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THE WILSON JOURNAL OF ORNITHOLOGY • Vol 123. No. 4. December 2011 
The Wilson Journal of Ornithology 123(4):808—813, 2011 
Nesting of the Pectoral Sparrow (Arremon taciturn us) in Southeastern Peru 
Simon O. Valdez-Juarez 1 - 4 and Gustavo A. Londono 2 * - 
ABSTRACT.—We report the first detailed account 
of the breeding biology of the Pectoral Sparrow 
(Arremon tacitumus). We found 15 dome nests, each 
containing two eggs in a spherical interior chamber. 
Eggs were variable in color, ranging from immaculate 
glossy white to white heavily spotted with brown. 
Incubation patterns were obtained for six nests for time 
spans that ranged from 1 to 15 days for a total of 28 days 
across nests. Incubation in all nests was solely by the 
female, spending an average of 51% (range 20-65%) 
of daylight incubating, leaving the nest an average of 
7.4 umes per day (range = 4-7) with an average trip 
length of 46.4 min (range = 6-263 min.). Nest 
temperature averaged 29.2 ± 2.64 C when the female 
was incubating and decreased to 26.6 ± 2,43 C during 
incubation recess. Eggs in only two nests hatched and 
were monitored for 2 and 9 days. The male provided the 
young with 75% of the food. Nestlings gained an 
average of 2.53 g per day. Incubation, provisioning 
behavior and egg coloration wem similar to other 
species or 4/re,u«/ ,; however, nest shape, location, and 
20 / A d ! f", 10,18 Spedes * tertwd 17 January 
2011. Accepted 3 June 2011 , 
The genus Arremon is composed of 10 species 
t K f ,o^, Ch u haVe published ne *» descriptions 
am a Haverschmidt 196 «- Tye and Tye 
1992. Auer et al. 2007); four only have informa- 
ton about incubation and chick-rearing behavior 
(Skutch 1954. Martin 2002). The Pectoral Spar¬ 
row (Arremon tacitumus ) is common throughout 
the Amazon rainforest from the eastern base of the 
Andes in Colombia. Brazil, Bolivia, and Peru to 
most of the Amazon rainforest in Venezuela 
Guyana. Suriname, and Argentina (Hilly and 
Brown 1986). It is common and widely distribut¬ 
ed but little ts known about its nesting biology 
with most of the information generated by 
MS- #l9 ' 4, Guadala i ara ’ Jalisco, CP 44620. 
2 Florida Museum of Natural History. Dickinson Hall 
University of Florida. Gainesville. FL .32611, USA 
,, Ten ‘ address: Department of Biology, 227 Bartram 
Hall, University of Florida. P O Box nsSi r. • ^ 
FL 32611. USA. B0X 1 IS525 - Gainesville. 
4 Corresponding author; 
e-maU: simon.octavio.valdez@gmail.com 
sporadic observations (Snethlage 1935. Haver¬ 
schmidt 1968). 
Detailed nesting biology descriptions are fun¬ 
damental to understanding variation in avian 
reproductive strategics, which can improve our 
understanding of the geographic diversity of avian 
reproductive traits and life history strategies (Auer 
et al. 2007). Nests and behaviors are useful !o 
reconstruct phylogenetic relationships (Zyskowski 
and Prum 1999), and filling gaps in current 
knowledge becomes relevant, especially since the 
number of species in the genus Ammon is still 
being debated (Cadena and Cuervo 2010). Our 
objective was to provide detailed observations of 
the nesting biology of Arremon tacitumus, audio 
compare it with the available information for this 
and other species of the genus. 
METHODS 
Study Area .—This study was conducted in the 
foothills of Manu National Park. Cusco. Pent, 
near the Tono River (12' 57'58.2" S; 71'34' 
05.3” W); the average annual temperature for the 
location is 24.4 C (range = 19.3-30.7 C). We 
searched for nests 6 days a week from 0600 w 
1700 hrs (local standard time) between mid- 
August to mid-December in 2008 and 2009 
covering 2 km J of forest at elevations between 
800 and 1.100 m. 
Nest and Eggs .—Once a nest was found, eggs 
were weighed to the nearest 0.05 g with a digital 
pocket Scale (FlipScale F2: My Weigh Inc.. 
Kelowna. BC. Canada; http://w-ww.myweigh. 
com) and measured to the nearest 0.1 mm with 
calipers. Two to three temperature sensors were 
placed in six of the nests. The first sensor was 
inside the nest directly under the eggs. A second 
record 
sensor was placed outside the nest to -- 
ambient temperature. An additional tempera!^ 
sensor was placed inside a fresh egg in one of the 
nests; the sensor was introduced by drilling a 
small hole in the shell, and sealing it with sll PC‘ 
glue after the sensor had been added. All sensors 
measured temperature every minute and the 
information was stored on a U12 4 -channel hobo 
data logger (Onset Computer Corporation. Poca s ' 
