740 THE WILSON JOURNAL OF ORNITHOLOGY 
y°i 124. No. 4. December 2012 
12 ^:^ ,' 4 ’ and adu " 
Morphological measurements 
Tarsus length (mm) 
Head-Bill length (mm) 
Wing length (mm) 
Total length of central rectrix (mm) 
Body length (nun) 
Mass (g) 
Distance to native forest did not influence nest- 
s.te selection (Z = -l.i. P = 0.27, „ = 6(„, as 
this factor did not affect any of the other variables 
studied, considering all sites or those that had 
nesting activity (laying of eggs: Z = -() 89 p = 
0.38. n - 60, Z = -0.96, P - 0.34. „ = 34: and 
pioduction of at least one fledging: Z = -() 88 P 
= 0.38. n = 60. Z = -0.28, P = 0.78, „ = 34) 
There were no significant associations between 
d.stance to nattve forest and egg mass (r = 0.3 P 
.* n ~ 22) ’ chick mass (/• = 0.2, P = (n „ = 
16). adult mass (r = -0.1. P = (). 6 . „ = )6) or 
clutch size 0- = 0.2. P = ().2, „ = 2 2). 
DISCUSSION 
artfllOM 1 StUdiCS ! laVe Sh0Wn that P rov ision of 
artdicial cav.ties during the reproductive period 
a> increase the abundance of cavity-nestim? 
btrds as well as their frequency of Jo" 
2003 m"' MU "° Z - Pedreros « “I- 1996, Bull 
-003, Maicas and Haeger 2004). We observed 
Thorn-tailed Rayadito using Monterrey nine 
presem ° nS ^ '***"* if nest b <>*^ were 
Nestlings (13 days) 
Adults 
/ 
p 
20.8 ± 0.7 
26.4 ± 0.9 
30 ± 5.1 
20 ± II 
69 ± 8 
13.1 ± 1.3 
22.1 ± 0.6 
30.6 ±0.7 
58 ± 2 
83 ± 6 
135 ± 7 
11.6 ± 0.3 
6.5 
13.2 
23.3 
17.1 
26.3 
-4.9 
<0.001 
<0.001 
<0.001 
<0.001 
<0.001 
<0.001 
Pine plantations may differ from native forests, 
m addition to scarcity of cavities, in other 
breeding habitat aspects for Thorn-tailed Rayadi- 
los. However, evidence of food abundance for 
small msectivores suggests pine plantations in 
southcentral Chile provide levels of foraging 
resources similar to native forests fbstades and 
Escobar 2003), Thus, the observed difference in 
clutch sizes may be more consistent with ihe 
hypothesis proposed by Lack (1968), which 
predicts that at higher latitudes (Cliiloe --41 S 
mid Constitucidn -35 S). clutch size increases, 
presumably because of longer day length, which 
pi ovules more time for parents to feed nestlings 
and reduces the possibility of re-nesting (Dunn 
and Machines 1987. Shamel and Tracy 1987, 
r oung 1994. Piersma 1996). A recent study of 
House Wren (Troglodytes aedon chilensis) on 
hiloe Island, also suggests that clutch size 
increases with latitude in the Southern Hemi¬ 
sphere (lppi et al. 2012). 
Lsludcs (2001b) argued that pine plantations 
mtg t offci a safe place to nest for cavity-nesting 
mds such as the Thom-tailed Rayadito/because 
Nest construction (days) 
Incubation period (days) 
clutch size 
Brood size 
Adult mass (g) 
Nest dry weight (g) 
Egg volume (cm 3 ) 
Hatching success (%)“ 
Breeding success (%) h 
b cggs batched lor all nests 
% young fledged for all egg* that hatched. 
61 ± 4.8 (J5) 
,2 - 8 ± 1.9 ( 16 ) 
4 - 1 ± 0.8 (30) 
4.2 ± ().7 ( 22) 
,(, x i 0.8 (41) 
137 — 5.1 (12) 
20 10 ± 200 ( 57 ) 
? 5 ' 2 ± 10.2 ( 26 , 
7 &.7 ± 3| (26) 
Consiiiucidn 
12.8 ± 4.9 (23) 
15.8 ± 1.2 (20) 
T3 ± 0.7 (22) 
2.9 ± 0.8 (19) 
116 - 0.3 (14) 
416 ± 14 (15) 
2010 ± 92 ( 16 , 
X9 ± J6 (| 9) 
72 ± 44 (19) 
<0.001 
<0.001 
<0.001 
<0.001 
<0.001 
0.05 
0.99 
0.15 
0.69 
