Assessing the conservation status of a species is important for designing effective conservation measures. Consequently, it is often vital to review it to update biodiversity management initiatives. The Parana Antwren Formicivora acutirostris is a bird found in pioneering formations (coastal marshes) of Brazil’s southern flood plains. It is considered threatened in Brazil but near threatened globally. In 2007, its distribution, habitat, and population size were estimated based on aerial photographs from 1978 and 1980. Since the species is threatened and occupies a small area across a region under pressure, we aimed to reassess its conservation status and assess its Green Status. We compiled new records, conducted new density estimates, and compared them with the previous mapping with satellite imagery to estimate the current distribution in terms of extent of occurrence (EOO), area of occupancy (AOO), area of habitat (AOH), habitat loss, and population size, and review its conservation status. The species is distributed across 10 populations, including two new populations further south. We estimated the EOO at 26,655 km², AOO at 320 km², AOH at 41 km², and the population as 6,285 mature territorial individuals. The previously mapped AOH decreased by 15.35 km² due to ecological succession. The loss of habitat due to invasion by exotic grasses is the main anthropogenic impact. We recommend that the species be considered “Vulnerable”. The Green Status indicates that the Conservation Legacy of actions taken thus far and the Conservation Dependence of ongoing actions are inefficient due to their small scales, but it highlights the importance of future actions for species conservation. We propose the establishment of exotic-free zones as small areas with a significant amount of minimally invaded environments, which we suggest as priority areas for the conservation of the species due to their cost-effective management potential. We also propose assisted colonisation to enhance its long-term conservation.

Collision with powerlines is a major cause of mortality for many bird species, including bustards and sandgrouse. In this work, we used GPS tracking data to identify the hour of collision of three threatened steppe birds, i.e. Little Bustard Tetrax tetrax, Black-bellied Sandgrouse Pterocles orientalis, and Pin-tailed Sandgrouse Pterocles alchata. Out of a data set of 160 GPS-tracked individuals collected over a 13-year period, we detected eight collision events with powerlines or fences. Of these, we were able to determine the timing of 87.5% of the collision events with a resolution accurate to within two hours. Our results reveal that collisions occurred throughout the year and at different hours of the day, presenting a challenge for implementing effective mitigation strategies. The use of dynamic and reflective or luminescent devices may therefore be appropriate to prevent collision of steppe birds with powerlines during the day and night. Overall, this study adds evidence to the utility of using tracking data to better understand anthropogenic mortality in birds.

The Secretarybird Sagittarius serpentarius is a charismatic raptor of the grasslands and open savannas of Africa. Evidence of widespread declines across the continent has led to the assessment that the species is at risk of becoming extinct. Southern Africa was identified as a remaining stronghold for the species, but the status of this population requires reassessment. To determine the status of the species in South Africa, Lesotho, and Eswatini, we analysed data from a citizen science project, the Southern African Bird Atlas Project (SABAP). We implemented novel time-to-detection modelling, as well as summarisation of changes in reporting rates, using standard metrics, to determine the trajectory of the population. To cross-validate our findings, we used data from another citizen science project, the Coordinated Avifaunal Roadcounts (CAR) project. While our results were in agreement with previous studies that have reported significant declines when comparing SABAP1 (1987–1992) and SABAP2 (2007 and onwards), all analysis pathways that examined data within the SABAP2 period only, as well as CAR data from this period, failed to show an alarming declining trend over this more recent time period. We did, however, find some evidence for decreases in Secretarybird abundance in urban grid cells. We used random forest models to predict probability of occurrence, as well as probability of abundance (reporting rates) for the assessed region and provided population estimates based on these analysis pathways. Continued monitoring and conservation efforts are required to guard this population stronghold.

Spix’s Macaw Cyanopsitta spixii, extinct in the wild since 2000, was successfully reintroduced in Brazil in 2022, leading to significant progress, including the hatching of wild chicks. However, recent restrictions on further releases by the Brazilian government have put the reintroduction programme into jeopardy. This study updates our 2023 population viability analysis (PVA) to assess the impact of these delayed releases on the wild population. Using six modelled scenarios, we confirm that without annual supplementation of captive-bred birds, the probability of extinction in the wild remains at 100%. Even a one-time release is insufficient to secure population stability. Our results highlight that those annual releases of at least 20 individuals are necessary to ensure long-term viability, with reduced but still essential growth achievable with 10 birds per year. Supplementation of the wild population does not compromise the long-term viability of the well-established captive population. We urge immediate action to resume the release programme in 2024 to prevent the species from once again facing extinction in the wild.

Collisions with powerlines affect birds worldwide, including countries such as Belgium where a nationwide model indicated high avian collision risk in the IJzerbroeken region (seasonally flooded riverside wetlands). Large numbers of waterbirds winter in this area, which is crossed by a 70-kV transmission line. To manage avian collision risk, the transmission system operator, Elia, installed AB Hammarprodukter’s FireFly™ FF line markers incorporating reflective, glow-in-the-dark, high contrast, and moving elements intended to increase the visibility of the transmission line to flying birds. We evaluated the effectiveness of FireFly line markers by comparing the numbers of avian carcasses found during 11 surveys annually in 2001 and 2018 (22 total surveys) before line markers were installed compared with 11 surveys conducted in 2021 after line marking. Before line marking, we found 30 avian carcasses attributable to collision in 2001 and 113 in 2018. After, we found six carcasses attributable to collision in 2021. In 2021, FireFly line markers correlated with a reduction in collision rate, depending on the pre-treatment year and species group, of at least 85% and up to 100%. The line was composed of two configurations, with half of the spans (two-thirds of the monitored line length) supported by tall pylons with shield wires, and half of the spans supported by shorter pylons without shield wires. After line marking, six collisions (100% in 2021) occurred on spans supported by tall pylons, and none (0%) occurred on spans supported by short pylons. Thus, in 2021, FireFly line markers correlated with an observed mortality reduction of at least 73% and up to 100%, depending on the configuration being considered. These findings suggest FireFly line markers substantially reduced wintering bird collisions in our study area.

The hoary-throated spinetail and Rio Branco antbird are two bird species endemic to the Rio Branco drainage of Brazil and Guyana, currently listed as Critically Endangered on the IUCN Red List. Previous assessments of both species’ global populations focused on the Brazilian state of Roraima but did not include most of its border with Guyana, where significant areas of suitable habitat remain along the Ireng (Maú) and Takutu (Tacutu) Rivers. In July and August 2021, we conducted a survey to determine the extent of each species’ geographic range along the two rivers, and to estimate population sizes. We used playback surveys along 219 km of river to ascertain each species’ distribution and intensively sampled three forest blocks to determine densities. Both species were locally abundant on both sides of the international border. Rio Branco antbird occurred over a greater geographic range than hoary-throated spinetail, particularly along the Takutu River, but was confined to a narrower zone along the river edges. Both species appear to have retreated from habitat along the Ireng River that was occupied in the past, possibly due to habitat degradation from increasingly frequent fires. Nevertheless, our minimum estimates of 1147 antbirds and 851 spinetails in the study area represent, respectively, 7.5% and 17.8 % increases over current estimates of global population sizes, and indicate that the Guyana-Brazil border region may become a critical stronghold for both species if effective conservation measures are implemented. We propose establishment of a Key Biodiversity Area encompassing the core of both species’ distributions along the border; extensive follow-up work including stakeholder engagement to explore possibilities for habitat management and protection; and further field study to increase general ecological knowledge of these two bird species.

The Black-cheeked Lovebird Agapornis nigrigenis has a highly restricted range in dry south-western Zambia, where its distribution is clumped and localised in association with mopane Colophospermum mopane woodland and permanent water pools. Fieldwork and monitoring over 30 months between December 2018 and October 2021 established that the lovebirds’ usage of pools for drinking was higher towards the centre of the bird’s distribution and influenced by the pools’ proximity to mopane woodlands, surrounding tree cover, and level of human activity. Of the four pool types available for use by lovebirds (i.e. mopane, grassland, river, and artificial), mopane and grassland pools were disproportionally susceptible to drying out in the dry season, hence showed greater variation in numbers of visiting birds compared with the other two types. Lovebirds showed a preference for pools with a perimeter of <50 m and tended to avoid those with a perimeter >100 m, consistent with a positive association between pool size and human activity. Convergence between humans and lovebirds in dependence on water resources and mopane woodland points to the need to find ways to overcome potential conflicts. Such ways include creating small, shallow-sided, undisturbed pools in or near mopane woodland, extending water retention in existing mopane pools, and enhancing the capacity of artificial pools to meet the needs of the lovebirds.

Newly elevated to species rank, the Bahama Nuthatch Sitta insularis is or was a bark- and twig-gleaning insectivore only known in life from the pine forests of Grand Bahama in the Bahamas archipelago. It became increasingly difficult to find in the past 50 years, seemingly in part in response to multiple hurricanes in this century. In spring (June–April) 2018, when it was still known to be extant, we divided the island into seven sections and carried out point count transects with playback and measured habitat variables at 464 locations in pine forest across Grand Bahama. We made only six observations at six locations, all in the region of Lucayan North and each involving a single nuthatch (possibly all the same individual). Fourteen count points were within 500 m of the six locations, and tree size at these sites was greater in height and girth than at sites with no observations and indeed than at other sites within Lucayan North. Count points within 500 m of nuthatch records in 2004–2018 had larger trees and more snags than survey points over 500 m away from previous detections, while count points within 500 m of our 2018 nuthatch records tallied more snags than did those within 500 m of the 2004–2007 records. Declines in habitat quality, habitat extent, nesting substrate, and food availability (driven by logging, attritional island development, and the direct and indirect effects of hurricanes), plus speculated increases in populations of invasive predators/competitors and in major mortality events (hurricanes, increasing in force and frequency with climate change), are suspected to be the ultimate causes of the decline of the nuthatch, with Hurricanes Matthew and Dorian the proximate causes of its evident extinction in 2019.

Heat stress from high temperatures has been recognised as a threat to several bird species and one that is likely to increase in severity and frequency as a result of global environmental change. Many seabirds are particularly vulnerable as their adaptations to forage in cold water can make it hard for them to resist heat gain while on land. The African Penguin Spheniscus demersus forages in cool water (10–20°C) but breeds and moults on land where temperatures can exceed 30°C. Little is known about its thermal physiology and when heat stress will occur. Here, we provide the first account of changes in body temperature and behaviour in African Penguins in response to an experimental increase in ambient temperature from 20°C to 35°C. Surprisingly, the highest body temperature observed (39.2°C) was recorded at the start of the study. Presumably, this response in body temperature was due to the stress of transport and handling. Penguins returned to normal body temperature (37.3°C) after 3.5 hours and maintained normothermia for roughly an hour. We then observed the onset of heat storage at an ambient temperature of 29°C, whereafter body temperature increased steadily at a rate of ca.0.2°C per 1°C increase in ambient temperature. Panting commenced at an ambient temperature of 31.4°C, when body temperature was 37.8°C. In addition to panting, penguins changed their posture to facilitate heat dissipation by standing, raising their heads, and extending their flippers. Our results corroborate field observations and support the argument that African Penguins are highly vulnerable to heat stress in the near future as extreme heat events become more severe and frequent due to climate change. Our results also confirm that penguins are sensitive to handling, which elicits a hyperthermic response. Given the general sensitivity of penguins to disturbance, from a conservation perspective, we advise that cautionary measures be implemented at colonies during critical life-history stages.

Reintroduction includes the captive propagation and movement of extirpated animals or plants into areas of historical and native distribution. Many biotic or abiotic factors can affect a founder population when small numbers are released into unfamiliar novel environments, particularly at the early stage of reintroduction. The inclusion of behavioural and ecological components plays a crucial role in the decision-making process of endangered species conservation efforts such as reintroduction. Since the resident population of Oriental Storks Ciconia boyciana was locally extirpated in South Korea in 1971, its founders have been established through reintroduction since 2015. The aim of this study was to investigate the demography, habitat use, and movement patterns of stork founders using the first two-year demographic and tracking data. Stork founders maintained their population size, which slightly increased in the long term. The patterns of habitat use and movement depended on rice paddy fields for foraging and breeding along with mixed effects of breeding status and season. Considering ecological and life history-related perspectives, we also discuss the potential adaptiveness of founder Oriental Storks as a resident population in a novel environment in South Korea.

Forests of urban/suburban areas are being increasingly restored, but before/after-control/impact studies addressing effects on biodiversity in peri-urban forest restorations are virtually lacking. Using a before/after-control/impact (BACI) design, we explored the effects on birds (commonly used as indicators for restoration impacts) of small-scale restoration interventions in 2019 targeting residual forests north of Milan, in the largest Italian conurbation, with trees and shrub planting around existing patches or in formerly cultivated areas. Birds were surveyed in 2018, 2019, and 2021, at 20 intervention and 20 control sites. We evaluated the short-term effects of restoration by analysing changes in avian communities (i.e. richness, richness and abundance of forest specialists, single species’ abundance), considering the effect of year and intervention (i.e. before/during/after intervention). Species richness of breeding birds was largely unaffected by on-going interventions, while it was positively related to concluded restoration. The abundance of five individual species varied according to restoration: on-going interventions had positive effects on two species, Common Blackbird Turdus merula and Hooded Crow Corvus corone cornix, and negative effects on Barn Swallow Hirundo rustica, while concluded restoration positively affected two species, Common Blackbird Turdus merula again, and the forest specialist Marsh Tit Poecile palustris. Even small-scale interventions in peri-urban areas may provide tangible benefits to breeding birds in the short term: peri-urban forest restoration could contribute to biodiversity conservation.

As a result of increasingly intensified agricultural practices in Europe over the last century, agroecosystems have experienced severe biodiversity declines. Among the species experiencing negative population trajectories in agricultural habitats are meadow and farmland birds, which have suffered a loss in both habitat and food availability in cultivated fields. In Denmark, biotope plans (a requirement to establish small agro-environmental habitats on properties with stocking of game birds) have been implemented as a measure to mitigate biodiversity declines in the agricultural landscape and, in this paper, we investigate to what extent these initiatives fulfil the intended purpose with respect to birds in the breeding season. We demonstrate that some initiatives like hedgerows, areas of open vegetation, scrub, and lakes seemed to increase avian diversity locally, but also that other measures such as vegetation strips, grass strips, and bare soil strips had little effect given the current implementation of these initiatives. Benefitting species were mostly scrub- and woodland species that now inhabited previously open landscapes after the establishment of suitable habitats, and the initiatives failed to show clear positive effects on meadow birds and farmland birds for which they were originally intended. The most commonly registered species in our data set was (released) Pheasant Phasianus colchicus, which emphasised that the stocking of game birds can have a clear effect on avian species composition in areas where this practice is exercised. Future studies are needed to clarify how this stocking may affect local biodiversity of different taxonomic groups.

Species’ declines are caused by a combination of factors that affect survival and/or breeding success. We studied the effects of a set of environmental and anthropogenic variables on the disappearance of Canarian Houbara Bustards Chlamydotis undulata fuertaventurae on Fuerteventura (Canary Islands), once the main stronghold of this endangered bird. Of 83 male display sites detected in 1997–1998, only 29 remained occupied in 2020–2021 (a 65% decrease in only 23 years). We compared habitat quality, density of conspecifics, other steppe birds and crows, presence of human infrastructure, and degree of environmental protection between these 29 extant sites and the 54 extinct sites using univariate analyses and generalised linear models (GLMs). The most influential variable in the abandonment of display sites was the Normalised Difference Vegetation Index (NDVI), an indicator of green vegetation productivity, which suggests a strong effect of habitat aridification due to climate change on the population’s extinction process. Powerline density was the second most important factor. This suggests that houbaras have survived where a greater abundance of food resources has enabled a higher breeding success, and where powerline fatalities have caused lower mortality over the years. Higher densities of houbaras, and other steppe birds and crows at extant display sites confirmed the better habitat quality in these areas. Extant display sites, located generally in protected areas, also had lower densities of human infrastructure (e.g. buildings, roads). We discuss the conservation implications of these results and provide management recommendations for this endangered subspecies.

We report the non-breeding range of an adult Rapa Shearwater Puffinus myrtae, as estimated from data collected by one light logger deployed from 31 August 2019 to 22 July 2020. The Rapa Shearwater is classified as “Critically Endangered”, with a strong decline in breeding numbers reported recently. As the species is threatened by various introduced mammals on the breeding colonies, the main objective of this tracking essay was to identify the oceanic regions where the birds forage during the non-breeding season. The non-breeding range of this bird was located south-east of Rapa Island, where fishery activities are limited. The conservation efforts for the Critically Endangered Rapa Shearwater should first focus on securing mammal-free sites for breeding colonies.

In the Anthropocene, recognising nature’s role in human well-being is pivotal for biodiversity conservation. Despite their significance, knowledge gaps persist regarding ecosystem services, even for well-studied species like vultures. Our study focuses on the Griffon Vulture Gyps fulvus in Sardinia, Italy, exploring their cultural and regulating services, including carcass disposal and resulting greenhouse gas (GHG) mitigation. Through surveys of natural reserve visitors and data on carcass provision and GHG emissions, we assess public perception, economic value, and environmental impacts associated with vultures. The public perception of Griffon Vultures is predominantly positive, with a strong acknowledgment of their role in disease prevention and carcass disposal, highlighting their contribution to regulation services. Furthermore, vultures are widely recognised as a key element characterising the agropastoral landscapes of Sardinia, underscoring their cultural importance. The economic evaluation, through willingness to pay for vulture-watching and photography opportunities, indicates a significant appreciation of these birds, with almost three-quarters of respondents willing to pay an entrance fee at vulture observation sites. We also show that supplanting the disposal role of vultures at studied feeding sites (during 2017–2022) would result in the emission of 96 tons of CO2 equivalent, which highlights the critical role of vultures in climate mitigation. This study not only sheds light on the ecological and cultural significance of Griffon Vultures in Sardinia but also underscores the economic and environmental benefits of their conservation. It emphasises the need for continued efforts in vulture conservation, integrating ecological, cultural, and economic perspectives to foster a sustainable coexistence between humans and wildlife.

Resource partitioning is a critical mechanism underlying the coexistence of close relative species that feed on similar resources. Based on foraging data, we built a plant–seedeater interaction network for three sympatric species of Neotropical seedeaters – namely Tropeiro Seedeater Sporophila beltoni, Black-bellied Seedeater Sporophila melanogaster, and Tawny-bellied Seedeater Sporophila hypoxantha, and tested to what extent the three species shared resources. The interaction network was non-nested and modular, forming three modules, each one comprising one seedeater species and their most consumed plants, indicating the existence of resource partitioning. Modules may result from multiple non-exclusive factors, including differences among seedeater species in habitat use, bill sizes, feeding habits, structure of vegetation for nesting, and abiotic factors that influence plant composition. Our results indicate that the effective conservation of these species requires the protection of areas that include the three distinct subsets of plants used by these birds during the breeding season and also indicates which plants may be used for the restoration of grasslands in the region.

Wilkins’s Finch Nesospiza wilkinsi is endemic to Nightingale Island (2.5 km2), Tristan da Cunha. It feeds on the woody fruits of the Island Tree Phylica arborea and in 2017 had a population of 120 breeding pairs. In 2021 it was uplisted from “Endangered” to “Critically Endangered” following damage to P. arborea woodland during severe storms in 2019. During a brief visit to Nightingale in February 2024, we confirmed that the finch population in the area of storm-damaged woodland has decreased by up to 75%, but the density in other areas was similar to that prior to 2019. Extrapolating from the 2017 survey, we estimated the current population to be 60–90 breeding pairs. Surveys of P. arborea structure in the storm-affected area indicated that some large trees had survived, despite being flattened, that recruitment of new trees is occurring, and that fruit loads on surviving trees are similar to those in 2017. Satellite imagery from 2005 showed similar woodland loss during another severe storm in 2001 to that experienced in 2019, indicating that the finch has survived similar events in the past. Coupled with the successful release of a biological control agent to limit the impact of the introduced brown soft scale Coccus hesperidum on Phylica fruit production, the future prospect for Wilkins’s Finch is less bleak than previously thought. However, the risk that global warming is increasing the frequency of severe storms remains a concern. Planting more woodland patches in sheltered areas would help to offset future storm damage.

There are six species of flamingos in the world, all under pressure from human activities in their wetland habitats. Obtaining global population estimates for flamingos is challenging because of their broad geographical range, nomadic movements, capacity for long-distance flight, and the complexity of international monitoring. Two species, the Andean Flamingo Phoenicoparrus andinus and Puna Flamingo P. jamesi, during key parts of their life cycle, use wetlands in the Andes of South America, where they coexist at various sites. We compiled historical information on population estimates and ecology for these two species and integrated data collected on regional simultaneous censuses to describe population trends, current and emerging threats, and provide recommendations for conservation action. Long-term population trends have been difficult to establish given the unreliability of population estimates prior to the late 1990s. Systematic, regional censuses carried out regularly since 1997 have produced robust population estimates for the Andean and Puna flamingos (most recently, 78,000 and 154,000, respectively) and show populations of both species to be stable and increasing. Increasingly rapid changes in wetlands caused by human activities such as industrial-scale mining in breeding and foraging sites in the high Andes wetlands, and agro-industrial activities in their lowland wintering sites, focused on areas of the highest concentrations of flamingos pose threats to their survival and ability to reproduce. In addition, climate change is projected to reduce wetland habitats and some localised effects have already been detected. Continued research on the ecological drivers of flamingo abundance, movements, and population genetics to understand population structure and dynamics are necessary, as well as the identification of response variables to changing environmental conditions. Interdisciplinary and systems-level approaches in the context of international collaboration in monitoring and conservation planning among a diversity of stakeholders will be required to safeguard flamingo populations and wetland habitats.

Poisonous birds are rare but on New Guinea, including Indonesia’s easternmost provinces, no less than nine poisonous species, eight pitohuis and one species of ifrita, are found. Pitohuis when handled can cause sneezing with numbness and burning of nasal tissue and nausea in humans. In the bird markets of western Indonesia novelty birds are traded at a premium and overexploitation of popular songbirds leads traders to find replacement species to meet demand. We conducted over 800 surveys in the bird markets of Sumatra, Java, Bali, Lombok, and Sulawesi between 1994 and 2023 and from 2015 onwards we assessed the online trade in pitohuis and Blue-capped Ifrit Ifrita kowaldi. We identified the species, recorded their prices and location, and the date when the birds were offered for sale. We analysed temporal trends, volumes, prices, and geographical origin of the sellers. Between 1994 and 2014 we did not encounter a single pitohui in the Indonesian bird markets. In the following years we recorded 113 pitohuis in 12 bird markets and we recorded 199 pitohuis for sale online; 248 were variable pitohuis and 54 were Hooded Pitohui Pitohui dichrous. No ifritas were recorded. Most pitohuis were recorded in eastern Java and Bali. Prices differed between eastern Java (mean of US$93) and western Java and Bali (US$185), possibly suggesting pitohuis arrive from West Papua in eastern Java and from there make their way to the outer markets. Pitohuis are marketed as “Papuan Straw-headed Bulbuls”; the Straw-headed Bulbul Pycnonotus zeylanicus is a very popular and expensive songbird from Southeast Asia, including western Indonesia, that has become rare both in the wild and in the markets due to overexploitation. Discussions about pitohuis on online forums rarely mention “poisonous” but when it is mentioned traders dismiss this as something not to worry about and they claim it to be dietary-dependent. Poisonous pitohuis are novelty, as well as master, birds in Indonesia, where they are marketed for their song ignoring any negative side-effects of them being poisonous. The trade in novelty species, when detected early, does allow for the authorities to intervene in a timely manner to ensure that this trade does not impede their conservation.

Owing to habitat loss, the entire breeding population of the globally threatened Aquatic Warbler Acrocephalus paludicola, a flagship bird species of fen mires, is now limited to scattered areas in east-central Europe. The breeding biology of the Aquatic Warbler was studied between 2012 and 2015 in calcareous fens dominated by the Cladietum marisci sedge community at the south-western range limit of the species, near Chełm, in south-east Poland. Two nesting peaks were observed during the breeding season, corresponding to first and second breeding attempts. Nest densities were greater during the first- rather than the second-brood period but singing male densities did not differ between the brood periods. Clutch size and post-hatching fledging success were significantly lower during the second-brood period. Total nest fledging success (whether or not a nest fledged at least one young) was 76.6% in 124 nests with known outcomes with an average of 2.7 (± SE 0.2) fledglings per nest. Mayfield probability of nest survival was 56.9% with losses mainly due to predation (55%), nest desertion or female predation (28%), and changes in water level (14%). Nest survival to fledging increased along the gradient of increasing levels of litter layer thickness, stagnating water, and vegetation height at the nest, and increasing height of the nest above the soil. Fledgling production tended to be lower than in the Biebrza Marshes (north-east Poland) habitats, assumed to be optimal for breeding. Otherwise, the reproductive success estimates did not deviate from nests found in the core breeding areas in north-east Poland or Belarus. Brood feeding frequency (15.5 ± 1.0/hour) was similar to that observed in the Biebrza Marshes. Our results suggest that the calcareous fens at the margins of the current species’ range provide a suitable breeding habitat. However, as the nesting area has contracted, management programmes tailored to the ecological requirements of the Aquatic Warbler are required.