The post-fledging period is still an understudied stage of avian life cycle, even in the case of otherwise frequently studied species. The general breeding biology of the White-throated Dipper is known well, but only a few studies have focused on survival and dispersal during the post-fledging period. In this study we report on results revealed by radio-telemetry, a method which has not been used in the species to date. Nestlings (37 individuals from 9 nests) in a mountain population of central Slovakia were radio-tagged on the mean expected fledging age (22 days post-hatch) and monitored daily until death, disappearance or reaching independence. Only 22–32% (depending on the handling of uncertain data) of fledglings survived the first 12 days post-fledging. Predation was the most frequently suspected cause of death. The daily survival rate was markedly lower during the first two days after fledging (0.717–0.758) than later (0.914–0.941). The daily movement distance remained stable during the first week post-fledging and increased around the age of reaching independence (c. 12 days post-fledging). On the other hand, the distance from the natal nest and the within-brood distance (length of river occupied by fledglings from the same nest) increased gradually since fledging. We propose that in our study population the low post-fledging survival could be potentially balanced by frequent renesting and/or double-brooding, timing of which corresponds well with the age of reaching independence when juvenile birds disperse outside the natal territory.

Monitoring waterbirds is fundamental to understand the health status of wetland habitats. However, this monitoring has to be conducted by means of reliable data collection that can provide accurate information on population trends. Usually, waterbird monitoring is difficult, as nesting grounds are usually located in inaccessible reedbed, and by eye detection of cryptic species is hard. Drones have the capacity to overcome most of these problems, as they can provide with an aerial view of places otherwise unreachable, while reducing the disturbance and time spent in the field. The present study aims to compare the accuracy, disturbance levels, and managerial efficiency between ground (traditional) and drone counts of a cryptic species, the Purple Heron Ardea purpurea. Traditional monitoring methods were only capable of detecting 35% of the nesting pairs detected by the drone surveys (8.0 ± 11.8 versus 22.9 ± 38.2 nesting pairs in ground and drone surveys, respectively). Consequently, colony size estimates between methods showed poor agreement, to the point that traditional methods missed colonies otherwise detected by the drone. No apparent negative effects on nesting pairs where found when flying the drone. In addition, mean time spent to survey breeding sites with a drone was far less than with the traditional approach, down to a six-fold time reduction. This reduction, together with a lack of disturbance observed when conducting the drone monitoring, and an increasing monitoring precision and accuracy, supports the use of drones as the least invasive option for studies on population monitoring on hardly accessible sites.

Waterbirds are declining globally due to different threats that affect their abundance and shift both their breeding and wintering ranges. Cormorants disperse over vast distances during winter and are suitable indicators of the impacts of human-wildlife interactions and abiotic factors. During wintering periods, Pygmy Cormorants Microcarbo pygmaeus use regular roosts where they overnight on suitable perches, a refuge from adverse weather conditions and disturbances. Our study aimed to determine the wintering population size of the Pygmy Cormorant and its dynamics across 23-years (1996–2019) at seven roosting sites in the Maritsa River valley, Southern Bulgaria. This is a critical site for the species conservation where 3065–8180 birds are wintering annually. The wintering Pygmy Cormorant population showed a tendency to increase between 1996 and 2019 (λ = 1.03 ± 0.001). Each year Pygmy Cormorants were most abundant in December (mean ± SE, 2609 ± 185 individuals), while the lowest numbers were recorded in March (1207 ± 106). Pygmy Cormorants aggregated to roost between 4:00 PM and 5:30 PM throughout the study. The area of wintering foraging habitat of the Pygmy Cormorant increased significantly across all roosting sites in the study period from 2675.97 ha to 22564.35 ha. The number of Pygmy Cormorants at the roost was positively affected by the drop in the daily air mean temperatures and the decrease of the day length. Despite the global population increase, the Pygmy Cormorant faces a high risk of human-induced mortality during wintering and is thus regionally classified as endangered.

Studies on the diet composition of bird species provide valuable insights on their habitat use, trophic interactions and prey selection. Prey abundance can drive movements of raptors in their wintering grounds. But such links have been difficult to establish due to the lack of dietary information for most raptor species. Estimating the wintering diet of raptors is a challenge that requires extensive fieldwork across a large geographical area which is often not possible. The methods used in breeding sites such as nest observations are not available in the non-breeding regions. Recently, several studies have demonstrated the use of web-sourced photographs as a tool for understanding the diet of raptors and also the need for combining multiple approaches to get a comprehensive overview of diet. In this study, we use a novel approach by using web-sourced photographs and pellets to estimate the variations in the diet of Montagu's Harrier Circus pygargus, a species in decline, across its wintering range in India. A total of 232 photographs and 391 pellets collected across western India, Deccan and south India during autumn, winter and early spring seasons were analysed. About 53% of photographs and 71% of pellets contained orthopterans, forming the major component of the harrier's diet. The proportion of reptiles, eggs and birds in the diet were similar across both methods. Presence of other insects in the diet was better estimated by photographs (23%) than pellets (8%) while rodent presence was higher in pellets (17%) than photographs (4%). Pellet analysis and photographs showed similar variation in diet across seasons while only pellets showed variation in diet across regions. Photographs also showed that there is significant variation in diet between the sexes of the species, with higher presence of insects and reptiles in the diet of males than females. Our results suggest that a combination of photographs and pellet analysis provide better estimates of wintering diet of Montagu's Harriers.

At present, the intensification of urban landcover is one of the most critical threats for biodiversity. Common side-effects of urban sprawl are anthropogenic noise and artificial light at night (ALAN). Although their negative effects have often been described, little research has concerned nocturnal wildlife, especially avian predators. Here, we investigated the effect of urban and tree cover, traffic noise and ALAN on the presence of the Tawny Owl Strix aluco, a common night-active predator in Europe. We conducted playback surveys along an urban gradient in Turin (Italy) to detect species presence. Traffic noise was measured in the field, the cover of built-up and (semi-)natural areas was estimated using GIS and multiple measures of ALAN were acquired from a light pollution map. We modelled species presence as a function of each environmental predictor and we found a significant negative relationship with light pollution, which was the foremost urban stressor affecting Tawny Owl occurrence. Our findings suggest that Tawny Owls are more likely to be found in less artificially illuminated areas and that their distribution in urban areas is not only influenced by noise pollution and the availability of suitable habitat, but also the intensity of ALAN. Therefore, light pollution could be a key driver of the spatial distribution of Tawny Owls and potentially other nocturnal species in urban ecosystems.

Understanding the niche differentiation between sympatric species that permit species to coexist and partition resource is the central concept in ecology. In this context, we evaluated the differences in roost site resources between two sympatric Otus species — Andaman Scops-owl Otus balli and Oriental Scops-owl Otus sunia in the Andaman Islands using a multi-scale approach. We measured variables that influence roost site use by owls at three different scales (tree, patch and macro). A total of 38 and 69 independent roost locations of O. balli and O. sunia respectively were recorded. We found that both species showed a high preference for Arecaceae plants at tree scale, possibly for their spiny structures that could offer protection. But both species showed different selection patterns at the patch and macro scales. At the patch scale, O. balli selected roosting sites in patches with relatively mature tree stands (characterised by higher tree height, girth at breast height and canopy cover) with thick understory cover (understory cover, height, and herbaceous elements). In contrast, O. sunia was found to select trees in secondary or highly disturbed forests. Land use and land cover types distinguish both species from their habitat preferences at a macro scale with a very low predicted overlap. The area of potential roost sites is very low for O. balli when compared to O. sunia. Our findings suggest that the two sympatric species' preferences for roost sites are shaped by the characteristics of evergreen forests of the Andaman Islands. Hence, any further changes to this forest type may have adverse effects on the endemic O. balli.

Shrikes from the genus Lanius are generalists in terms of diet, even consuming highly toxic species, as blister beetles (Coleoptera, Meloidae). Despite the fact that regular predation on these coleopterans have never been described both in recent and historical literature, birds stand out as one of the groups to most often prey upon these insects. In the Old World, records of shrikes preying on oil-beetles — most of them treated as anecdotal — have been published since the 19th century. However, despite being repetitive, no review or in-depth study of this behavior has been conducted. After a literature study and new data collected in the Iberian Peninsula, it seems an extended behaviour within the clade. As could be observed in a high number of cases, birds even apply a specific technique, selecting specific body parts to kill the beetle, more sclerotic and presumably less toxic. In some cases, strict predation has been demonstrated. To date, at least six different shrike species — Red-backed Shrike Lanius collurio, Great Grey Shrike L. excubitor, Iberian Grey Shrike L. meridionalis, Loggerhead Shrike L. ludovicianus, Lesser Grey Shrike L. minor, and Woodchat Shrike L. senator — have been found to show signs of preying on at least nine Meloidae species throughout Europe, North Africa and North America, constituting a line of research that should be studied in greater detail.

Nest construction may result in niche creation by the bird, i.e., modification of the immediate environment in terms of temperature or humidity. Here thermal insulation of nests of the Common Blackbird Turdus merula was investigated using a heat source placed inside the cup. The temperature profile of the nest wall was recorded using thermistors placed at different positions in the nest wall. Temperatures were affected by the layers in the wall with the grass cup lining and mud cup offering more insulation than the outer wall. Thermal conductance of the wall of Common Blackbird nests was relatively high compared to other reports for this variable in other passerine species from Australia. Variation among Common Blackbird nests in terms of temperature differences across layers, and thermal conductance overall, correlated with the thickness of the grass cup lining. Thermal insulation provided by a nest wall is dependent on the thicknesses and types of materials used in each part of the wall. Previous studies using nest deconstruction have demonstrated that the various layers in a wall have differing thermal characteristics. This is the first report of clear differences in the temperature profile across the different parts of the intact nest wall. Whether this pattern is also observed in nests of other species requires further investigation. The placement of different materials within the nest wall by the bird is not a random process and the results support the idea that the avian nest is involved in niche creation.

Mast-seeding is widely considered to be an adaptation that minimizes seed predation. The superabundance of seeds during mast years greatly exceeds the capacity of seed predators to consume them. These notions were based on research on food specialists such as insects and rodents. However, mast-seeding may have different impact on the behavior of corvids that are food generalists. The Eurasian Jay Garrulus glandarius is a widespread scatter-hoarding corvid that uses acorns as a food reserve for winter. In mast-years, the birds are supposed to be satiated by the greater seed supply and are able to store their surplus, acting as dispersal agents, whereas in poor crop seasons they use most of the crop for current consumption and thus become seed predators. In such a situation, a dispersal agent may become a seed predator, and vice versa. The main task of this study was to determine the levels of pre-dispersal acorn predation by Jays during non-mast years to verify the notion that under such conditions Jays act mostly as seed consumers. During two consecutive non-mast years, tagged acorns were radio-tracked and the acorns' fate (cached or eaten) was assessed. We found extremely low pre-dispersal acorn predation by Jays (0.9%). The possible reason is that temperatures in period of acorns collecting (September–October) are high enough to allow invertebrates to remain active, so the Jays may supplement their diet with insects and also fleshy fruits. Therefore, almost all acorns were cached and scatter-hoarding Jays provided effective seed dispersal, with extremely low consumption of acorns.

In August 2018 remains of several birds of prey were recorded at one Eagle Owl Bubo bubo eyrie in southeast Romania. Among these, still articulated wings and leg bones of an adult female Booted Eagle Aquila pennata, feathers and several bone fragments of one adult Long-legged Buzzard Buteo rufinus and several individuals of Common Buzzards Buteo buteo were identified. While predation of Eagle Owls on different raptor species is well known, booted Eagles and Long-legged Buzzards are rarely preyed upon. Based on changes that occurred in the overall diet of owls at this particular eyrie, it is hypothesized that a shortage in the main prey species (induced by land use changes in the region) may be the cause of these extraordinary predation events. While predation of Eagle Owls on large diurnal raptors is more an exception than a norm, in areas where threatened diurnal raptors breed, the presence of Eagle Owls may cause conservation concerns/prove to be problematic.

Underground burrow nests of three bird species: Amazonian Motmot Momotus momota, Rufous-tailed Jacamar Galbula ruficauda and Swallow Tanager Tersina viridis were monitored for eight years on stream banks, in a Seasonal Semideciduous Forest, to enable determining whether, or not, being a burrow excavator bird is associated with nest predation, and how important the role played by nest dimensions in this nesting system is. Predation was the main cause of nest failures, although there was no significant difference in nest predation between secondary (SCN) and primary (PCN) cavity (burrow)-nesting species. Offspring predation rate was the only one recording significant result; the lowest offspring predation rate was associated with PCN species — Amazonian Motmot but, again, there was no significant difference between PCN and SCN species. On the other hand, SCN species — Swallow Tanager has compensated offspring losses due to its increased fecundity, which enabled two broods per breeding season. No nest parameter has influenced predation rates, although our data suggested the need of further investigating the length of the nest access tunnel.