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THE WILSON JOURNAL OF ORNITHOLOGY • Vol 124, No. 3. September 2012 
results with studies of House Wrens from North 
America, Central America, and other localities in 
South America. We predicted smaller reproductive 
investments (e.g., smaller clutch size) by the 
Southern House Wren compared to House Wrens 
in the Northern Hemisphere. 
METHODS 
Study Area .—The study was conducted on 
Chiloe Island, southern Chile (41 52' S. 73 
39 W ) at 50-100 m asl in the austral spring (Oct— 
Jan) of 2002-2005. Chiloe Island is < 10 km from 
the mainland and supports similar forest bird 
communities (Johnson and Goodall 1967. Fjeldsfl 
and Krabbe 1990). The continuous distribution of 
temperate rainforests as experienced by Charles 
Darwin in 1834-1835 have been cleared in large 
areas ol northern Chiloe Island with remaining 
fragments embedded in an agricultural landscape 
(Willson and Armesto 1996). 
Field Procedures.— Three hundred nest boxes 
were placed in scrublands and forest edges in Scnda 
Darwin Biological Station (described by Carmona 
et al. 2010) and 50 at Fundo ‘Los Cisnes’ at the 
northern tip of the island close to mainland Chile 
(nest boxes are described in Moreno et al. 2005, 
2007). Both study sites included large fragments of 
regenerating evergreen forests of Drimvs winteri 
Nothojagus niticla , Weinmannia tddwspenna . sev¬ 
eral myrtaceous species, and the conifer Podocarpu y 
nubtgena (Veblen et al. 1996. Aravena et al 2002) 
Nest boxes were suspended from tree branches or 
fastened to tree trunks or shrub branches 150 cm 
above the ground in scrublands and forest edges 
with some up to 100 m within the forest. The mean 
distance ± SD between nest boxes was 34 () ± 
2x2 m as measured with a Global Positioning 
System (GPS) (Garmin e-TREX: Olathe, KS. USA); 
the mean distance among active nests (i.e., nest 
boxes actually used) was 117.1 ± 79.3 m 
101-7015. Z&Y Tool Supply Co. Ltd.. Guangxi. 
China). Egg volume was estimated when clutch 
size was also assessed using Hoyt's (1979) equa¬ 
tion for egg volume; volume = 6.51 x (length > 
breadth-). Nests that were depredated or aban 
doned before incubation were excluded from 
clutch and egg size analyses. 
Adults were captured with nest-box traps when 
chicks were 10-13 days of age (hatching dav = 
day 0) and marked with metal leg bands (Model 
1242-3. National Band and Tag Co.. Newport, 
KY. USA) under the authority of Servicio 
Agncola y Ganadero, Chile. We measured tarsus 
length and beak length to the nearest 0.1 mm 
using digital calipers, wing length (mm) as 
flattened wing chord, and tail (mm) following 
Svensson (1984). Adult males and females were 
classified using morphology as only females have 
a brood patch (Johnson 1998). Mass was recorded 
to the nearest 0.1 g with a Pesola spring balance 
(Baar, Switzerland). We also weighed nestlings 
on the day ol adult trapping, and measured their 
tarsus, beak (from lip to skull), and wing length 
using the same technique as for adults. 
Statistical Analyses .—We checked for normal¬ 
ity of data and homogeneity of variance with 
Kolmogorov-Smirnov and Levene tests, respec¬ 
tively. We used non-paranietric statistics when 
these assumptions were violated. We addressed 
variation in clutch size within the breeding season 
and among years using non-parameirie correlation 
analysis and Kruskal-Wallis tests, respectively 
( Siegel and Castellan 1988). Differences in bod) 
size between males and females were evaluated 
using a one-way MANOVA. We conducted this 
analysis although not all variables were normal, 
hut all variances were homogeneous among the 
groups. This analysis is considered robust to 
violation of the assumption of normality (Sokal 
and Rohlf 1995). We also conducted a posteriori 
univariate analyses, correcting the significance 
Nest Monitoring.—Nest boxes were checked 
for occupation on a weekly basis beginning in 
October each year. Nest boxes occupied by 
Southern House Wrens were frequently checked 
to detect laying dates (date of first egg), hatching 
dates (first visit when eggs were observed to 
natch), and fledging dales (empty nest box) Nests 
were cheeked on a daily basis 2 weeks after lav ing 
of the last egg to record the exact date of hatching 
Some nests were visited daily 10 days after 
breadmi 10 ,eCO ' d fle ? gi " 8 dale ' E S« lcn S"' and 
th enearest T ^ e “ s in clutch Co 
nearest 0.1 mm with a digital caliper (Model 
(Quinn and Keough 2002). Nested ANOVA wa 
used to analyze clutch size and egg volume, and ti 
investigate differences in body size of nestling 
measured at 10 to J3 days of age. All analyse: 
were conducted with STATISTICA 6.0 (StatSof 
Inc. 2001) and were considered significant at P < 
0.05. Values reported are means ± SD. 
RESULTS 
Breeding Phenology. —Laying dates of the 
Southern House Wren on Chiloe Island ranged 
