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The undeniable presence of microplastics (MPs) in soil, air and, especially, in the aquatic environment has revealed them to be an emerging pollutant. One of the main sources contributing to the release of these microplastics into the environment is wastewater treatment plants (WWTPs). During the treatment of wastewater, these microparticles undergo incomplete retention, which leads to their discharge in huge amounts into water masses. The microplastics removed from the wastewater during the treatment processes usually become entrained in the sewage sludge, which is commonly employed as organic fertilizer. Alarming data regarding the occurrence of MPs in nature and the increasing public awareness of environmental concerns have led to the appearance of numerous studies on this topic in recent years. So, this work is focused on providing an overview of available processes for the removal of microplastics from water and also from sediments. Social demand for the correct and effective management of microplastics is constantly increasing and should be given careful consideration before future action is taken. Recycling is a good option, and policies might be developed in this direction, moving towards a circular and sustainable economy for plastics.

While human-induced rapid environmental changes are putting many organisms at risk of extinction, others are doing better than ever. This raises the question of why organisms differ in their tolerance to environmental alterations. Here, we ask whether and how behavioural adjustments assist animals in dealing with the urbanization process, one of the primary causes of biodiversity loss and biotic homogenization. Based on a literature review, we present both theoretical and empirical arguments to show that behavioural adjustments to urban habitats are widespread and that they may potentially be important in facilitating resource use, avoiding disturbances and enhancing communication. While a growing number of studies report behavioural differences between urban and nonurban animals, very few studies directly address the underlying mechanisms. In some cases, the changes in behaviour occur very rapidly and involve learning, and hence can be attributed to behavioural plasticity. In other cases, however, it cannot be ruled out that behavioural differences between urban and nonurban animals result from natural selection or nonrandom sorting of individuals by behavioural traits that affect dispersal, habitat selection or establishment. Because the urbanization process is expected to continue to threaten biodiversity in the near future, there is some urgency to improve our understanding of the mechanisms through which behaviour helps animals to cope with such environmental alterations.

Extreme personality traits in humans often have detrimental life consequences, so they have long been supposed to be diseases. However, many other species display personality variants that are maintained due to their fitness advantages; in this case, they are construed as strategies. To examine the fitness costs and benefits of pathological personality traits in humans, we measured features of the A (socially odd, distrustful), B (incentive-seeking, selfish) and C (fearful, inhibited) clusters with the Personality Diagnostic Questionnaire-4 + (PDQ-4 +) in a sample of 738 outpatients. Fitness relevant parameters like mating success, reproductive output, self preservation, and access to status were assessed with the Life Outcome Questionnaire. No fitness advantages were found for high-A subjects. In contrast, high-B subjects tripled low-B subjects with regard to mating success and had 39% more offspring. Further, high-C subjects outperformed low-C subjects in attaining status and avoiding risks. These findings help explain the commonness of some extreme personality traits in humans, and suggest that they should be seen as evolutionary strategies rather than as diseases.

Behavioural innovation is believed to be an important way in which animals devise solutions to new problems, yet the factors underpinning individual differences in innovation remain unclear. Here, we asked how motivational states and emotional responses to novelty shape the innovation process with a series of experiments in common mynas, Sturnus tristis. To this aim, we measured experimentally the willingness of adult individuals to eat a new food (consumer innovation) and to develop a new foraging technique (motor innovation), as well as their degree of neophobia, exploration, shyness, motivation and activity levels. Common mynas showed some propensity for consumer and motor innovations, with 55% and 22% of individuals solving the respective tasks. Moreover, individuals that solved the task significantly decreased their latency to solve it subsequently, indicating that learning had occurred. Differences in problem-solving performance were not related to sex, and individuals that solved the consumer task did not solve the motor innovation task faster. The likelihood of solving the motor task increased with propensity of the individual to explore the test apparatus, suggesting that the task was solved by trial and error. Exploration increased with the motivation to feed and decreased with the degree of neophobia. Thus, while differences in innovation propensity between individuals may result from cognitive differences, our results highlight that they may also reflect particular motivational states or emotional responses of individuals to novel situations.

Kleptoparasitism, the stealing of food items already procured by others, is a widespread foraging strategy in animals, yet the reasons why some taxa have evolved this strategy and others have not remain unresolved. It has been hypothesized that kleptoparasitism should be more profitable, and hence have more often evolved, in lineages featuring certain characteristics, such as a large body mass, an enlarged brain or a dependence on vertebrate prey. Alternatively, the evolution of kleptoparasitism could have been facilitated in certain ecological contexts, such as open habitats or mixed-species foraging groups. Here, we test these hypotheses for the evolution of food stealing with a comparative analysis in birds, using information on 856 field reports of interspecific kleptoparasitism from all over the world. In multivariate analyses controlling for common ancestry, the probability that a family uses kleptoparasitism was positively associated with residual size of the brain, habitat openness and the presence of vertebrate prey in the diet, but showed no association with body size or participation in mixed-species foraging groups. The conclusion that kleptoparasitism is associated more closely with cognition than with aggression is further supported by the finding that kleptoparasites have a larger residual brain size than their respective hosts, while their body size is not significantly larger. By emphasizing the central role of cognitive abilities in avian kleptoparasitism, our results offer a novel perception of avian food stealing, which in the past was primarily seen in terms of ‘brawn’ rather than ‘brains’.

Dunking behaviour, the dipping of food in water, has been anecdotally observed in more than 25 species of birds in the wild, but its function and ecology have not been systematically studied. In experiments conducted in the field and in captivity on Carib grackles, Quiscalus lugubris, in Barbados, we showed that: (1) dunking rate in the field was influenced by food type and that moistening dry food seems to be one of the major benefits of dunking; (2) most dunking observed in the field was performed by a minority of individuals, but the vast majority (86%) of grackles tested in captivity were capable of dunking; (3) a higher density of conspecifics at a water source was associated with a lower dunking rate and an increased risk of kleptoparasitism when dunking; and (4) there were consistent individual differences in dunking and stealing frequency. We conclude that dunking is part of the normal behavioural repertoire of Carib grackles in Barbados, and that the low frequency of the behaviour in the field did not result from the inability of some individuals to perform the technique, but more likely from the balance of costs and benefits affecting its expression.

The number of species varies greatly among taxa. In birds, for example, the parvorder Passerida contains 3556 species while the Odontophorida contains only six species. This uneven distribution of species among bird groups is not a consequence of random branching patterns and therefore warrants an explanation. According to the behavioural drive hypothesis, behavioural innovation coupled with social transmission of the new skill to other members of the population may lead to accelerated rates of evolution, and could therefore account for differences in species richness. In this paper, we test the behavioural drive hypothesis by examining the link between behavioural flexibility and the number of species per taxon. We estimate flexibility with relative brain size and feeding innovation rate and predict that both will be positively associated with the number of species per taxon. Since the number of species at any given time results from a balance between speciation and extinction rates, we also examine the link between flexibility and the number of species threatened with extinction. We predict that the two flexibility correlates will be negatively associated with the number of species at risk. In simple regressions, both flexibility correlates were significantly associated with species number per taxon. However, only innovation rate remained in the final model. Relative brain weight dropped out of the multiple regression due to its association with innovation rate. Relative brain weight, innovation rate and species number per taxon were all significantly correlated with the number of threatened species in the simple regression, but only the latter remained significant in the final model. The same results were obtained on independent contrasts, indicating that behavioural flexibility predicts richness but not extinction risk in birds.  2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.

Behavioural flexibility has long been thought to provide advantages for animals when they invade novel environments. This hypothesis has recently received empirical support in a study of avian species introduced to New Zealand, but it remains to be determined whether behavioural flexibility is a general mechanism influencing invasion success. In this study, we examined introduction success of 69 bird species in different regions of the world as a function of their degree of behavioural flexibility. Specifically, we predicted that species with relatively large brains and a high frequency of foraging innovations in their area of origin should show a higher probability of establishing themselves where they were introduced than species with small brains and low innovation frequencies. An analysis with general linear modelling (GLM) supported the prediction for relative brain size, even when controlling for phylogenetic biases and potential confounding variables. The only covariates that remained with relative brain size were plumage dimorphism, human commensalism and nest site. A pairwise comparison of closely related species also revealed that successful invaders showed a higher frequency of foraging innovations in their region of origin. This result held even when differences in research effort between species were considered. Overall, the results confirm and generalize the hypothesis that behavioural flexibility is a major determinant of invasion success in birds.  2002 The Association for the Study of Animal Behaviour

Invasion biology has often been criticized for its dissociation from the rest of ecology and its lack of rigor in adopting and rejecting new hypotheses and theories [1xInvasion Biology. Davis, M.A. See all References][1]. A new book by Blackburn, Lockwood and Cassey proves that this is no longer true. In this book, three leading experts combine theory with a rigorous analysis of the evidence to ask what are the causes and consequences of avian invasions. And they succeed formidably.What sets this book apart from others is its focus on a single group of organisms: birds. Whereas this reduces generality, a detailed knowledge of the studied system is essential to interpret and integrate findings into a coherent framework.Why should birds be a good model system in invasion biology if their economic and ecological harm is less than that of other organisms? The reason primarily lies in the high quality record of past avian introductions, which provides unique opportunities for research. The book is largely built on the enormous body of evidence drawn from the analysis of these historical introductions, which for some will be the strength and for others the weakness of the work. A comparative approach provides general results that apply across taxa and over broad regions, and allows for questions to be addressed that would be difficult to answer with experimental approaches. Nevertheless, past introductions were not well-designed experiments and have their own shortcomings. The authors discuss these shortcomings and convincingly argue that the comparative analysis of past introductions is still a powerful tool provided that its limitations are acknowledged and appropriate statistics are used.Avian invasions is set out in two sections that respectively cover the causes and consequences of invasions. The chapters on the causes decomposes invasion into four stages: transport, release, establishment and spread. These stages are not only governed by different processes, but each stage shapes the subsequent stages both for ecological and non-ecological reasons. For example, evidence is provided in Chapter 2 for a non-random pattern in the species that are transported and introduced, and the regions where they are released. Because this non-randomness could confound efforts to identify factors that influence subsequent stages, the authors advocate use of transport and introduction patterns as a ‘null model’ in invasion biology. The authors adopt this null model when asking why alien species can succeed in establishing and spreading in environments to which they have not had the opportunity to adapt. The paradox is classically resolved by invoking pre-adaptations to the new environment and environmental conditions that increase region invasibility. However, in Chapter 3 the authors propose a simpler explanation: luck. Most avian introductions involve a few individuals and consequently many populations die out as a result of stochasticity and Allee effects. Beyond a certain number of individuals released, however, success is no longer determined by propagule size. The properties of the species and locality gain then greater importance. Chapter 4 proposes that key adaptations during establishment reduce Allee effects and assist individuals in finding appropriate niches in the novel environment, notably ecological generalism and behavioural flexibility. Whereas these latter traits could aid establishment in regions where invasive species have had no opportunity to adapt, in Chapter 5 the authors show that establishment is also facilitated if the environment is climatically similar to that found in the native region of the invader and has been altered by human actions. This highlights the importance of species-by-habitat interaction during invasions.The second section, as fascinating as the first, focuses on the consequences of invasions. Biological invasions enable researchers to study ecological processes in real time, rather than inferring them, and this provides unique opportunities to address important issues in ecology and evolution. For example, we read that exotic birds influence biodiversity patterns primarily through changes in entry rules, and that the common view that invaders pass through a genetic bottleneck during the first stages of the invasion process does not hold for birds. The authors also propose that avian exotics provide some of the best evidence of contemporary evolution by natural selection.Overall, I very much enjoyed reading Avian invasions. It is informative, comprehensive, rigorous, stimulating and highly readable. The book is a must read for anyone interested in biological invasions, and will inspire students and academic researchers alike.

We agree with Roth and Dicke [1xEvolution of the brain and intelligence. Roth, G. and Dicke, U. Trends Cogn. Sci. 2005; 9: 250–257Abstract | Full Text | Full Text PDF | PubMed | Scopus (345)See all References][1] that a focus on behavioral flexibility can provide useful operational measures of intelligence [2xBrains, innovations and evolution in birds and primates. Lefebvre, L., Reader, S.M., and Sol, D. Brain, Behav. Evol. 2004; 63: 233–246Crossref | PubMed | Scopus (315)See all References][2]. However, we would like to raise a number of issues for discussion. Firstly, the authors do not specify how they have assessed taxonomic differences in behavioral flexibility. Secondly, we believe that using humans as the benchmark against which all other animals are assessed can obscure the elucidation of general evolutionary patterns. We would not argue with the idea that humans excel in a number of cognitive domains, but to search for one defining characteristic of the human brain and to argue that this underpins animal intelligence risks generalizing from a single case. Comparisons of just two or three groups run a similar risk. Instead, comparative analysis is better served by objective, quantitative measures of intelligence on many species and taxa, allowing general patterns to be established.Thirdly, we are puzzled by Roth and Dicke's partial review of the different ways in which relative brain size has been estimated. Roth and Dicke correctly point out that considering brain mass as a percentage of body mass is often unsatisfactory because such ratios can be confounded with body mass depending on the taxonomic level where they are used. However, other measures of relative brain size (and relative size of certain brain areas) are available and have, in birds and primates, shown very convincing relationships with quantitative measures of cognition such as rate of innovation, rate of tool use, reversal-learning performance, social-learning rate and deception frequency, as well as a number of social and ecological variables [2xBrains, innovations and evolution in birds and primates. Lefebvre, L., Reader, S.M., and Sol, D. Brain, Behav. Evol. 2004; 63: 233–246Crossref | PubMed | Scopus (315)See all References, 3xNeocortex size predicts deception rate in primates. Byrne, R.W. and Corp, N. Proc. R. Soc. Lond. Ser. B. 2004; 271: 1693–1699Crossref | PubMed | Scopus (146)See all References, 4xComparative tests of primate cognition: different scaling methods produce different results. Deaner, R.O., Nunn, C.L., and van Schaik, C.P. Brain Behav. Evol. 2000; 55: 44–52Crossref | PubMedSee all References]. These relative brain measures include residual size of the whole brain regressed against body mass, residual size of the mesopallium regressed against body mass, and the volume of the neocortex divided by that of the brainstem. Roth and Dicke may well be correct in espousing the number of neurons or the number of synapses as the ideal neural variable, but until we have such data on many species, we cannot test predictions.Finally, it must be noted that understanding the evolution of enlarged brains cannot be simply reduced to the demonstration of an association between brain structure and behavioral flexibility. Progress also requires that we understand how enlarged brains and enhanced intelligence help animals to survive and reproduce, and hence increase Darwinian fitness, as well as identifying the costs and constraints that might limit their evolution [5xBig brains, enhanced cognition and response of birds to novel environments. Sol, D. et al. Proc. Natl. Acad. Sci. U. S. A. 2005; 102: 5460–5465Crossref | PubMed | Scopus (386)See all References][5].