Phenotypic plasticity in breeding plumage signals in both sexes of a migratory bird: responses to breeding conditions

Abstract

Adaptive phenotypic plasticity may respond to present ambient conditions. Sexual and social signals in both sexes may express phenotype performance. Plumage signals that change discontinuously allow relating discrete variation to previous performance. Both sexes of the pied flycatcher Ficedula hypoleuca present white patches on the wings and on the forehead, which constitute sexual and social signals. Forehead patches are moulted together with body plumage in Africa, while wing patches are partly moulted in Africa and partly in the breeding area soon after breeding. We studied individual inter‐year changes (corrected for regression to the mean) in the size of forehead and wing patches of both sexes in seven years for females or six years for males in two nearby study areas in central Spain. We found that initial signal extent strongly delimits the possible subsequent changes negatively. There is a negative association of male age with forehead patch changes. Cold and rainy springs are associated in females with decreases in both patch areas and vice versa, while no association with climate is observed in male wing patch changes. Cold pre‐breeding conditions predict positive changes in female wing and male forehead patches. Breeding success is positively associated with forehead patch changes in females. Late‐breeding males experience more positive changes in forehead patch size than early‐breeding males. Some of these trends can be explained by variable costs of breeding in certain conditions for subsequent signal production and/or maintenance, while absence of trends in some cases may be explained by sex differences in costs of breeding and interactions with phenotypic quality of breeders.

Ecological Effects on Female Bill Color Explain Plastic Sexual Dichromatism in A Mutually-Ornamented Bird

“…Conversely, males may prioritize allocating resources to ornamentation, even in suboptimal environmental or physiological condition, because they have the most to gain from sexual ornamentation, in the form of attracting mates and increasing paternity rates. According to this view, bill color in American gold nches (Spinus tristis) was found to re ect individual differences in female immune function but not in males, who consistently invest in bill coloration irrespective of immune function 12 , and a recent eld study with pied ycatchers (Ficedula hypoleuca) found that changes in female but not male plumage ornaments were affected by climate during breeding, such that cold and rainy breeding seasons decreased female ornamentation, likely re ecting a greater cost of breeding in those years 59 .…”

Extra‐pair paternity is not repeatable between years in Pied Flycatchers (Ficedula hypoleuca): a role for social context

“…It has been previously shown that plumage traits in the study populations show marked phenotypic plasticity and are affected by previous conditions in both the breeding and wintering ranges (Moreno et al . 2019). Plastic individual traits interacting with a variable social context may remove any potential for repeatability of mating outcomes (but see male wing patch size for a repeatable trait linked to EPY).…”

Adaptive coloration in pied flycatchers (Ficedula hypoleuca)—The devil is in the detail

“…Forehead patch size is highly repeatable across years ( r = .72) (Järvistö et al., 2016) indicating high heritability or a permanent environmental effect on trait expression. Older males have slightly larger forehead patch size than young males (Gálvan & Moreno, 2009; Järvistö et al., 2016), and in addition, an Iberian population very old males tended to reduce their forehead patches (Moreno et al., 2019). Environmental variables experienced during the molting period on the wintering grounds do not predict within‐individual variation of the trait (Järvistö et al., 2016).…”

“…Environmental variables experienced during the molting period on the wintering grounds do not predict within‐individual variation of the trait (Järvistö et al., 2016). There is some evidence that the trait is signaling early‐life individual quality (Dale et al., 1999) and that costs of breeding, that is, unfavorable conditions during breeding and relatively early timing of breeding are followed by forehead patch decrements in males (Moreno et al., 2019). The experimental activation of immune defense reduced the expression of male forehead patch size compared with the control males within the same season (Kilpimaa et al., 2004), indicating that immune defense costs may trade‐off with the maintenance costs of a white forehead patch.…”

“…This suggests that after dry nonbreeding conditions, large wing patch size can be a more informative indicator of male quality than during other years as only individuals with good condition or resources have been able to produce large with patches in such conditions. Opposite to wintering conditions, weather conditions experienced during breeding have not been observed to be associated with between‐years within‐individual changes in the size of the wing patches (Moreno et al., 2019). Some of the results on the potential covariation between wing patch size and oxidative stress suggest that the trait could signal individual quality (Lopez‐Arrabe et al., 2014, see Table 2).…”