Nest Surveys Research Articles

Monitoring active osprey nests with drones is more time efficient and less disturbing than conventional methods

Drones are used to monitor bird nesting sites at less accessible locations, such as on cliffs, human infrastructure, or within the tree canopy. While there are a growing number of studies documenting avian behavioral responses to various drones, there is a continued need to monitor taxa‐specific responses to different drone models. We explored both the time efficiency and impact of different nest survey methods (drones, nest climbing, and observations from a bucket truck) and different drone model sizes (small, medium, large) on the nest defense behavior of breeding ospreys. We conducted 166 surveys (126 drone, 25 climbing, 15 bucket truck) at 85 active nests across three nesting stages. We found variation in four of six pre‐defined behavioral categories, namely for calling, flying, at nest, and perching behaviors with survey method, sex, and nest stage. Females were more responsive to all survey methods compared to males and engaged in nest‐protection behaviors most frequently during incubation. Ospreys spent greater time at their nests during drone surveys compared to other methods. Agitated calling and flying were also less frequent during drone surveys. We recorded defensive behaviors across all survey types and there were no strikes on drones or researchers. Drone size appeared to influence behavior, with female ospreys spending, on average, 18% of survey time calling when surveyed with medium‐sized drone compared to smaller (8%) or larger (6%) models. Surveys with drones took less time to complete compared to the other methods tested. Based on our findings, drones appear to be the best choice for monitoring osprey nests as they are adaptable, time efficient, and result in less apparent disturbance to nesting ospreys than other methods tested. Our research aids in setting best practices, optimizing drone size, and developing evidence‐driven approaches for monitoring avian nests across a variety of landscapes and contexts.

Conservation implications of habitat selection by nesting diamondback terrapins (Malaclemys terrapin) investigated via an automated radio telemetry system

BackgroundDespite considerable research on nest site selection of diamondback terrapins and the risks that coastal roads pose to populations of this obligate estuarine turtle, there are gaps in our understanding of movements and habitat use by female terrapins during the nesting season. In particular, movements within salt marshes, shallow water habitats, and nest site-adjacent developed habitats remain relatively understudied. To investigate habitat use and risk exposure of this semiaquatic species, we employed an automated radio telemetry system featuring 31 passive receivers. In 2021, concurrent with annual nest surveys, we tracked 60 telemetered female terrapins near a nesting area in southern New Jersey subject to impacts from road mortality. We triangulated terrapin locations based on the relationship between radio signal strength at each receiver and distance, generated utilization distributions using kernel density estimation, and classified habitat using multispectral imagery.ResultsWe detected differences in habitat use versus relative availability within general (95% KDEs) and core (50% KDEs) use areas at a population level. Core use areas suggested more frequent use of salt pools, marsh, and upland habitats and less frequent use of developed and wide tidal creek habitats than expected based on availability alone. To further characterize variability in habitat use, we compared selectivity between terrapins grouped by proximity of their capture location to a road. Terrapins nesting closer to the road showed relatively more frequent usage of developed habitats and less frequent usage of narrow creeks and regularly flooded marsh throughout the nesting season.ConclusionsPatterns of habitat selection across all terrapins underscore the importance of shallow water habitats such as salt pools near nesting areas. Individuals tended to spend more time in habitat types close to their nesting locations, such that terrapins initially captured near roads spent more time in high-risk developed areas throughout the study period. Road mortality risk may not be homogenous within this nesting population, which may be a critical consideration for demographic modeling. This study expands our understanding of terrapin movements while demonstrating the effectiveness of a novel radio telemetry approach, and contributes to conservation planning in a rapidly changing salt marsh landscape.

Great ape surveys and the implications of long-term monitoring in the Djéké Triangle, Republic of Congo.

Existing protected areas are anchors for conservation. Safeguarding flora and fauna within their peripheral areas is essential to maintaining their integrity and to potential increases to the area under effective conservation. With the decline in tropical forests, initiatives to increase the area of undisturbed forests under strict protection, particularly those neighboring protected areas, is of critical importance. Applied research has informed such land-management decisions for areas surrounding the Nouabalé-Ndoki National Park (NNNP) in Republic of Congo since the park's inception three decades ago. Here, we present results of the first systematic line transect survey of great ape nests conducted in the Djéké Triangle, a 100 km2 unlogged continuous forest in the Kabo Forestry Management Unit adjacent to the NNNP. Distance sampling methods applied along 26 line transects on two different occasions (2016 and 2018, with total effort of 69.4km) provided density estimates of 0.75 (95% confidence interval (CI) 0.52-1.09) and 0.61 (95% CI 0.40-0.92) chimpanzees/km2 and 2.15 (95% CI 1.36-3.40) and 1.19 (95% CI 0.78-1.82) gorillas/km2 for each of the two surveys, respectively. Estimated ape densities were compared to others across the landscape. The findings provide a unique baseline in an area that supports ongoing behavioral research and future gorilla tourism opportunities in the Djéké Triangle. More importantly, results provided empirical evidence of the environmental value and strategic conservation importance supporting inclusion of the Djéké Triangle into the NNNP in 2023. These long-term monitoring results inform best-practice standards and ape tourism certification.

Comparing three common nest survey methods, using double-crested cormorants as a proposed sentinel for monitoring plastic pollution in freshwater environments

Many bird species use plastic as nest-building material, and nest surveys represent a unique opportunity to monitor environmental plastic pollution. However, the current literature lacks consistent, repeatable methodologies, making comparison across studies challenging. This study evaluated three common nest survey methods to assess the use of nest debris: photographic assessment, visual assessment, and nest deconstruction. We applied these methods to double-crested cormorant nests (Nannopterum auritum) at two locations on Lake Ontario, Canada. We found that for this species, nest deconstruction yielded the greatest accuracy and detail for detecting debris abundance, type, and colour. Of the two non-invasive methods, visual surveys outperformed photographic surveys across all metrics assessed. In our mainland colony, 100% of nests contained debris based on visual assessment, while at our offshore colony only 37.4% of nests contained debris, suggesting that location influences nest debris for this species. We detected Personal Protective Equipment (PPE)-related debris in 20% of all nests across survey years at our mainland colony (2022 and 2023), representing the first time that PPE has been documented in the nests of this species and demonstrating that nest surveys can be a useful tool for capturing changes in an evolving pollution landscape. This study contributes evidence that double-crested cormorants may be a useful sentinel species for monitoring plastic pollution in understudied, freshwater environments. Our results also demonstrate that the chosen method can greatly impact the results of a nest survey, and careful consideration of methodology should be undertaken before implementing a nest survey to monitor plastic pollution.

Tree architecture model of Sumatran Orangutan Pongo abelii Lesson, 1827 (Mammalia: Primates: Hominidae) nests at Soraya Research Station, Leuser Ecosystem, Indonesia

The relationship between tree architectural models and the nesting behavior of the Sumatran Orangutan Pongo abelii Lesson, 1827 at the Soraya Research Station, Sumatra, Indonesia was determined by examining the preference for particular nest tree architectural models in relation to the frequency of nest occurrence. This investigation included the study of tree architectural models, tree types, nest profiles, vegetation, environmental factors, and geospatial data, collected within a 20 × 1,000 m (2 ha) observational area during a nest survey. A total of 59 orangutan nests were identified across 47 trees, categorized into 31 species and nine varied tree architectural models. Among these, the most prevalent models observed were Cook, Scarrone, and Attims, which exhibit features assumed to enhance orangutan nesting behaviors. Based on the Neu approach to nest qualities, the analytical test findings show a correlation between the preference ratings for nesting trees. Our results are expected to serve as a reference for selecting tree species in rehabilitation or habitat restoration programs and the development of separated forest block corridors as conservation efforts for orangutans.

Current Distribution of the Turkestan White Stork (Ciconia ciconia asiatica) in Kazakhstan

Over the last 100 years, the range of the White Stork Ciconia ciconia asiatica (Linnaeus, 1758) in Kazakhstan has greatly diminished; it has entirely disappeared in its former eastern and northern ranges, while the number of nesting sites has decreased in the remaining part of its habitat. The most recent specialized studies on the distribution of the White Stork here were conducted in the 1980s. Subsequently, ornithologists were only aware of isolated nests, and in the last 15 years, up until recently, in Kazakhstan, there was only one known active nest in the Zhambyl region. To clarify the current distribution of the White Stork in Kazakhstan, we conducted field research during the breeding season in places of its former distribution in the Zhambyl and Turkestan Regions. Nest surveys were conducted by visual observations using binoculars and a camera with a telephoto lens. During the expedition, 43 inhabited nests of the White Stork were found; information about another 4 nests was obtained from data survey and social networks. Analysis of satellite images allowed us to identify 12 nests located on power line pylons in the southern regions of the republic, specifically in the Keles, Zhetisay, and Maktaaral districts. In total, 59 White Stork nests were found in Kazakhstan. In addition, satellite images revealed more than 120 power line pylons with White Stork nests in the territory of Uzbekistan in close proximity to the Kazakhstan border. All literary and electronic sources available to the authors have been meticulously reviewed. By synthesizing these data, two maps were created: one delineating all recorded White Stork nesting sites across Kazakhstan and its neighboring territories, and the other illustrating the known contemporary and historical ranges of the White Stork in Kazakhstan. A cadastral survey accompanies new nest discoveries of the White Stork. Based on the newly acquired data, we conclude that the White Stork population in Kazakhstan is currently on the rise.

Comparison of waterbird communities in a Mediterranean salina – saltmarsh complex

Coastal wetlands provide habitat for large numbers and many species of waterbirds. Man-made salinas are a particu-lar habitat type often found in such wetlands. This study is an initiative to understand the differences in bird communities between a salina (including evaporation ponds and prebasin) and a saltmarsh. Bird counts and nest surveys took place in the wetlands of Angelochori, Thessaloniki, Greece, in 1991, when the salina was inactive, and in 1997, 2000-01 when it was active. Counts in evaporation ponds were richer in species, abundance and nests compared to the prebasin and the saltmarsh. These three wetland types supported different bird communities. Similarities among bird communities depended on the inundation of the salina with seawater. Evaporation ponds in their inactive period presented low similarity with the communities of the prebasin and the saltmarsh ; in the active period this was observed only for the saltmarsh. Species showing clear selection for the evaporation ponds were Charadrius alexandrinus, Calidris alpina, Calidris minuta, Recurvirostra avosetta, Sterna hirundo, Sternula albifrons, Sterna sandvicensis and Haematopus ostralegus; the prebasin was preferred by Phoenicopterus roseus and Anas platyrhynchos, and the saltmarsh by Anas querquedula, Anas clypeata, Plegadis falcinellus, Tringa totanus, Tringa glareola, Tringa stagnatilis and Himantopus himantopus.

A Systematic Review of Population Monitoring Studies of Sea Turtles and Its Application to Conservation

Sea turtles are keystone species in marine environments due to their essential role as seagrass grazers and population regulation of jellyfish and sponges in coral reefs. However, due to their predominant presence in coastal areas, sea turtle populations face significant threats due to the impact of human activities. In this systematic review, 655 peer-reviewed publications were analyzed to assess the extent of population monitoring for all seven sea turtle species. The analyses revealed that, although population monitoring studies have increased for sea turtles in the past four decades, these have been biased towards certain species and oceanic regions. Furthermore, sea turtle population monitoring has been undertaken primarily using field-based methods, with satellite tracking and nest surveys being the most commonly used methods; however, the implementation of genetic methods for population monitoring has increased since the 2000s. Direct conservation recommendations from this study include the urgent need to establish population monitoring studies in the Critically Endangered Kemp’s ridley and hawksbill and the Data Deficient flatback. Furthermore, population monitoring programs should be implemented in Southeast Asia and Northern and Central Africa, where knowledge on sea turtle populations is still limited. Finally, due to the long-distance movements of sea turtles, we also advocate for international cooperation and collaboration of local communities to protect these ecologically important and iconic marine species.

Green and Hawksbill Sea turtles of Eastern Atlantic: New insights into a globally important rookery in the Gulf of Guinea.

Sea turtles are critical components of marine ecosystems, and their conservation is important for Ocean Governance and Global Planet Health. However, there is limited knowledge of their ecology in the Gulf of Guinea. To fill this knowledge gap, this study presents the first integrative assessment of green and hawksbill turtles in the region, combining nesting surveys over 9 years and telemetry data, to offer insights into these population dynamics, and behaviours, including nesting preferences, morphological and reproductive parameters, diving patterns and inter-nesting core-use areas. Both green and hawksbill turtles are likely making a recovery on São Tomé, potentially driven by sustained conservation efforts. There are preliminary indications of recovery, but we interpret this cautiously. Coupled with satellite tracking, this study estimated that 482 to 736 green turtles and 135 to 217 hawksbills nest on the beaches of São Tomé. Their movements overlap significantly with a proposed Marine Protected Area (MPA), which suggests they may be well placed for conservation if managed appropriately. However, the presence of artisanal fisheries and emerging threats, such as sand mining and unregulated tourism, highlight the urgent need for robust management strategies that align global conservation objectives with local socioeconomic realities. This study significantly enhances our understanding of the ecology and conservation needs of the green and hawksbill turtles in the Gulf of Guinea. The insights gleaned here can contribute to the development of tailored conservation strategies that benefit these populations and the ecosystem services upon which they depend.

NILE CROCODILE NESTING ECOLOGY UNDER VARYING HUMAN DISTURBANCE INTENSITIES ALONG LOWER RIVER TANA, KENYA

The Nile crocodile (Crocodylus niloticus, Laurenti, 1768) supports important ecological and socio-economic functions; however, its survival in most of its ranges in Africa continues to be threatened by anthropogenic activities. Here, we compared selected attributes of Nile crocodile nests (abundance, clutch size, distance from water, and presence or absence of eggs, tending and predation) across three human disturbance regimes (low, intermediate and high), indexed by coverage of cropland and settlement, along lower River Tana, Kenya. We conducted a crocodile nest survey in January 2019 and overlaid the resultant data on the most recent land cover map of a 1-km wide strip on both sides of the river, segmented into the different disturbance regimes using remote sensing and geographical information system techniques. The low, intermediate and high disturbance regimes comprised combined cropland and settlement coverage of 2%, 9% and 15%, respectively, and covered 28%, 27% and 47% of the surveyed river segment. We counted a total of 99 nests, with 45, 34 and 20 nests located in low, intermediate and high disturbance regimes, respectively. Nests were 56% less frequent than expected under high disturbance, whereas they were 69% more frequent than expected under low disturbance and showed expected frequency under intermediate disturbance. In addition, nests were 56% and 41% less frequent under high disturbance compared to low and intermediate disturbance, respectively. However, nest abundance was statistically similar between the latter two regimes. No significant differences were observed in other assessed attributes across disturbance regimes. Our study underscores the importance of minimizing land conversion in such human-dominated landscapes for enhanced sustainable utilization and conservation of crocodiles.

Survey and distribution of native stingless bee nests (Hymenoptera: Apidae, Meliponini) in a remnant area of Cerrado, Minas Gerais, Brazil

Survey and distribution of native stingless bee nests (Hymenoptera: Apidae, Meliponini) in a remnant area of Cerrado, Minas Gerais, Brazil

Variation in reproductive success in a fragmented Meadow Pipit population: a role for vegetation succession?

Most farmland birds experience strong declines across Europe. These declines are typically associated with agricultural intensification but research on alternative local causes remains scarce. We investigated variation in reproductive success as a potential driver for the observed population declines in a fragmented population of the Meadow Pipit Anthus pratensis, a representative inhabitant of extensively managed mountain grasslands across Europe. Intense nest surveys in the entire Meadow Pipit metapopulation of the Northern Black Forest (SW Germany) between 2020 and 2022 provided information on reproductive success for 53 females distributed across nine habitat patches along an 18 km ridge of the Northern Black Forest. Hatching dates delayed by approx. 5.0 days per 100 m altitude and were almost 10 days later in a year with cold and rainy spring weather. Mean reproductive success per female and year (3.45 fledglings) was low compared to literature values (approx. 4.5) and may thus drive ongoing population declines. Mayfield nest survival estimates (approx. 51% across the nesting period) were comparably high, with most nest failures linked with predation or adverse weather. Low reproductive success further associated with comparably small clutch sizes and low fractions of second broods in habitat patches characterized by homogeneously dense swards. We suggest that restoration through extensive permanent cattle grazing coupled with succession control may be a key factor to increase population productivity.

Forest management, forest vegetation, and climate influence nesting ecology of a focal bird species in the western USA

Landscape-scale forest restoration aims to restore ecological structure and function and provide habitat for wildlife. However, forest management likely has varying impacts across wildlife life stages, with consequences for population persistence. Using 10 years of nest (n = 294) survey data for a focal bird species, white-headed woodpecker (Dryobates albolarvatus), we assessed how forest management (tree removal and prescribed burning) at two spatial scales (stand [2.25 ha] and landscape [314 ha]), forest vegetation variables at three spatial scales (nest tree, local [0.4 ha], and landscape [314 ha]), and climate influenced nest initiation date, egg production, egg survival, and nestling survival. We applied Bayesian hierarchical mixed effects models to these data to identify and compare drivers at each life stage. None of the variables we considered influenced egg production; white-headed woodpeckers laid an average of four eggs. As the extent of the landscape with tree removal increased, nests initiated later. Egg survival was higher in nests with prescribed burning at the stand scale. Nestling survival was higher in sites that had been managed with burning and tree removal at the stand scale, but the relationship with burning switched to negative at the landscape scale. Only nestling survival was shaped by attributes of the nest cavity itself. Egg survival increased with increased variation in forest patch sizes at the landscape scale. Woodpeckers initiated nests earlier under warmer conditions, with previous August and September temperatures being particularly influential. Both egg and nestling survival increased with cumulative precipitation. While increased temperatures decreased egg survival, nestling survival peaked at an optimal maximum temperature (∼32 °C). This study illustrates how forest management, forest vegetation, and climate factors affecting nesting ecology vary throughout the nesting season. Additionally, effects that switch directions (positive versus negative) across spatial scales indicate spatially dependent ecological processes (e.g., nest suitability versus adult foraging). This study provides a model for assessing the effects of forest management on bird population persistence by considering the nesting season as stages with distinct ecological limitations linked to spatially-dependent factors.

Habitat suitability mapping of white stork Ciconia ciconia in one of its key European breeding areas

Due to rapid changes of the agricultural practice, the traditionally managed farmland became currently-one of the most endangered habitats in Europe. Species related to the rural landscape have been facing a great challenge of adaptation to quickly changing conditions. Therefore, recognizing and characterizing highly suitable areas for white storks is very important to plan conservation measures in the era of changes in agriculture and land use. Here, combining nest survey data (811 occupied nest), GIS-data on habitat availability and modelling approach, we characterize the current foraging conditions of the white stork Ciconia ciconia, an indicator of the agricultural habitat biodiversity and an umbrella species for organisms associated with agriculture landscape. The studied population breeds in the Warmińska Refuge Natura 2000 site (N Poland), one of the key breeding areas of this species in Europe. Breeding pair presence was predicted by the area of pasture, meadows, field ponds, and linear water within a 1 km buffer around the nest. The main hotspots of habitat suitability were located in the central and western parts of the study area, characterized by a more traditional model of agriculture. The distance to important foraging habitats does not influence white stork fecundity indicating that landscape composition is important when choosing the breeding site. The pairs with higher number of young were located further from other neighbouring pairs and at the areas with lower density of pairs in general. This is probably linked to the lower competition for food between more distant breeding pairs. Our results show that the traditional agricultural use in mosaics of pastures, meadows and aquatic habitats promotes white storks nesting.

Feasibility of urban bird occurrence and nest amount evaluation by the street-view image virtual survey.

Bird observation mainly relies on field surveys, which are time-consuming and laborious. In this study, we explored using street-view images in the virtual survey of urban birds and nests. Using the coastal city of Qingdao as the study area, 47 201 seamless spherical photos at 2741 sites were collected using the Baidu street-view (BSV) map. Single-rater-all photo checks and seven-rater-metapopulation checks were used to find inter-rater repeatability, the best viewing layer for BSV collection, and possible environments affecting the results. We also collected community science data for comparison. The BSV time machine was used to assess the temporal dynamics. Kappa square test, generalized linear model, redundancy ordination and ArcMap were used in the analysis. Different rater repeatability was 79.1% in nest evaluations and 46.9% in bird occurrence. A re-check of the different-rating photos can increase them to 92% and 70%. Seven-rater statistics showed that more than 5% sampling ratio could produce a non-significant different bird and nest percentage of the whole data, and the higher sampling ratio could reduce the variation. The middle-viewing layer survey alone could produce 93% precision of the nest checks by saving 2/3 of the time used; in birds, selecting middle and upper-view photos could find 97% of bird occurrences. In the spatial distribution, the nest's hotspot areas from this method were much greater than the community science bird-watching sites. The BSV time machine made it possible to re-check nests in the same sites but challenging the re-check of bird occurrences. The nests and birds can be observed more in the leafless season, on wide, traffic-dense coastal streets with complex vertical structures of trees, and in the gaps of tall buildings dominated by road forests. Our results indicate that BSV photos could be used to virtually evaluate bird occurrence and nests from their numbers, spatial distribution and temporal dynamics. This method provides a pre-experimental and informative supplement to large-scale bird occurrence and nest abundance surveys in urban environments.

Bald eagle mortality and nest failure due to clade 2.3.4.4 highly pathogenic H5N1 influenza a virus

The bald eagle (Haliaeetus leucocephalus) is a culturally and ecologically vital species in North America that embodies conservation success but continues to face threats that include emerging pathogens. The introduction of A/goose/Guangdong/1/1996 lineage highly pathogenic (HP) clade 2.3.4.4b H5N1 influenza A virus (IAV) in North America in late 2021 resulted in high rates of mortality among bald eagles. Here we show an alarming rate of bald eagle nest failure and mortality attributed to HP IAV. We documented fatal, systemic HP IAV infection in breeding adult and nestling bald eagles along the southeastern U.S. coast. Concurrently, annual bald eagle nest surveys in Georgia and Florida revealed a precipitous drop in success in coastal counties compared with previous years, portending negative impacts on population recruitment. As an apex predator and efficient scavenger, it is likely that bald eagles become infected through consumption of infected waterfowl. These results and similar reports of raptor mortality in Europe, Asia, and Africa, indicate a clear threat to raptor health. The possible long-term persistence of HP H5N1 IAV in North America poses an impending threat to bald eagle populations not only related to direct mortality but also decreased recruitment and warrants continued efforts to understand these potential impacts.

Study of Breeding and Migrations of the Golden Eagle in Mongolia

Golden Eagles (Aquila chrysaetos) play a crucial role in the ecosystems of the Bayan-Ulgii province and its neighboring regions. Our research focuses on the comprehensive survey of Golden Eagle nests and study of their migration patterns via the satellite tracking, providing valuable insights into population dynamics and migratory behaviors. In the years 2021 and 2022, we accomplished an extensive search for Golden Eagle eyries across 13 diverse counties in Bayan-Ulgii province, including Altai, Altantsugts, Bayannuur, Bayan-Ulgii, Bugat, Deluun, Erdeneburen, Nogoonnuur, Sagsai, Tolbo, Tsagaannuur, Tsengel, and Ulaankhus. This collaborative effort in partnership with local communities and herders allowed us to identify and document a total of 75 Golden Eagle nests, with 49 being active during this two-year period. To deepen our understanding of these majestic birds, a satellite tracking program was started in September 2019 during the Ulaankhus Eagle Festival. Through GPS tagging, we monitored the migration of five Golden Eagles, previously used in Kazakh falconry and subsequently released. This tracking initiative provided us with valuable data on their movements and behaviors, shedding light on their survival challenges and migration routes. Our research not only contributes to the conservation efforts of Golden Eagles but also enhances our understanding of the interconnectedness of various raptor species within the region, including Bearded Vultures (Gypaetus barbatus), Cinereous Vultures (Aegypius monachus), Black Kites (Milvus migrans), Steppe Eagles (Aquila nipalensis), Peregrine Falcons (Falco peregrinus), and Saker Falcons (Falco cherrug). The study of these species in their natural habitats enriches our understanding of the intricate ecological dynamics at play. By sharing our findings, we aim to foster a deeper appreciation for these iconic birds and promote their conservation in the Bayan-Ulgii province and beyond. Our presentation will highlight the results of our Golden Eagle nest survey and tracking, emphasizing the importance of community involvement in wildlife research and conservation.

Loss of Mississippi Diamondback Terrapin (Malaclemys terrapin pileata) Nesting Habitat in the Northern Gulf of Mexico

Diamondback terrapins (Malaclemys terrapin) are a species of turtle that occupy coastal tidal marshes and nest on sandy areas above the high-tide line. Within the Grand Bay National Estuarine Research Reserve, Mississippi diamondback terrapin (M. t. pileata) shoreline nesting habitat at Grand Battures (also known as South Rigolets Island) has decreased from a 2.34-km length of surveyable shoreline in 2014 to a 1.45-km length of shoreline in 2021. Depredated nest surveys in 2021 detected the lowest number of nests to date at this location, with increased search effort, and this is likely due to the high rates of erosion described for this area.

Monitoring population change using ’citizen science’ data: case study of the Hungarian White Stork(Ciconia ciconia)population between 1999 and 2021

AbstractIn Hungary, changes in the White Stork population are monitored using two methods that involve a large number of volunteers: nest surveys since 1941, and since 1999 within the framework of the Common Bird Monitoring Scheme (MMM) programme. In our article, we briefly present the results of the nest survey data between 1999 and 2021, the population trend calculated on the basis of them, and the comparison of the latter with the trends shown by the MMM programme, which – among other species – counts all stork individuals on 2.5×2.5 km sample areas. Both sets of data show a decreasing trend, but there is a significant difference between them, which may be partly due to the inaccuracies of the nest database, considering the fact that the MMM also counts non-breeding adult and immature individuals. However, both methods have the characteristics that make them suitable for monitoring population trends.

Integrated population modeling identifies low duckling survival as a key driver of decline in a European population of the Mallard

Abstract Europe’s highest densities of breeding Mallards (Anas platyrhynchos) are found in the Netherlands, but the breeding population there has declined by ~30% since the 1990s. The exact cause of this decline has remained unclear. Here, we used an integrated population model to jointly analyze Mallard population survey, nest survey, duckling survival, and band-recovery data. We used this approach to holistically estimate all relevant vital rates, including duckling survival rates for years for which no explicit data were available. Mean vital rate estimates were high for nest success (0.38 ± 0.01) and egg hatch rate (0.96 ± 0.001), but relatively low for clutch size (8.2 ± 0.05) compared to populations in other regions. Estimates for duckling survival rate for the three years for which explicit data were available were low (0.16–0.27) compared to historical observations, but were comparable to rates reported for other regions with declining populations. Finally, the mean survival rate was low for ducklings (0.18 ± 0.02), but high and stable for adults (0.71 ± 0.03). Population growth rate was only affected by variation in duckling survival, but since this is a predominantly latent state variable, this result should be interpreted with caution. However, it does strongly indicate that none of the other vital rates, all of which were supported by data, was able to sufficiently explain the population decline. Together with a comparison with historic vital rates, these findings point to a reduced duckling survival rate as the likely cause of the decline. Candidate drivers of reduced duckling survival are increased predation pressure and reduced food availability, but this requires future study. Integrated population modeling can provide valuable insights into population dynamics even when empirical data for a key parameter are partly missing.