Birds

Network approaches are commonly used to study mutualistic interactions between frugivorous birds and plants at the community level. However, most fruit–bird networks aggregate individual data and rely on species-level traits, often overlooking intraspecific variation. Here, we downscale a fruit–bird network to the individual level to evaluate intraspecific diet variation and individual specialization in the four main frugivorous passerine species of an island community. Fruit consumption was identified from fecal samples collected from mist-netted birds and individuals’ diets were modeled with a Bayesian approach. Intraspecific diet variation was quantified using the E and NODF indices, individual specialization using the Psi index, and clustering of individuals sharing fruit resources using the Cws index. We detected low intraspecific diet variation and individuals’ diets were not nested. Individual specialization was mainly related to recapture of individuals and weakly related to phenotypic traits. Clustering mainly involved heterospecific individuals whose diets matched plant fruiting phenology during the capture period. Accordingly, future community-level studies addressing the role of mutualistic interactions in biodiversity maintenance may benefit from integrating network approaches with complementary information on interindividual and interspecific competition. Full article

Wild birds are increasingly exposed to anthropogenic threats that compromise population viability. Wildlife rehabilitation centers provide valuable data to monitor these pressures and their conservation implications. This retrospective study analyzed wild bird admissions to the Wildlife Recovery Center of the University of Trás-os-Montes and Alto Douro (CRAS-UTAD) in northern Portugal between January 2007 and October 2025. A total of 5090 birds from 135 species and 44 families were admitted. Causes of admission were grouped into 11 categories, and outcomes into 7. Admissions increased over time, rising from approximately 160 birds in 2007 to more than 430 in 2025, although the overall temporal trend was not statistically significant. Birds of prey were the most frequently admitted group, particularly Strix aluco (9.16%) and Buteo buteo (8.00%). The most common causes of admission were orphaned birds (26.2%), followed by seizures from illegal captivity (12.2%) and collisions (5.0%). Overall, 43.2% of birds were released, while 29.4% died and 18.3% were euthanized. Admission cause was strongly associated with outcome, with electrocution showing the poorest prognosis and seizure from illegal captivity the highest probability of release. These findings highlight the major impact of human activities on wild bird morbidity and mortality and reinforce the importance of rehabilitation centers as sentinels for conservation and mitigation strategies. Full article

New Guinea, the world’s largest tropical island, supports the planet’s richest insular avifauna. Large areas of New Guinea remain poorly surveyed, however, in part due to the island’s challenging terrain. In hard-to-access areas, like many mountainous parts of New Guinea, automated surveying tools, like camera traps, may be especially helpful to address the survey deficit. Here we present the results of a camera-trap survey of the avifauna of the Cyclops Mountains, a range in New Guinea’s western, Indonesian provinces (Indonesian Papua). To our knowledge, our results represent only the second published camera-trap survey of birds from Indonesian Papua. We deployed 73 camera traps along an elevation gradient (143–1963 m) of the Cyclops Mountains for 11,869 camera-trap nights, recording 22 bird species from 1696 independent detections. Our species list is, to our knowledge, the first to include observations from the upper northern slopes of the Cyclops Mountains. It documents the first record of Masked Bowerbird (Sericulus aureus) in the range and provides photographic rediscoveries of two ‘lost’ species: Mayr’s Honeyeater (Ptiloprora mayri) and Mayr’s Forest Rail (Rallicula mayri). We also report substantial elevation range extensions for several species, including numerous records of Northern Cassowary (Casuarius unappendiculatus) over 1000 m above its historically known elevation ceiling. These findings provide new insights into species distributions and ecological flexibility in New Guinea’s montane systems, highlighting the potential for previously undocumented biodiversity in under-surveyed regions. Although camera traps detected fewer species than traditional ornithological methods, they were effective in documenting several elusive, ground-dwelling bird species, highlighting their value as a complementary tool for ornithological research in challenging terrain like New Guinea. Finally, we use our data to publish an updated bird species checklist for the Cyclops Mountains. Full article

Solitary living is an evolutionarily widespread yet comparatively under-theorized social system, despite its occurrence across diverse animal taxa. Shrikes (family Laniidae) are small predatory passerines that combine raptorial behavior, strong territoriality, and predominantly solitary space use, making them a powerful model for examining the ecology and evolution of solitary living. Here, I synthesize published work on shrike behavioral ecology and explicitly link these traits to the costs and benefits of a solitary lifestyle. I argue that shrikes exemplify how solitary species can offset the absence of social buffering through cognitive innovation, finetuned habitat selection, and flexible yet tightly bounded sociality. I then compare shrike ecology to solitary mammals and reptiles, highlighting convergent patterns in resource dispersion, spatial memory, risk management, and juvenile dispersal. I further examine how anthropogenic pressures, such as habitat fragmentation, climatic instability, and urbanization, interact with solitary life histories and review evidence from management interventions in both European farmland and North American systems that demographic recovery is achievable but remains contingent on addressing broader land-use conflicts and sources of adult mortality. Finally, I outline five interconnected research priorities—spanning cognitive ecology, trophic interactions, movement ecology, genomics, and formal comparative analyses—that would move shrike research from its current observational foundation toward a more experimental, mechanistic, and phylogenetically informed programme. By reframing shrikes as a model taxon for solitary living, this review aims to integrate avian behavioral ecology into broader comparative frameworks of social organization, cognition, and resilience under global change. Full article

Bird migration is an awe-inspiring phenomenon that causes massive global shifts in bird distributions twice a year. To understand the evolution of this phenomenon, it is crucial to know the mortality costs of these journeys. Extreme weather-related events can lead to abnormally high mortality rates among migratory birds, while high mercury concentration may reduce the survival of songbirds in the field, especially for the long-distance migrant insectivores. Yet the specific vulnerability factors remain largely unknown. We collected the opportunistic dead Eastern Red-rumped Swallows (Cecropis daurica) in a mass-mortality event caused by a cold wave in autumn migration in Southern China. Mercury concentration in their tail feathers is 0.57 ± 0.37 µg g⁻¹, lower than the established toxicity threshold for birds. The claws’ hydrogen stable isotopic (δD) values ranged from −116 to −78 ‰, with a mean of (−88.00 ± 8.22) ‰. Stable hydrogen isotopes indicated broad origins for the Eastern Red-rumped Swallows, ranging from ~30° N to ~62° N and ~10° E to ~150° E. Considering subspecies ranges, most of the dead swallows likely came from their almost furthest breeding sites. Our results indicated the primary cause of the mass-mortality event was likely fatigue or starvation resulting from long-distance flight during an extreme cold wave. Mercury exposure may not be the main direct cause of death. Full article

For the first time, an attempt has been made to comprehensively summarize data on the past distribution of bustards on the territory of Bulgaria based on their fossil and subfossil finds. The collected data refer to a total of 32 Quaternary localities (natural and of anthropogenic origin), of which three are Pleistocene and 29 of Holocene age. The earliest locality of an otidid identified to the species level dates back to 2.4 million years ago. A total of three species have been identified. Among them, one species, Khosatzki’s Houbara (Otis aff. khosatzkii), has disappeared from the modern fauna of the country. Great Bustard (Otis tarda) was found in 20 Quaternary localities, Little Bustard (Tetrax tetrax) in eight, Otis tarda/Tetrax tetrax in two, Khosatzki’s Houbara in one and Otididae gen. in one locality. Chronostratigraphically both Great Bustard and Little Bustard were spread from Greenlandian to Meghalayan (i.e., last ca. 117,000 ya), while the earliest Khosatzki’s Houbara is known only from Gelasian (2.23–2.40 Mya). All finds originated from localities at between 20 and 670 m. a.s.l. in plains, lowlands and low hills. The presence of extant species of bustards on the territory of Bulgaria is rather a post-Pleistocene (Holocene) phenomenon. Besides their primary use as a source of meat for food, bustards in Bulgaria were also used as a source of materials for tool making by ancient people. Full article

Vigilance is used to detect distant threats in many species of birds. Allocation of time to vigilance is shaped by the social and physical environment of individuals, but little research has focused on how weather variables affect vigilance. Wind speed, in particular, can influence vigilance by decreasing manoeuvrability during escape, increasing energy costs or by decreasing the ability to communicate and assess risk. We examined how wind speed influenced vigilance in sentinels of a cooperative breeder, the Florida Scrub-Jay (Aphelocoma coerulescens). Sentinels in this species occupy vantage points to monitor their surroundings and can devote all their time to vigilance during sentinel bouts. We found that head turns in sentinels, which allow individuals to monitor different areas, became more frequent under windier conditions. Wind speed is not likely to affect manoeuvrability in sentinels that are already close to cover. Energy costs during high wind likely are not as relevant to sentinels as they may be to other group members, since sentinels do not forage. We conclude that the ability to assess risk visually was probably compromised by movements in the vegetation caused by wind. The study highlights behavioural adjustments to weather-related environmental variability. Full article

Elevated perches allow songbirds to better transmit their songs and increase the visibility of territorial displays, but there is a cost: increased predation risk. To investigate how grassland birds evaluate these tradeoffs, we placed artificial perches in one of four meadows kept open by mowing in Williamstown, Massachusetts. We tracked meadow and perch usage by passerine birds using both a weekly census and monthly counts of fecal boli as a proxy for occupancy of the artificial perches. The same species were observed in the meadow with artificial perches and the meadows without such perches. Nevertheless, all of the artificial perches were used, some extensively. Much of the variation in perch use could be explained by perch height. Birds preferred taller perches, which are the most visible to predators, but also provide the largest advantages in terms of song propagation and visibility for better territory advertisement. Other advantages include increased visibility for foragers hunting insects, as well as possible earlier detection of predators. The increased predation risk of perching in the open on higher perches appears to be offset by the advantages gained by being seen, being heard, and having a better view of the surrounding area. Full article

Predation risk influences how animals approach predictable food sources where ambush predators may be present. In parids, chick-a-dee calls are used in a wide variety of contexts related to social cohesion and are well known as mobbing signals. Here, we examined whether they are also produced in the absence of visible predators in contexts in which predation risk may nevertheless be latent or uncertain. We tested whether chick-a-dee calls emitted by Willow Tits (Poecile montanus) during feeder approach exhibit acoustic and recruitment characteristics comparable to mobbing calls elicited by predator models. The study included repeated observations of 44 individuals across 11 flocks, enabling within-individual comparisons across habitat contexts. We analyzed call structure, calling duration, and recruitment latency in relation to habitat visibility and dominance status. Calls produced during the feeder approach showed overlapping structural features with mobbing calls and were associated with the recruitment of flock members, particularly in dense habitat. Mixed-effects models confirmed significant effects of habitat structure, predator presentation, and social rank on calling behavior and recruitment dynamics. These patterns are consistent with mobbing-like signaling under conditions of uncertain predation risk. Because predator presence and detection outcomes were not directly measured, our findings provide behavioral evidence compatible with proactive signaling rather than functional confirmation of predator probing. Full article

The Turtle Dove is a regular migratory species widely distributed in Italy, though the information on its abundance in each Italian region is modest; thus, action plans have been implemented to improve its conservation. This is a preliminary study meant to provide information on the distribution and abundance of the TD in Apulia. We analyzed data collected during 2019–2023 within the Farmland Bird Index (FBI) project, whose sampling design was intensified to achieve more homogeneous coverage of the region. The survey method was based on unlimited-distance point counts lasting 10 min. Counts were carried out between 15 May and 15 June of every year, beginning from dawn until 12:00 AM, with each station visited once. A total of 211 TD birds were recorded across 147-point counts. The MaxEnt analysis showed that olive orchards, needle-leaved woodlands, and evergreen broad-leaved woodlands had a positive effect on species occurrence, whereas winter precipitation had a negative effect. The total estimate of pairs fell within the range 47.14–66. The estimated density for TD in Apulia was 0.87–1.16 birds/km², while that of pairs was 0.69–0.97/km². By relating the estimated densities to the area suitable for the species’ presence, the abundance of TD was estimated at approximately 17,337–24,303 birds. Full article

Behavioral flexibility allows animals to adjust their behavior in response to environmental changes. Hummingbirds, with their tetrachromatic color vision and enlarged hippocampal formation, represent an excellent model for studying cognitive flexibility in color discrimination. We evaluated three components of behavioral flexibility (exploration, exploitation, and inhibition) in two sympatric hummingbird species, the resident White-eared Hummingbird (Basilinna leucotis) and the migratory Broad-tailed Hummingbird (Selasphorus platycercus), using a reversal learning task with artificial flowers of different colors for evaluating exploration, exploitation, and inhibition simultaneously. Birds were trained to associate nectar rewards with either spectrally similar (red-yellow) or dissimilar (red-violet) color pairs. Our results revealed interspecific differences in exploration behavior depending on the rewarding color during training, while both species showed similar exploitation and inhibition capacities. The migratory S. platycercus showed stronger neophobia toward non-red flowers compared to the resident B. leucotis. Both species quickly learned the color-rewarding association when red was rewarding but required more visits when non-red colors were rewarding. These findings suggest that while both species can flexibly adjust their foraging behavior, differences in their ecology and migratory behavior may influence their initial responses to novel color cues. Full article

Avian morphology is a product of complex interactions among ecology, behavioral traits, and phylogeny. The wing, as a primary aerodynamic structure, is particularly indicative of these selective pressures, which are especially pronounced in migratory species. This study investigates interspecific variation in wing morphology among three migratory warblers of the family Sylviidae: the Garden Warbler (Sylvia borin), Eurasian Blackcap (Sylvia atricapilla), and Common Whitethroat (Curruca communis). We combined traditional morphometric measurements (body mass, wing length, primary feather lengths, and wing area) with functional aerodynamic indices (wing loading, aspect ratio, Kipp’s index) and geometric morphometric analysis of wing shape. Data were collected during autumn migration on the Greek island of Antikythera, a key stopover site in the Mediterranean. Our analysis revealed distinct morphological adaptations: Garden Warblers possessed elongated, pointed wings with a high aspect ratio, indicative of selection for long-distance, energy-efficient flight. Conversely, Eurasian Blackcaps exhibited shorter, rounder wings, a morphology associated with high maneuverability and quicker takeoffs in dense habitats. Common Whitethroat displayed an intermediate wing morphology, balancing aerodynamic efficiency with maneuverability. These findings possibly demonstrate how wing morphology reflects a compromise shaped by selective pressures, including migratory distance, habitat structure, foraging behavior and predation risk. Full article

Bird survival is influenced by both natural and anthropogenic factors, including weather conditions and oil spills. In this study, we examined the impact of a major oil spill (Prestige oil tanker) and climatic conditions (precipitation and wind) on survival and recapture probability in the Kentish plover (Anarhynchus alexandrinus) population in Galicia (NW Spain). To this end, we applied the Cormack–Jolly–Seber (CJS) live recapture model to a sample of 372 adult birds captured between 1994 and 2023. The best-fit model indicated that survival was best explained by the interaction between precipitation and the Prestige oil spill, indicating a decrease in survival post-spill, especially in the periods Post1 (years 2003–2007) and Post2 (2008–2015). Precipitation showed a negative influence on adult survival, but wind had no significant influence. Recapture probability was influenced by the interaction between time, sex, and Prestige, with males showing higher values, probably due to behavioural and detectability differences. Environmental monitoring and preparedness for pollution events are therefore essential to improve the long-term viability of the species. Full article

Birds are a popular group of organisms for researchers and laymen alike, and citizen science data are widely used in understanding bird ecology. This study investigates the correlates of bird visits to a single tree in the suburb of Westville, located in the city of Durban (eThekwini Municipality), in coastal subtropical South Africa. Of the 416 bird species recorded locally (within the quarter-degree square where the tree is located), 47 visited the tree during the 108 observation hours spread over one year. Of the 636 bird visits, most were very brief (shorter than one minute), with birds departing in a direction different from the one from which they came, suggesting that the tree was most often used as a stopover. Feeding (mostly on insects) was observed during 112 visits, while other behaviors were rare. Bird activity was higher in spring/summer and in the early morning, with a weak second peak in the late afternoon. Larger birds used larger branches as perches and paid longer visits. There was a negative relationship between bird activity and butterfly activity, driven by different seasonal patterns, and this creates an opportunity for butterfly watching at a time of the year with low bird activity. These results are used to discuss potential directions for similar projects while harnessing citizen science. Full article

The gut microbiota plays a key role in the health of wild birds, reflecting the influence of diet, habitat, and social behavior. Migratory and highly gregarious species such as the yellow-headed blackbird (Xanthocephalus xanthocephalus) provide valuable opportunities to explore host–microbe–environment interactions within a One Health framework. During migration, birds are exposed to diverse environments and dietary sources, which can promote highly diverse intestinal microbial communities and facilitate transient acquisition of environmental microorganisms. Here, we present the first taxonomic characterization of the fecal bacterial microbiota of X. xanthocephalus in northern Mexico based on 16S rRNA gene sequencing of the V3–V4 region. In addition, we performed a conservative screening to assess whether any bacterial taxa tentatively assigned at the species level have been previously reported as human pathogens or as having potential zoonotic relevance. Fecal samples were collected noninvasively from communal roosts within an urban–agricultural landscape of the Comarca Lagunera region during a winter season. A highly diverse bacterial community (39 phyla, 369 families, and 1195 bacterial species) was identified. Firmicutes_D, Actinobacteriota, and Campylobacterota were the dominant phyla. Among the bacterial taxa tentatively assigned at the species level, only three have been reported to exhibit zoonotic potential in the literature; however, none corresponded to avian-adapted pathogens or bacterial species historically associated with major zoonotic outbreaks, and all were detected at very low relative abundances. Overall, our findings establish an initial microbiological baseline for X. xanthocephalus and underscore the role of migratory birds as indicators of environmental microbial dynamics rather than direct sources of zoonotic risk in semiarid regions of northern Mexico. Full article

The combined effects of plateau pikas and yak grazing on the distribution or occupancy of endemic passeridae birds on the Qinghai-Tibetan plateau, China remain largely unknown. To assess habitat selection patterns within the frameworks of niche construction theory and the rivet hypothesis, we measured the occupancy rates of passeridae species along five sample strips of transects established in a treeless ecosystem. Each transect was surveyed three times within each seasonal sampling window (spring, summer, and autumn 2024), and repeated visits were treated as detection occasions for occupancy modeling. We used plateau pika density and yak grazing patterns as key variables to investigate their influence on the occupancy of alpine passeridae birds. We found that the occupancy of both the White-rumped and Rufous-necked Snowfinch was positively associated with proximity to yak bedding sites and high densities of plateau pika burrows. However, the occupancy of both species declined with increasing distance from yak bedding areas. In contrast, the Ground Tit showed no detectable association with these variables. This strong interspecific variation underscores the importance of disentangling mechanistic linkages among large herbivores, ecosystem engineers, and avian niche specialization in this fragile biome. Further research should explore how cross-taxa interactions mediate habitat availability and species resilience under ongoing environmental change. Full article

Ground-nesting shorebirds face growing pressure from recreational activities in coastal urban areas. We monitored the breeding success of Kentish Plover (Charadrius alexandrinus) and Little Ringed Plover (Charadrius dubius) over six consecutive years (2020–2025) at the Promenade of Sablettes, a heavily visited waterfront in Algiers, Algeria. We combined field surveys with multi-sensor remote sensing analysis using Sentinel-1, Sentinel-2, and Dynamic World data to quantify habitat change. A total of 105 nests were recorded across both species. Breeding success reached 70% during the COVID-19 lockdown period (2020–2021), when human visitation dropped sharply. In contrast, complete reproductive failure occurred in 2022 and 2023, coinciding with resumed tourism and unplanned construction activities. Remote sensing revealed that 80–85% of the study area experienced severe habitat degradation between 2020 and 2025, while suitable refuge zones shrank to less than 10% of the total surface. Fledged chicks consistently moved toward a less disturbed vegetated zone, highlighting its functional importance for brood survival. Our results show that human disturbance is the primary factor limiting breeding success at this site, operating through two pathways: direct disturbance of nesting birds and progressive habitat degradation driven by recreational use and unplanned construction. When disturbance was reduced during the pandemic, the habitat proved fully functional for both species. These findings suggest that simple management measures such as seasonal access restrictions and symbolic fencing during the April–July breeding period could restore breeding conditions without major habitat engineering. This study provides one of the first integrations of long-term field breeding data with landscape-scale remote sensing to document the effects of the anthropause and subsequent recovery on urban shorebird populations. Full article

The post-fledging dependence period is a crucial stage in the development of altricial birds that may influence their future performance and fitness. This period is regulated by parental investment, in terms of food provisioning and protection, and the young’s demands associated with their development and physical condition. We examined post-fledging dependence regulation in 21 Booted Eagle (Hieraaetus pennatus) nestlings in southern Spain. We compared the dependence timing among juvenile birds from different territories. Here, we analyzed the blood plasma chemistry of nestlings in southern Spain and compared blood biochemistry parameters, including urea levels and a body condition index with the hatching date. Urea levels showed a stronger negative relationship with the length of dependence period than with the hatching date or body condition index. Our results support that better nourished nestlings attain independence later than those in an inferior condition, highlighting the potential of urea levels as a reliable indicator of nestling status. In this study, we describe the concentrations of selected chemical parameters in the plasma of free-living Booted Eagle nestlings, including chemical parameters that have been shown to be related to nutritional condition. Young with a better nutritional condition started dispersal later. Blood parameters can be used as a very useful complementary technique when approaching ecological issues. Early dispersal onset seems to be controlled by endogenous factors that are evolutionarily selected since it should provide inherent benefits in terms of future fitness. Full article

This study evaluated heavy metal accumulation in bird feathers across four contrasting environments in Jalisco, Mexico (urban, semi-urban, agricultural, and semi-natural). We analyzed 370 feather samples from 58 species spanning seven trophic guilds using XRF spectrometry. Fifteen metals were quantified, with zinc (Zn) showing the highest concentrations overall. Multivariate analyses identified trophic guild as the strongest predictor of metal variation, while spatial differences were present but less pronounced. CUAltos was the only site consistently distinct from the others, mainly due to lower concentrations of several metals. Despite quantitative differences among guilds, their proportional metal profiles were similar—dominated by Zn, Y, Mo, and Hf—suggesting broad regional exposure rather than guild-specific accumulation. Redundancy Analysis indicated that atmospheric pollutants (COV and PM10) were the main environmental drivers of spatial variation, especially in Guadalajara’s urban sites. Agricultural variables, including agave cover, showed minor and non-significant effects. Neither sex nor migratory status influenced metal loads, consistent with feathers reflecting exposure during feather growth at the molt site, while potentially also incorporating locally deposited external contaminants. Overall, this study demonstrates the effectiveness of feathers as a non-invasive biomonitoring tool and highlights air quality as a key determinant of regional heavy metal contamination. Full article