Segura and Reboreda • BOTFLY PARASITISM OF RED-CRESTED CARDINALS 
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(A) 
Intensity (botflies/nestling) 
(B) 
FIG. 2. Frequency distributions of the number of botfly 
larvae per nestling of Red-crested Cardinals; (A) = parasite 
intensity and (B) = time elapsed since hatching of the first 
nestling and nest parasitism (latency). 
-4; non-parasitized: 0.86 ± 0.02, n = 74; Mann- 
Whitney U- test: Z = 3.35, P = 0.0008). We did 
not detect an association between nestling surviv- 
a * and parasite intensity/nestling (Spearman’s 
rank correlation; p = -0.19, P = 0.37, n = 24; 
3A), but nestling survival was positively 
ass °ciated with latency of parasitism (Spearman’s 
rank correlation: p = 0.59, P = 0.002, n = 23; 
fig- 3B). Intensity and latency of parasitism were 
negatively associated (Spearman’s rank correla- 
tlon: P = -0.48, P = 0.02, n = 23). 
fiedation outcome did not differ between 
Parasitized and non-parasitized nests (.X 2 i = 
133, df = 1, p = 0.56) for the three breeding 
seas °ns combined. Young that fledged from 
Parasitized nests had lower growth rates for body 
(A) 
(B) 
FIG. 3. Red-crested Cardinal nestling survival as a 
function of the number of botfly larvae/nestling; (A) = 
parasite intensity and (B) = time elapsed since hatching of 
the first nestling and nest infestation (latency). 
mass (Fig. 4A), tarsus length (Fig. 4B), beak 
length (Fig. 4C), and wing length (Fig. 4D) than 
young that fledged from non-parasitized nests 
(Mann-Whitney LMest; body mass: Z = -2.94, 
P = 0.003; tarsus length: Z = -3.02, P = 0.002; 
beak length: Z = -2.54, P = 0.01; wing length: 
Z = -2.13, P = 0.03). 
Characteristics of the Vegetation and Botfly 
Parasitism.—We did not detect a significant 
association between occurrence of botfly parasit¬ 
ism and species of nest trees (Tala: 22/44; 
Coronillo: 15/23; X 2 = 0.04, P = 0.52). We also 
did not observe a significant association between 
botfly parasitism and other characteristics of the 
vegetation at the nest-tree level (logistic regres¬ 
sions for nest height: X 2 , = 1-24, P = 0.26; 
distance from the nest to the edge of the canopy: 
X 2 , = 0.04, P = 0.83; and cover of the canopy: 
