The plastic homes of hermit crabs in the Anthropocene.

Plastic is the most pervasive element of marine waste, with harmful impact on wildlife. By using iEcology (i.e., internet Ecology, use of online data sources as a new tool in ecological research), we report on the emergence of a novel behaviour in hermit crabs related to the use of plastic or other anthropogenic materials as protective shells. We analysed images posted on social media to identify 386 individuals with artificial shells - mainly plastic caps (85 %). We report that 10 of the world's 16 terrestrial hermit crabs use artificial shells, a behaviour observed on all of the Earth's tropical coasts. Four non-exclusive mechanisms may drive individual choice for artificial shells: sexual signaling, lightness of artificial shells, odour cues, and camouflage in a polluted environment. Further research is needed to determine the impact of this behaviour on hermit crab evolutionary trajectories.

Why do some bird species incorporate more anthropogenic materials into their nests than others?

Many bird species incorporate anthropogenic materials (e.g. sweet wrappers, cigarette butts and plastic strings) into their nests. Anthropogenic materials have become widely available as nesting materials in marine and terrestrial environments globally. These human-made objects can provide important benefits to birds such as serving as reliable signals to conspecifics or protecting against ectoparasites, but they can also incur fundamental survival and energetic costs via offspring entanglement and reduced insulative properties, respectively. From an ecological perspective, several hypotheses have been proposed to explain the use of anthropogenic nest materials (ANMs) by birds but no previous interspecific study has tried to identify the underlying mechanisms of this behaviour. In this study, we performed a systematic literature search and ran phylogenetically controlled comparative analyses to examine interspecific variation in the use of ANM and to examine the influence of several ecological and life-history traits. We found that sexual dimorphism and nest type significantly influenced the use of ANMs by birds providing support for the 'signalling hypothesis' that implies that ANMs reflect the quality of the nest builder. However, we found no support for the 'age' and 'new location' hypotheses, nor for a phylogenetic pattern in this behaviour, suggesting that it is widespread throughout birds. This article is part of the theme issue 'The evolutionary ecology of nests: a cross-taxon approach'.

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.

The effect of climate change on avian offspring production: A global meta-analysis.

Climate change affects timing of reproduction in many bird species, but few studies have investigated its influence on annual reproductive output. Here, we assess changes in the annual production of young by female breeders in 201 populations of 104 bird species (N = 745,962 clutches) covering all continents between 1970 and 2019. Overall, average offspring production has declined in recent decades, but considerable differences were found among species and populations. A total of 56.7% of populations showed a declining trend in offspring production (significant in 17.4%), whereas 43.3% exhibited an increase (significant in 10.4%). The results show that climatic changes affect offspring production through compounded effects on ecological and life history traits of species. Migratory and larger-bodied species experienced reduced offspring production with increasing temperatures during the chick-rearing period, whereas smaller-bodied, sedentary species tended to produce more offspring. Likewise, multi-brooded species showed increased breeding success with increasing temperatures, whereas rising temperatures were unrelated to reproductive success in single-brooded species. Our study suggests that rapid declines in size of bird populations reported by many studies from different parts of the world are driven only to a small degree by changes in the production of young.

Breeding in the pandemic: short-term lockdown restrictions in a European capital city did not alter the life-history traits of two urban adapters.

Humans are transforming natural habitats into managed urban green areas and impervious surfaces at an unprecedented pace. Yet the effects of human presence per se on animal life-history traits are rarely tested. This is particularly true in cities, where human presence is often indissociable from urbanisation itself. The onset of the SARS-CoV-2 outbreak, along with the resulting lockdown restrictions, offered a unique, "natural experiment" to investigate wildlife responses to a sudden reduction in human activity. We analysed four years of avian breeding data collected in a European capital city to test whether lockdown measures altered nestbox occupancy and life-history traits in terms of egg laying date, incubation duration and clutch size in two urban adapters: great tits (Parus major) and blue tits (Cyanistes caeruleus). Lockdown measures, which modulated human presence, did not influence any of the life-history traits investigated. In contrast, the interaction between year and tree cover, a distinct ecological attribute of the urban space, was positively associated with clutch size, a key avian life-history and reproductive trait. This highlights the importance of inter-year variation and habitat quality over human activity on urban wildlife reproduction. We discuss our results in the light of other urban wildlife studies carried out during the pandemic, inviting the scientific community to carefully interpret all lockdown-associated shifts in biological traits. Supplementary Information: The online version contains supplementary material available at 10.1007/s11252-022-01309-5.

The extended avian urban phenotype: anthropogenic solid waste pollution, nest design, and fitness.

Solid waste pollution (garbage discarded by humans, such as plastic, metal, paper) has received increased attention given its importance as a global threat to biodiversity. Recent studies highlight how animals incorporate anthropogenic materials into their life-cycle, for example in avian nest construction. While increasingly monitored in natural areas, the influence of solid waste pollution on wildlife has been seldom explored in the urban habitat. There is limited data on the relationship between anthropogenic solid waste pollution, nest design, and reproductive success in an urban context. We address this knowledge gap (i) by investigating the presence of environmental solid waste pollution in the breeding habitats of great tits Parus major and blue tits Cyanistes caeruleus reproducing in a gradient of urbanisation, and (ii) by quantifying (ii) the contribution of different anthropogenic materials in their nests. We further examine potential drivers of solid waste pollution by inferring three distinct properties of the urban space: environmental solid waste pollution on the ground, human presence, and the intensity of urbanisation (e.g impervious surfaces) in nestbox vicinity. Finally, (iii) we explore the relationship between anthropogenic nest materials and reproductive success. We found that environmental solid waste pollution was positively associated with human presence and urbanisation intensity. There was also a positive relationship between increased human presence and the amount of anthropogenic materials in great tit nests. Interestingly, in both species, anthropogenic nest materials covaried negatively with nest materials of animal origin (fur and feathers). We suggest that fur and feathers - key insulating materials in nest design - may be scarcer in areas with high levels of human presence, and are consequently replaced with anthropogenic nest materials. Finally, we report a negative relationship between anthropogenic nest materials and blue tit reproductive success, suggesting species-specific vulnerability of urban birds to solid waste pollution.

Distance to landfill and human activities affects the debris incorporation into the white stork nests in urbanized landscape in central Spain.

Human's activities dominates many aspects of the Earth's environment; thus animals are forced to adapt and respond to the resulting changes in habitat structure and functioning due to anthropogenic pressure. Along with the growing human population and the associated amount of waste produced, the amount of different type of physical contamination component in environment is increasing. Incorporation of debris in nests may be a mounting avian response to anthropogenic pollution. In this research, we quantified the constituent pieces and total mass of human-derived materials incorporated in white stork nests. The study was conducted on four locations in central Spain where white storks nest along a urbanization gradient. In total, we examined 49 nests. This study demonstrates that the incorporation of debris by white storks into their nests is related to human activity, measured by the Human Footprint Index (HFI). Moreover, the distance between these nests and landfills predicts the occurrence of debris incorporated into nests. Our study shows that birds nest building behaviour is impacted by human activities and pollution in environment.

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.

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.