Parasites play pivotal roles in host population dynamics and can have strong ecological impacts on hosts. Knowledge of the effects of parasites on hosts is often limited by the general observation of a fraction of individuals (mostly adults) within a population. The aim of this study was to assess the prevalence of malaria parasites in adult (≥1 year old) and nestling (7–11 day old) Tawny pipits Anthus campestris, to evaluate the influence of the host sex on parasite prevalence in both groups of age, and explore the association between infections and body condition (adults) and growth (nestlings). Two hundred Tawny pipits (105 adults and 95 nestlings) from one Spanish population were screened for avian malaria parasites (Haemoproteus and Plasmodium) using the polymerase chain reaction (PCR)-based methods. Body condition (body mass against a linear measure of size) was measured in adults and growth rate (daily mass gain) was calculated for nestlings. The overall prevalence of infection was 46 %. Sixteen different mitochondrial cytochrome b haplotypes of Plasmodium spp. and one Haemoproteus spp. haplotype were found. Malaria parasites were equally prevalent in nestlings and adults (45 and 46 %, respectively). Males were more likely to be infected by parasites than females, and this sex-bias parasitism was evident in both adults and nestlings. Furthermore, a lower daily mass gain during nestling growth in males than in females following infections were found, whereas the effect of infections on body condition of adults was detrimental for females but not for males. Age-specific differences in physiological trade-offs and ecological factors, such as nest predation would explain, at least in part, the observed host sex and age-related patterns in Tawny pipits.

Numerous studies have highlighted a major role of isolation by both geographic distance and current landscape resistance in controlling bird population genetic differentiation. However, the importance of past landscape features or landscape temporal stability in shaping population genetic structure remains undervalued, particularly in birds. We assessed the role of isolation by landscape resistance – derived from current landscape attributes and measures of landscape stability –, in comparison to geographic isolation, as drivers of genetic differentiation of the Iberian bluethroat (Luscinia svecica azuricollis ), a migratory bird whose populations breed in fragmented and dynamic landscapes affected by land use change. First, we characterized bluethroat genetic structure using microsatellite genotypes and evaluated genetic distances. Then, we built species distribution models using as a predictor a time series (two decades) of values of the Normalized Difference Vegetation Index as proxies of recent past landscape stability and current landscape features to ultimately generate landscape resistance values through different functions. Finally, we used maximum‐likelihood population effects models to evaluate the relationships between genetic distances and both geographic and landscape resistance distances. We found a genetic structure of four clusters in the Iberian bluethroats populations, as well as a high level of genetic differentiation. Genetic structure was better associated with landscape resistance, rather than with geographic distance. The highest values of habitat suitability corresponded to areas where vegetation remained mostly stable during the two decades prior to bird surveys, with low annual precipitation and spring temperature, being the relationship between gene flow and presence of intervenient habitat among populations linear or quasi‐linear. Our results suggest that conservation policies and land management practices that promote the maintenance of semi‐open pasture‐shrub mosaics (e.g. through extensive livestock grazing) can strongly benefit Iberian bluethroat populations, improving gene flow and population connectivity.