Alien Birds Research Articles

Estimating changes in distribution trend of alien birds in urban areas using citizen science data

Urban ecosystems are suitable for the introduction and spread of alien bird species, and early detection of their establishment and expansion is crucial to reduce potential negative impacts. In this context, the use of opportunistic citizen science data can have considerable advantages in relation to conventional scientific approaches. We gathered records of parakeets and parrots (Psittaciformes) and mynas and starlings (Sturnidae) for the urban area of Lisbon (Portugal) from the eBird database. We used this opportunistic citizen science data to document the establishment and expansion and to estimate distribution trends of alien bird species in urban ecosystems. In the last decade there has been a considerable increase in the amount of opportunistic citizen science data available in eBird for our study area. The probability of presence of the Senegal parrot, rose-ringed parakeet, blue-crowned parakeet, and crested myna was positively influenced by the number of lists. For the rose-ringed parakeet, blue-crowned parakeet, and crested myna, the year positively influenced the probability of presence, suggesting an increase in distribution range. We observed that spatio-temporal variations in effort associated to opportunistic citizen science data sources may generate bias in trend estimates, and therefore we recommend the effort should always be accounted for. Our approach agreed with the documented expansion of alien bird species in the study area, supporting the potential usefulness of opportunistic citizen science in providing early detection on biological invasions in urban ecosystems, particularly where this is the best or the only source of information available.

Big-brained alien birds tend to occur climatic niche shifts through enhanced behavioral innovation.

Identifying climatic niche shift and its influencing factors is of great significance in predicting the risk of alien species invasions accurately. Previous studies have attempted to identify the factors related to the niche shift of alien species in their invaded ranges, including changes in introduction history, selection of exact climate predictors, and anthropogenic factors. However, the effect of species-level traits on niche shift remains largely unexplored, especially those reflecting the species' adaptation ability to new environments. Based on the occurrence data of 117 successful alien bird invaders at a global scale, their native and invaded climatic niches were compared, and the potential influencing factors were identified. Our results show the niche overlap was low, with more than 75% of the non-native birds representing climatic niche shift (i.e. >10% niche expansion). In addition, 85% of the species showed a large proportion (mean ± SD, 39% ± 21%) of niche unfilling. Relative brain size (RBS) after accounting for body size had no direct effect on niche shift, but path analysis showed that RBS had an indirect effect on niche shift by acting on behavioral innovation primarily on technical innovation rather than consumer innovation. These findings suggested the incorporation of species' important behavioral adaptation traits may be promising to develop future prediction frameworks of biological invasion risk in response to the continued global change.

The anthropocene biogeography of alien birds on islands: Drivers of their functional and phylogenetic diversities.

A branch of island biogeography has emerged to explain alien species diversity in the light of the biogeographic and anthropogenic context, yet overlooking the functional and phylogenetic facets. Evaluating alien and native birds of 407 oceanic islands worldwide, we built structural equation models to assess the direct and indirect influence of biotic, geographic, and anthropogenic contexts on alien functional diversity (FD) and phylogenetic diversity (PD). We found that alien taxonomic richness was the main predictor of both diversities. Anthropogenic factors, including colonization pressure, associated with classic biogeographical variables also strongly influenced alien FD and PD. Specifically, habitat modification and human connectivity markedly drove alien FD, especially when controlled by taxonomic richness, whereas the human population size, gross domestic product, and native PD were crucial at explaining alien PD. Our findings suggest that humans not only shape taxonomic richness but also other facets of alien diversity in a complex way.

Design and preparation of a thematic showcase on alien species at the Museum of Zoology of the University of Catania (Italy)

As part of the Interreg FAST (Fight Alien Species Transborder) project, in which the Zoology Museum of the University of Catania (Italy) is involved, in the Museum main room a thematic exhibition relating to alien species, also equipped with interactive supports, has been planned. This action is part of the communication strategy of the aforementioned project, providing for the promotion of Citizen Science initiatives that bring all citizens closer to this problem, increasing their awareness and participation. Some of the most representative and iconic animals linked to this issue will be exhibited within this space. Visitors will be able to observe both vertebrates such as the Nutria (Myocastor coypus Molina, 1782) or the American pond turtle (Trachemys scripta Thunberg in Schoepff, 1792), and invertebrates such as the Red palm weevil (Rhynchophorus ferrugineus Olivier, 1790) or the Louisiana red crayfish (Procambarus clarkii Girard, 1852). Also, a large poster illustrating all the species of alien birds in Europe will complete the exhibition, which will also be accompanied by information panels in Italian and English regarding not only the animals on display but also the aims and objectives of the FAST project. Adjacent to the exhibition space an 80-inch touch screen monitor will be installed with a software, also for children, for the recognition of native and alien species, accompanied by information collected in a database on alien invasive species present in Sicily and in Malta.

Global economic costs of alien birds.

The adverse impacts of alien birds are widespread and diverse, and associated with costs due to the damage caused and actions required to manage them. We synthesised global cost data to identify variation across regions, types of impact, and alien bird species. Costs amount to US$3.6 billion, but this is likely a vast underestimate. Costs are low compared to other taxonomic groups assessed using the same methods; despite underreporting, alien birds are likely to be less damaging and easier to manage than many other alien taxa. Research to understand why this is the case could inform measures to reduce costs associated with biological invasions. Costs are biassed towards high-income regions and damaging environmental impacts, particularly on islands. Most costs on islands result from actions to protect biodiversity and tend to be low and one-off (temporary). Most costs at mainland locations result from damage by a few, widespread species. Some of these costs are high and ongoing (permanent). Actions to restrict alien bird invasions at mainland locations might prevent high, ongoing costs. Reports increased sharply after 2010, but many are for local actions to manage expanding alien bird populations. However, the successful eradication of these increasingly widespread species will require a coordinated, international response.

Testing the links between bird diversity, alien species and disturbance within a human‐modified landscape

Introduced alien species are associated with lower taxonomic, functional and phylogenetic diversity of native communities and negative impacts on ecosystem functioning. This is particularly evident in habitats where human disturbance may favour alien species, posing an additional stressor on native communities. Following the community resistance hypothesis (higher diversity promotes higher resistance to invasion), we predicted: 1) higher taxonomic, functional and phylogenetic diversity (TD, FD and PD respectively) in non‐invaded bird communities (i.e. no alien bird species); and 2) higher diversity and resistance to invasion in less human‐disturbed areas. We surveyed bird communities in a modified Mediterranean landscape subject to varying levels of human disturbance. We tested whether TD, FD and PD were significantly different between non‐invaded and invaded bird communities, and assessed the effect of land classes (forest, agriculture, urban), landscape composition and heterogeneity on these metrics. We found that non‐invaded communities retained higher TD and FD, but not PD, than invaded communities. Alien birds occupied marginal niches in invaded communities, and did not fully compensate for the taxonomic and functional diversity loss caused by the absence of native species. These results were consistent across different land classes, suggesting weak environmental filtering of communities. Generally, less human‐modified and more heterogeneous areas supported higher TD regardless of the presence of alien species. FD and PD of invaded communities decreased with increases in human‐modified areas, whereas non‐invaded communities were not affected. Our results suggest that even within a human‐modified landscape, invaded community diversity is more affected by, and thus has a lower resilience to, disturbance. Restoring and protecting natural habitats within human‐modified landscapes is likely to increase the resilience of native species.

Identifying links between the biodiversity impacts and monetary costs of alien birds

Abstract Alien species can be damaging to native biodiversity, human well‐being and the economy. Identifying the complete range of impacts they cause, and the ways that these impacts are connected, may inform the prioritisation of management actions to mitigate impacts. Using datasets on the biodiversity impacts and monetary costs (damage and management costs) of alien birds, we aimed to establish whether species with the most severe biodiversity impacts also had the highest costs; whether types of biodiversity impact were associated with high costs; and whether specific factors associated with alien species are linked to both damaging biodiversity impacts and high costs. We identified a positive relationship between a specific type of biodiversity impact (predation) and costs, possibly because predation by alien birds can be severely damaging to native species and therefore attracts management actions. However, predation impacts are likely to occur more frequently and to be easier to identify than some other impact mechanisms such as hybridisation and transmission of diseases, and they are therefore likely to be more frequently managed and hence to have costs. We identified a specific species characteristic (generalism) to be associated with severe biodiversity impacts and high costs, probably because generalist species have greater opportunity to cause impacts, whether they be on biodiversity or the economy, or both. We also found widely distributed alien birds to be associated with high costs, probably because these species also have greater opportunity to cause impacts. Management interventions that prevent the introduction of both predatory and generalist alien bird species, or that reduce their geographic distribution at early stages of invasions, may have significant biodiversity and economic benefits. Read the free Plain Language Summary for this article on the Journal blog.

Vacant niches help predict invasion risk by birds

AbstractAimIf communities have a ceiling determining the number of species that can coexist, then the ability of alien species to establish at any given location should be related to the quantity of vacant niches available. We developed a new approach to estimate the extent to which niches are vacant and then explored the relationship between vacant niches and alien species.LocationGlobal with focal tests in Europe and North America.TaxonBirds.MethodsDrawing on a global classification of trophic structures for birds, we calculated a ‘vacant niche ratio’ metric to quantify the expected level of saturation (i.e. number of vacant niches) for each 1° × 1° grid cell globally, based on the difference between expected and observed numbers of bird species for all trophic guilds. Next, we used random forests to examine if the presence of plant‐invertivore (whose food source represents plants, seeds, fruits and invertebrates) and granivore alien bird species was associated with the vacant niche ratio across well‐sampled regions.ResultsIn Europe, we found a significant relationship between alien species and vacant niches, with greater numbers of alien species being found in communities that offered greater numbers of vacant niches overall, and across habitat types. In North America, we found no significant relationship between plant‐invertivores and vacant niches, while for granivores, we found that areas with fewer vacant niches had greater numbers of alien species, especially in forests. However, vacant niches alone correctly predict 69% of the presence of alien bird species when combining both regions and trophic guilds.Main ConclusionsMost regions of the world have unsaturated bird communities, with the level of saturation in communities varying within regions and trophic guilds. We found that although often‐neglected, vacant niches are likely to be, at least partially, related with the successful establishment of alien bird species.

Trait‐environment associations diverge between native and alien breeding bird assemblages on the world's oceanic islands

AbstractAimTo investigate spatial variations in the ecological trait structure of breeding bird assemblages on oceanic islands. To test the hypothesis that native and naturalized alien bird species are filtered by different processes, leading to diverging associations between traits and insular environmental gradients.LocationOceanic islands worldwide.Time PeriodCurrent.Major Taxa StudiedTerrestrial breeding birds.MethodsWe assessed the composition of breeding terrestrial bird assemblages from the extent‐of‐occurrence maps of 3170 native and 169 naturalized alien species on 4660 oceanic islands. We quantified their ecological trait structures with respect to diet, mobility and body mass as the standardized distance between a mean pairwise trait distance index and its expectation from a null model. We used spatial generalized additive models to relate trait structures to proxies of environmental conditions and human impact on land, accounting for all species, native species only and alien species only.ResultsDiet and mobility traits tended to be more diverse than expected by a null model, while body mass tended towards clustering. Trait‐environment associations were idiosyncratic, but environmental variables tended to explain trait structures better than human impacts on habitats. Islands invaded by alien species had similar trait structures as noninvaded ones, although they hosted assemblages with more clustered body masses. However, trait‐environment relationships diverged when considering all islands and all species, invaded islands only or alien species only.Main ConclusionsDespite their ecosystem‐level influences, alien species have a limited effect on the global patterns of trait structures in the breeding bird assemblages of the world's islands, either because they account for a low proportion of species or because successful invaders and native species have similar trait suites. Trait‐environment associations suggest that filters related to the conditions of alien species' introductions explain their distributions in island assemblages better than the constraints associated with isolated environments.

Research on the bird image in Shanhai Jing

The Classic of Mountains and Seas is the original work of Chinese mythology, which records rich images of gods and mythological stories. Bird is a very important mythological image among them. Through the review of the literature, it can be seen that the birds in Shanhai Jing can be divided into four categories according to their physical characteristics: normal birds, alien birds, human-bird combinations and other categories. According to their functions, they can also be divided into four categories: auspicious bird, ominous bird, medicinal bird, and defensive bird. The paper comprehensively analyzes the bird imagery in the Book of Mountains and Seas from the surface to the inside by classifying the morphological characteristics of birds, analyzing their own functions, and exploring the reasons for ancient bird worship. The bird imagery in Shanhai Jing is a product of totem worship by ancient people. The study not only deepens the understanding of the text of Shanhai Jing, but also provides a deeper exploration of ancient Chinese mythology, with certain research value.

When origin, reproduction ability and diet define the role of birds in invasions.

The ecological impacts of invasive alien species (IAS) are increasingly documented; however, they are usually studied through the lens of either the IAS or the affected species (IAS-threatened species). A clear understanding of how both protagonists of biological invasions are characterized is still lacking. We investigated the morphology, life history and ecology of birds involved in biological invasions. Evaluating the distribution of 450 IAS-threatened birds and 400 alien birds in a functional space, we found that both groups retained various strategies. Aliens had larger clutches and were more likely to be herbivores than IAS-threatened and worldwide birds, while IAS-threatened birds were more insular endemic from the Australia region than alien and worldwide birds. IAS-threatened species showed opposite strategies to aliens regarding traits related to diet, origin and reproduction. Further comparing traits associated with impact magnitude, we found that even if aliens were mostly herbivorous, those with high impact had more a generalist behaviour and an animal-based diet compared to aliens with low impact. By emphasizing differences relating to the distribution of bird groups in a functional space, we opened new opportunities to identify the role of birds in biological invasions.

Abiotic and Biotic Factors from the Past as Predictors of Alien Bird Richness and Temporal Beta-Diversity

The challenge of predicting the distribution of alien species has long been a focus of invasion ecology. Herein, we assessed biotic and abiotic factors from the 1980s as potential predictors of alien bird species patterns 20 years later in the state of New York. To assess the ability of each factor to predict future alien species patterns, we analysed the influence of biotic (native taxonomic, functional and phylogenetic diversity, and human population density) and abiotic (climate and land use) factors from the 1980s on the observed alien species richness patterns in the 2000s and the temporal change in the composition of the alien communities between the 1980s and the 2000s using both single-predictor and multivariate models. Alien species richness from the 1980s was a reliable predictor of the alien species richness and temporal beta-diversity patterns in the 2000s. Among abiotic factors, maximum temperature and agricultural land-uses constituted sufficient predictors of future alien species richness and better predictors than the native biotic factors. The performance of single-predictor models was generally weaker in predicting temporal alien beta-diversity; however, past alien species richness and maximum temperature again outperformed the other factors. Predictions and management decisions should focus on warm and agricultural areas, as well as areas with an already high number of established alien species.

Breeding success of an endangered island endemic kestrel increases with extent of invasion by an alien plant species

The Mauritius Kestrel Falco punctatus, once the rarest kestrel worldwide, became an icon of bird conservation after it recovered from four to six individuals in 1974 to some 800 by 2005 following intense conservation management. Its population however then halved within about a decade prompting a re-evaluation of the IUCN status and up listing of the species in 2014 and an increased conservation attention. Drivers of this new decline are unclear and the influence of habitat structure and diet on breeding success may be important contributors but have received relatively little attention, particularly in the way they may interact to influence production of new fledglings. We address this knowledge gap by studying whether breeding success is influenced by habitat structure (in terms of cover of the invasive Ravenala in native habitats, an alien plant causing strong structural shift in the forests that it invades, and extent of cleared area), diet composition and food pass frequency (as a proxy for food intake) and food quality at 28 nests of a re-introduced kestrel population in south east Mauritius during the 2015–2016 breeding season. The kestrel’s diet comprised native and alien birds, reptiles, insects, and small alien mammals, with a disproportionately high proportion of Phelsuma gecko. A higher frequency of food provisioning and percentage cover of Ravenala both contributed to higher breeding success. Ravenala may increase gecko density or increase gecko detectability and predation by the kestrel, or both, while changed land use (pasture and sugar cane fields) may increase prey diversity in the form of non-forest prey known to be eaten by Kestrels (e.g. alien agamids, small mammals and birds). These prey related influences on breeding suggest that the Bambou mountain range provides a human-generated novel ecosystem altering food availability and increasing the kestrel’s breeding success. However, Ravenala is an invasive alien species harmful to the wider forest biodiversity. Progressive weeding of Ravenala and concurrent re-introduction and augmentation of native palms and Pandanus species which geckos can use at comparable densities to Ravenala, is recommended. This would likely improve the kestrel’s hunting habitat quality and maintain high gecko density or detectability and the vegetation structure required for hunting manoeuvrability and prey availability without the negative consequences of invasive Ravenala.

Du chaos à la métaphore. Le régime des vents dans Néferti VIe–VIg

“From chaos to metaphor. The wind regime in Neferti VIe–VIg” This paper re-examines Neferti VIe–VIg, principally known from pPetersburg 1116B, verso 28–30 and oUC 39637, 2–3. First, the transcription of Neferti VIe in pPetersburg, 28 is discussed, concluding that the restoration of the preposition m after xsf is to be discarded. Secondly, the differences between this version of Neferti VIe and the version in oUC 39637, 2 are reviewed, deducing that they cannot be regarded as “errors”, the London version being in fact a rewriting of the section. Although both versions seem to be incompatible, the Lower Egypt wind regime, where the south wind and the north wind alternate, allows us to understand that they both actually tell the same story: Lower Egypt is dominated by the north wind. In the light of this reinterpretation of Neferti VIe, Neferti VIe–VIg can be read as a metaphor instead of a description of chaos: The north wind blowing continuously, and thereby enabling the “alien bird” (#pd DrDr) to nest and reproduce, is a metaphor for the lack of royal authority extending up to the Delta, so that the Asiatics (o#m.w) can invade it and settle there. As such, Neferti VIe–VIg is in perfect accordance with the outcome of the Prophecy of Neferti, which predicts that the saviour king will come from the South, restore royal power and sovereignty in Lower Egypt and repel the Asiatics.

Seed dispersal phenology of encroaching woody species in the Free State National Botanical Garden, South Africa

AbstractWe investigated seed dispersal phenology of bird‐dispersed and encroaching woody species in the Free State National Botanical Garden (FSNBG), South Africa, over a 12‐month period. Results from defecated seeds' collection in 17 roosting sites show that a total of 22,161 seeds belonging to 14 woody species under 11 families were eaten and dispersed by foraging birds with seeds of six species being frequently dispersed. The native species had a larger number of dispersed bird‐ingested seeds than the alien and invasive species. Seeds' collection suggested that out of five fruiting species, birds mostly preferred the red (Ziziphus mucronata, Ehretia rigida and Viscum rotundifolium) and black fruits (Olea europaea subsp. africana and Diospyros lyciodes). Ziziphus mucronata and O. subsp. africana seeds were dispersed in significantly higher numbers between March and July (mean ± SE: 47.1 ± 11.6; 51.4 ± 9.0), while Searsia lancea and E. rigida were mostly dispersed between August and December (221.6 ± 74.1; 373.6 ± 91.5)—a dichotomy that could minimise competition for dispersal agents while sustaining the resident bird species. Over 480 h of camera trapping, 22 bird species were captured, of which seven displayed high foraging frequency, and were resident in behaviour, while six species were migratory and colonial avian frugivores, including two alien bird species. We conclude that the reported bush encroachment is a likely result of high propagule pressure by resident frugivorous birds and colonial wintering birds in FSNBG, together with low fruit diversity in the grassland habitat.

Rescue data as an alternative for assessing trends and phenological changes in two invasive parakeet species

Monitoring population trends of alien species is pivotal to design effective management plans to preserve native biodiversity, particularly urban areas, where most populations of alien birds are established. Urban wildlife rescue centers, with personnel trained to record species, age and sex of each individual brought by the public, may represent a reliable citizen-science based method to estimate both local changes in alien species phenology and population trends. In this work, we analysed records of monk and ring-necked parakeets by comparing rescue records in the urban area of Rome from the last 15 years. We also tested whether breeding phenology of alien parakeets showed any changes since the start of the invasion processes.We recorded a strong correlation between the number of rescued parakeets and their population trends, thus confirming the importance of wildlife rescue centers in monitoring populations of alien species in urban areas. We also observed a shift in the breeding phenology of these parakeet species. The hatching peak for ring-necked parakeet occurred in early spring, in line with previous studies on the reproduction of this species, but with a slight increase in the number of months with evidence of breeding in the last years. As to the monk parakeet, our findings support the expansion of its reproductive season between 2006 and 2020 in Rome, with chicks currently being observed for seven months a year. Therefore, data collected through wildlife rescue centers may help improving models of population growth of alien species established in urban areas.

Drivers of alien species composition in bird markets across the world.

The global pet trade is a major pathway for the introduction of invasive alien species. The composition of species selected for transport is driven by market demands, which may be influenced by a combination of both historical and cultural factors. We compared Eastern (Taiwan) and Western (Australia and the Iberian Peninsula) bird markets to explore factors associated with the species composition and geographic origin of the birds for sale. We used a bespoke randomization test to compare species composition, geographic origins, and species overlap at different taxonomic levels among bird markets across countries. Alien species identified in the study accounted for more than 10% of the world's bird species. Parrots and songbirds were the most common alien bird taxa traded across all markets. In both Iberian and Australian markets, there was a strong bias toward parrots, waxbills, gamebirds, and finches. In Taiwan, species traded more than expected were parrots, waxbills, starlings, and leafbirds. Neotropical species were the most traded group in the three markets. Afrotropical species were also traded more than expected in Iberian and Australian markets, while the Taiwanese traded more alien species from neighboring Asian regions. The bird trade focuses on the same few bird groups worldwide. The composition and origin of species preferred in the Western markets may be influenced by colonial histories, cultural similarity, and strict regulations on wildlife importation, while species preferences in Eastern markets are strongly influenced by regional culture and proximity. Propagule pressure is a dominant factor influencing the success of biological invasions; it is important to recognize differences in the composition of bird markets among regions because they can translate into different invasion risks, among other factors.

American fall webworm in China: A new case of global biological invasions

American fall webworm in China: A new case of global biological invasions

Incorporating phylogeographic information in alien bird distribution models increases geographic extent but not accuracy of predictions

Species distribution models (SDM) have been proposed as valuable first screening tools for predicting species responses to new environmental conditions. SDMs are usually conducted at the species level, assuming that species-environment relationships are a species-specific feature that do not evolve and show no variability across a species’ range. However, broad environmental tolerances at the species level can encompass narrower and different environmental tolerances for specific lineages or populations. In this study, we evaluate whether SDMs that account for within-taxon niche variation in climate and human-habitat associations provide better fits between projected distributions and real occurrence data for alien bird species than species-level SDMs. Our study focuses on eight alien bird species with established alien populations for which detailed phylogeographic information was available. Similarity in climates and human disturbance conditions occupied by different phylogenetic groups within species was low and not greater than random expectations. Accounting for intraspecific niche variation in SDMs modified the distribution and extent of suitable habitat predicted as susceptible to invasion, but did not result in more accurate model predictions in alien ranges. Until more accurate information on intraspecific variability is available, species-level models can be reasonable candidates. When phylogeographic information is available, the use of the most conservative criterion (i.e. to model both species and lineages on the basis of the actual range) is recommended.

Trait‐habitat associations explain novel bird assemblages mixing native and alien species across New Zealand landscapes

AbstractAimSpecies introductions have reshaped island faunas for the last 200 years, often threatening native biodiversity. Approximately equal numbers of native and alien species currently co‐occur in the New Zealand avifauna, but they show distinct habitat use. Antagonistic interactions, habitat affinities and legacies of introduction history may concur to explain their segregation along habitat gradients. To investigate these processes, we explored how habitat, ecological traits and introduction history relate with the current composition of bird assemblages.LocationNew ZealandTaxonBirdsMethodsWe analysed 917 bird point counts spread along habitat and elevation gradients in the Canterbury region, South Island and related 10 ecological traits to landscape composition using a three‐table ordination method known as “RLQ analysis”, accounting for spatial autocorrelation and phylogeny. We tested whether alien species’ positions in the RLQ were related to proxies of introduction history.ResultsEighteen endemic, 11 native and 19 alien species were distributed along a gradient from forest to open‐habitat assemblages, in relation to foraging mode, nesting site and body size. A second gradient segregated species between native and exotic forests according to territoriality, sedentarity and diet. Traits accounted for the separation of native and alien bird species in forests, but not in open habitats. Phylogenetic signals emerged from the separation of native and alien species by forest type, and spatial structures suggested a landscape‐level, rather than regional or local determinism. These correlations were independent of introduction history, although open‐habitat assemblages tended to host alien species introduced later in time.Main conclusionsHabitat type and resource availability explain the spatial partitioning of New Zealand bird assemblages between native and alien species more consistently than competitive exclusion. We conclude that trait‐mediated ecological differences among species have likely played a predominant role in species’ segregation among landscapes, while maintaining endemic bird assemblages in native forests.