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The role of plumage ornamentation as a signal of parasite infection is a hot topic in the evolution of animal behaviour. Despite the undeniable role of host-parasite interactions in sexual selection, it is still unclear how parasites influence the variance in the expression of females displaying multiple ornaments. Here, by taking advantage of a long-term and individual-based monitored population of pied flycatchers Ficedula hypoleuca in a Mediterranean area, we investigated the variation in the expression of wing patch (size) and forehead patch (occurrence and size) in relation to infections with haemosporidian parasites in breeding adult females. Haemosporidian infection was related to wing patch size, and this association varied in direction and magnitude depending on the origin of birds (locally born vs. immigrant) and the type of breeding habitat (oakwood vs. pine plantation). Specifically, differences in wing patch size were most evident among immigrant females breeding in the pine plantation, with non-infected females expressing larger wing patches than infected ones. Regarding the forehead patch, its occurrence was also modulated by haemosporidian infection through two-way interactions with bird origin (lower occurrence in locally born females) and breeding habitat type (lower occurrence among infected than uninfected females in the oakwood, whereas the opposite was true in the pine plantation). Only bird age predicted forehead patch size. Therefore, in addition to haemosporidia infection, the expression of these ornaments was related to extrinsic (breeding habitat) and intrinsic (age, origin) factors, which suggests the existence of trade-offs between physiological responses to infection and the expression of secondary sexual traits. Overall, our results suggest that plumage ornaments provide independent and reliable information on the haemosporidian infection status of female pied flycatchers.

Wild birds are hosts of Culicoides from as early on as the nesting stage when constrained to their nests. However, the environmental factors which determine the abundance and composition of Culicoides species within each bird nest are still understudied. We sampled Culicoides from Eurasian blue tit (Cyanistes caeruleus) nests found in two types of forest located in southern Spain. Firstly, we monitored the abundance of Culicoides species in bird nests from a dry Pyrenean oak deciduous forest and a humid mixed forest comprising Pyrenean and Holm oaks throughout two consecutive years. During the third year, we performed a cross-fostering experiment between synchronous nests to differentiate the role of rearing environment conditions from that of the genetically determined or maternally transmitted cues released by nestlings from each forest. We found 147 female Culicoides from 5 different species in the birds’ nests. The abundance of Culicoides was higher in the dry forest than in the humid forest. Culicoides abundance, species richness, and prevalence were greater when the nestlings were hatched later in the season. The same pattern was observed in the cross-fostering experiment, but we did not find evidence that nestling’s features determined by the forest of origin had any effect on the Culicoides collected. These results support the notion that habitat type has a strong influence on the Culicoides affecting birds in their nests, while some life history traits of birds, such as the timing of reproduction, also influence Culicoides abundance and species composition.

In terrestrial snails, thermal selection acts on shell coloration. However, the biological relevance of small differences in the intensity of shell pigmentation and the associated thermodynamic, physiological, and evolutionary consequences for snail diversity within the course of environmental warming are still insufficiently understood. To relate temperature-driven internal heating, protein and membrane integrity impairment, escape behavior, place of residence selection, water loss, and mortality, we used experimentally warmed open-top chambers and field observations with a total of >11,000 naturally or experimentally colored individuals of the highly polymorphic species Theba pisana (O.F. MuLLER, 1774). We show that solar radiation in their natural Mediterranean habitat in Southern France poses intensifying thermal stress on increasingly pigmented snails that cannot be compensated for by behavioral responses. Individuals of all morphs acted neither jointly nor actively competed in climbing behavior, but acted similarly regardless of neighbor pigmentation intensity. Consequently, dark morphs progressively suffered from high internal temperatures, oxidative stress, and a breakdown of the chaperone system. Concomitant with increasing water loss, mortality increased with more intense pigmentation under simulated global warming conditions. In parallel with an increase in mean ambient temperature of 1.34 degrees C over the past 30 years, the mortality rate of pigmented individuals in the field is, currently, about 50% higher than that of white morphs. A further increase of 1.12 degrees C, as experimentally simulated in our study, would elevate this rate by another 26%. For 34 T. pisana populations from locations that are up to 2.7 degrees C warmer than our experimental site, we show that both the frequency of pigmented morphs and overall pigmentation intensity decrease with an increase in average summer temperatures. We therefore predict a continuing strong decline in t