Bait traps are a standard technique for studies of tropical butterfly community ecology and long-term assessment of population trends, with butterflies often regarded as biodiversity indicators. Fermented banana is the standard bait, but carrion baits, which may attract more individuals, species, and taxonomic groups, are also commonly used. However, the influence of carrion bait type on the butterfly sample is unknown. Here, we assessed the efficiency of three sources of carrion bait (shrimp, snapper, and tilapia), with banana as a comparison, in sampling butterflies in a west Ecuadorian premontane rainforest. Different carrion baits resulted in minor variation in sampled abundance and species diversity and minimal variation in species composition. All carrion baits recorded up to four times higher butterfly abundance than banana. Species composition was virtually identical among carrion baits, but only about half as similar to that sampled with banana. Choosing a consistent carrion bait for a monitoring scheme will facilitate temporal and spatial comparisons, but, given the minimal differences among carrion baits, practical considerations such as accessibility or cost may help determine bait choice. Finally, in agreement with other researchers, we support the simultaneous use of carrion and fruit baits to significantly increase sampled taxonomic diversity.

The heligmosomid nematodes Heligmosomum mixtum and Heligmosomoides glareoli are dominant helminths infecting bank voles (Clethrionomys glareolus) in the temperate forests of NE Poland. Both are relatively long-lived species that accumulate in hosts with increasing host age. Based on studies showing that the closely related species, Heligmosomoides bakeri is immunomodulatory in murine hosts, we hypothesized that heligmosomid-infected bank voles should show higher prevalence and abundance with other helminths. To test this hypothesis, we analysed a database containing quantitative data on helminth parasites of bank voles (n = 922), comprising worm burdens recorded during 4 surveys, conducted at 3- to 4-year intervals, in 3 forest sites, during late summer of each year. After controlling for both intrinsic and extrinsic factors, the presence of heligmosomid nematodes was significantly associated with higher species richness of other helminth species, with the greater likelihood of voles carrying other helminth species, with higher worm burdens of other helminths and with significant positive covariance of heligmosomid burdens with those of other concurrently residing helminths. These patterns might be explained by a number of biological processes, including correlated host exposure or correlated host susceptibility not driven by the parasitic infections themselves. However, we consider it most likely that these results are consistent with the idea that like H. bakeri, the heligmosomid nematodes of bank voles employ non-specific immunomodulation to facilitate their own long-term survival, with the consequence that other concurrently infecting intestinal helminths benefit.

Central African great ape populations are in serious decline as a result of poaching, habitat loss and disease. Reliable estimates of population size are urgently needed for informed management action. We estimate the abundance and distribution of central chimpanzee Pan troglodytes troglodytes and western lowland gorilla Gorilla gorilla gorilla populations in the c. 11,000 km2 Dja-Ngoyla Complex in Cameroon, a critical component of the Tri National Dja-Odzala-Minkébé (TRIDOM) transboundary landscape, which covers 178,000 km2. We compare our results with previous site estimates and with other population estimates from the region. We completed 1,096.64 km of line transects (n = 559) in 2021 using the standing-crop nest counts method. The Dja-Ngoyla Complex supported c. 11,787 great apes. Chimpanzee abundance was significantly higher in Dja, and Ngoyla-Mintom supported 71% of the gorilla population. Thirty-seven per cent of the gorilla population and 17% of the chimpanzee population occurred in logging concessions. There was no significant change in the species’ abundance in Dja Faunal Reserve compared to our 2018 estimate using the same methodology. The chimpanzee population density was much higher in Dja and Ngoyla Faunal Reserves compared to other protected areas in the region. There was large variation in great ape densities across logging concessions, and those with implemented management certification schemes supported higher densities. This study also highlights the high risk of Dja’s great ape population becoming isolated. Promoting forest management certification to strengthen wildlife and habitat protection in all logging concessions in the Complex is urgently needed and will also allow local communities to benefit from these forests.

Marbled Teal Marmaronetta angustirostris is a globally threatened species that has been undergoing population declines across much of its range in recent years. This is particularly true in the Middle East and the Caucasus, where the species once commonly bred across much of the region. However, there is a dearth of recent literature and population-level assessments of the species in the countries in this region. For example, the last update of conservation status for Marbled Teal in Armenia was undertaken in 2009 and in Türkiye in 2008. Therefore, this study addresses the urgent need for an updated evaluation of the species’ status in both Armenia and Türkiye. For Armenia, the current population estimate is 8–11 breeding pairs, with a steep decline of 87% between 2003 and 2019. In Türkiye, the species appears to be functionally extirpated from the country due to an absence of breeding in almost a decade and multiple years without any records, with only a handful of wandering individuals detected in recent years. This study highlights the threats facing the species, particularly changes to wetland habitat and quality as well as hunting pressures and illegal poaching. Based on our findings, we propose that the conservation status of Marbled Teal in both countries be updated from “Endangered” to “Critically Endangered”. Finally, we note the conservation requirements for the species in the region and provide a set of recommendations for its protection, including a species recovery plan. Without urgent conservation measures such as the creation of new protected areas and establishment of new populations from released birds, the long-term viability of Marbled Teal populations in the region is in jeopardy.

The Puerto Rico Plain Pigeon Patagioenas inornata wetmorei suffered a severe population decline after hurricanes Irma and Maria in September 2017. We used distance sampling to estimate abundance (density and population size) in April–June 1986−2024, accounting for changes in detection probability. We used the distance-sampling abundance estimates to populate a Bayesian state–space logistic model and update posterior estimates of population carrying capacity, maximum population growth rate, population recovery time, and predicted abundance in April–June 2025−2034, accounting for observation and process variances. In addition, we used predicted abundance to assess potential extinction risk (probability Pr[N2025−2034 = 0|data]), population self-sustainability above 5,000 individuals (Pr[N2025−2034 >5,000|data]), and population surpassing the 2.5th percentile of carrying capacity (Pr[N2025−2034 >30,000|data]). The population has not recovered from the hurricanes, with estimated density averaging 0.0015 individuals/ha (bootstrapped standard error [SE] = 0.0006) and population size averaging 1,097 individuals (SE = 455) at the 749,000-ha survey region in April–June 2018−2024. Posterior mean estimates were 41,580 individuals (Markov Chain Monte Carlo standard deviation [SD] = 8,052) for population carrying capacity, 0.183 (SD = 0.056) for maximum population growth rate, six years (SD = 2) for recovery time, and 7,173 individuals (SD = 12,309) for predicted abundance in April–June 2025−2034. The population may reach self-sustainability levels (range Pr[N2025−2034 >5,000|data] = 0.326−0.631) but currently is undergoing a prolonged bottleneck and may become extinct (range Pr[N2025−2034 = 0|data] = 0.199−0.332), particularly if reproduction continues to be mostly unsuccessful, anthropogenic disturbances remain unabated, and on top of that another devastating hurricane makes landfall during the next 10 years. The Puerto Rico Plain Pigeon subspecies is in urgent need of management aiming to increase and maintain abundance above 5,000 individuals but preferably surpassing the 2.5th percentile of population carrying capacity as in the late 1990s (range Pr[N2025−2034 >30,000|data] = 0.000−0.181).

Wetlands contribute to economic development through the provisioning of ecosystem services. In Rwanda, the exploitation of wetlands for agriculture is a recent phenomenon, introduced in response to food shortages in the dry season and drought periods. Few studies have documented the biodiversity of wetlands in Rwanda, such as the high altitude Rugezi marshland; a Ramsar site located in the north of Rwanda. To fill this gap, the first arthropod inventories were conducted in 2023, from June to July (dry season) and from November to December (rainy season) at Rugezi marshland. Data was collected in sites located in the northeast and northwest of the marshland using hand collection, pitfall traps, and sweep nets. Collected specimens were preserved in 75% ethanol and identified to the order and family levels using dichotomous keys. A total of 26,944 individuals of arthropods were sampled with 17,074 recorded during the dry season and 9,870 during the rainy season. High abundance was found in the northwest (N = 14,739) compared to the northeast (N = 12,151). Using this data, we found that there was a statistically significant difference in the diversity of arthropods between seasons and sites, with the dry season having higher arthropod diversity in northeast side while the rainy season had a more pronounced increase in northwest site. We recommend future studies to establish a list of arthropod bioindicators of land use change and the use of participatory governance for effective management of Rugezi marshland.

Many European farmland bird populations are rapidly declining because of agricultural intensification and land-use changes. Robust estimates of population sizes and trends, habitat use, and protected area coverage within the distribution range are crucial to inform the conservation and management of threatened species. Here we report on the results of the 2019 Black-bellied Sandgrouse Pterocles orientalis (BBS) survey promoted and coordinated by SEO/BirdLife to update its breeding distribution, population size, and trends in continental Spain. A total of 660 grid cells, 10 × 10 km, Universal Transverse Mercator (UTM), were surveyed (81% of the distribution area), with 2,257 visits to 1,750 walked transects (7,001 km in total; 10.6 km per UTM). BBS was detected in 43% of sampled UTMs. At transect level, occupancy was 11% higher inside protected areas. At UTM level, occupancy was estimated at 0.58 (Bayesian credible interval [BCI] 95%: 0.55–0.61), revealing that BBS occupied about half of its previous breeding range (2003–2005). Using hierarchical distance sampling modelling, we estimated an average density of 1.33 individuals/km2 in occupied areas, and a population of 4,025 individuals (confidence interval: 1,840–7,609) within sampled areas, with an additional 697 individuals (confidence interval 461–1,075) in areas that were not surveyed. Further, the relative abundance of BBS (Kilometric Abundance Index) declined by 63% between 2005 and 2019 (annual decline rate of 4.5%). BBS used agricultural habitats (73%) and unprotected areas (54%) despite a higher occupancy within protected areas. Given the recent decline rate and persistent threats, the BBS conservation status should be upgraded to “Endangered” in peninsular Spain. Its future depends on land-use changes and agricultural practices, in particular the maintenance of fallows, semi-natural habitats, and pastures for extensive grazing. Better protection of important areas and targeted conservation initiatives should be promoted to halt and reverse the population decline in this key western Palearctic stronghold.

Observations of radiocarbon (14C) in Earth’s atmosphere and other carbon reservoirs are important to quantify exchanges of CO2 between reservoirs. The amount of 14C is commonly reported in the so-called Delta notation, i.e., Δ14C, the decay- and fractionation-corrected departure of the ratio of 14C to total C from that ratio in an absolute international standard; this Delta notation permits direct comparison of 14C/C ratios in the several reservoirs. However, as Δ14C of atmospheric CO2, Δ14CO2 is based on the ratio of 14CO2 to total atmospheric CO2, its value can and does change not just because of change in the amount of atmospheric14CO2 but also because of change in the amount of total atmospheric CO2, complicating ascription of change in Δ14CO2 to change in one or the other quantity. Here we suggest that presentation of atmospheric 14CO2 amount as mole fraction relative to dry air (moles of 14CO2 per moles of dry air in Earth’s atmosphere), or as moles or molecules of 14CO2 in Earth’s atmosphere, all readily calculated from Δ14CO2 and the amount of atmospheric CO2 (with slight dependence on δ13CO2), complements presentation only as Δ14CO2, and can provide valuable insight into the evolving budget and distribution of atmospheric 14CO2.

Grey seals from both the Atlantic and Baltic Sea subspecies are recovering from dramatic declines and recolonising former ranges, potentially leading to overlapping distributions and an emerging subspecies transition zone in Kattegat between Denmark and Sweden. The two subspecies have asynchronous moulting and pupping seasons. We present aerial survey data from 2011 to 2023 in Danish Kattegat during the Atlantic subspecies' moulting (March–April) and pupping (December–January) seasons, as well as the Baltic subspecies' moulting season (May–June). During the Atlantic subspecies' peak moulting season, 82% of the grey seals were recorded north of the island of Læsø (N57°18′, E11°00′). In contrast, during the Baltic moulting season in those years, only 9% of the grey seals were recorded here. This indicates a predominance of Atlantic grey seals in the north and Baltic grey seals in central and southern Kattegat. In 2022 and 2023, three pups were recorded around Læsø during early January, which coincides with the pupping season of northern Wadden Sea grey seals. Previously, pups have been recorded in the same locations during the Baltic pupping season, which demonstrates overlapping breeding ranges. Grey seals are known to have plasticity in the timing of pupping indicated by a west to east cline of progressively later pupping in the eastern North Atlantic. Historical sources document that the Baltic pupping season in Kattegat was earlier than it has been in recent years. Thus, the expanding ranges may be associated with convergence of Atlantic and Baltic subspecies' pupping seasons and potential hybridisation in this emerging transition zone.

Lice were collected from 579 hummingbirds, representing 49 species, in 19 locations in Brazil, Costa Rica, Honduras, Paraguay and Peru, at elevations 0–3000 m above sea level. The following variables were included in an ecological analysis (1) host species' mean body mass, sexual size dimorphism, sexual dichromatism, migratory behaviour and dominance behaviour; (2) mean elevation, mean and predictability of temperature, mean and predictability of precipitation of the host species' geographic area; (3) prevalence and mean abundance of species of lice as measures of infestation. Ordination methods were applied to evaluate data structure. Since the traits are expressed at different scales (nominal, interval and ratio), a principal component analysis based on d-correlations for the traits and a principal coordinates analysis based on the Gower index for species were applied. Lice or louse eggs were found on 80 (13.8%) birds of 22 species. A total of 267 lice of 4 genera, Trochiloecetes, Trochiliphagus, Myrsidea and Leremenopon, were collected, with a total mean intensity of 4.6. There were positive interactions between migration behaviour and infestation indices, with elevational migrants having a higher prevalence and abundance of lice than resident birds. Further, we found weak negative correlations between host body mass and infestation indices and positive correlations between mean elevation and prevalence and abundance of Trochiliphagus. Thus, formerly unknown differences in the ecological characteristics and infestation measures of Trochiliphagus and Trochiloecetes lice were revealed, which allows a better understanding of these associations and their potential impacts on hummingbirds.