Quail eggs in artificial nests change their coloration when exposed to ambient conditions: implication for studies on nest predation

Abstract

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.

No Evidence of Deliberate Egg Soiling in the Pied Avocet Recurvirostra avosetta to Improve Camouflage

“…The digital images of nests were linearised and normalised to a grey standard in order to obtain reflectances (Troscianko & Stevens, 2015; Gómez & Liñán-Cembrano, 2017; Liñán-Cembrano et al ., 2021). The image processing, for both UV and VIS sets, was executed using the SpotEgg tool (Gómez & Liñán-Cembrano, 2017), which allowed us to obtain equivalent reflectance images from the RAW files and draw regions of interest (RoIs).…”

“…The mathematical description of the process behind the creation of these visual-models mapped images is summarised in Liñán-Cembrano et al . (2021).…”

“…Since our goal was to check whether changes in avocet egg coloration may affect their detection by predators, the images subject to texture analysis were the result of mapping these images to the visual systems of the main predators in the study areas: domestic dogs and cats, and weasels, all with a dichromatic visual system (which was modelled using the visual system of the Ferret Mustela putorius, with sensitivity peaks at [430, 538] nm) (Calderone & Jacobs, 2003), and Yellow-legged Gulls with a tetrachromatic violet-sensitive visual system (we used the visual system of Peafowl Pavo cristatus with peaks at [421,457,505,566] nm) (Hart, 2001). The mathematical description of the process behind the creation of these visualmodels mapped images is summarised in Liñán-Cembrano et al (2021).…”