A new enantiornithine bird is described on the basis of a well preserved partial skeleton from the Upper Cretaceous Qiupa Formation of Henan Province (central China). It provides new evidence about the osteology of Late Cretaceous enantiornithines, which are mainly known from isolated bones; in contrast, Early Cretaceous forms are often represented by complete skeletons. While the postcranial skeleton shows the usual distinctive characters of enantiornithines, the skull displays several features, including confluence of the antorbital fenestra and the orbit and loss of the postorbital, evolved convergently with modern birds. Although some enantiornithines retained primitive cranial morphologies into the latest Cretaceous Period, at least one lineage evolved cranial modifications that parallel those in modern birds.

An annotated checklist of the cestode parasites of Argentinean wild birds is presented, as the result of a compilation of parasitological papers published between 1900 and April 2021. This review provides data on hosts, geographical distribution, sites of infection, location of material deposited in helminthological collections, references and taxonomic comments. A host/parasite list is also provided. During this period, 38 papers were published that gather information about 34 cestode nominal species and 11 taxa identified at generic level, belonging to three orders, ten families and 35 genera. The highest number of cestode taxa was recorded in the family Hymenolepididae, with 12 nominal species and two taxa identified at generic level, followed by Dilepididae, with eight nominal species and three taxa identified at generic level. Of the 1042 species of birds reported in Argentina, only 29 (2.8%) were reported as hosts of adult cestodes. The families of birds with the highest number of reported taxa were Laridae and Anatidae, with 20 and 14 taxa, respectively.

A large bone from the upper Eocene Totland Bay Formation of Hordle Cliff (Hampshire), originally described by Seeley (1866) as Macrornis tanaupus and interpreted by him as belonging to a ‘large Struthious bird’, is redescribed and illustrated for the first time. It is not a reptile bone, as previously suggested, but the proximal part of a left avian tibiotarsus. A mass estimate of 43 kg, comparable to that of an emu, suggests that it was flightless. A precise identification is difficult because of the incompleteness of the specimen, and Macrornis tanaupus should probably be considered as a nomen dubium. We exclude Seeley’s interpretation as a ratite, as well as previous attributions to gastornithids. We tentatively suggest that the specimen may belong to a phorusrhacid, which would extend the stratigraphic record of this group in Europe by a few million years. The presence of a large terrestrial bird in the upper Eocene of Europe may have a bearing on the interpretation of enigmatic footprints of very large birds from the upper Eocene Paris gypsum.

Diversity changes can be evaluated at various spatial scales, and the relationship between changes in diversity at the local, landscape and regional scales is not evident. The overall patterns of functional and beta diversity of bird assemblages were evaluated along a five-stage urbanization gradient, censused over the months of January to April in the years 2010–2013, in and around Amravati city, Deccan Plateau, Central India. We expected the abundance of large and predatory species to decline along the gradient, and urbanization to homogenize species richness at the landscape level. Overall, 112,829 birds belonging to 89 species were identified in the region, and species richness decreased from the rural forest (73 species) to more urbanized areas (lowest at the centre of Amravaty city with 29 species). Along the urbanization gradient, bird assemblages contained more small species, and the share of frugivorous and omnivorous species also increased, while that of insectivorous species decreased. Diversity partitioning indicated that of the overall pattern, local (alpha) diversity accounted for 50.1% of the total (gamma) diversity, and urbanization stages another 36.2%; the contribution of within-stage, local diversity was rather small (2.7%), indicating fairly homogeneous assemblages.

The Paleocene locality of Menat (Puy-de-Dôme, France) has yielded several avian fossils, which remained poorly studied, even though some were found almost a century ago. Here, we review some of the material in public collections and show that those birds from Menat, which are at least tentatively identifiable, resemble taxa from early Eocene fossil localities. A largely complete skeleton of a medium-sized bird with strong feet shows affinities to the early Eocene Halcyornithidae and Messelasturidae, which are considered to be representatives of the clade including Psittaciformes and Passeriformes. Another skeleton of a small species resembles the Songziidae from the lower Eocene of China, which are representatives of Ralloidea, the clade including Rallidae and Heliornithidae. A new and previously unreported specimen exhibits exceptional soft tissue preservation, in that the bones appear to be largely dissolved but the podotheca of the feet and even the soft parts around the shank are visible; the plumage remains of this specimen furthermore show an unusual bluish hue.

Remains of Late Cretaceous birds are rare, which is especially true for Europe and the type area of the Maastrichtian Stage (southeast Netherlands, northeast Belgium) in particular. In the present paper, we record new remains (isolated tarsometatarsus and radius) that document the presence of both enantiornithine and ornithurine birds in the Maastrichtian area. These fossils, although fragmentary, are important in view of their stratigraphic age: all bird remains discovered to date in the Maastricht area are amongst the youngest ’non-modern’ avians known, originating from strata deposited less than 500,000 years prior to the end of the Cretaceous Period.

Eggshell fragments attributed to large birds have been known from the Palaeogene of southern France for half a century, but reconstructing their original dimensions and identifying the birds that laid the eggs has been fraught with difficulties. On the basis of numerous newly collected specimens and using geometrical calculations, the original size of the thick-shelled eggs is reconstructed, showing that they were slightly larger than ostrich eggs, with a greatest length of 17.8 cm and a mean diameter of 12.0 cm in transversal section. The estimated volume is 1330.4 cm3. The fossil eggs from southern France are thus among the largest known avian eggs, being only surpassed by Aepyornis and some moas. Estimated egg mass is about 1.4 kg. On the basis of egg mass, the body mass of the parent bird is estimated at between 135.4 kg and 156.4 kg, assuming that the hatchlings were precocial. These calculations are in good agreement with the dimensions and mass estimates for the Palaeogene giant bird Gastornis, a probable anseriform, which lived in Europe at the time the eggs were laid. Other large Early Tertiary birds from Europe (Remiornis, Palaeotis) are too small to have laid these eggs. In all likelihood, the large eggs from the Palaeogene of southern France were laid by gastornithid birds.

The first fossil avian feather from Antarctica is reported here, from the early to middle Eocene Fossil Hill Formation at Fildes Peninsula, King George Island, Antarctica. Characteristics such as its form, asymmetry of vanes, closed-pennaceous vanes with barbules and a deep ventral groove indicate that the feather was used for flight. The site from which the feather was collected is known to yield a variety of well-preserved trace fossils, palaeobotanical and palaeoenvironmental remains, suggesting a shorebird ecotype for the owner of this feather, certainly belonging to a Neornithes. The continental position, preservation as an external mould and type of feather makes this specimen a novel and an exceedingly rare record.

A large heterocoelous cervical vertebra from the Late Cretaceous of Cruzy (Hérault, southern France) is described and referred to the giant bird Gargantuavis philoinos Buffetaut & Le Loeuff, 1998, confirming its avian nature. Gargantuavis appears to have been a long-necked bird with possibly a relatively small skull. Derived features such as heterocoely suggest that Gargantuavis was an advanced ornithuromorph, close to ornithurines.

A fragmentary bone from the Dinosaur Park Formation (Campanian) of Dinosaur Provincial Park (Alberta, Canada), originally described as a pterosaur tibiotarsus, is reinterpreted as the distal end of the tibiotarsus of a basal bird, probably an enantiornithine, on the basis of several distinctive characters. It is the first report of such a bird from the Dinosaur Park Formation and shows that this group was present, together with various more derived ornithurines, in the relatively high-latitude environments of Late Cretaceous western Canada.

Philornis is a neotropical, monophyletic genus of Muscidae (Diptera) (Couri et al. 2007) that includes many bird parasites (Skidmore 1985). The interaction system of Philornis and birds is very peculiar: fly adults are free-living and only larvae interact with birds (Couri 1985, 1999; Dodge 1963). Larval trophic habits are known for 22 of the 49 species (de Carvalho et al. 2005) and are divided into three groups: coprophagous (P. aitkeni and P. rufoscutellaris), free-living haematophagous (P. falsificus) and subcutaneous (18 spp.). Philornis downsi is unusual because the first and the early second instars display a subcutaneous phase, whereas the late second and third phases show a nest-dwelling haematophagous phase (Fessl et al. 2006).

The pattern of the evolutionary radiation of modern birds (Neornithes) has been debated for more than 10 years. However, the early fossil record of birds from the Paleogene, in particular, the Lower Eocene, has only recently begun to be used in a phylogenetic context to address the dynamics of this major vertebrate radiation. The Cretaceous-Paleogene (K-P) extinction event dominates our understanding of early modern bird evolution, but climate change throughout the Eocene is known to have also played a major role. The Paleocene and Lower Eocene was a time of avian diversification as a result of favourable global climatic conditions. Deteriorations in climate beginning in the Middle Eocene appear to be responsible for the demise of previously widespread avian lineages like Lithornithiformes and Gastornithidae. Other groups, such as Galliformes display replacement of some lineages by others, probably related to adaptations to a drier climate. Finally, the combination of slowly deteriorating climatic conditions from the Middle Eocene onwards, appears to have slowed the evolutionary rate in Europe, as avian faunas did not differentiate markedly until the Oligocene. Taking biotic factors in tandem with the known Paleogene fossil record of Neornithes has recently begun to illuminate this evolutionary event. Well-preserved fossil taxa are required in combination with ever-improving phylogenetic hypotheses for the inter-relationships of modern birds founded on morphological characters. One key avifauna of this age, synthesised for the first time herein, is the Lower Eocene Fur Formation of Denmark. The Fur birds represent some of the best preserved (often in three dimensions and with soft tissues) known fossil records for major clades of modern birds. Clear phylogenetic assessment of these fossils will prove critical for future calibration of the neornithine evolutionary timescale. Some early diverging clades were clearly present in the Paleocene as evidenced directly by new fossil material alongside the phylogenetically constrained Lower Eocene taxa. A later Oligocene radiation of clades other than Passeriformes is not supported by available fossil data.

The Paleogene (Paleocene–Oligocene) fossil record of birds in Europe is reviewed and recent and fossil taxa are placed into a phylogenetic framework, based on published cladistic analyses. The pre-Oligocene European avifauna is characterized by the complete absence of passeriform birds, which today are the most diverse and abundant avian taxon. Representatives of small non-passeriform perching birds thus probably had similar ecological niches before the Oligocene to those filled by modern passerines. The occurrence of passerines towards the Lower Oligocene appears to have had a major impact on these birds, and the surviving crown-group members of many small arboreal Eocene taxa show highly specialized feeding strategies not found or rare in passeriform birds. It is detailed that no crown-group members of modern ‘families’ are known from pre-Oligocene deposits of Europe, or anywhere else. The phylogenetic position of Paleogene birds thus indicates that diversification of the crown-groups of modern avian ‘families’ did not take place before the Oligocene, irrespective of their relative position within Neornithes (crown-group birds). The Paleogene fossil record of birds does not even support crown-group diversification of Galliformes, one of the most basal taxa of neognathous birds, before the Oligocene, and recent molecular studies that dated diversification of galliform crown-group taxa into the Middle Cretaceous are shown to be based on an incorrect interpretation of the fossil taxa used for molecular clock calibrations. Several taxa that occur in the Paleogene of Europe have a very different distribution than their closest extant relatives. The modern survivors of these Paleogene lineages are not evenly distributed over the continents, and especially the great number of taxa that are today restricted to South and Central America is noteworthy. The occurrence of stem-lineage representatives of many taxa that today have a restricted Southern Hemisphere distribution conflicts with recent hypotheses on a Cretaceous vicariant origin of these taxa, which were deduced from the geographical distribution of the basal crown-group members.

The white-winged guan Penelope albipennis (Aves, Cracidae) is a Critically Endangered bird endemic to northern Peru. We surveyed a protected area suitable for its reintroduction north of the species' current range. Following IUCN guidelines, four factors were evaluated: diversity and quantity of plant species that are part of the white-winged guan's diet, year-round water sources, resting and roosting cover, and extent of undisturbed forest. Several suitable small valleys or quebradas were inspected, but our evaluation focused on three. We identified all shrub and tree species to compare with habitat currently used by the guan. Cover for nesting places was assessed visually. We found species composition and microhabitat types to be similar to habitat presently used by wild guans. Thus, all habitat components are favourable for reintroduction. The high degree of protection of the area makes it particularly suitable as a reintroduction site. We recommend experimental extension of the species current range to mitigate the risk of extinction posed by catastrophic events.

This paper reviews the current state of knowledge of the avian basophilic leukocyte. It includes a description of the general morphology of the cell derived from light and electron microscopy. The relative and absolute counts of basophils in different species are described, including the current status of the cytochemical constituents in their characteristic granules. The role of the basophil during the acute inflammatory response following exposure to non-infectious and infectious agents is examined. In birds basophils appear to play an important role in early inflammatory and immediate hypersensitivity reactions, but differ from those in mammals by not contributing to delayed hypersensitivity. They are crucial participants in cutaneous basophilic hyper-sensitivity reactions and in passive cutaneous and systemic anaphylaxis. The role of the basophil in the stress response in birds is discussed. When some birds are exposed to severe stress a basophilia develops – a physiological response that may be unique to birds.