The structure of a species assemblage at given sites constitutes a key ecological parameter to understand the dynamics of bird assemblages. The aim of this paper is to (1) quantify how variable is a passerine assemblage associated with an inter-tidal reedbed area at a main stopover site in the Atlantic flyway in northern Iberia and to explore potential factors explaining the variation, with emphasis on the vegetation productivity, and (2) to test whether inter-annual fluctuations reflect possible demographic trends. Migratory birds, especially those species which show high flexibility to stop over in some places or others using an opportunistic strategy, should be expected to land in larger numbers and stay for longer periods at given stopover sites in years with higher vegetation productivity, thus with a higher amount of insect prey, since this would permit achieving higher fuel deposition rates. We used ringing data collected at Txingudi marshlands during the autumn migration of 2007–2016. The assemblage had a relatively simple structure, because few species dominated in number over the rest. Reed Warblers Acrocephalus scirpaceus dominated the assemblage in nine out of ten study years, supporting the importance of the site for the species. As compared with the other two most abundant passerines (the Sedge and Willow Warblers, A. schoenobaenus and Phylloscopus trochilus, respectively), the ratio between these three warblers varied from year to year, with the Willow Warblers having much higher annual fluctuations than the other two species. This is likely linked to an opportunistic exploitation of the reed bed by this species, but we did not find significant effect of vegetation productivity (quantified by Normalized Difference Vegetation Index, NDVI) on the structure and diversity of the bird assemblage. Annual fluctuations in species' contribution to the assemblage did not vary linearly, except for the Bluethroat Luscinia svecica. Only for Bluethroats the proportion of captures and the mean number of captures declined from year to year. The structure and diversity of the assemblage did not seem to be affected by local conditions hence factors working at larger spatial scales or at the origin region of the migrants captured at Txingudi apparently may be more relevant at explaining the structural traits of the assemblage.

Understanding the effects of anthropogenic and environmental factors on species richness and occurrence is important for conservation. Still, comparatively fewer efforts are conducted in areas of low species richness, such as deserts. We estimated avian species richness and occurrence in response to environmental factors and anthropogenic activity in Aldesa Valley, Saudi Arabia. Because of the presence of permanent water and associated vegetation in the valley, this region is suitable to support high biodiversity. During a two-year study, we divided the valley into 40, 250 m-segments and used time area-searches from May 10 to August 10 in 2014 and 2015 to estimate bird species richness and occurrence. We used generalized linear models to assess drivers of species richness. We analyzed the local distributions of the six most commonly detected bird species: House Sparrow Passer domesticus, Laughing Dove Spilopelia senegalensis, Tristram's Starling Onychognathus tristramii, White-spectacled Bulbul Pycnonotus xanthopygos, Palestine Sunbird Cinnyris osea, and Sinai Rosefinch Carpodacus synoicus using occupancy modeling. We recorded 24 avian species belonging to 18 families and seven orders. Observed species richness was positively correlated with search duration, segment area, and extent of herbaceous coverage. Ecological covariates influential in determining occupancy varied across commonly-observed species. Tristram's Starling selected for sand areas, unlike the House Sparrow who appeared to avoid sand and rocky areas. Palestine Sunbird occupancy was positively correlated with herbaceous cover types. Species detectability was overall positively correlated with search duration. House Sparrow's detectability was negatively correlated with tree canopy area. Signs of anthropogenic activities (such as number of vehicles, people, and domestic animals) affected detectability for species differently e.g. positively for House Sparrow and negatively for Palestine Sunbird.

Nest predation is a major cause leading to reproductive failure of many avian species. Identifying nest predators is crucial for understanding the ecological context of nest predation and habitat management. The mountains of Southwest China harbors numerous species in the Phasianidae family, many of them endemic or threatened, however, little is known on the nest predation pressure on these ground breeders. We placed 32 artificial nests (each containing two chicken eggs) in broadleaf montane forests with different vegetation structure, and monitored predators with infrared-triggered cameras. The artificial nests were resembling nests of Golden Pheasant Chrysolophus pictus, a representative of the threatened species inhabiting montane broadleaf forest. We analyzed how environmental factors impact survival of artificial nests using Cox proportional hazards regression. With a failure rate of 62.5%, we recorded 40 predations where eggs were preyed or moved away, 19 predation attempts where animals spotted and contacted with, but failed to prey on or move away the eggs, and 109 pass-by events. Corvids, especially Large-billed Crow Corvus macrorhynchos was the primary culprit, committing all but one predations on artificial nests. Other potential predators included Père David's Rock Squirrel Sciurotamias davidianus, Eurasian Jay Garrulus glandarius, Red-billed Blue Magpie Urocissa erythrorhyncha, Chinese Porcupine Hystrix hodgsoni and muridaes. We found that understory cover and vertical openness were the determining factors on survival of artificial nests. Presence of understory cover and low vertical openness significantly increased survival time of artificial nests. We didn't detect significant effects from horizontal openness and distance to nearest patrol trail. Further studies with real nests are however required to examine these conclusions, and to explore reproduction strategies of ground nesting pheasants coping with threats from avian predators.

Post-fledging behaviour and mortality between the place of birth and wintering sites can be crucial to populations of raptors. We studied this phenomenon during the autumn migration of immature Red Kite Milvus milvus using telemetry data on the population breeding in western Poland. In total 34 immatures from 17 nests were ringed and GPS–GSM transmitters were attached, but only half of them survived the post-fledging period and started their first migration to wintering sites. The main mortality factors after fledging were collisions with power lines (6 individuals — 26.1%) and poisoning in wintering grounds (3 individuals — 8.8%). The mean (± SD) duration of migration and the mean distance between the breeding and wintering sites were 91.5 ± 45.2 day (range: 27–236) and 1328.0 ± 442.4 km (range: 690–2070), respectively. The daily mean speed of migration was 17.8 ± 9.4 km/day. On migration kites stopped on average 4.3 ± 3.1 times (range 1–12) for longer than 3 days, and spent a total of 37.5 ± 10.7 days (range 20–51) at stopovers. The migration duration was negatively correlated with the day of beginning of the migration, i.e. birds that started to migrate late in the season reached the wintering grounds faster. However, when the number of days at stopovers was excluded from the migration duration, this relationship was not significant, which means that the total number of days that kites spent at stopover sites significantly influenced the total duration of autumn migration. The wintering sites of birds from western Poland were located in the Iberian Peninsula and southern France and less important was Greece where single bird followed. Regular stopping over of immature Red Kites during their autumn migration indicates the need to focus more on protecting the staging areas.

Molecular data suggest that the traditional Rallidae (rails) are polyphyletic and that some species actually belong to a clade that is the sister taxon of the Heliornithidae (sungrebes). This clade includes the African taxon Sarothrura and the Madagascan Mentocrex and has been termed Sarothruridae. It was noted that White-spotted Flufftail Sarothrura pulchra and Sungrebe Heliornis fulica share a distinctive morphology of the hypotarsus, which guides the tendons for the flexor muscles of the toes. Owing to the scarcity of skeletons in osteological collections, however, other species of the Sarothruridae and Heliornithidae have not yet been studied. Here, the hypotarsus of extant and fossil members of the Ralloidea is examined. It is shown that the characteristic hypotarsus morphology is also present in Buff-spotted Flufftail Sarothrura elegans (Sarothruridae), Madagascan Wood Rail Mentocrex kioloides (Sarothruridae), and African Finfoot Podica senegalensis (Heliornithidae). Grey-throated Rail Canirallus oculeus, by contrast, which was traditionally considered closely related to Sarothrura and Mentocrex, exhibits the hypotarsus morphology found in the Rallidae. To foster future communication, it is here proposed to use the taxon name Heliornithes for the clade including Heliornithidae, Sarothrura, and Mentocrex. A previously unknown derived hypotarsus morphology is described, which characterizes the rallid taxon Porphyrio (swamphens) and may be functionally correlated with the fact that the species of this taxon manipulate food items with their feet.

The European avifauna on agricultural land has been permanently diminished over the past few decades. This phenomenon is clearly connected with agricultural intensification and the recent land cover changes. The main aims of this study were to identify the land cover preferences of a farmland bird species, the Eurasian Skylark Alauda arvensis in Hungary and investigate the link between the recent trend of the abundance of this species and the land-cover change. We employed GIS and statistical methods to assess the link between the abundance of this species based on the Hungarian common bird monitoring database (MMM) and the spatial proportion of the Corine Land Cover (CLC) categories in different buffer zones with 300, 600 and 1200 m from the observation points. Based on the significant statistical connections, we could identify and select land cover categories that serve as habitats and land cover categories that this bird species does not inhabit. The land cover preference of the Eurasian Skylark, in case of some land cover category, is depending on the grain scale (circle radius distance from the observation points). In analyses arable lands has been omitted because this land cover type is the well-known habitat of the species. According to our results, the Eurasian Skylark prefers permanent crops (vineyards, fruit trees and berry plantations) inside 600m and 1200m buffer zones, and pastures inside 1200m buffer zones, while it does not prefer urban fabric areas and heterogeneous agricultural, forests, and wetlands or water bodies inside 300m and 600m, scrub and/or herbaceous vegetation associations (transitional woodland-shrub and natural grassland areas) inside the 600m and 1200m radius buffer areas. The identification of these regional (European level) land-cover categories allowed us to analyse the recent (1990–2012) and the predicted (2006–2050) characteristics of habitat changes of this bird species, associated with land cover change. Based on our results, we could estimate that the Skylark habitat will decrease by 188 560 ha between 2006–2050 in Hungary.

In birds, adaptations that mitigate predators' impact are usually ineffective in confrontation with introduced and rapidly expanding invasive non-native predators. As a consequence, bird populations often decline in the period following the time when predator population is established. Changes in bird numbers and nest spatial distributions in breeding populations of the Eurasian Coot Fulica atra and Great Crested Grebe Podiceps cristatus were studied in Mazurian Lakeland, northeastern Poland in 2002–2003 and 2016, and were analyzed with reference to the abundance of invasive American Mink Neovison vison, whose density declined since mid 1990s. The study was based on a census of breeding pairs and a search of nests at 31 lakes. The numbers of breeding Coots and Grebes increased 2.6-fold and 1.2-fold, respectively. In both study periods Grebes displayed a strong tendency to nest in the vicinity of human settlements and in colonies; however, the percentage of Grebe pairs nesting near settlements and in colonies decreased from 51% to 34% and from 73% to 57%, respectively. Coots also preferred to nest in the vicinity of human settlements. Distributions of their nests have not changed significantly over time: in both periods 55–60% of Coot nests were found in close proximity to human settlements and 13–19% in Grebe colonies. The obtained results suggest that breeding populations of the Coot and Great Crested Grebe can cope with the invasive American Mink, whose predation was considered to be the main reason for waterbird declines in Mazurian Lakeland at the end of 20^th century.

Information on nestling diet composition is crucial for understanding the variation in birds breeding seasons at both the ultimate and proximate levels. We studied Nuthatch nestling food composition along with availability of its presumed main food resource — folivorous caterpillars — in a primeval forest, free from direct human impact (Białowieża National Park, Poland), in 1998–2004. Food brought to young during 4281 feeding visits (235 broods) was recorded. Nestlings were fed mostly caterpillars (53% of visits), but winged insects (14%), beetles (11%) and spiders (10%) were also regularly provided. The proportion of caterpillars increased with increasing caterpillar availability (measured by frassfall), with a maximum around the seasonal peaks and a later decline. The proportion of caterpillars in the diet was lower on days when frassfall was low (< 0.1 g/0.25 m²/day), irrespective of the temporal distance from the frass peak, while the proportion of winged insects increased on such days. Above the 0.1 g frassfall threshold, the proportion of caterpillars regularly exceeded 50%, reaching 90% on individual days. As in the majority of years the ‘caterpillars’ remained above the 0.1 g level over long periods, this could account for a comparably small interyear variation in the proportion of caterpillars in the diet, despite nearly tenfold differences in caterpillar abundance across years. ‘Caterpillars’ were brought significantly less often to the smallest, 5-day old, nestlings (52%), than to older ones (64%, 71% and 72% for 10-, 15- and 20-days old young, respectively). Spiders were most often provided to the smallest nestlings.

Bird communities wintering in the mosaic-like farming landscapes of SW Poland were studied to assess drivers of intra-seasonal changes in numbers and habitat associations of birds. During two severe winters (November–March) the complete area search method was applied to count birds and link their occurrence with weather and habitat in six plots (320 ha in total). A modelling approach was used to test birds' responses to environmental factors at community and species levels. These farmlands were inhabited by diverse and dense populations of wintering birds, including a significant proportion of species of conservation concern. Bird numbers revealed decreasing trends, with winter- and species-specific fluctuations, affected in particular by snow cover. The lowest population indices were recorded in mid-winter (February) and remained low until mid-March. Field margins (6.6% of the total area) supported 35.6% of individuals and 55.0% of flocks. The preference for field margins over other farmland habitats was particularly prominent during severe weather conditions. Our results suggest that during severe winters, complex farmlands are important areas for birds, enhancing their known importance to breeding birds. Intense snowfall in mid-winter rather than temperature drops lead to immediate population declines, aggravating the effects of natural food depletion. Adverse weather keeps populations at low levels until mid-March, despite the influx of spring migrants. Behavioural adjustments to winter conditions elicit the characteristic habitat distribution of birds, exposing the crucial importance of non-cropped landscape elements. In particular, the variety of field margins significantly contributes to the persistence of internationally important populations of farmland birds in Poland.

Although many waterbirds breed in colonies, documented colonisation events are rare. I studied the establishment and growth of a new breeding colony of the globally Near Threatened Dalmatian Pelican Pelecanus crispus at the newly created Karla Reservoir, Central Greece, between 2012 and 2017. The reservoir began filling with water in 2009. The first pelicans were observed in 2009 and numbers increased to 950 in June 2015. Since then the occurrence pattern changed and numbers fluctuated seasonally, being high during breeding and almost zero during summer and autumn. The first pair bred in 2011 and breeding pairs reached 445 in 2017, becoming the second largest colony of Dalmatian Pelican in Europe and manifesting an annual growth rate of 176.4%. The high rate of increase and re-sightings of ringed and tagged Dalmatian Pelicans suggest that colonisers must have been immigrants from the nearest two colonies in Kerkini Reservoir and/or Lake Prespa (northern Greece). Breeding success ranged from 0.54 to 0.88 young/nest, which is low for the species. Both the change in occurrence pattern and the low breeding success must be attributed to reasons other than nesting conditions. From a conservation point of view this new breeding colony may act as an ecological trap for Dalmatian Pelicans, as low water quality will probably continue favouring conditions leading to mass pelican mortality.

Enduring changes in the surrounding environment cause long-term stress in birds, which can affect the activity of the immune system and lead to changes in heterophil-to-lymphocyte ratios (H:L). The aim of this paper is to investigate if the H:L ratios of male and female Great Tits Parus major during the first breeding attempt differ between two sites of dissimilar habitats – an urban parkland site and a deciduous forest site. In the final model we found a difference between sites, while separate submodels for the study sites showed that females had higher H:L ratio than males in the urban parkland site, with the opposite result being found in the forest site. We suppose that the pattern of variation in H:L ratios we found may result from greater parental expenditures of females as compared to males. Such difference in the H:L ratio between habitats could be the reason for the substantial difference in trophic conditions between the forest and park areas during the breeding of tits.