult 
remained at nests SI and S2 during hatching. 
Nestlings were naked with eyes closed and a pale 
pink body. 
Nestling .—Nests were occupied by nestlings 
during 58 days from late November to mid- 
January (Fig. 1). Nestlings remained in nests for 
an average of 44 days (range = 40-48 days). The 
shortest period was recorded for the single chick 
in nest S3, while the longest was for the two 
chicks in nest S1. 
Fledging .—Nestlings Hedged in January over a 
time interval of 15 days (Fig. 1). First departure 
was at age 25-33 days. This was a temporary 
event and, after 2 hrs, fledglings reoccupied the 
nests. Fledglings were quiet and stayed close to 
the nests while they were outside. Adults were 
also observed inside or near the nests. Definitive 
departure occurred at age 35-43 days, although 
fledglings stayed near nests until leaving the 
breeding site at age 40-48 days. Contrary to first 
departure, fledglings were active outside the nests 
flapping their wings rhythmically and clinging to 
the wall without taking flight. Intense vocaliza¬ 
tions were also recorded. No adults were observed 
inside or near the nests during these displays. 
Fledging asynchrony was recorded in nest S6 with 
a difference of 5 days between nestlings. Some 
adults and juveniles were observed at the study 
site during February and March. On these 
occasions, adults reoccupied nests, but juveniles 
did not. 
DISCUSSION 
The breeding chronology of the White-collared 
Swift was recorded in five nests, which is a 
considerable number, given the ecological com¬ 
plexity of swifts. Reproduction lasted ~2': 
months, from egg laying in November to fledging 
in late January, and was similar to other 
Streptoprocne swifts (Table 2). 
Breeding occurred with seasonal rains as lor 
other neotropical swifts (Snow 1962, Rowley and 
Orr 1965. Collins 1968, Ayarzaguena 1984 , Mann 
and Stiles 1992). This could be interpreted as an 
adaptive behavior to take advantage of the 
maximum abundance of food (Marin and Stiles 
1992). It has been suggested that reproduction by 
Streptoprocne species with large body size would 
begin before the rainy season because, unlike 
other swifts, these species depend mainly on 
moisture to build and adhesion their nests 
(Rowley and Orr 1965. Collins 1968. Foerster 
1987, Mann and Stiles 1992. Pichorim 20021 
Eggs were similar to those reported in previous 
studies (Rowley and Orr 1965, Stockton de Dod 
1979, De la Pena 1982, Marin and Stiles 1992, 
