Donald (2007) showed that the adult sex ratios of wild bird populations tended to be male-biased, and that this bias was stronger in threatened species than in those of least concern. Here we show that, in 2004, the world population of the Critically Endangered Raso Lark was 65 individuals, 70% of which were male (adult sex ratio 0.70). In 2008, the population numbered approximately 175 (including juveniles) and the adult sex ratio was 0.58. Both ratios were significantly different from parity. All adult females were observed to be both paired and holding a territory. The observations therefore support Donald’s (2007) suggestion that a shortage of females can be an important constraint on the growth of threatened bird populations, a constraint that needs attention in conservation planning.

The White-breasted Parakeet Pyrrhura albipectus, a threatened parrot known from three general areas of south-east Ecuador, was investigated in the only one of these areas to receive any protection, Podocarpus National Park, in 1990 and 1992. Its habitat there is upper tropical and subtropical forest, with some evidence that it can tolerate disturbed areas; six food-plants were added to the one (liana) already known, two euphorbs, another liana, a Miconia, a Ficus and Mollia gracilis (on which feeding was regular in August and September). Food-passing to one possible and another evident juvenile at this time suggested local breeding. Three adult and one juvenile call were distinguished. The species was found at nine sites in or immediately adjacent to the park, but mining concessions, currently suspended, may soon be granted and the park thereby seriously affected.

Pyrrhura albipectus es un psitácido amenazado conocido exclusivamente en tres zonas del sudeste de Ecuador; en 1990 y 1992 se estudió en el Parque Nacional Podocarpus (única zona donde recibe algun tipo de protectión). El hábitat en el área está constituido por bosque tropical y subtropical de las cotas mas elevadas, con cierta evidencia de que la especie puede tolerar hábitats alterados; seis tipos de plantas se añaden a la dieta hasta ahora conocida para la especie (una liana), éstas incluyen: dos euforbias, otra liana, una Miconia, un Ficus y Mollia gracilis (de la que se alimentaba de forma regular en agosto y septiembre). Se detectó transferencia de alimentos de un adulto a un juvenil y a un segundo posible juvenil, lo que sugiere reproductión local. Se identificó el reclamo de tres adultos y un juvenil. La especie fue localizada en nueve zonas del parque o en su inmediata proximidad, pero concesiones mineras, detenidas en la actualidad, pueden ser subvencionadas con el consiguiente impacto a la integridad del parque.

Habitat loss, the primary driver for loss of biodiversity worldwide, is of special concern for species that have a small area of occurrence, such as those restricted to islands. The Forest Thrush Turdus lherminieri is a ‘Vulnerable’ (VU) species endemic to four islands in the Caribbean, and its population has declined dramatically over the past 15 years. Because this decline is poorly understood, we studied its habitat associations on Montserrat. We conducted three repeat point count surveys and measured forest structure and habitat at each of 88 randomly placed locations in the largest forest area remaining on the island. We related Forest Thrush abundance to habitat using binomial mixture models that account for imperfect detection. Detection probability was a function of survey time, survey date, location of the survey point, and wind. Local habitat structure had the greatest influence on Forest Thrush abundance, with birds being more abundant at mid-elevations under closed canopies. We conclude that the Forest Thrush prefers mature mesic and wet forests on Montserrat. Assuming similar habitat selection in the rest of its range, the species’s long-term future depends on good protection of these natural forests on all four islands where it occurs.

Bustards comprise a highly threatened family of birds and, being relatively fast, heavy fliers with very limited frontal visual fields, are particularly susceptible to mortality at powerlines. These infrastructures can also displace them from immediately adjacent habitat and act as barriers, fragmenting their ranges. With geographically ever wider energy transmission and distribution grids, the powerline threat to bustards is constantly growing. Reviewing the published and unpublished literature up to January 2021, we found 2,774 records of bustard collision with powerlines, involving 14 species. Some studies associate powerline collisions with population declines. To avoid mortalities, the most effective solution is to bury the lines; otherwise they should be either routed away from bustard-frequented areas, or made redundant by local energy generation. When possible, new lines should run parallel to existing structures and wires should preferably be as low and thick as possible, with minimal conductor obstruction of vertical airspace, although it should be noted that these measures require additional testing. A review of studies finds limited evidence that ‘bird flight diverters’ (BFDs; devices fitted to wires to induce evasive action) achieve significant reductions in mortality for some bustard species. Nevertheless, dynamic BFDs are preferable to static ones as they are thought to perform more effectively. Rigorous evaluation of powerline mortalities, and effectiveness of mitigation measures, need systematic carcass surveys and bias corrections. Whenever feasible, assessments of displacement and barrier effects should be undertaken. Following best practice guidelines proposed with this review paper to monitor impacts and mitigation could help build a reliable body of evidence on best ways to prevent bustard mortality at powerlines. Research should focus on validating mitigation measures and quantifying, particularly for threatened bustards, the population effects of powerline grids at the national scale, to account for cumulative impacts on bustards and establish an equitable basis for compensation measures.

The White-bellied Heron Ardea insignis is currently known to be restricted to Bhutan, Myanmar, and north-east India. This ‘Critically Endangered’ species is under threat from the ever-changing river systems, primarily due to anthropogenic pressures including the large number of proposed hydropower projects. We report results of the first systematic, large-scale river survey for this species in the states of Arunachal Pradesh and Assam in north-east India with the aim of establishing its evidence-based distribution and assessing the severity of threats on the river systems in the region. We conducted river surveys along all seven major river basins in Arunachal Pradesh (October 2017–March 2018) and one in Assam (January 2019) along with 200 key informant surveys from 23 localities across the region. We encountered the White-bellied Heron six times in only three of 81 sites surveyed. Three interviewees reported observing the herons in three new localities, but we did not have a direct observation of the birds in any new sites. From field observations during the river surveys as well as the interview results, we found that certain fishing methods, garbage, and sand/gravel mining could be potential reasons for restricted occurrence of the White-bellied Heron in the region. Hunting is also a threat that prevails across the region. Our study calls for governmental commitment for the protection of the species and its vulnerable ecosystem and focussed research on understanding the anthropogenic impacts on the heron.

The Ibadan Malimbe Malimbus ibadanensis is a globally Endangered but poorly known forest species endemic to a small region of south-western Nigeria, where almost all forest has been severely fragmented. We carried out the first comprehensive survey of Ibadan Malimbe, and tested whether forest fragmentation is important in determining the distribution of this and related species in south-west Nigerian forest patches. Ibadan Malimbes were found at 19 of 52 sites surveyed but these were all clustered in a relatively small part of what appears to have been the former range. Unlike other malimbes, Ibadan Malimbes were less abundant in, or absent from, relatively isolated forest patches. Red-headed Malimbe M. rubricollis, Red-vented Malimbe M. scutatus and Crested Malimbe M. malimbicus were significantly more abundant in forest patches that retained vegetation characteristic of primary forest (i.e. tall trees and high tree densities). The average density of Ibadan Malimbes was 0.22 birds/ha (95% confidence limits (CL): 0.14–0.34) across all sites, but varied with degree of isolation, with densities of 0.06 birds/ha (0.03–0.14) in the 50% of fragments that were most isolated, compared with 0.33 (0.19–0.56) in the 50% of fragments that were least isolated. This gives a population estimate of 2,469 individuals (1,401–4,365) for the remaining potentially occupied forest area of 112 km2. Given that our survey covered most forest patches within the majority of the historical range of Ibadan Malimbe this can probably be considered a reasonable maximum world population estimate. Ibadan Malimbes appear to be restricted to a small number of relatively small forest patches most of which are highly vulnerable to further destruction, degradation and fragmentation. Conservation effort should urgently focus on the protection of currently occupied sites and increasing the number and extent of forest patches within and around the existing range.

Understanding habitat selection and assessing habitat quality have an important role in habitat management and prioritisation of areas for protection. However, interpretations of habitat selection and habitat quality can be confounded by social effects such as conspecific attraction. Using 7 years’ data from a well monitored Great Bustard Otis tarda population in Central Europe, we investigated the roles of human disturbance and social cues in display site selection of male Great Bustards Otis tarda. The spatial distribution of displaying males was best predicted by human disturbance. In addition, the number of males attending display sites was strongly correlated to the number of females present and not with disturbance. This suggests that abundance could be a misleading metric for habitat quality in social species. Our results highlight the roles of disturbance and social cues in male habitat choice, and suggest that social factors need to be taken into consideration for management of endangered populations.

We used artificial social stimulation (decoys, vocalization playbacks, and artificial nests) to initiate group displays in six (two females, four males) Caribbean Flamingos Phoenicopterus ruber ruber that had not successfully bred since their introduction to Guana Island, British Virgin Islands, in 1992. During a control period prior to the introduction of stimuli, flamingos exhibited no social displays or nest building activities. All flamingos were observed approaching the decoy area as a flock within four hrs of the decoys being introduced, and Head-Flagging displays were exhibited by two birds within the first 24 hrs. In a 12-hr watch conducted two-weeks post decoy introduction, there were significantly more group display behaviours, as well as nest-building, as compared with the control period and immediately after the introduction (3.6% as compared with 0% and 0.35%). Two individuals performed the majority of group displays (although at least one social display posture was observed for each bird) and three birds exhibited nest-building behaviour. Overall, individuals spent most of their time feeding and resting/sleeping (> 95%) during all observation periods. We show for the first time that decoys and vocalization playbacks could have a positive impact on breeding success in the wild by inducing group displays and nesting behaviours in this group of introduced flamingos. We suggest that social attraction techniques may be a useful tool to stimulate breeding in small captive and wild small populations of flamingos.

Pink-headed Duck Rhodonessa caryophyllacea is a Critically Endangered species that has not been confirmed in the wild since 1948–1949. Historical records of the species are concentrated in India, although there are also a few from Myanmar. Between 2003 and 2005, BirdLife International and the Biodiversity and Nature Conservation Association (BANCA) conducted a series of field surveys of wetland habitats in the lowlands of Kachin state, an area with a cluster of historical records of the species. These were the first targeted efforts to assess the status of the species in Myanmar. These surveys were complemented by reviews of museum specimens and literature relating to the species in Myanmar. Two specimen records represent very strong evidence that the species occurred in Myanmar historically, although they shed little light on its seasonal status in the country. The surveys conducted by BirdLife International and BANCA were unable to confirm the continued occurrence of Pink-headed Duck in Myanmar. However, they did generate a limited amount of equivocal direct evidence, most notably two possible but unconfirmed sightings. There are several reasons for believing that the species may still persist in the lowlands of Kachin state and, perhaps, elsewhere in Myanmar. Shyness, combined with rarity, possible nocturnal habits and the impenetrability of its habitats, means that the species tended to be under-recorded historically, and may continue to be so currently. Further surveys are required to confirm this.

Swamp Francolin Francolinus gularis is endemic to the Indian sub-continent, being found in India, Nepal and Bangladesh. It is threatened with extinction and is listed as ‘Vulnerable’, mainly as a result of habitat degradation and loss. This study investigated the distribution, habitat use, threats and most appropriate method for surveying the species at Koshi Tappu Wildlife Reserve in southeastern Nepal from February to July 2004. The most appropriate method, which recorded the highest number of birds (without double-counting), was identified as point counts undertaken early in the morning during the breeding season. The abundance estimate for the species was 15.5 ± 2.50 birds km−2. Habitat use, as compared with availability, differed significantly between seasons, with Woodland-Grassland and Wet Grassland preferred in the breeding season and summer. Dry Grassland and Woodland were preferred during the monsoon months. On average, 40.4 (± 15.6) people were recorded in the study area each day and there was a general trend for the number of birds to decrease with increasing numbers of people. Each day an average of 31.6 (± 16.7) livestock was recorded in the study area and more than 120 were regularly present throughout the eastern section, although there was no significant relationship between number of cattle and Swamp Francolin. We conclude that as long as the degree and distribution of anthropogenic pressures does not increase, the Swamp Francolin should survive at Koshi Tappu Wildlife Reserve. However, as the species is reliant on different habitats in different seasons, deterioration in the quality or extent of either of these could have a serious impact on the species.

Hill Mynah Gracula religiosa is one of the most popular bird pets worldwide due to its ability to mimic diverse sounds, especially human speech. However, Mynahs have rarely been bred in captivity, so nestlings from natural populations are in large demand, resulting in many populations being threatened with extinction. Both subspecies in Thailand, intermedia and religiosa, are costly and desired in the pet market. Captive breeding is one of the most practical strategies to solve a conservation problem of this nature and this report describes a success in breeding Hill Mynahs in captivity. Mated pairs were given free access to food, nest-cavities and nest materials. Reproductive behaviour in captivity was not different from that in the wild, with the exception that breeding occurred throughout the year, even during the non-breeding season for wild populations. Although there are doubts concerning the reintroduction of captive-bred birds and whether successful Hill Mynah breeding in captivity is an economically competitive alternative to poaching, it ensures species survival in captivity as the risk of extinction increases.

The average population size of Capricorn Yellow Chat Epthianura crocea macgregori was estimated at 251 +/-31 (SE) by repeated surveys over seven years (2004–2010) using consistent search effort at known occupied sites. Because the survey period coincided with a mixture of dry and wet years (drought from 2004 to 2007 followed by flood rainfall in early 2008 and 2010), it is particularly valuable as a preliminary benchmark upon which to base management decisions. Most of the population (74.5%) was in the Broad Sound area in the north, with lower numbers in the Fitzroy River delta area in the south (22%) and at Curtis Island (3.5%). Sites on Torilla Plain in Broad Sound accounted for two-thirds of the estimated population, making it a priority for conservation efforts. Depending on habitat configuration, some Capricorn Yellow Chats showed a seasonal pattern of habitat use, moving from flooded breeding habitats as they dried to refuge sites such as salt fields or upper marine plains in the dry season; distances moved being < 10 km. Standard surveys from Torilla Plain showed that the chat count during a sequence of above-average rainfall years was almost double that of the average for drought years: 162 +/-28 (2008–2015) compared with 85 +/-15 (2004–2007) respectively. Low population size, large annual fluctuations in population with prior rainfall, rapid declines in low rainfall years, a fragmented distribution and almost half the population concentrated at one site point to a subspecies vulnerable to chance events. Increased climatic extremes predicted by climate change such as higher temperatures, evaporation rates, extended droughts and more intense rainfall events add to its vulnerability.

The critically endangered Mariana Crow now exists in a single population on the island of Rota, Northern Mariana Islands. Targeted management requires an accurate measure of the population status of this species. In Mariana Crows the breeding population is both the easiest cohort to accurately survey and the most important segment of the population in terms of population recovery. The total number of Mariana Crow territorial pairs was estimated on the island of Rota using a direct count method, and total population size was calculated using a Chapman estimate. From September 2013 to April 2014, 46 crow pairs were found and up to an additional eight pairs were estimated in unsearched areas. The total population was estimated to be 178 individuals. This represents a 10–23% decline in pairs in the six years since 2007 and a 46–53% decline since 1998. This number is also considerably lower than the minimum 75 pairs recommended to maintain a viable population on Rota.

During 1998–2011, in an area of western Cyprus spanning about one-quarter of the global breeding range of the endemic Cyprus Warbler Sylvia melanothorax, the species declined at a rate of c.59% decade-1, suggesting that there is an urgent need to review its global conservation status. This decline has coincided with the recent, rapid colonisation of western Cyprus by the Sardinian Warbler S. melanocephala, whose numbers have increased substantially within the study area, as might be expected of a newly colonising breeding species. To identify possible causes of the Cyprus Warbler’s decline we compared its rate of change with measures of land-cover, vegetation density, altitude, rainfall and the presence of Sardinian Warblers at survey sites. The rate of decline in the Cyprus Warbler’s abundance was strongly correlated with land-cover and with the duration of site occupancy by Sardinian Warbler; Cyprus Warbler abundance had declined more steeply on sites colonised by Sardinian Warblers early in the survey period than on sites colonised later. Furthermore, on sites surveyed by BirdLife Cyprus in 2006–2014, Cyprus Warbler abundance had continued to decline significantly (also by c.59% decade-1) in western Cyprus, while Sardinian Warbler abundance had continued to increase. In contrast, Cyprus Warbler abundance showed no significant change in central and eastern Cyprus, where Sardinian Warblers were sparse or absent during the breeding season. These findings are consistent with at least two contrasting scenarios: that changes have occurred in land-cover or climatic conditions in Cyprus, to the detriment of Cyprus Warbler and to the benefit of Sardinian Warbler; or that in western Cyprus at least, the two species may compete for similar resources, despite a lack of evidence of this in an earlier, more detailed study. In either case, we suggest the need for a thorough, nationwide breeding survey of the two species.

Knowledge of a species’ ecological requirements is a prerequisite for effective conservation, particularly if the species is assumed to be declining due to modification of its primary habitats. Information about habitat suitability allows both the inference of specific habitat management measures as well as population size estimates which can facilitate the setting up of conservation priorities. As one of the least known Palaearctic breeding birds, the current knowledge of Baillon’s Crake Zapornia pusilla comprises only very general information about the species’ ecological requirements, habitat selection, extent and dynamics of home ranges or population densities within its Palaearctic-Afrotropical range. We used a multi-scale approach to assess the species’ habitat requirements in the Senegal River Delta, north-west Senegal. At the individual level, we calculated Manly selection indices for 17 radio-tracked Baillon’s Crakes, allowing for different levels of resource availability. Considering the entire Djoudj area including the Parc National des Oiseaux du Djoudj (PNOD), we modelled presence probability as well as population density of Baillon’s Crakes based on high-resolution satellite images and capture data from field surveys in 2009–2013. Using 95% kernels, home range size was on average 1.77 ± 0.86 ha with significant differences between habitats. Both at the individual as well as population level, Baillon’s Crakes preferred edge structures, selecting for trampling paths and edges along open water bodies as well as boundaries of specific vegetation stands while species composition was of less importance. Based on the regression models, we identified 9,516 ha of suitable habitat within the Djoudj area and a potential population size of 10,714 individuals (range 3,146–17,408). Although global population estimates are highly tentative, we assume the Senegal River Delta and the PNOD of outstanding significance for African and possibly also European populations of Baillon’s Crake.

The Spoon-billed Sandpiper Calidris pygmaea is a ‘Critically Endangered’ migratory shorebird. The species faces an array of threats in its non-breeding range, making conservation intervention essential. However, conservation efforts are reliant on identifying the species’ key stopover and wintering sites. Using Maximum Entropy models, we predicted Spoon-billed Sandpiper distribution across the non-breeding range, using data from recent field surveys and satellite tracking. Model outputs suggest only a limited number of stopover sites are suitable for migrating birds, with sites in the Yellow Sea and on the Jiangsu coast in China highlighted as particularly important. All the previously known core wintering sites were identified by the model including the Ganges-Brahmaputra Delta, Nan Thar Island and the Gulf of Mottama. In addition, the model highlighted sites subsequently found to be occupied, and pinpointed potential new sites meriting investigation, notably on Borneo and Sulawesi, and in parts of India and the Philippines. A comparison between the areas identified as most likely to be occupied and protected areas showed that very few locations are covered by conservation designations. Known sites must be managed for conservation as a priority, and potential new sites should be surveyed as soon as is feasible to assess occupancy status. Site protection should take place in concert with conservation interventions including habitat management, discouraging hunting, and fostering alternative livelihoods.

The Black-capped Petrel or Diablotin Pterodroma hasitata has a fragmented and declining population estimated at c.1,000 breeding pairs. On land, the species nests underground in steep ravines with dense understorey vegetation. The only confirmed breeding sites are located in the mountain ranges of Hispaniola in the Caribbean, where habitat loss and degradation are continuing threats. Other nesting populations may still remain undiscovered but, to locate them, laborious in situ nest searches must be conducted over expansive geographical areas. To focus nest-search efforts more efficiently, we analysed the environmental characteristics of Black-capped Petrel nesting habitat and modeled suitable habitat on Hispaniola using openly available environmental datasets. We used a univariate generalized linear model to compare the habitat characteristics of active Black-capped Petrel nests sites with those of potentially available sites (i.e. random pseudo-absences). Elevation, distance to coast, and the influence of tree cover and density emerged as important environmental variables. We then applied multivariate generalized linear models to these environmental variables that showed a significant relationship with petrel nesting activity. We used the top performing model of habitat suitability model to create maps of predicted suitability for Hispaniola. In addition to areas of known petrel activity, the model identified possible nesting areas for Black-capped Petrels in habitats not previously considered suitable. Based on model results, we estimated the total area of predicted suitable nesting habitat for Black-capped Petrels on Hispaniola and found that forest loss due to hurricanes, forest fires, and encroachment from agriculture had severely decreased availability of predicted suitable habitat between 2000 and 2018.

The frequency and intensity of extreme weather events represent a threat for biological diversity and are expected to increase in many regions over the following decades due to climate change. Our current knowledge about the impact of extreme weather events on the population dynamics of bird species is very limited. Here, we evaluated the impact of an extreme winter snowstorm on the abundance of 14 populations of the threatened Dupont’s Lark Chersophilus duponti, a resident bird whose European population is restricted to Spain. We found a drastic and significant population decline in the next reproductive season following the extreme weather event. During the control period (2017–2020) the species suffered an overall annual decline of 19.4% (±5.0, SE). However, the overall annual decline after the storm was 67.6% (±9.4, period 2019–2021), with a mean decline of 66.5% (±15.9) for seven populations monitored both the year before and the year after the snowstorm (period 2020–2021). The snow covered the ground for over 10 days in central and eastern Spain, which together with a subsequent extreme cold wave could have reduced the species ability to find food resources and properly thermoregulate, forcing the species to move to unknown areas. Indeed a few days after the storm, several individuals were reported in areas typically avoided. Such displacements may increase the mortality risk for dispersing individuals, besides the direct effects of the extreme cold event, such as thermal challenges to energy balance or a reduced immune function. We discuss the potential role that extreme weather events may have on the population dynamics and conservation of the species.

The Dusky-legged Guan Penelope obscura is the southernmost species of the family Cracidae, reaching its southern distributional limit in the delta of the Paraná River. Habitat loss, together with uncontrolled harvest, has led to local-scale decreases or extirpation of the species, but no quantitative evaluation of habitat preferences has been made. We surveyed Dusky-legged Guans in the Delta del Paraná Biosphere Reserve, Argentina, by motorboat along 543.9 km of nine waterways during both January and July 2009 and used occupancy modelling to estimate habitat and seasonal effects on occupancy. Detectability was 21–22% on average and occupancy estimates were highly variable within habitats, but highest in secondary forest, followed by mature plantation, and lowest in occupied residences. There were no significant differences in occupancy or detectability among habitats or seasonally. There was a strong positive effect of length of riparian habitat segments on occupancy and detectability. Habitat management efforts should address increasing the suitability of mature plantation forest for guans by increasing their similarity to native forest in structure and composition. Furthermore, we illustrate that surveys by boat can be logistically effective for surveying cracids associated with riverine habitats and that it is important to account for incomplete detectability since in our case failing to do so would have underestimated occupancy by 78–79% on average. Given this, the use of commonly accepted methodologies for surveying cracids that do not account for incomplete detectability should be reconsidered and methodologies that can produce robust, reliable estimates applied.

The world population of Red-legged Cormorant Phalacrocorax gaimardi is reasonably small and has showed rapid declines. In Argentina, this species breeds in 13 localities and is considered as ‘Endangered’ by the national government. In this study, we provide information about population trends of the Red-legged Cormorant on the Argentine coast, between 1990 and 2009. We also discuss whether these trends could be related to sea surface temperature and marine primary productivity, both of which are considered oceanographic factors that can affect breeding seabirds. The long-term trend in the breeding population showed a slight decrease of 1.2% per year. Seven colonies showed an average population change < 1. Periods of stability and increase were identified over the study period, but they were insufficient to compensate for the decreases. The largest colony of Red-legged Cormorants (La Mina, with more than 55% of the entire breeding population) seems to determine the overall population trend. We did not find a direct relationship between the overall number of Red-legged Cormorants and the two oceanographic factors analysed. However, our analysis detected a positive effect of ocean productivity close to the coast on the largest colony at the beginning of the breeding season, suggesting that coastal ocean productivity could be an important factor affecting temporal variations in the Argentinian population.