Summary 1.Climate warming has led to shifts in the seasonal timing of species. These shifts can differ across trophic levels, and as a result, predator phenology can get out of synchrony with prey phenology. This can have major consequences for predators such as population declines owing to low reproductive success. However, such trophic interactions are likely to differ between habitats, resulting in differential susceptibility of populations to increases in spring temperatures. A mismatch between breeding phenology and food abundance might be mitigated by dietary changes, but few studies have investigated this phenomenon. Here, we present data on nestling diets of nine different populations of pied flycatchers Ficedula hypoleuca, across their breeding range. This species has been shown to adjust its breeding phenology to local climate change, but sometimes insufficiently relative to the phenology of their presumed major prey: Lepidoptera larvae. In spring, such larvae have a pronounced peak in oak habitats, but to a much lesser extent in coniferous and other deciduous habitats. 2. We found strong seasonal declines in the proportions of caterpillars in the diet only for oak habitats, and not for the other forest types. The seasonal decline in oak habitats was most strongly observed in warmer years, indicating that potential mismatches were stronger in warmer years. However, in coniferous and other habitats, no such effect of spring temperature was found. 3. Chicks reached somewhat higher weights in broods provided with higher proportions of caterpillars, supporting the notion that caterpillars are an important food source and that the temporal match with the caterpillar peak may represent an important component of reproductive success. 4. We suggest that pied flycatchers breeding in oak habitats have greater need to adjust timing of breeding to rising spring temperatures, because of the strong seasonality in their food. Such between-habitat differences can have important consequences for population dynamics and should be taken into account in studies on phenotypic plasticity and adaptation to climate change.

Animal vocalizations play an important role in individual recognition, kin recognition, species recognition, and sexual selection.Despite much work in these fields done on birds virtually nothing is known about the heritability of vocal traits in birds. Here, we study a captive population of more than 800 zebra finches (Taeniopygia guttata) with regard to the quantitative genetics of call and song characteristics. We find very high heritabilities in nonlearned female call traits and considerably lower heritabilities Animal vocalizations can function as cues for the recognition of particular individuals, kin versus nonkin, or conspecifics versus heterospecifics. Moreover, vocalizations often play a major role in male-male competition and female choice. To fully understand the function and evolutionary implications of vocalizations in each of these contexts, it is important to know the sources of variation in vocal traits. However, the quantitative genetics of vocal traits have been studied only in a few taxa, predominantly in insects (Butlin and

BackgroundPlumage coloration is important for bird communication, most notably in sexual signalling. Colour is often considered a good quality indicator, and the expression of exaggerated colours may depend on individual condition during moult. After moult, plumage coloration has been deemed fixed due to the fact that feathers are dead structures. Still, many plumage colours change after moult, although whether this affects signalling has not been sufficiently assessed.Methodology/Principal FindingsWe studied changes in coloration after moult in four passerine birds (robin, Erithacus rubecula; blackbird, Turdus merula; blue tit, Cyanistes caeruleus; and great tit, Parus major) displaying various coloration types (melanin-, carotenoid-based and structural). Birds were caught regularly during three years to measure plumage reflectance. We used models of avian colour vision to derive two variables, one describing chromatic and the other achromatic variation over the year that can be compared in magnitude among different colour types. All studied plumage patches but one (yellow breast of the blue tit) showed significant chromatic changes over the year, although these were smaller than for a typical dynamic trait (bill colour). Overall, structural colours showed a reduction in relative reflectance at shorter wavelengths, carotenoid-based colours the opposite pattern, while no general pattern was found for melanin-based colours. Achromatic changes were also common, but there were no consistent patterns of change for the different types of colours.Conclusions/SignificanceChanges of plumage coloration independent of moult are probably widespread; they should be perceivable by birds and have the potential to affect colour signalling.

The mTOR (mechanistic target of rapamycin) inhibitor rapamycin has long been known for its immune suppressive properties, but it has shown limited therapeutic success when given systemically to patients with psoriasis. Recent data have shown that the mTOR pathway is hyperactivated in lesional psoriatic skin, which probably contributes to the disease by interfering with maturation of keratinocytes. This study investigated the effect of topical rapamycin treatment in an imiquimod-induced psoriatic mouse model. The disease was less severe if the mice had received rapamycin treatment. Immunohistological analysis revealed that rapamycin not only prevented the activation of mTOR signalling (P-mTOR and P-S6 levels), but almost normalized the expression of epidermal differentiation markers. In addition, the influx of innate immune cells into the draining lymph nodes was partially reduced by rapamycin treatment. These data emphasize the role of mTOR signalling in the pathogenesis of psoriasis, and support the investigation of topical mTOR inhibition as a novel anti-psoriatic strategy.

Avian breeding populations have been shown to be regulated by territorial behaviour, often creating a surplus of non-breeding individuals. However, most evidence is of a male non-breeder surplus, whereas for a surplus to actually buffer a population both non-breeding males and females should be present. Here, we provide descriptive and experimental evidence for the existence of a population buffer consisting of mostly male and potentially also female Pied Flycatchers using nest box areas. First we show that local recruits often do not breed in their first year, with 23% of all recruiting males observed breeding in their first year, and 51% of females. When accounting for mortality in the years prior to observed first breeding, we estimate that only 9% of all first-year males breed locally, and 29% of first-year females. Similar percentages of first-year flycatchers skipping breeding have been observed in other study populations. We show that in the year of new establishment of our nest box plots, most known-aged flycatchers were first-year birds (77%), whereas after establishment, recruiting immigrants from the same source population were mostly older (28% first-year birds). An experimental removal of paired flycatchers from one study plot in two years (19 and 58 individuals removed) resulted in complete replacement by males and females. Male but not female replacements were younger than removed individuals. These results imply that a non-breeding surplus is present in Pied Flycatcher populations. The average later age at firstbreeding in males compared to females, suggests that this non-breeding surplus is strongly male-biased. Skipping breeding in the first year(s) is not just caused by shortage of suitable nesting sites, as we observed on average 12% of males defending a nest box without pairing up with a female. Using stable isotopes ratios, we show that non-breeding first-year individuals do not stay at their African wintering grounds. Competition for nest sites is one cause for refraining from breeding, as shown by our experiments, but cannot be the sole cause, as many nest boxes remain unused in a season, and up to 20% of territorial males defend a nest box without pairing up with a female. We hypothesize that many young flycatchers arrive too late for breeding and are therefore not seen in their first year. Indeed first-year Pied Flycatchers that do breed/defend a nest box arrive on average later at the breeding grounds, and we argue that the nonobserved group arrives even later. The causes of their later arrival could be the need for learning, lower quality wintering sites resulting in later departure, and/or a trade-off between low breeding success and the costs of early arrival. These could be general factors in long-distance migrants, and this pleads for a better understanding of how migration develops during ontogeny.