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.
Our current understanding of the function of coordinated acoustic displays usually comes from studies conducted over a short period of the breeding season. However, the function of particular types of vocalizations may vary according to sex and context, and such displays can extend beyond the time of reproduction. To fully understand this phenomenon, analyses of year-round singing behavior are required. In the current study, we focused on a small, year-round territorial Afrotropical songbird, Chubb’s Cisticola (Cisticola chubbi). We analyzed the structure of songs during the breeding season as well as year-round changes in the proportion of solos, duets, and choruses to investigate the potential function(s) of each type of vocalization. We found that: (1) females produced whistling notes, while males generated trilling ones; (2) up to five individuals formed coordinated choruses, and (3) individuals were always near to each other during cooperative singing. Over the course of a year, the majority of syllables recorded were duets (82%), with rarer choruses (16%) and extremely rare solos (2%). Outside of the breeding season, males produced the most solos, while females produced more at the beginning of the breeding season. The proportion of choruses was highest at the end of breeding season. Frequent year-round production of duets and choruses strongly supports territory defense as the main function of joint singing, while the highest proportion of choruses at the end of the breeding season suggests that offspring take part in the chorus. To better understand cooperative singing, it is essential to extend our looking beyond the breeding season.
Comparative research conducted during the past two decades revealed ecological and evolutionary consequences of inter-species differences in relation to brain size. However, relatively much fewer studies have focused on intra-specific variation in brain sizes. This may arise from the lack of a reliable and universal methodology to estimate brain size that can be employed in wild populations in vivo and in a minimally invasive manner. Here, we assessed whether variation in brain mass of Common quails (Coturnix coturnix Linnaeus, 1758) was predicted by external measurements of the head. Contrary to previous work, we found that the height of the head and not the volume of the head was the best predictor of brain mass in the Common quail. However, we found that the height of the head explained only a relative small proportion of variance in brain masses (i.e. 74.4%). Our data suggest that the external measurements of the head may not represent a universally applicable methodology to estimate brain sizes in birds and should, therefore, be used cautiously and validated for the studied species.
Many bird species have experienced short- or long-term population declines. However, the mechanisms and reasons underlying such negative changes are often not fully understood, making it difficult to identify effective conservation measures to recover populations. In this study, we focused on local changes in the abundance and distribution of calling male Corncrakes Crex crex in relation to: (1) within- and between-season site fidelity of adult males, (2) spatial distribution of territories in consecutive years and (3) the effect of habitat conditions on population size. We counted the number of calling males at ten randomly selected study plots (1 km2) in 2014–2018. Additionally, males were caught and individually marked in years 2015–2017. We found significant between-year changes in Corncrake abundance, from a 34% decrease to a 21% increase. On average, 32% of males established territories in the same locations as males recorded in the previous year. Breeding site fidelity was very low, with only 2–5% of males recaptured in the following year. Males selected areas characterized by higher values of NDVI (Normalized Difference Vegetation Index–higher values indicate more biomass) than on average within the study area. Population size in a particular year was significantly affected by the NDVI of the previous year but not by the NDVI in the current breeding season. We suppose that Corncrakes may exhibit a nomadic breeding behavior, and settle at territories when they encounter optimal habitat conditions. Moreover, as population size was negatively correlated with habitat conditions at the beginning of the previous breeding season, we suppose that local population changes may reflect more general trends in a whole population rather than local breeding success. Therefore, we highlight the need for better knowledge of Corncrake dispersal within the main European population and for the coordination of monitoring and conservation efforts, especially in those regions where most Corncrakes breed.
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.
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