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Orange-crowned warblers, Leiothlypis celata sordida, breeding on the
California Channel Islands exhibit remarkable variation in their nest
structure and placement, providing an intriguing exception to the general
pattern that avian nest structure and nest site selection are highly
conserved characters. We examined nest construction at both the population
and individual scale to test whether warblers on Santa Catalina Island
change their nest construction in response to nest height. At the
population level, warblers built both lighter, grass-dominated ground
nests and heavier off-ground nests that contained more ridged materials
and less grass. The probability of nest success was significantly and
positively correlated with nest height. At the individual level, we found
the same individuals were capable of building on- and off-ground nests
between nesting attempts within the same season. However, nest
construction was highly variable among individuals and not significantly
correlated with nest success after controlling for nest height. We suggest
this observed behavioural plasticity in nest construction and nest height
is a hierarchical response to the absence of avian predators. Reduced risk
from avian predators appears to allow the warblers to use a variety of
nest sites, thereby necessitating increased flexibility in nest
construction.
102 views reported since publication in 2021.