Carotenoids are molecules that birds are not able to synthesize and therefore, must be acquired through their diet. These pigments, besides their function of giving birds red and yellow colouration when deposited in feathers, seem to act as immune-stimulators and antioxidants in the organism. Hence, only the healthiest individuals would be able to express carotenoid-based ornaments to a larger extent without compromising the physiological functions of carotenoids. Various studies have reported that birds infected by parasites are paler than those uninfected, but, to our knowledge, none of them has assessed the possible eVect of multiple infections by blood parasites on plumage colour. By comparing the yellow colour in the breast plumCommunicated by Heli Siitari. age of blue tits, Cyanistes caeruleus, between birds infected by diVerent numbers of blood parasite genera, we found that those birds infected by more than one genus were paler than those parasitized just by one. In addition, we examined the potential role of carotenoid-based plumage colour of blue tits as a long-term indicator of other parameters of health status, such as body condition and immunoglobulin and heat shock protein (HSP) levels. Our results indicate that more brightly coloured birds had lower HSP70 levels than paler birds, but we did not Wnd any signiWcant association between colour and body condition or immunoglobulin levels. In addition, we found a positive signiWcant association between Haemoproteus density of infection and HSP60 levels. Overall, these results support the role of carotenoid-based colours as indicators of health status in blue tits and show detrimental eVects of parasitism on this character.

The impact of feather-degrading bacilli on feathers depends on the presence or absence of melanin. In vitro studies have demonstrated that unmelanized (white) feathers are more degradable by bacteria than melanized (dark) ones. However, no previous study has looked at the possible effect of feather-degrading bacilli on the occurrence of patterns of unmelanized patches on otherwise melanized feathers. The pied flycatcher Ficedula hypoleuca Pallas, 1764 is a sexually dimorphic passerine with white wing bands consisting of unmelanized patches on dark flight feathers. These patches are considered to be a sexually selected trait in Ficedula flycatchers, especially in males, where the patches are more conspicuous (larger and possibly whiter) than in females. Using in vitro tests of feather bacterial degradation, we compared the degradability of unmelanized and melanized areas of the same feather for 127 primaries collected from the same number of individuals in a population breeding in central Spain (58 males and 69 females). In addition, we also looked for sex differences in feather degradability. Based on honest signalling theory and on the fact that there is stronger sexual selection for males to signal feather quality than in females, we predicted that unmelanized areas should be more degradable by bacteria than melanized ones within the same feather, and that these unmelanized areas should also be more degradable in males than in females. We confirmed both predictions. Microstructural differences between cross-section dimensions of unmelanized and melanized barbs, but not differences in the density of barbs within unmelanized and melanized areas of feathers in males and females, could partly explain differences in degradability. This is the first study to show differences in bacterial degradability among markings on the same feather and among unmelanized feather patches between males and females as predicted by sexual selection theory.

There are often marked differences in the incidence of nest-dwelling ectoparasite species on different coexisting and similar avian host species. This has been shown especially for fleas (Siphonaptera), larvae of flies (Diptera), and mites (Acarina) in nests of tits and flycatchers breeding in nest-boxes in close proximity to each other. One of the possible reasons for these differences is the marked differences in nest composition between avian species. We show here differences in ectoparasite presence and nest composition for blue tits (Cyanistes caeruleus) and pied flycatchers (Ficedula hypoleuca) coexisting in oak forests in central Spain. There also may be intraspecific differences in local preferences for nest-building materials according to availability of plant materials, which could be due to arthropod repellent properties of different potential nest components. We show here a local difference in nest composition between 2 pied flycatcher populations in relation to availability of a preferred material associated with higher ectoparasite presence in the locality without the preferred nest material. We test the hypotheses that differential incidence of ectoparasites at the interspecific and intraspecific levels may depend on nest composition. We conducted a nest exchange experiment in one study locality in 2007 placing in nest-boxes occupied by flycatchers 1) nests constructed by blue tits in 2006 in another locality and removed before use and stored frozen, 2) nests constructed by flycatchers in 2006 in another locality with different nest composition and removed before use and stored frozen, and 3) nests constructed by other flycatcher pairs in the same study locality in 2007. Another group of flycatcher nests was kept as pure control, while a few blue tit nests constructed in 2007 and taken over by flycatchers were used for comparison with nests of treatment 1. No effect on presence of mites and blowflies of either nest-constructing species or locality of construction was observed for pied flycatcher nests, and for fleas only an effect of locality but not of nest constructing species was detected. On the other hand, presence of mites and blowflies differed between nests constructed by blue tits and occupied by either blue tits or pied flycatchers. Nest composition does not explain the differential incidence of nest-dwelling ectoparasites on coexisting avian host species.

Despite many studies of how male characteristics affect paternity in predominantly monogamous birds, relatively little attention has been given to the traits of females that may influence extra‐pair paternity (EPP). However, the occurrence of EPP may be the result of behavioural interactions in which both male and female traits are important for determining the outcome. If EPP is driven mainly by female choice of extra‐pair sires, older, more experienced or larger females would be better able to evade mate guarding tactics and more capable of selecting extra‐pair mates and resisting unwanted suitors. This would be especially noticeable in females paired with unattractive mates. On the other hand, if EPP is driven mainly by male pursuit, we should expect that young, inexperienced or small females would be more exposed to coercive male approaches independently of social mate traits. In a study of an Iberian population of the pied flycatcher Ficedula hypoleuca, we found that EPP affected 38% of the broods and 17% of the nestlings. These values are relatively high, allowing a relatively large number of affected within‐pair mates to be included. We found that EPP is related to both female and male traits although not to any interaction between male and female traits. EPP was higher at nests tended by both younger and short‐winged females and by browner males. Older females may be more experienced and dominant while long‐winged females may be faster fliers, these traits enabling them to avoid extra‐pair copulations, while brown males are less aggressive towards male intruders. In our study population, EPP appears to be caused by male pursuit, which in some cases may overwhelm female attempts to avoid extra‐pair copulations and their social partner's ability to prevent them.

Bacteria grow on avian eggshells and thus can potentially cause diseases in developing embryos. Little is known about culturable bacteria colonizing avian eggshells in free‐living birds, with most studies restricted to poultry. Our objective was to examine the culturable bacterial array growing on eggshells during incubation that could negatively affect hatching success of Pied Flycatchers (Ficedula hypoleuca) in a temperate montane habitat in central Spain. Cloacal culturable bacteria of females were also analyzed because bacteria can be vertically transmitted from females to eggs. We used fecal samples as surrogates of cloacal samples due to the small size of sampled birds. We found that eggshells and female cloacae of Pied Flycatchers harbored 24 and 40 bacterial families and species, respectively, but only a few in each clutch and each cloaca. Rod‐shaped gram‐negative bacteria and bacteria in the family Pseudomonadaceae were the most common bacteria on eggshells during early and late incubation and in female cloacae. Although based on small sample sizes, we found that females with rod‐shaped gram‐negative bacteria in their cloacae laid eggs that also had these bacteria, providing possible evidence for vertical transmission. We found no evidence for vertical transmission of Pseudomonadaceae, suggesting a possible environmental source for these bacteria. The prevalence of bacterial morphological types and major taxonomical categories on eggshells did not vary from early to late stages of incubation, providing support for the hypothesis that incubation may have bacteriostatic effects on bacterial proliferation on eggshells. Despite being primary egg invaders in poultry, we detected no effects of culturable Pseudomonadaceae or Pseudomonas luteola on hatching success. Our study represents the first to examine the culturable bacteria growing on the eggshells of a wild bird in a temperate habitat and additional studies based on culture‐independent techniques are required to confirm our results.