Does egg colouration reflect male condition in birds?

Abstract

How colouration provides information about individuals in birds has been a central issue in recent decades. Although much information has been derived, little is known about the adaptive significance of egg colouration in birds. A recent idea suggests that biliverdin- and porphyrin-pigmented eggs may act as a post-mating sexual signal for males to assess female quality. In birds, it is common for males to influence prelaying female condition by courtship feeding. Using Eurasian kestrels, a species that lays protoporphyrin-pigmented eggs, we descriptively assessed the influence of male feeding on egg pigmentation by considering female phenotype, condition, breeding parameters and male body condition. We found that older females and females with greyer tails (an index of individual quality) produce highly pigmented eggs. However, male body condition was the only variable that explained egg colouration when considered together with the female-related variables. Therefore, females that mated with males in better condition laid highly pigmented eggs. With the same species, we also explored the cost of producing protoporphyrin-pigmented eggs using a food-supply experiment before the laying period. Food supplementation did not increase egg pigmentation, but hatching success and egg mass were positively related to egg colouration only in food supplied pairs. We suggest that egg colouration might be costly to produce and probably suggests egg quality. However, this cost cannot be explained by female quality, but by male condition instead. In general, our results do not support the theory that egg colouration is a post-mating sexual signal in species where males determine female condition at the time of laying.

Darker eggshell spotting indicates lower yolk antioxidant level and poorer female quality in the Eurasian Great Tit (Parus major)

“…We found no support for the hypothesis that protoporphyrin-based eggshell spotting indicated the body condition or the body size (tarsus length) of female Great Tits. Similar to our results, egg color was not related to female body condition or body size in a Belgian population of Great Tits (De Coster et al 2013), in the Eurasian Kestrel (Martínez-Padilla et al 2010), the Ringbilled Gull (Larus delawarensis; Hanley and Doucet 2009), or the Eurasian Reed-Warbler (Krištofík et al 2013). By contrast, in British Great Tits (Stoddard et al 2012) and Blue Tits (Martínez-de la Puente et al 2007), heavier females laid less spotted eggs with paler spots.…”

“…These latter studies support the view that darker pigmentation indicates poorer condition of the female. Additionally, female body condition and body size were not related to eggshell coloration in Eurasian Kestrels (Falco tinnunculus;Martínez-Padilla et al 2010) or in a Belgian population of Eurasian Great Tits (Parus major;De Coster et al 2013). However, to our knowledge, no study has tested the relationship between red-brown eggshell pigmentation and female oxidative status.…”

“…Moreover, Blue Tit and House Sparrow females that laid larger clutches laid eggs with a more even distribution of spots García-Navas 2009, López de Hierro andDe Neve 2010). In studies of Eurasian Kestrels (Martínez-Padilla et al 2010), British Great Tits (Stoddard et al 2012) and Eurasian ReedWarblers (Krištofík et al 2013), no significant relationships between eggshell spot color and clutch size were found. Therefore, it appears that there is no clear pattern between clutch size and eggshell spotting pattern among bird species, and the relationship may depend on average clutch size, annual number of breeding attempts, and various physiological mechanisms and limitations during laying, all of which may differ among species and populations.…”

“…Several studies measured eggshell reflectance using a spectrophotometer and expressed it as brightness and red or brown chroma (Avilés et al 2007, Martínez-de la Puente et al 2007, Hanley and Doucet 2009, Maurer et al 2011b, Holveck et al 2012, Duval et al 2013, Krištofík et al 2013. Others determined pigment concentration of the eggshell by chemical analysis (Maurer et al 2011b, Cassey et al 2012, Duval et al 2013, Brulez et al 2014, or analyzed digitized pictures of eggshells to determine the percentage of spotted eggshell surface (Martínez-de la Puente et al 2007, Sanz and García-Navas 2009, Bulla et al 2012, Holveck et al 2012, Brulez et al 2014), or to determine hue, saturation, and brightness derived from HSB and RGB (Martínez-Padilla et al 2010, Cassey et al 2012, Holveck et al 2012), or to determine other spotting pattern variables, such as pattern contrast and marking size (Stoddard et al 2012). Finally, many studies used visual scoring of photographs, and spotting pattern was expressed as spot intensity, spot size, and spot distribution (Gosler et al 2005, Sanz and García-Navas 2009, López de Hierro and De Neve 2010, Bulla et al 2012, Holveck et al 2012, De Coster et al 2013, Hargitai et al 2013, Brulez et al 2014.…”

Genetic basis and fitness correlates of dynamic carotenoid‐based ornamental coloration in male and female common kestrels Falco tinnunculus

“…In common kestrels, CS is influenced by female condition, which as females are fed by their mates from courtship until halfway through of the nestling period (Village, 1990), and is highly dependent on characteristics of her partner (Aparicio, 1994;Martinez-Padilla et al, 2010a). Whereas CS largely captures variation in female fecundity, NF also captures variation in offspring survival between hatching and fledging.…”