Ippiet al. • BREEDING BIOLOGY OF THE SOUTHERN HOUSE WREN 
533 
TABLE 1. 
Dates for first and last laying, hatching, and Hedging of the Southern 
House Wren during three breeding 
seasons (2002-2004) on Chiloe Island. Chile. 
Season 
Laying dale 
n 
Hatching date 
n 
Fledging date 
n 
2002-2003 
8 Nov to 2 Jan 
1 
27 Nov to 1 Jan 
5 
13 Dec to 4 Jan 
3 
2003-2004 
28 Oct to 3 Dec 
18 
24 Nov to 20 Dec 
15 
30 Nov to 18 Dec 
3 
2004-2005 
19 Oct to 8 Jan 
16 
5 Nov to 15 Jan 
16 
8 Jan to 26 Jan 
3 
from mid October to January, while hatching 
dates were from November to January (Table 1). 
Hedging occurred from the end of November to 
January (Table 1). Wrens were not color banded 
and we have no information about polygyny in 
our population. One female reared a second brood 
in a neighboring nest box. ~60 m distant, hut we 
have no information about the success of its first 
clutch. Two males and one female bred in our 
study site for two consecutive breeding seasons, 
and one male for three consecutive seasons. All 
bred in nest boxes that were nearby in the 
previous year. 
Clinch and Brood Size.— Clutch si/.e in nests 
with at least one hatched egg was two and five 
eggs with an average of 4.3 ± 0.7 eggs (// = 59) 
(Table 2). The modal clutch size was four eggs. 
There was no seasonal trend in clutch size within 
year (Spearman correlation coefficient, i\ = 0 . IS; 
P - 0.24), and there were no differences in clutch 
size among years (Kruskal Wallis; H = 1.2; P = 
0.75; n = 59). The mean brood size was 3.9 ±1.1 
chicks (range = 1 to 5, n = 27). 
Egg Size .—Southern House Wren females laid 
eggs measuring 17.3 ± 0.7 mm in length and 13.2 
- 0.3 mm in width (// = 66 ) in 15 nests monitored 
during the 2003 breeding season. Egg volume was 
1-532.8 ± 103.8 mm' (n = 66). Mean egg volume 
decreased with clutch size (F 1.50 = 20.4. P < 
0 . 001 ) if only four- and five-egg clutches are 
considered. The number of successful clutches 
with two and three eggs was small; they were 
excluded from the analysis. 
TABLE 2. 
Mean ± SD clutch and brood si/.e 
of the 
Southern House Wren during four breeding seasons 
1 2002— 
-005) on Chiloe Island. Chile. 
Year 
Dutch ± SD n 
Brood sire - SD 
n 
2002-2003 
4.2 ±0.6 11 
No data No data 
2003-2004 
4.4 ± 0.7 21 
3.9 ± 1.2 
14 
2004-2005 
4.3 ±0.7 19 
3.9 ± 1 
10 
2005 
4.2 ± 0.7 8 
4.3 ± 0.6 
3 
Incubation and Nestling Period —The incuba¬ 
tion stage, the period between the last laid egg and 
first hatched egg. ranged between 14 and 19 days 
(16.0 ± 1.0 day; n = 32 nests). There was no 
seasonal trend in incubation period w ithin year (r s 
= 0.14: P = 0.45). All eggs in the clutch hatched 
within 1 day. The nestling period was 16.0 ± 
1.0 days (/) = 5 nests) and was 33.8 ± 1.6 days (n 
= 5) from laying to Hedging. 
Chick and Adult Body Size. —Chicks were 
measured between days 10 and 13 (11.4 ± 1.1) 
in 24 nests (Table 3). Significant morphological 
differences occurred between nestlings measured 
in different days (10 to 13; /• 12.101 = 29.2: P < 
0.001; 11 = 88 ). Univariate results revealed length 
of wing (/"A hi = 133.1; P < 0.001). beak (F 3.61 
41.9; P < 0.001), and tarsus (F 3 . 6l = 23.2; P < 
0 . 001 ) differed, while mass of nestlings at 10 . 11 , 
12, and 13 days did not (F S 6 1 = 0.7; P = 0.54). 
Mean tarsus length did not differ between adults 
and nestlings measured after 10 days of age 
(Fi .,26 = 0.3; P = 0.61; n = 128). 
We measured 38 adults (21 females and 17 
males) (Table 3), There were no significant 
differences in morphological measurements be¬ 
tween males and females (F 5,30 = 2.4, P = 
0.064). No difference was detected in body mass 
(f , , fi = 0.004; P = 0.95), tarsus length (F u6 = 
0.1; P = 0.78). tail length <F 1,34 = 0.01; F = 
0.92), and beak length (F t .36 = 0.04; P = 0.84) 
between males and females. How-ever, wing 
length was significantly longer for males than 
for females, after sequential Bonferroni correction 
( F,.36 = 8.7: P = 0.006J. 
DISCUSSION 
Clutch Size— The mean clutch size of the 
Southern House Wren in our study was compa¬ 
rable to that observed by Young (1994; 4.5 eggs in 
Nahuel Huapi National Park in Argentina vs. 4.3 
at Chiloe Island) at a similar southern latitude, 
although the Argentina data were obtained from 
museum samples ot natural nests. Artificial nest 
boxes did not appear to have a major influence on 
