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THE WILSON JOURNAL OF ORNITHOLOGY • Vol 124, No. 3, September 2012 
2001): thus the low rate of IBP in altricial species 
may reflect researcher bias rather than an actual 
biological pattern. It is possible rates of IBP are 
underestimated since they are higher in areas 
where most ornithologists work (Yoin-Tov 2001). 
Only a few cases of IBP have been reported in the 
Neotropics. (Dyrcz 1983, Langen 1996, Carvalho 
et al. 2006. Rios-Chelen et ai. 2008). probably due 
to the lack of detailed nesting behavior studies in 
this region (Auer et al. 2007). 
We report the first evidence for IBP in a 
neotropical songbird species, the Pale-breasted 
Thrush (Turdus leucomelas ), in southeast Brazil. 
METHODS 
We examined nests of the Pale-breasted Thrush 
during a breeding behavior study on the campus 
of Sorocaba's Engineering University, Sao Paulo 
State, in southeastern Brazil (23 28' S, 47 25' W). 
and in an adjacent urban park. The campus totals 
10.5 ha and has extensive lawns and gardens where 
exotic trees (predominantly Pinus sp„ Eucalyptus 
sp.. Mangifera sp„ and Grevilleu robusta) are 
interspersed with native species typical of the 
Cerrado habitat. Buildings and streets are widely 
spaced and cover -30% of the campus. The 
adjacent park is a 2-ha sensu strictu Cerrado 
habitat. These locations are traversed by two 
streams and form a patch of partially' open 
vegetation isolated within a densely urbanized 
area. 
We systematically searched for nests during 
three breeding seasons (2006-2007, 2007-2008, 
2008-2009), by covering the entire area two to 
three times a week (0700-1000 hrs) from August 
to May. We located nests by following adults 
while they were carrying materials for nest 
construction or delivering food to nestlings. 
Nests were bulky open cups made of rootlets, 
mosses, and dead leaves compacted with mud. We 
checked nest contents daily during late nest con¬ 
struction and during the laying stage to document 
clutch initiation dates and onset of incubation. 
Pale-breasted Thrushes lay their eggs between 
0600 and 0730 hrs (PVD, unpubl. data), and we 
checked nests 4 hrs after sunrise (0900-1000 hrs) 
to avoid counting eggs before additional eggs 
could have been laid in the same day. We report 
observations ol nests as evidence for IBP in which 
(1) more than one egg was laid in the same day, 
. ® gg . s Were la,tl - or more days after onset of 
incubation, and (3) eggs were laid 2 or more days 
before nest construction ended (Yom-Tov 1980. 
Pieman and Belles-Isles 1988, Latif et al. 2006 
Peer 2010). 
RESULTS 
We monitored 15 nests of Pale-breasted Thrush 
from building through hatching and observed 
evidence for intraspecific brood parasitism in four 
nests (27%). One nest was found on 8 October 
2008 in the early construction stage. The first egg 
was laid on 16 October and. on the following day. 
three eggs were observed in the nest, suggesting 
that one egg had been laid by a parasitic female. 
Incubation was initiated on 17 October and one 
egg hatched on 28 October and another on 30 
October. One of the eggs w as inf ertile. One of the 
nestlings disappeared a few days later and the 
other fledged on 15 November. 
A second nest was found on 21 October 2008 in 
the middle of the construction stage. The first egg 
was laid on 25 October and the nest contained three 
eggs the following day. Incubation started on 27 
October, and eggs hatched on 7 (n = 2) and 8 
November (n = I). All young fledged successfully 
on 22 November. 
A third nest was found on 2 September 2007 in 
the middle of the construction stage, but already 
contained one egg. The female continued carrying 
and arranging nest materials until 5 September. 
Two additional eggs were laid between 6 and 9 
September, and incubation started on 10 Septem¬ 
ber. Only one egg hatched on 21 September and. 
on 26 September, the young and the remaining 
infertile eggs were depredated. 
A fourth nest was found on 3 November 2008 
in late construction stage. The first egg was laid 
on 8 November, and a second egg was laid on 10 
November when incubation started. A third egg 
was laid 6 days after onset of incubation. The first 
two eggs hatched on 23 November and the third 
egg hatched on 29 November. All young fledged 
on 8 December with the younger individual flying 
weakly due to poorly developed feathers. 
DISCUSSION 
Proposed explanations for intraspecific brood 
parasitism in precocial species and colonial 
nesters are not regularly applicable to territorial 
passerines (reviewed by Yom-Tov 2001). Several 
alternative hypotheses have been proposed to 
explain IBP in songbirds, such as a scarcity ol 
suitable nesting sites, nest loss during the laying 
stage, and a high proportion of unmated females 
or floaters in the breeding population (Yom-Tov 
