The Great Auk Pinguinus impennis was a large, flightless alcid, endemic to the North Atlantic Ocean. It became extinct around 1844. Skeletal remains are used to document its (pre-)historic range. While these remains were considered rare from the southern North Sea, over the past five years 91 (sub-)fossil specimens have been recovered by citizen scientist fossil collectors from Dutch beaches that were nourished with sediments dredged from the bottom of the North Sea. Some of this material is now stored in museum collections. This paper lists the new remains and documents them through measurements and photographs. The material was recovered from fourteen new localities and one previously known locality in The Netherlands and has yielded four radiocarbon dates (1425–1300 BC till beyond 48,000 cal BP) which significantly increase the Great Auk's temporal range in this area. The sheer volume of remains alters our image of the Great Auk in the southern part of the North Sea from a rare bird to most likely a common or regular wintering bird over the past millennia.

Despite increasing interest in moult in birds, there are still clear gaps in our knowledge of this topic. For example, many aspects of the moult of several European passerines remain unknown. Here, I describe the extent of the postjuvenile and the post-breeding moult of Black Wheatears Oenanthe leucura in south-eastern Spain and analyse the possible influence of ecological factors on moult in this species. The post-juvenile moult of Black Wheatears involved a variable number of greater coverts (six in most cases), but tertials, alula feathers and the carpal covert were also moulted frequently. Primaries were never moulted, while secondaries and tail feathers were moulted in 1.5% of 65 birds. The number of feathers moulted in the post-juvenile moult was not related to sex or individuals' body size. The post-breeding moult occurred between late June and mid-November and followed the typical sequence of European passerines. It had a mean duration of 145 days, with no differences between sexes or years. The body condition of wheatears did not decrease as the moult advanced. The duration of the post-breeding moult of Black Wheatears was almost double the mean duration described for European passerines and is among the longest period ever described for passerines. The resident status and medium size of the species may partly explain the long duration of the post-breeding moult, but the low seasonality and high aridity of the study area seem to be the main drivers of the pattern found.

If the number of eggs in a clutch is reduced by predators, birds have to decide whether to continue investing time and energy in this clutch or begin a new one. The aim of this study was to assess the desertion frequency of nests with an experimentally reduced number of eggs depending on the stage of incubation, degree of clutch reduction and advancement of the breeding season in the Blackcap Sylvia atricapilla. Only five-egg clutches, most typical for Blackcaps, were investigated. At the beginning of the incubation period (one day after the last egg was laid) or at the end of incubation (10 days after the last egg), two or three eggs were removed. On the next day the clutch was monitored for desertion/incubation. Blackcaps deserted clutches significantly more often when these were reduced by three eggs at the onset of incubation (56 out of 59 clutches) compared to clutches reduced at the end of incubation (33 out of 81 clutches). As the breeding season progressed there was a significant decrease in the proportion of nests that were deserted after a three-egg clutch reduction at the end of incubation. The advancement of the breeding season did not affect the desertion frequency when eggs were removed at the beginning of incubation. Blackcaps continued incubation of all clutches reduced by two eggs (n = 20), despite reduction occurring at the beginning of incubation and early in the breeding season. These results are consistent with predictions from life-history theory in general, and the brood value hypothesis in particular.

Carotenoids are exogenously sourced pigments that determine plumage coloration in many species of birds. Aside from plumage coloration, carotenoids play a role in mounting an immune response and neutralizing the by-products of cytotoxic activity. We determined whether colorimetric descriptors of carotenoid-based plumage predict infection occurrence of malarial parasites (order Haemosporida, Plasmodium, Parahaemoproteus and Haemoproteus). We captured birds in an area of sensu strictu Cerrado in southeastern Brazil, used PCR to molecularly detect haemosporidian infections and microscopy to confirm all infections. We collected five feathers from the region below the furcula of each individual to retrieve plumage coloration descriptors, namely saturation, carotenoid chroma, hue and the maximum reflectance at the ultraviolet spectrum. We analysed feathers of 58 individuals from three bird species: Lesser Elaenia Elaenia chiriquensis, Flavescent Warbler Myiothlypis flaveola and Red Pileated Finch Coryphospingus cucullatus. Colour saturation and carotenoid chroma predicted the individual occurrence of an infection with malarial parasites. We suggest that infected individuals may trade carotenoid investment between the immune system and plumage coloration, as carotenoid chroma was negatively associated with parasite occurrence. Our results indicate that haemosporidian parasites are important in influencing physiological trade-offs in natural bird populations.

The breeding biology of the Santa Marta Parakeet Pyrrhura viridicata is described based on the study of the population inhabiting the San Lorenzo Ridge, an Important Bird Area within the Sierra Nevada de Santa Marta, Colombia. We performed surveys during 2005–2008 and installed 48 nest boxes at four sites in May 2006. Nineteen nesting attempts were recorded: nine were made in nest boxes and ten occurred in natural cavities. Clutches of the Santa Marta Parakeet averaged 4.5 eggs per nest and up to seven eggs were observed in a single cavity. Previously undescribed breeding behaviours are reported for the species: cooperative breeding and replacement clutching. The only natural cavities used for nesting were in dead Wax Palms Ceroxylon ceriferum. This palm is one of the most common and numerous tree species in the San Lorenzo Ridge between 2300–2700 m elevation and key for the species' breeding cycle.

Land management intensification has caused declines in many grassland bird species. Corncrakes breed in agriculturally managed meadows and are mainly threatened by nest loss during mowing operations, but may also be affected by alternations in habitat and food availability. We analysed faecal samples to identify the diet composition of Corncrakes in a river floodplain in north-eastern Germany and related the abundance of ground-dwelling invertebrates, sampled with pitfall traps, to management practice. The most frequent food sources were beetle imagines (43%) of which one third belonged to the Carabidae family, followed by snails, beetle larvae, spiders and earthworms. Prey length was on average 11.2 ± 9.8 mm (±SD). Gastropoda species and large beetles (>10 mm) were consumed more often compared to their availability at the capture sites of Corncrakes. Invertebrate abundance peaked in June and decreased in the course of the breeding season. Total biomass, species richness, and in particular the numbers of large ground beetles, were substantially higher on sites unmanaged than on sites mown or grazed in the preceding year. Highest invertebrate abundance occurred in the first and second year after management abandonment, but strongly decreased afterwards to a similar level as under annual management. Our results suggest that rotational mowing at intervals of two or three years would be most beneficial for invertebrates. Under eutrophic conditions in floodplains, meadows undergo rapid succession and habitat quality for Corncrakes deteriorates already in the subsequent year after management cessation. Corncrake protection measures, like uncut refuge areas and delayed mowing dates, may also mitigate the negative effects of annual mowing for grassland invertebrates and enhance potential prey resources for Corncrakes in floodplain meadows.

In waterbirds, formation of mixed-species aggregations has been attributed to social facilitation and might also allow birds to exploit the ability of other species to make prey more accessible, to reduce their own time or effort spent in foraging and correspondingly increase foraging efficiency. However, some participants in mixed-species flocks may not benefit from the association. Dalmatian Pelicans often exhibit mixed-flock fishing with Great Cormorants, but there are no quantitative studies about the pattern and efficacy of mixed-flock fishing in Dalmatian Pelicans. Therefore, we studied the foraging behaviour of 328 Dalmatian Pelicans at the Lakes Mikri and Megali Prespa (Greece), during August 1993 and 2016. We examined the foraging patterns and the foraging success of Dalmatian Pelicans in relation to Cormorants' presence, water depth, Pelicans' age and flock size. Mixed-flock fishing with Cormorants was the dominant foraging behaviour of Pelicans, especially in deep waters and among adult Pelicans. Foraging effort was higher in adult Pelicans, in shallow waters, when Cormorants were absent and when occurring in larger flocks. Moreover, the number of successful dips per minute was higher in adults and when Cormorants were present. Finally, the number of successful prey captures per dip was higher in adults, in deeper waters and when Cormorants were present. However, in all cases interactions between the examined variables affected the observed differences between sexes and foraging conditions. These findings suggest that Dalmatian Pelicans can adjust their feeding tactics to the local habitat characteristics. We advocate that it is a case either of commensalism or of mutualism between the two species.

The Egyptian Vulture is a partial migrant that is globally endangered. Recent satellite tracking in Oman suggests that the resident population of Egyptian Vultures is larger than previously estimated. We used information from tracked vultures as a framework for searches for Egyptian Vulture territories in northern Oman. We found 61 occupied territories, and identified 19 additional presumed territories for which occupancy was unconfirmed. The sum of those and the territories recently discovered on Masirah Island exceeds the published national estimate of 100 pairs. An initial conservative estimate suggests a breeding density of 0.26 pairs/km² in our study area, indicating that it holds around 225 pairs. Although the nesting density in suitable habitat across Oman appears to be variable, the number of pairs of Egyptian Vultures is certainly multiple times greater than estimated. This is encouraging news for this endangered species, and suggests that under certain conditions Egyptian Vultures can thrive, even in places where anthropogenic development is rapidly increasing, as in Oman. Because Oman is developing, threats to Egyptian Vultures and other large soaring birds (e.g. due to electrocution and poisoning) may be reduced or partially avoided by planning and regulation that includes installation of safe electricity infrastructure, ensuring that food consumed at dump sites is safe for scavenging birds, and raising public and government awareness.

The eggshell colouration among and within certain bird species is highly variable. Although many studies have addressed this variation, the reasons for it remain largely unclear. Consistent individual differences in egg colouration may improve the ability of colonially breeding birds to recognise their clutch among other neighbouring nests. Moreover, in species with a high incidence of intraspecific brood parasitism, such as the Black-head Gull Chroicocephalus ridibundus, egg colouration patterns may allow parents to expel foreign eggs from their own clutch. Here, we used standardised photography and image processing, including UV spectral information, to investigate egg colour patterns in female Black-headed Gulls (476 eggs in 170 clutches) during four breeding seasons, from 2015 to 2018 in NE Germany. We confirmed maternity by comparing DNA extracted from eggshells with feathers from the breeding female. Our results showed a greater similarity of eggs within a clutch than among clutches (ANOSIM: R = 0.43, P = 0.001). Black-headed Gulls showed consistent individual-specific eggshell colour pattern across consecutive breeding seasons. Genetic analyses further revealed one foreign egg was present in three out of 25 clutches (12%), but these eggs were not expelled by the gulls, possibly because these eggs did not differ significantly in colouration from their own. Additionally, we conducted a clutch exchange experiment to assess the reaction of the breeding pair to a foreign clutch. After 21 neighbouring clutches had been exchanged, adults came back immediately and incubated the interchanged clutch without any negative reaction. It seems that they do not use the specific colour pattern for recognition of their clutches, but possibly use other cues that remain to be investigated. While the function of individual egg colour patterns remains unclear, our results strongly suggest colour variation is driven by internal rather than external factors in this colonially breeding species.

Climate variability is one of the most important forces affecting the distributional range dynamics of species and consequentially plays a significant role in shaping biogeographic patterns. This study aims to infer the role of climate in the recent evolutionary history of the Common Grackle Quiscalus quiscula. Studies of other migratory North American birds have shown that their populations were isolated in two or three refugia in southern North America during the Last Glacial Maximum (LGM). In contrast, preliminary genetic work suggests that Common Grackles may have occupied a single refugium during that time. They subsequently became widespread and northern populations evolved highly migratory behaviour. We used an ecological niche modelling approach that involved the use of three general climate models for the past (the LGM, approximately 22,000 years before present) and for present environmental conditions to identify climatically stable areas. Extrapolations to the past showed contraction to a large continuous refugium located in the southern part of North America, and projection to the present showed expansion that covers much of eastern and middle North America. The most important bioclimatic variable for model predictions was annual mean temperature, which explained 74% of the variation in the model. Results suggest that the Common Grackle has expanded its distributional range by more than 300% after the LGM.