Brain size mediates the choice of breeding strategy in the red-backed shrike Lanius collurio.

The brain size of vertebrates represents a trade-off between natural selection for enhanced cognitive abilities and the energetic constraints of brain tissue production. Processing information efficiently can confer benefits, but it also entails time costs. Breeding strategies, encompassing timing of breeding onset and nest-site selection, may be related to brain size. In this study, we aim to elucidate the relationship between brain size, breeding timing, nest-site choice, and breeding success in the red-backed shrike Lanius collurio. Our findings revealed that the timing of the first egg-laying date was associated with female head size, with larger-headed females tending to lay eggs later in the breeding season. Additionally, we observed that breeding success was positively correlated with increased nest concealment. However, this relationship was stronger in males with smaller heads. In turn, nest concealment was not related to head size but primarily influenced breeding onset. These results suggest that the choice of breeding strategy may be moderated by brain size, with differences between sexes. Larger-headed females may invest more time in selecting nesting sites, leading to delayed breeding onset, while larger-headed males may compensate for suboptimal nest concealment. Our study sheds light on the intricate interplay between brain size, breeding timing, nest-site preferences, and breeding success in passerine birds, underscoring the potential role of cognitive capacity in shaping individual decision-making processes.

Controlled expression of avian pre-migratory fattening influences indices of innate immunity.

While immunity is frequently dampened when birds engage in strenuous migratory flights, whether and how immunity changes during the rapid accumulation of energy stores in preparation for migration remains largely unknown. Here we induced pre-migratory fattening through controlled changes of daylight in common quails (Coturnix coturnix) and regularly assessed changes in three markers of constitutive innate immunity (leukocyte coping capacity or LCC, hemagglutination and hemolysis titres) and measures of body composition (lean and fat mass). All the three markers showed similar changes over the pre-migratory fattening process. LCC responses, hemagglutination titres, and hemolysis titres, were on average higher in the mid-fattening phase compared to the peak-fattening phase, when values were similar to those observed prior the start of pre-migratory fattening. At mid-fattening, we found that the birds that showed a larger accumulation of fat mass (as % of body mass) had lower LCC peak responses and hemolysis titres. Reversibly, at mid-fattening, we also found that the birds that kept a higher proportion of lean mass (as % of body mass) had the highest LCC peaks. Our results indicate that migratory birds undergo changes in immune indices (over 8 weeks) as they accumulate energy stores for migration and propose that this could be due to competing or trade-off processes between metabolic remodelling and innate immune system function.

Mites Living in the Nests of the White Stork and Black Stork in Microhabitats of the Forest Environment and Agrocenoses.

The White Stork (Ciconia ciconia) and the Black Stork (Ciconia nigra) are well-known model organisms for the study of bird migration, as well as the selectivity of nesting sites and the choice of living environment. The former breeds mainly in open areas, while the latter inhabits forest areas. The acarofauna, and in particular Oribatida, inhabiting the nests of these species, has not been thoroughly explored so far. Therefore, we analyzed the material collected from 70 White Stork nests and 34 Black Stork nests in Poland, between Poznan and Rawicz, and in Kampinos National Park. Our research has increased the faunal and ecological knowledge of the mite fauna inhabiting the nests of large migratory bird species. Oribatida constituted 5-12% of the total mites identified in the nests of White and Black Storks. Their average number was several times higher in the Black Stork nests (80.2 individuals in 500 cm3). Also, the species diversity of moss mites was greater in the Black Stork nests (47 species). In total, the nests of the two stork species were inhabited by 62 moss mite species, with only 22 recorded in both the White and the Black Storks' nests. The most numerous species included Ramusella clavipectinata, R. fasciata, Oppiella subpectinata, Acrogalumna longipluma, and Scheloribates laevigatus. In addition, we found that juvenile oribatid mites accounted for 0.6% of all the mites in the White Stork nests, with tritonymphs having the largest share, while juveniles in the Black Stork nests comprised 1.4%, of which larvae and protonymphs had the largest share. Our research shows that the nests of large migratory birds provide living space for many mite species. In addition, we noted the potential importance of White and Black Stork nests for mite dispersion and the evolution of interspecies interactions.

Age, brood fate, and territory quality affect nest-site fidelity in white stork Ciconia ciconia.

BACKGROUND: A particular type of site fidelity is faithfulness to the nest site, where birds are not only reoccupying breeding territories but also reusing nests built in previous breeding seasons. Staying faithful to the nest site is believed to be an adaptive strategy, and based on the ability to predict an individual's own breeding success, a hypothesis of "win-stay:loose-switch" was proposed. In this study, we aimed to resolve which factors affect the nest-site fidelity of white stork Ciconia ciconia, species known for reusing nests available in the breeding sites. Basing on ring recoveries from 31 years of studies in Western and Southern Poland, we analysed the impact of intrinsic and extrinsic factors on nest-site fidelity. RESULTS: We found that increasing age and breeding success (i.e. producing any fledglings or not) increased the probability of reusing the nest, but in the oldest individuals, the probability decreased. In turn, the probability of breeding success increased with age, the increasing number of reproductive events on the particular nest, and the presence on the nest in the previous year. However, the oldest individuals had lower probability of success, as the relationship was curvilinear. The number of fledglings, however, was influenced only by an individual's age. The number of reproductive events on the nest was, in turn, affected by age, with the youngest and oldest individuals using the current nest for the least number of years. CONCLUSIONS: Our study shows that the decision process of whether to stay faithful to the nest or switch is based on the experience from the previous breeding event, consistently with the "win-stay:loose-switch" hypothesis. Our results also show that site fidelity benefits white storks, as the probability of breeding success increases if the nest is reused. Results also show the senescence effect that lowers breeding success and site fidelity probabilities.

Presence of the cloud cover and elevation angle of the sun affect measurements of eggshell coloration and patterning obtained from calibrated digital images.

Calibrated digital photography is frequently used in studies focusing on avian eggshell appearance to measure colour and pattern features. Photographs are often taken in natural light conditions, yet little is known to what extent the normalisation process is able to control for varied light. Here, we photographed 36 blown eggs of the Japanese quail Coturnix japonica at five different elevation angles of the sun on both sunny and uniformly overcast days alongside grey standards. We normalised and processed the photographs in the MICA Toolbox software and checked how much noise was introduced by different natural light conditions to the colour and pattern measurements of the same set of eggs. Our results indicate that natural variation of light conditions affects eggshell colour and pattern measurements obtained by means of calibrated digital photography. Depending on a trait, the elevation angle of the sun had similar or even greater effect on the measurement than the presence of the cloud cover. Furthermore, measurements taken in cloudy conditions were more repeatable than those taken in sunny conditions. Based on the results, we propose practical guidelines regarding measuring colour and pattern of eggshells using calibrated digital photography in outdoor conditions.

The prevalence of anthropogenic nest materials differs between two distinct populations of migratory birds in Europe.

A major impact of human development is the transformation of natural habitats into farming lands and the expansion of built-up areas. Also, plastic pollution is affecting wildlife on a global scale. Discarded plastic is ubiquitous and accessible for birds, which can incorporate them into the nest structure. Here, we describe the differences in type, prevalence, and the amount of anthropogenic nest materials between two populations of terrestrial, mainly farmland bird, the white stork Ciconia ciconia, on a broad geographical scale, from two migratory divides-eastern in Poland and western in Spain (in total 303 nests). In the two populations, we detected significant differences in the incorporation of anthropogenic nest material, as measured by the Human Footprint Index (HFI) and the Impervious Surface Areas (ISA). We found that ISA was positively related to anthropogenic nest material incorporation in the Spanish population, and HFI was positively related to anthropogenic nest material, in contrast to the Polish population, in which the relationships were not significant. Moreover, we showed that the prevalence of nests with anthropogenic nest material was two times higher in Spanish than in the Polish white stork population. This study demonstrates that the behavior of incorporation of the anthropogenic nest material differs between two distinct populations of a single bird species.

Unused railway lines for conservation of pollinators in the intensively managed agricultural landscape.

Pollinating insects are under high human pressure due to agricultural intensification and urbanization. Although many research and conservation projects have been applied worldwide, there is still a need for a comprehensive approach that meets local conditioning and capabilities. This paper investigated the composition, abundance, richness, alpha, beta, and gamma-diversity of pollinators between unused railway embankments and semi-natural grasslands. On 50 study sites (25 sites in unused railways and 25 their reference on grasslands), we collected data on the abundance, species richness and species diversity of bees, butterflies, and hoverflies. We conducted five samplings yearly (April-September) for two years, 2017-2018. To assess differences in abundance, species richness, alpha and beta diversity of pollinators between unused railways and controls, we used generalized linear mixed models (GLMM). To compare the composition of pollinator species, we applied non-metric multidimensional scaling (NMDS). Abundance, species richness, and Shannon-Wiener diversity index of all three groups of pollinators were significantly higher in unused railway lines than in control grasslands. Pollinator communities were more constant in unused railway lines than in grasslands. The NMDS analysis highlighted the importance of these structures for bee, butterfly and hoverfly communities, which were a subset of grassland species, but were more abundant. We indicated the highest total taxonomic beta-diversity for bees, butterflies, and hoverflies and species turnover for bees and butterflies in control grassland compared with unused railway lines. The taxonomical nestedness was significantly higher in unused railways lines for bees and butterflies than in control grasslands. In the case of hoverflies, we did not found any significant differences in species turnover and nestedness. Unused railway lines may act as a conservation tool for pollinator communities in intensively managed farmland and complement the declining semi-natural habitats.

Not so black, not so white: differences in microorganism load of contiguous feathers from white stork chicks.

Many organisms are characterized by strikingly contrasting black and white coloration, but the function of such contrasts has been inadequately studied. In this article, we tested the function of black and white contrasting plumage in white stork Ciconia ciconia chicks. We found greater abundance and diversity of microorganisms on black compared with adjacent white feathers. In addition, nest size was positively correlated with the abundance and diversity of microorganisms on white feathers. Flight initiation distance (FID), defined as the distance at which adult white storks took flight when approached by a human, was negatively correlated with most measurements of microorganism abundance. Breeding success was generally positively correlated with the abundance and diversity of microorganisms on black feathers. The feather growth rate was positively correlated with some and negatively correlated with other measurements of microbial abundance and diversity. Finally, chick growth was negatively correlated with the number of microbial species on black feathers and positively with the abundance and diversity of microorganisms on white feathers. These findings are consistent not only with the role of microorganisms in the maintenance of a benign microbial environment which differs between black and white feathers, but also with the hypothesis that several taxa of microorganisms found in black and white plumage are virulent, with negative effects on the fitness of their hosts.

Impact of land cover and landfills on the breeding effect and nest occupancy of the white stork in Poland.

Food wastes are among the factors with the greatest effects on animal populations. The white stork is among bird species that clearly profit from feeding at landfills, at least in Western Europe and North Africa. However, the rate and the consequences of this feeding are still unknown in the Central-Eastern European population, which differs from the western population not only in terms of migration routes but also in the greater availability of suitable natural breeding habitats due to less intensified agriculture. The aim of the study was to describe the use of landfills and its consequences in terms of probability of nest occupation and breeding effects in different regions of Poland. Although the most important factors influencing nest-site selection and breeding effect are still habitat quality and weather conditions, distance to landfills is important in selection of nest sites. White storks use landfills most intensively late in the breeding season, independently of the density of breeding pairs. The results suggest that the use of landfills is not currently essential in the Central-Eastern European population of the white stork, does not affect breeding effect, and may be more frequent in non-breeders. However, this phenomenon is still developing and requires continuous monitoring.

Campylobacter in wintering great tits Parus major in Poland.

Domestic and wild mammals, domestic birds and particularly wild birds are considered to be reservoirs of many species of Enterobacteriaceae, and also important human enteric pathogens, e.g., the bacteria of the genus Campylobacter that occur in their digestive tracts. These species may be vectors of antimicrobial resistance dissemination in the environment, because they may have contact with an environment contaminated with antibiotics. Bird feeders have been suggested as potential dispersal centres between wild wintering birds whose feeding is supported by humans. Therefore, we checked for the presence of Campylobacter bacteria among great tits Parus major, the most common bird species on bird feeders in Poland. Samples (n = 787 cloacal swabs) were collected in urban and rural areas of Poland. Bacterial species were identified using multiplex PCR, and 23 (2.9%) positive tests for Campylobacter spp. were found; in ten samples, C. jejuni was detected. The odds ratio of Campylobacter infection in rural birds was over 2.5 times higher than urban birds. Ten samples with C. jejuni were tested for antibiotic resistance, and all were sensitive to azithromycin, erythromycin and gentamycin, while six isolates were resistant to tetracycline, and five were resistant to ciprofloxacin. Four Campylobacter isolates were resistant to both these antibiotics.

Determination of nest occupation and breeding effect of the white stork by human-mediated landscape in Western Poland.

Choosing an appropriate nest site is essential for successful breeding. Changes in land use cause populations of many species to decline although some species adapt to anthropogenic changes. The white stork Ciconia ciconia commonly uses artificial nest sites. Recently, white storks from Western Europe have been using landfills as feeding sites; the beginnings of this process are being observed in Central-Eastern Europe. The study aimed to determine factors influencing the probability of nest occupation and breeding effect in a Central-Eastern European population of white storks. We used long-term data from Western Poland on breeding effect, nest occupation, the structure supporting the nest, the proximity of the nearest landfills, landfill area, and land cover. The probability of nest occupation was significantly dependent on habitat quality (based on the share of the preferred type of land cover), the structure supporting the nest, and landfill proximity within a specific year. The breeding effect was influenced by habitat quality and nesting structure. We demonstrate that the type of nesting structure is an important factor influencing both the probability of nest reoccupation and breeding effect. However, the significance of landfills appears to be growing, and in recent years, storks prefer occupying nests closer to landfills, which may have significant consequences for the population of the white stork.

Life in a polluted world: A global review of anthropogenic materials in bird nests.

Human pressure exerts a significant influence on animals and the environment. One of its consequences, plastic pollution is considered one of the major threats to fauna as well as a significant conservation issue. In this research, we examined the global pattern of one example of avian behavior in response to pollution-namely, the incorporation of anthropogenic materials into nests-as well as the existing knowledge on this subject. Based on 25 articles, we studied 51 populations, involving 24 bird species, and checked 10,790 nests; as a result, we found that incorporation of debris is correlated with increasing human influence on the environment, measured as the Human Footprint Index. Moreover, the probability of debris incorporation is higher in terrestrial than in marine species. We also identified knowledge bias in favor of marine as opposed to terrestrial species: namely, marine species attract more scientific attention than terrestrial. Furthermore, research approaches to these two ecosystems differ. Undeniably, the factors which influence debris incorporation by birds, the scale of this behavior, and particular forms of use of debris in bird nests are aspects which require long-term standardized research. This is the first global review paper on debris incorporation by birds to demonstrate a close link to human pressure as a driver.

How weather conditions in non-breeding and breeding grounds affect the phenology and breeding abilities of white storks.

BACKGROUND: It has often been suggested that conditions in wintering grounds affect the breeding abilities of migratory birds. This is known as the carry-over effect. Heretofore, many studies have reported the relationship between conditions in wintering grounds, dates of departure from and arrival at breeding grounds, and breeding success. However, very few studies have shown how these conditions affect the capacity of females for egg production. AIMS: To describe how conditions in the remote non-breeding areas in Africa affect reproductory abilities of migratory birds breeding in Europe. METHODS: We recorded 863 arrival dates for 191 nests (in 2005-16), clutch sizes of 412 clutches, and egg dimensions of 1725 eggs (in 2003-16) of white storks in western Poland. We used generalised climatic indicators such as the Sahel precipitation index (SPI) and Indian Ocean Dipole (IOD) to assess conditions in wintering grounds prior to breeding and precipitation and temperature in breeding grounds during the breeding season. RESULTS: The white stork arrived significantly earlier in seasons preceded by a warmer and rainier March, while conditions in Africa did not affect arrival dates. Females laid more (and larger) eggs in seasons preceded by rainier winters in Africa. Breeding success was not affected by conditions in wintering grounds, but only by the weather during breeding season. CONCLUSIONS: Conditions in wintering grounds may affect migratory birds, not only in terms of their arrival dates, but rather with respect to females' egg production capacities. Studies on stable isotopes may yield more detailed findings as to how this process takes place.

Factors determining the occurrence of anthropogenic materials in nests of the white stork Ciconia ciconia.

Birds have been using anthropogenic materials for nest construction for the past few decades. However, there is a trade-off between the use of new nesting material, which is often linked to greater breeding success, and the higher risk of nestling mortality due to entanglement or ingestion of debris. Here, we investigate the incorporation of anthropogenic materials into nests of the white stork Ciconia ciconia, based on a long-term study of a population in Western Poland. We recorded at least one item of debris in 50 and 42% of nests at the egg and nestling stages, respectively. More debris was found in nests located in territories with higher number of anthropogenic material in the surrounding environment. We found a relationship between the age of females, the number of debris in the area surrounding a nest, and the number of debris in the nest. We found no significant effect of the total number of debris in nests on clutch size, number of fledglings, or breeding success. Studies on the influence of the age and sex of individuals in understanding this behaviour and its drivers in bird populations should be continued.

Relatedness of wildlife and livestock avian isolates of the nosocomial pathogen Acinetobacter baumannii to lineages spread in hospitals worldwide.

The natural habitats and potential reservoirs of the nosocomial pathogen Acinetobacter baumannii are poorly defined. Here, we put forth and tested the hypothesis of avian reservoirs of A. baumannii. We screened tracheal and rectal swab samples from livestock (chicken, geese) and wild birds (white stork nestlings) and isolated A. baumannii from 3% of sampled chicken (n = 220), 8% of geese (n = 40) and 25% of white stork nestlings (n = 661). Virulence of selected avian A. baumannii isolates was comparable to that of clinical isolates in the Galleria mellonella infection model. Whole genome sequencing revealed the close relationship of an antibiotic-susceptible chicken isolate from Germany with a multidrug-resistant human clinical isolate from China and additional linkages between livestock isolates and human clinical isolates related to international clonal lineages. Moreover, we identified stork isolates related to human clinical isolates from the United States. Multilocus sequence typing disclosed further kinship between avian and human isolates. Avian isolates do not form a distinct clade within the phylogeny of A. baumannii, instead they diverge into different lineages. Further, we provide evidence that A. baumannii is constantly present in the habitats occupied by storks. Collectively, our study suggests A. baumannii could be a zoonotic organism that may disseminate into livestock.

Factors determining presence of passerines breeding within White Stork Ciconia ciconia nests.

Nests of White Stork Ciconia ciconia are commonly used by various passerines as nesting sites. In this study, we investigated factors determining presence and number of pairs of species breeding within White Stork nests in an extensive farmland in NE Poland. In 133 (57%) out of 233 White Stork nests, we found at least one breeding pair of passerine bird. These were from three species: House Sparrows Passer domesticus (68% of 133 nests with co-breeding), Tree Sparrows Passer montanus (65%), and Starlings Sturnus vulgaris (30%). The probability of breeding passerines within White Stork nests increased with increasing nest thickness, and was significantly higher in currently occupied nests. Sparrows were more likely to breed in White Stork nests located on electricity poles, situated closer to settlements and surrounded mainly by arable fields where meadows were not prevalent. In this paper, we show that White Stork nests are favorable nesting sites for passerines, as they are well insulated and provide an anti-predatory shield.

Constant and seasonal drivers of bird communities in a wind farm: implications for conservation.

Background. One of the most difficult challenges for conservation biology is to reconcile growing human demands for resources with the rising need for protecting nature. Wind farms producing renewable energy have been recognised to be a threat for birds, but clear directives for environmental planning are still missing. Methods. Point counts were performed to study the relationship between eight environmental variables and bird populations in different parts of a year on the largest Polish wind farm between March 2011 and February 2013. Variables potentially related to species richness (Chao 1 estimator) and the abundance of the entire bird community as well as five selected farmland species were analysed with the use of generalized linear mixed models. Results. Some associations between the studied variables and bird populations were season/year specific, while others had a constant direction (positive or negative) across seasons and/or years. The latter were distance to the nearest turbine, field size, number of wind turbines, proximity of settlements and water bodies. Spatial autocorrelation and counting time were significantly correlated with bird population estimates but the directions of these relationships varied among seasons and years. Associations between abundance of individual species and environmental variables were species-specific. Conclusions. The results demonstrated a constant negative relationship between wind turbine proximity and bird numbers. Other environmental variables, such as field size, proximity of settlements and water bodies that also had constant associations with bird populations across seasons may be taken into account when minimizing adverse effects of wind farm development on birds or choosing optimal locations of new turbines.

How to reduce the costs of ornaments without reducing their effectiveness? An example of a mechanism from carotenoid-based plumage.

ABSTRACT: Carotenoid-based ornaments are often considered to be honest indicators of individual quality assessed by potential mates. However, males can use a variety of strategies that minimize the amount of costly carotenoids used while retaining the effectiveness of color signaling. Birds could do this by altering pigment intake, metabolism, or its presentation to a potential signal receiver. Here, we propose a new mechanism of lowering the costs of carotenoid displays in birds: differential allocation of pigments within single feathers. We studied the coloration of the yellow terminal tail bands of rectrices of male Bohemian waxwings. Using reflectance spectrometry, we show that the two central rectrices are most intensively colored compared to other rectrices. More detailed analyses reveal that these differences result from feather-specific patterns of rectrices coloration. The outer feather vanes of the outermost rectrices are more intensively colored compared to the inner vanes. However, the central rectrices have equally colored vanes that are, on average, more intensively pigmented than the outermost rectrices. When the waxwing tail is folded, the outermost rectrices are covered by other feathers, except for the narrow, outer vane. Central rectrices, however, form the outermost layers which are not obscured by other tail feathers. Thus, the feather vanes that are the most visible to potential viewers are also the most pigmented. These results support the occurrence of a previously overlooked mechanism to reduce the costs of carotenoid-based ornaments: precise pigment distribution to maximize efficiency of signals within single feathers. SIGNIFICANCE STATEMENT: Males of many bird species use bright carotenoid-based plumage coloration to attract females. These traits are physiologically expensive such that only individuals in prime condition can develop the most vivid colors. Males often "cheat" to obtain attractive appearances at lower costs. We showed that this goal could be achieved by differential deposition of pigments into the most conspicuous feather regions. Bohemian waxwing males have yellow tips on their rectrices of which the outer vanes are more brightly colored compared to the inner vanes. These inner feather vanes are usually covered by other feathers and are, thus, less visible to conspecifics. The only exception is the pair of central rectrices that are fully exposed, and both feather vanes are equally colored. In this species, males minimize the use of costly carotenoid pigments while maintaining elaborate ornamentation of plumage regions that are most visible to potential mates.