Urban environments cover vast areas with a high density of humans and their dogs and cats causing problems for exploitation of new resources by wild animals. Such resources facilitate colonization by individuals with a high level of neophilia predicting that urban animals should show more neophilia than rural conspecifics. We provided bird-feeders across urban environments in 14 Polish cities and matched nearby rural habitats, testing whether the presence of a novel item (a brightly coloured green object made out of gum with a tuft of hair) differentially delayed arrival at feeders in rural compared to urban habitats. The presence of a novel object reduced the number of great tits Parus major, but also the total number of all species of birds although differentially so in urban compared to rural areas. That was the case independent of the potentially confounding effects of temperature, population density of birds, and the abundance of cats, dogs and pedestrians. The number of great tits and the total number of birds attending feeders increased in urban compared to rural areas independent of local population density of birds. This implies that urban birds have high levels of neophilia allowing them to readily exploit unpredictable resources in urban environments.

Haemoparasites represent a diverse group of vector-borne parasites that infect a wide range of vertebrate hosts. In birds, haemoparasite infection rates may be associated with various ecological and life history traits, including habitat choice, colony size and migration distance. Here, we molecularly assessed the prevalence of 3 main haemoparasite genera (Plasmodium, Haemoproteus and Leucocytozoon) in 2 bird species with different habitat preferences and migratory behaviour: black-headed gulls (Chroicocephalus ridibundus) and common terns (Sterna hirundo). We found that gulls showed a much higher prevalence and diversity of Plasmodium or Haemoproteus (ca. 60% of individuals infected) than terns (zero prevalence). The prevalence of Leucocytozoon was low in both species (<3%). The differences in haemoparasite prevalences may be primarily driven by varying vector encounter rate resulting from different habitat preferences, as black-headed gulls mainly use vector-rich vegetated freshwater habitats, whereas common terns often use vector-poor coastal and brackish habitats. Since common terns migrate further than black-headed gulls, our results did not provide support for an association between haemoparasite prevalence and migratory distance. In gulls, we found a negative association between colony size and infection rates, suggestive of an ideal despotic distribution, and phylogenetic analyses of detected haemoparasite lineages provided evidence for higher host specificity in Haemoproteus than Plasmodium. Our results suggest that the preference for coastal areas and less vegetated habitats in terns may reduce haemoparasite infection rates compared to other larids, regardless of their migratory distance, emphasizing the role of ecological niches in parasite exposure.

Data collected out of the breeding season suggest that House sparrows (Passer domesticus) from the urban populations are characterized by a smaller body size and poorer body condition compared to birds from rural populations. Considering an urbanized Eurasian Sparrowhawk (Accipiter nisus) and other potential predators, a new predator-prey dependency is developing that can also be a reason for the House sparrow's poorer condition. This study was aimed at comparing the multivariate biometrical characteristics and few body condition indices of adult birds from urban and rural populations during the breeding season. It was hypothesized that a higher predation risk during the breeding season concerns mainly males, thus affecting their poorer condition. Most of the condition indices of males were significantly lower in the urban population. Males from the urban populations had lower body mass, shorter tarsus, longer alula, greater Kipp's distance and higher wing pointedness index in comparison to the birds from rural populations, whereas these differences were not found between females. We suggest that the lower body condition and biometric differences in the analyzed birds are a means of adapting to the new predator-prey scheme in accordance to the tradeoff theory between starvation and predation risks. A lower condition of birds in poor foraging urban habitats and higher predation risk may be indicative of a declining population.

No abstract

Mycoses of wild birds are rarely addressed in scientific research. We tested the hypothesis that urban populations of House Sparrow Passer domesticus, which in many cities showed downward trends in their number and are characterized by lower body mass and poorer body condition, would be more frequently colonized by fungi. To evaluate the degree of bird colonization by fungi, swabs were taken from the beak cavity and cloaca of birds from urban and rural populations in the breeding season. A high degree of bird colonization by fungi was determined in both types of habitats (urban: 86% of population; rural: 92% of population). In total, 26 species of fungi were isolated (urban: 15 species; rural: 22 species). No significant differences were determined between the number of fungi species identified in birds from urban and rural habitats and between the degree of colonization of the two ontocenoses (beak cavity and cloaca). In both environments, Candida krusei turned out to be the prevalent fungus, with a clear predominance in the urban population. The extent of ontocenoses colonization was higher in adult than in juvenile birds, which indicated that the colonization of ontocenoses progresses with age. A significant correlation was found between the presence of fungi, lower values body condition parameters from the urban population (F -degree of fat score, logBM -body mass logarithm, logT -tarsus length logarithm, BM/WL -body mass/wing length, logBM/logWL, BM/TL -body mass/tail length), physiological condition, and age of birds, which may suggest that adults birds with worse condition, and higher haemoglobin level were more often colonized by fungi. No important differences in the fungal colonization were detected between urban and rural areas, thus, the hypothesis that fungal infection may be the cause of decline of sparrows in urban habitats is still to be demonstrated.

There is increasing evidence that melanin-based plumage ornaments play a role in the sexual selection of birds, although there seems to be little consensus on the mechanisms underlying the signalling function of melanin-based plumage. The aim of this study was to assess the potential of a melanin-based plumage ornament (brown hood) to reflect components of individual quality (condition and physiological stress) in a common larid species, the Black-headed Gull Chroicocephalus ridibundus. For this purpose, we measured the size of the hood in over 500 Black-headed Gulls captured in several breeding colonies distributed across Poland. We found that hood size correlated positively with blood haemoglobin concentration, although we found no evidence for a relationship with blood glucose concentration or body mass. There was also a negative relationship between hood size and physiological stress, as assessed by leucocyte profiles (heterophil/lymphocyte ratio). We found this correlation in both sexes, suggesting that hood size may be an honest signal of individual quality in males and females, which implies a mutual mate choice in the Black-headed Gull. Finally, the relationship between hood size and blood haemoglobin concentration was primarily attributed to the parallel variation of these traits among the colonies, suggesting that Black-headed Gulls may settle in colonies in a despotic manner. As far as we are aware, our study is one of the first to show an honest signalling role of melanin-based ornaments in the gull family, Laridae. It remains to be tested whether different melanin-based plumage ornaments in gulls are developmentally and functionally integrated with each other and with carotenoid-based integument coloration.

Modernization of urban buildings can decrease the availability of nesting sites in buildings, leading to sudden decreases in the density of avifauna. In this study, we investigated the use of nest boxes as a bird conservation measure after buildings were thermally modernized. In a 10 ha experimental area we mounted five types of nest boxes of different sizes and dimensions (a total of 132). Nest boxes were dedicated to species that lost access to their previous nesting sites. All species associated with the buildings significantly declined or disappeared. In the first year after the modernization, the House Sparrow (Passer domesticus) decreased by 66% compared with the period before the modernization, Eurasian Jackdaw (Corvus monedula) by 68%, Common Starling (Sturnus vulgaris) by 70%, and Common Swift (Apus apus) by 100%. In the first two years after the modernization, the birds nested only in nest boxes. Five years of monitoring showed that using nest boxes as compensation for bird nesting sites lost during the renovation of buildings can cause a population to recover to ca. 50% of its original level. To optimize deployments of nest boxes, wildlife managers should consider target species’ preferences for the dimensions and placement of boxes and limit the time boxes are used if a species prefers nesting outside nest-boxes, but in buildings (e. g. the House Sparrow) and does not require additional support.

Background Nesting in large aggregations provides several important advantages for colonially breeding birds. However, it also imposes certain costs, associated with facilitated pathogen transmission and social stress. The cost-benefit ratio is not similar for all the birds in a colony and it might be mediated by nest density. To investigate the influence of nest density on cell-mediated immune function and on physiological condition of nestlings, we arranged a cross-fostering experiment in three breeding colonies of black-headed gulls Chroicocephalus ridibundus. First, we exchanged eggs between plots of high and low nest density. Afterwards, we performed phytohaemagglutinin (PHA) skin test and we measured blood haemoglobin concentration in nearly 350 nestlings from experimental (exchanged) and control (non-exchanged) groups. Results We found that PHA response was lowest in high nest density control group, indicating that depressed immune function of offspring, likely caused by social stress, can be considered as a cost of colonial breeding. Contrastingly, body condition of nestlings was the poorest in low density control group. Conclusion Nestlings hatched and raised in high nest density plots did not have higher blood haemoglobin concentration in comparison to other study groups. Furthermore, they were affected with depressed cell mediated immune function, which is possibly driven by combined maternal (corticosteroid hormones deposited in yolk) and environmental (elevated social stress) effects. These results indicate that breeders from high nest densities do not benefit by rising offspring in better quality, in terms of immune function and body condition, although, in the light of previous studies, high nest densities are occupied by birds of higher individual quality, than low density areas. Our study provides a novel insight into the mechanisms of density-dependence that govern fitness of colonially nesting birds.