Effects of food limitation on the intensity of blue‐green and brown eggshell coloration: an experimental study with the canary

Abstract

Variation in blue-green and brown coloration of avian eggshells could be affected by several factors, including environmental nutritional constraints. Better availability of nutrients could influence the synthesis and deposition of pigments into the eggshell, so we may expect a link between the food availability during egg formation, the body condition of the female and intensity of eggshell coloration. This hypothesis has received mixed support so far: in some bird species a positive correlation between female body condition and eggshell blue-green coloration could be demonstrated, but other studies failed to find a significant link. In this study, we experimentally limited the food availability for domestic canaries Serinus canaria prior to and during egg laying, and examined its effects on the biliverdin-and protoporphyrin-based eggshell coloration. Treatment had no significant effect on eggshell blue-green chroma and biliverdin concentration. However, we found a significant positive relationship between female body condition and eggshell background blue-green chroma in the control group, but not in the food restricted group. Females possibly experiencing a decline in antioxidant capacity due to food limitation may not be able to produce a blue-green eggshell colour intensity reliably indicating their body condition. Furthermore, foodrestricted canary females laid eggs with significantly higher eggshell brown chroma, spot intensity, and protoporphyrin concentration. Therefore, our results suggest that limitation in actual nutrient availability increases deposition of protoporphyrin into the eggshell, and it may also modify the association between female body condition and intensity of blue-green eggshell coloration.

Protoporphyrin‐based eggshell pigmentation predicts hatching success and offspring sex ratio in the barn swallow

“…While we observed consistency among females in all four eggshell pigmentation scores over different years, suggesting that genetic characteristics may affect eggshell pigmentation patterns, significant differences in pigment intensity and spot size among breeding colonies, associated with moderately large effect sizes (Table 6), is suggestive of environmental effects on patterns of eggshell protoporphyrin deposition, that may either directly or through diet (Hargitai et al 2017a).…”

Eggshell spotting pattern is related to hatching asynchrony, hematocrit value and growth of nestling great titsParus major

“…In our population, female great tits that lay eggs in the beginning of the breeding season, when caterpillar food availability is scarce, and those that have smaller clutches lay darker-spotted eggs (Hargitai et al 2016a, c), indicating that food limitation may lead to more pigmented eggshells. Moreover, some experimental and observational studies of other bird species also indicated that food limitation resulted in darker spotted eggshells (Duval et al 2013, Hargitai et al 2016b, 2018a, Badás et al 2017). Therefore, it is possible that females in less favourable conditions laid darker spotted eggs, and due to energetic constraints they delayed the start of incubation, resulting in more synchronous broods.…”

Pigmentation of White, Brown, and Green Chicken Eggshells Analyzed by Reflectance, Transmittance, and Fluorescence Spectroscopy

“…The spectra are converted into the CIE color space or into hexadecimal color codes . Some authors additionally specify blue‐green chroma as reflectance differences R max –R min at significant wavelengths of the BV‐spectrum in the shell or brown chroma for PPIX‐containing shells . The representation of eggshell colors in the avian tetrachromatic color opponent space is practiced .…”

“…[8,22] Some authors additionally specify blue-green chroma as reflectance differences R max -R min at significant wavelengths of the BV-spectrum in the shell [29][30][31] or brown chroma for PPIX-containing shells. [32] The representation of eggshell colors in the avian tetrachromatic color opponent space is practiced. [33,34] Optical spectroscopy is furthermore beneficial for the separation of specular from diffuse reflectance with emphasis on highly glossy specimens, [35] for the investigation of reflectance spectra under the aspect of correlation with the pigment concentration, [3,[36][37][38] as well as for the aspect of the pigment stability against strong photoirradiation.…”