Quail eggs have been widely used in field experiments, mainly to study factors
associated with the risk of nest predation. Some shortcomings of using quail eggs in
this type of study have been previously addressed (e.g., these eggs might be too big for
some predators of eggs of small birds). Here, we show experimental evidence of
another shortcoming of the use of these eggs in field experiments. Quail eggs exposed
to sunlight rapidly faded in colour after three days, both in the visible and UV
spectra, and this change was related to the amount of solar radiation received. This
caused changes in the camouflage of the eggs, which may be perceived by predators
with different visual systems (dichromatic, trichromatic, and tetrachromatic (for
both violet- and UV-sensitive species)). Therefore, the results of field studies of
nest predation using quail eggs might be questioned in those cases in which the
camouflage has been altered due to the rapid changes in coloration, as this can affect
the resulting predation rates. We recommend that researchers planning to use quail
eggs should perform a prospective assessment of changes in coloration of eggs
exposed to environmental conditions in the nest sites used by the target species.This study was funded by grant CGL2017-83518-P from Ministerio de Economia, Industria y Competitividad, Spain, with EU-ERDF financial support. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript