Patterns of extinction risk can vary across taxa, with species of some groups being particularly vulnerable to extinction. Rails (Aves: Rallidae) represent one of the most extreme yet well-documented cases of mass extinction within a modern vertebrate group. Between 54 and 92% of rail species became extinct following waves of human contact during both the Holocene and the Anthropocene eras, and a third of the extant species are currently threatened or near-threatened. Here, we (1) examine extinction filters through consecutive human contacts with rails, investigating the role of intrinsic life-history traits and (2) investigate the drivers of contemporary vulnerability. During the most recent wave of extinction, we found that body size was an important correlate of rail extinctions, with both smaller and larger bodied species more likely to become extinct. Island endemism and small clutch size were the strongest predictors of contemporary vulnerability. Overall, island endemic rails tend to follow the same trajectory as extinct species, suffering mostly from invasive predators and overhunting, but with different traits targeted contemporarily compared to past extinctions. Moreover, modern anthropogenic threats have created the potential for new intricate pathways – or a contemporary ‘field of bullets’ – making future vulnerability potentially less predictable.

For centuries, fossils from the Maastrichtian type locality and adjacent quarries have provided key evidence of vertebrate diversity during the latest Cretaceous, yet until recently the Maastrichtian type area had revealed no important insights into the evolutionary history of birds, one of the world’s most conspicuous groups of extant tetrapods. With the benefit of high-resolution micro-CT scanning, two important avian fossils from the Maastrichtian type area have now been examined in detail, offering profound, complementary insights into the evolutionary history of birds. The holotype specimens of these new taxa, Janavis finalidens Benito, Kuo, Widrig, Jagt and Field, 2022, and Asteriornis maastrichtensis Field, Benito, Chen, Jagt and Ksepka, 2020, were originally collected in the late 1990s, but were only investigated in detail more than twenty years later. Collectively, Janavis and Asteriornis provide some of the best evidence worldwide regarding the factors that influenced stem bird extinction and crown bird survivorship through the Cretaceous-Palaeogene transition, as well as insights into the origins of key anatomical features of birds such as an extensively pneumatised postcranial skeleton, a kinetic palate, and a toothless beak. Asteriornis also provides scarce evidence of a Cretaceous-aged divergence time calibration within the avian crown group, while together, Janavis and Asteriornis constitute the only documented co-occurrence of crown birds and non-neornithine avialans. Here, we review key insights into avian evolutionary history provided by these discoveries from the Maastrichtian stratotype, document undescribed and newly discovered Maastrichtian fossils potentially attributable to Avialae and provide the first histological data for the holotype of Asteriornis, illustrating its skeletal maturity at the time of its death.

Biodiversity systematic monitoring programmes have been expanding across the globe, especially in protected areas (PAs). Amongst sustainable-use PAs, medium- to large-sized mammals and birds comprise crucial groups to monitor, given their importance to forest functionality and subsistence for local residents. Here, we used 6 years of community-based monitoring data from a sustainable-use PA in the Brazilian Amazonia (Tapajós–Arapiuns Extractive Reserve) to examine the influence of anthropogenic stressors and time on the density and biomass of forest mammal and bird game species. We further assessed trends in population density of target groups over the period. A total of 1915 km of line-transect surveys were completed by trained local monitors along eight established transects, providing data from 12 medium-sized and five large-sized game genera. Generalized linear mixed models of all medium-sized species, all large species and four individual taxa (Tinamidae, Dasyproctidae, primates and Cervidae) showed that some species (e.g., Dasyprocta croconota) exhibited great density, whereas others (e.g., Tapirus terrestris and Tayassu pecari) were rarely detected. Anthropogenic variables did not affect the density and biomass of the overall medium-sized and large vertebrates. Dasyproctidae, Tinamidae and primates were the only taxa influenced by anthropogenic stressors, with negative influence occurring only for Tinamidae. Moreover, density of groups and taxa remained stable throughout the period in the Reserve, although the frequency of some species may indicate past population losses. Continuation of this monitoring programme is required to improve understanding of population fluctuations, but over the 6 years studied, game population density and biomass were not linked to anthropogenic stressors.

Antioquia Brushfinch Atlapetes blancae is a recently rediscovered Colombian microendemic species with a restricted distribution. Although the species might use a variety of habitats, current information suggests that it is a shrubland specialist. It is categorised as “Critically Endangered” because due to habitat loss its population has been estimated to be smaller than 50 individuals. Such estimates are based on indirect measurements of its population and assumptions regarding its restricted range/habitat. We provide the first direct population estimates and adult sex ratio for seven localities, using mark-resighting techniques. Individuals were captured using mist-nets, bled, and colour banded. Subsequently, we performed censuses along transects to record banded and non-banded individuals. Population estimates were obtained using the classic closed population mark-resighting model. In addition, we used the abundance–area relationship to estimate population size at other sites where the species has been previously recorded. Finally, individuals were sexed by amplifying the Z and W-linked Chromo-Helicase DNA-binding gene (CHD) genes. In total, we banded 55 individuals at four locations. Summarising across the seven sampled localities, we found that the population is most likely composed of 109 individuals in the 122 ha sampled. Based on the abundance–area relationship, we estimated that the population of Antioquia Brushfinch could be as large as 405 individuals in 322 ha of suitable habitat. We found that male/female sex ratio was 0.45 (95% confidence interval [CI] 0.32–0.6) and that it was not significantly biased. Our results suggest that the population of Antioquia Brushfinch is at least eight times larger than suggested by secondary information. We found that populations are properly structured at least regarding sex ratio, although we caution for further research on sex biases of immature and juvenile individuals. We recommend that future studies should focus on population trends and the impact of habitat transformation on the demography of this iconic species.

Avian malaria parasites or haemosporidia are found in bird species worldwide. This special issue focuses on 3 most commonly studied genera: Haemoproteus, Plasmodium and Leucocytozoon. Seven research articles and reviews are provided to illustrate the breadth of knowledge of the diversity of avian malaria parasites in different regional habitats and across bird species, and the use of avian haemosporidian systems to examine host–parasite eco-evolutionary questions.

Understanding how selective logging affects biodiversity is crucial to planning cost-effective conservation strategies in tropical forests, yet there is limited understanding of its impacts on fauna functional diversity in the tropical Americas. We assessed how selective logging intensification and time since logging influence multiple metrics of fauna functional integrity in the Brazilian Amazon by collecting bird and dung beetle data within 48 logging management units that had experienced varying exploitation intensities between 1.5–2.0 and 5.0–6.0 years before the faunal surveys. We investigated assemblage responses and used functional attributes to assess changes in functional diversity, specialization, originality and species rarity. Using point counts and pitfall traps, we collected 5081 records of 182 bird species and 7892 dung beetles from 45 species. Logging intensification led to significant declines in most dung beetle responses and bird body mass, whereas time since logging was a key driver of dung beetle and bird functional and taxonomic diversity. Our study presents novel empirical evidence of how logging intensification effects vary across taxa, ecological metrics and time since logging, which is key to informing forest conservation and further investigating environmental degradation impacts on tropical biodiversity.

Investigations of the parasites associated with extinct avian species provide unique insights into the ecology and evolution of both hosts and their parasitic counterparts. In the present paper, a new quill mite species, Peristerophila conuropsis sp. n., belonging to the family Syringophilidae (Prostigmata: Cheyletoidea) is described from the Carolina parakeet Conuropsis carolinensis Linnaeus (Psittaciformes: Psittacidae). This new species was collected from museum dry skin of the Carolina parakeet, the only native representative of the Psittacidae in the United States, which was an abundant resident of the southeastern and midwestern states and has been extinct in the beginning of the 20th century. Comment on the current taxonomic state and host associations of the genus Peristerophila are provided. Based on the host associations and habitats occupied by Peristerophila and related genera on parrots, it is hypothesized with the high probability that P. conuropsis has been extinct along with its host.

Population size is one component of several criteria in the International Union for Conservation of Nature (IUCN) Red List of Threatened Species (Red List). For these criteria, the quality of the population estimation can therefore have significant impact on the assessed status. To evaluate population estimate quality, we selected 473 species of land birds from the Americas considered by the Red List to be “Critically Endangered”, “Endangered”, or “Vulnerable” at the end of 2021, of which 414 (88%) had a population size estimate. For these species, we determined the age of the estimate and how the population estimate was derived, grouped into eight categories. For 87 species (18%) the population estimate was derived by sampling a small area and extrapolating to the entire range of the species; for these, the population size estimate depends on the estimate of range size. For the subset of 22 of these with complete data, we compared range size estimates obtained from maps published by IUCN with maps produced using the methods of Huang et al. (2021) to see how range map differences could affect population size estimates and therefore Red List status. Potentially half of these species (11 of 22) could change status using the new maps. More than one-third of the population size estimates (38%, 161 species with a date of population estimate) were made in 2000 or earlier. A majority of the species, 63% (300 of 473 species), do not have population size estimates made using a scientific sampling method, although the majority since 2010 have been made using a sampling method, reflecting an effort by Red List assessors to include more scientific information. We encourage the ornithological community to work to obtain current, high quality population size and range estimates to improve the quality of Red List status assessments.

India has an extensive bird trade that provides income and livelihoods for many people but involves considerable unregulated and illegal activity, threatening both native and exotic species and posing potential health risks to people and wildlife. Action to curb illegal trade is vital, but there is currently a lack of information on trade routes and the species involved to inform the development of strategies to address such trade. We therefore examined media reports of bird trade seizures published during 2010–2020 as a cost-effective approach to gaining insights into the composition and structure of the bird trade in India. We collected 182 media reports referring to 109 seizure events by searching for keywords on popular search engines and Indian newspaper websites. We found that 25,850 birds were seized, most frequently members of the family Psittacidae. Of the 58 species identified, 18 were native and 40 non-native to India. The greatest numbers of birds were seized in Uttar Pradesh. Analyses of trade networks indicate that Uttar Pradesh is an important trade hotspot particularly for native species and has strong transnational connections with neighbouring Nepal. We identified West Bengal as an important trade hotspot, particularly for non-native species, probably because of its extensive land borders with neighbouring countries, including Bangladesh. Our study highlights priority areas for interventions as well as key knowledge gaps that need to be addressed to facilitate the development of strategies to manage illegal, unsustainable and otherwise harmful trading of birds.

Coconut farming contributes to the livelihoods of millions of people in tropical countries but is less frequently considered as a threat to biodiversity compared to other palm commodities such as oil palm. The expansion of coconut farming alongside other smallholder agriculture in Sulawesi, Indonesia, is of potential concern as the region is a centre of species endemism. We studied bird diversity and community structure in forests, coconut palm plantations and mixed farmland in Gorontalo Province, northern Sulawesi. Forest and non-forest sites supported similar numbers of species overall, but compared to agricultural areas, forest sites had communities that were more diverse and more even (i.e. different species were present at similar abundances). We found far fewer endemic species in agricultural areas compared to forests, and the communities in palm plantations and mixed farmland sites were dominated by generalist birds, with few indicator taxa. Nevertheless, there was a higher number of endemic species in coconut palm plantations than in mixed farmland sites. These findings mirror patterns of biotic homogenization documented elsewhere in the Wallacea centre of endemism, and imply that coconut palm plantations have comparable biodiversity value to other farmland systems. Increased protection of lowland forests and improved management of coconut farms could be important for supporting the conservation of the endemic birds of Sulawesi in the long term, but this warrants further study.

Although the impacts of intensive agriculture on biodiversity and strategies for mitigating these effects have been widely described, small-scale, diversified farms and the opportunities they present for bird conservation have been less thoroughly examined. This omission is potentially significant, because this form of agriculture represents a growing sector of the industry in the populous northeastern USA, and the diverse habitats on these farms contrast with larger, structurally homogeneous intensive agriculture. To evaluate bird-habitat associations and conservation opportunities for supporting species of conservation concern on these small, diversified farms, we conducted avian point count and vegetation surveys across 23 farms in western Massachusetts during the summers of 2017 and 2018. We used Poisson-binomial mixture models and canonical correspondence analysis to assess the effects of a suite of microhabitat-, field- and landscape-scale (1 km buffer around the field) variables on the abundance of bird species. Our results confirmed that shrubland birds, a group of species of elevated conservation concern, accounted for 52% of the total observations, including song sparrow (Melospiza melodia), gray catbird (Dumatella carolinensis), common yellowthroat (Geothlypis trichas) and American goldfinch (Spinus tristis). Species–habitat relationships were diverse; however, smaller field sizes, and increased cover of tall, dense, woody or non-productive vegetation types were associated with higher abundance of shrubland species as well as lower abundance of crop pests such as European starling (Sturnus vulgaris) and house sparrow (Passer domesticus). These findings support the hypothesis that small, diversified farms are supporting birds of high conservation concern, and we provide species-specific guidelines for farmers interested in conserving birds on their land.

Growing urban expansion can alter ecological processes within trophic networks. Predation on herbivores is known to vary with the size of the area covered by vegetation, successional stage, altitude and predator community structure; however there are gaps in understanding how this occurs in urban and suburban environments. The purpose of this study was to determine whether predation pressure on artificial models of caterpillars varied with the degree of urbanisation and type of substrate. Artificial caterpillars were placed on two types of substrates (leaf vs. stem) in two areas of the city (urban vs. suburban). Total predation was measured as the number of models with evidence of attack by predators, with the predation rate estimated on a weekly basis. Predation was affected by the degree of urbanisation, being higher in urban (x̄ = 9.88%; SD = 4.09%, n = 8) than suburban areas (x̄ = 5.75%, SD = 4.21%, n = 8). Attack marks were observed in 23.8% (n = 125) of artificial caterpillars. The weekly predation rate on leaves (x̄ = 9.63%, SD = 5.95%, n = 8) was higher than that on stems (x̄ = 6%, SD = 4.2%, n = 8). These results suggest that the incidence of predation might vary with the degree of urbanisation and by the type of substrate on which prey organisms are found.