Cretaceous origins of the vibrotactile bill-tip organ in birds

Some probe-foraging birds locate their buried prey by detecting mechanical vibrations in the substrate using a specialized tactile bill-tip organ comprising mechanoreceptors embedded in densely clustered pits in the bone at the tip of their beak. This remarkable sensory modality is known as ‘remote touch’, and the associated bill-tip organ is found in probe-foraging taxa belonging to both the palaeognathous (in kiwi) and neognathous (in ibises and shorebirds) clades of modern birds. Intriguingly, a structurally similar bill-tip organ is also present in the beaks of extant, non-probing palaeognathous birds (e.g. emu and ostriches) that do not use remote touch. By comparison with our comprehensive sample representing all orders of extant modern birds (Neornithes), we provide evidence that the lithornithids (the most basal known palaeognathous birds which evolved in the Cretaceous period) had the ability to use remote touch. This finding suggests that the occurrence of the vestigial bony bill-tip organ in all modern non-probing palaeognathous birds represents a plesiomorphic condition. Furthermore, our results show that remote-touch probe foraging evolved very early among the Neornithes and it may even have predated the palaeognathous–neognathous divergence. We postulate that the tactile bony bill-tip organ in Neornithes may have originated from other snout tactile specializations of their non-avian theropod ancestors.     

Remote touch prey‐detection by Madagascar crested ibises Lophotibis cristata urschi

Birds that forage by probing must often rely on sensory systems other than vision to detect their buried prey. Such senses may include hearing (e.g. Australian magpies (Atramidae), American robins (Turdidae)) or chemical senses/olfaction (e.g. kiwi (Apterygidae) and some shorebirds (Scolopacidae)). Probe foraging kiwi and shorebirds are also able to use vibrotactile cues to locate prey buried in the substrate at some distance from their bill‐tips (‘remote touch’). These birds possess an organ consisting of a honey‐comb of sensory pits in bone of the bill‐tips, packed with mechanoreceptive nerve ending (Herbst corpuscles). Such a bill‐tip organ has recently also been described in ibises (Threskiornithinae), but its function not elucidated. We designed a foraging experiment presenting mealworm prey to three captive Madagascar crested ibises Lophotibis cristata urschi under a variety of trial conditions to discover whether they were using remote touch, mediated by their bill‐tip organ; chemosense/olfaction; or hearing to locate buried prey. The ibises were reliant on remote touch for prey detection – the first time this sensory system has been demonstrated for this group of birds. They did not appear to use hearing or chemical senses/olfaction to aid in prey detection.     

Interordinal relationships of birds and other reptiles based on whole mitochondrial genomes

Several different groups of birds have been proposed as being the oldest or earliest diverging extant lineage within the avian phylogenetic tree, particularly ratites (Struthioniformes), waterfowl (Anseriformes), and shorebirds (Charadriiformes). Difficulty in resolving this issue stems from several factors, including the relatively rapid radiation of primary (ordinal) bird lineages and the lack of characters from an extant outgroup for birds that is closely related to them by measure of time. To help resolve this question, we have sequenced entire mitochondrial genomes for five birds (a rhea, a duck, a falcon, and two perching birds), one crocodilian, and one turtle. Maximum parsimony and maximum likelihood analyses of these new sequences together with published sequences (18 taxa total) yield the same optimal tree topology, in which a perching bird (Passeriformes) is sister to all the other bird taxa. A basal position for waterfowl among the bird study taxa is rejected by maximum likelihood analyses. However, neither the conventional view, in which ratites (including rhea) are basal to other birds, nor tree topologies with falcon or chicken basal among birds could be rejected in the same manner. In likelihood analyses of a subset of seven birds, alligator, and turtle (9 taxa total), we find that increasing the number of parameters in the model shifts the optimal topology from one with a perching bird basal among birds to the conventional view with ratites diverging basally; moreover, likelihood scores for the two trees are not significantly different. Thus, although our largest set of taxa and characters supports a tree with perching birds diverging basally among birds, the position of this earliest divergence among birds appears unstable. Our analyses indicate a sister relationship between a waterfowl/chicken clade and ratites, relative to perching birds and falcon. We find support for a sister relationship between turtles and a bird/crocodilian clade, and for rejecting both the Haemothermia hypothesis (birds and mammals as sister taxa) and the placement of turtles as basal within the phylogenetic tree for amniote animals.     

The sensory trigeminal system in birds: input, organization and effects of peripheral damage. A review.

The primary sensory trigeminal system in birds comprises the mesencephalic trigeminal nucleus and the trigeminal ganglion with projections to the principal sensory nucleus (PrV) and the descending tract with its subnuclei. Other cranial nerves can contribute to PrV and the descending system that together form the somatosensory system of the head. There is also a proprioceptive component. The somatosensory system comprises a component serving tactile sense and a nociceptive component. The former processes information from many mechanoreceptors in beak and tongue; both PrV and subnuclei of the descending system are involved. The nociceptive component consists of small ganglion cells projecting presumably to layers I and II of the caudal subnucleus of the descending trigeminal system and cervical dorsal horn; this is the only trigeminal region showing immunoreactivity for substance P. The effects of amputation of the tips of the beak of chickens (debeaking) are estimated by fiber counts in electron microscopic preparations of the trigeminal branches innervating that area, and by cell counts in Nissl stained sections of the trigeminal ganglion. Our data indicate that debeaking causes a loss of exteroceptive units, but not of nociceptive units. Comparison of sections stained for the presence of substance P (immunohistochemistry) did not reveal a long-term effect on the nociceptive system suggestive of the occurrence of chronic pain.     

Medium‐term changes in coastal bird communities in the Western Cape,South Africa

There are few studies of medium‐term, quantitative changes in faunal communities in the southern hemisphere. The linear nature of coastlines makes populations of coastal birds easy to count. Repeat surveys of 278 km of coastline in three regions of the Western Cape, South Africa show marked differences in coastal bird community structure over the last 30 years, despite limited human impacts on coastal habitats (mainly increased human disturbance). The total number of birds has not changed, but species richness increased following colonization of the coast by Egyptian geese (Alopochen aegyptiaca, Anatidae) and three species of ibises (Threskiornithidae). Biomass also increased due to greater numbers of large‐bodied birds. Contrary to the prediction that large birds are more susceptible to human disturbance, most small birds decreased in abundance. Among waders that breed along the coastline, numbers of African oystercatchers (Haematopus moquini, Haematopodidae) doubled, linked to increased food availability following invasions by alien mussels (Mytilidae). By comparison, numbers of white‐fronted plovers (Charadrius marginatus, Charadriidae) decreased by 37% (59% close to Cape Town), at least in part as a result of increasing human disturbance. The greatest decreases occurred among migrant waders (Scolopacidae and Charadriidae), with numbers of the four most abundant species falling by >50%, and both common Calidris species by >90%. Migrant wader populations decreased in all three regions, irrespective of whether surveys were in protected areas or not, suggesting that factors outside the region are driving these trends. Some species may have decreased due to changes in their preferred wintering areas, but others probably reflect population decreases, confirming the generally poor conservation status of migrant waterbirds worldwide.     

Vocal cooperation between the sexes in Little Spotted Kiwi Apteryx owenii

Sexual call dimorphism in birds is usually associated with sexual size dimorphism. Departures from this relationship can be used to infer call function, but research into inter‐sexual call differences, as with song function in general, has been restricted by a bias towards male passerines. The nocturnal and flightless New Zealand kiwi (Apterygidae) are acoustically similar but taxonomically and ecologically very different from other birds, so provide a contrast in exploring avian call function and evolution. However, kiwi acoustic ecology is poorly understood, with the calls of only one of the five kiwi species spectrally described, and acoustic differences between the sexes virtually unknown. We conducted the first bioacoustic study of Little Spotted Kiwi Apteryx owenii, and assessed sexual call dimorphism in this species. There were significant inter‐sexual differences in call temporal and frequency characteristics that were not related to size dimorphism. Contribution to duets and variation in temporal structure with call context also differed between the sexes. We suggest that these differences indicate divergent call function, with male calls more suited for territory defence, and female calls for pair contact. There was a striking lack of overlap in the frequency spectrum distributions of male and female calls, which was also unrelated to size and was further emphasized by the presence of formants in female calls. We propose that this provides evidence for inter‐sexual acoustic cooperation in call frequency, of a type which to our knowledge has not previously been described in birds. This may result from selection for enhanced joint resource defence in kiwi.     

Maintenance and dissemination of avian-origin influenza A virus within the northern Atlantic Flyway of North America

Wild waterbirds, the natural reservoirs for avian influenza viruses, undergo migratory movements each year, connecting breeding and wintering grounds within broad corridors known as flyways. In a continental or global view, the study of virus movements within and across flyways is important to understanding virus diversity, evolution, and movement. From 2015 to 2017, we sampled waterfowl from breeding (Maine) and wintering (Maryland) areas within the Atlantic Flyway (AF) along the east coast of North America to investigate the spatio-temporal trends in persistence and spread of influenza A viruses (IAV). We isolated 109 IAVs from 1,821 cloacal / oropharyngeal samples targeting mallards (Anas platyrhynchos) and American black ducks (Anas rubripes), two species having ecological and conservation importance in the flyway that are also host reservoirs of IAV. Isolates with >99% nucleotide similarity at all gene segments were found between eight pairs of birds in the northern site across years, indicating some degree of stability among genome constellations and the possibility of environmental persistence. No movement of whole genome constellations were identified between the two parts of the flyway, however, virus gene flow between the northern and southern study locations was evident. Examination of banding records indicate direct migratory waterfowl movements between the two locations within an annual season, providing a mechanism for the inferred viral gene flow. Bayesian phylogenetic analyses provided evidence for virus dissemination from other North American wild birds to AF dabbling ducks (Anatinae), shorebirds (Charidriformes), and poultry (Galliformes). Evidence was found for virus dissemination from shorebirds to gulls (Laridae), and dabbling ducks to shorebirds and poultry. The findings from this study contribute to the understanding of IAV ecology in waterfowl within the AF.     

Inducible Prrxl1-CreER(T2) recombination activity in the somatosensory afferent pathway

Prrxl1-CreER(T2) transgenic mice expressing tamoxifen-inducible Cre recombinase were generated by modifying a Prrxl1-containing BAC clone. Cre recombination activity was examined in Prrxl1-CreER(T2); Rosa26 reporter mice at various embryonic and postnatal stages. Pregnant mice were treated with a single dose of tamoxifen at embryonic day (E) 9.5 or E12.5, and X-gal staining was performed 2 days later. Strong X-gal staining was observed in the somatosensory ganglia (e.g., dorsal root and trigeminal ganglia) and the first central sites for processing somatosensory information (e.g., spinal dorsal horn and trigeminal nerve-associated nuclei). When tamoxifen was administered at postnatal day (P) 20 or in adulthood (P120), strong Cre recombination activity was present in the primary somatosensory ganglia, while weak Cre recombination activity was found in the spinal dorsal horn, mesencephalic trigeminal nucleus, principal sensory trigeminal nucleus, and spinal trigeminal nucleus. This mouse line provides a useful tool for exploring genes' functions in the somatosensory system in a time-controlled way.     

The costs of migration: Injuries in migratory waterbirds along the west coast of India

The long distant, transcontinental migration of shorebirds entails many well identified costs in terms of time, energy, and direct mortality risk. Injuries from debris or from human structures and activities were observed as the major reasons for the direct mortality of shorebirds during migration worldwide. We recorded injured birds in major coastal wetlands of Kerala, for a period of 15 years from 2005 to 2019. The injured birds were observed in 9 different sites in various districts of Kerala. The highest instances of injuries were observed in Kadalundi-Vallikunnu Community Reserve, the major wintering and stop over site of migrant shorebirds in the west coast of India. During the study period, fifty-eight individuals of shorebirds belonging to four families were found to be injured. The highest proportion of injuries was recorded among the families Scolopacidae and Charadriidae comprising long distance migrant shorebird species and the lowest among Laridae and Ardeidae. We recommend that environmental authorities pay special attention to minimize anthropogenic debris along the flyways used by migratory birds thereby reducing the risk of injuries to some of these species. Proactive measures such as removal of discarded fishing gear or plastic debris from wintering areas as well as stopover areas could greatly reduce injuries in migratory birds arising from anthropogenic sources.     

Functional implications of species differences in the size and morphology of the isthmo optic nucleus (ION) in birds

In birds, there is a retinofugal projection from the brain to the retina originating from the isthmo optic nucleus (ION) in the midbrain. Despite a large number of anatomical, physiological and histochemical studies, the function of this retinofugal system remains unclear. Several functions have been proposed including: gaze stabilization, pecking behavior, dark adaptation, shifting attention, and detection of aerial predators. This nucleus varies in size and organization among some species, but the relative size and morphology of the ION has not been systematically studied. Here, we present a comparison of the relative size and morphology of the ION in 81 species of birds, representing 17 different orders. Our results show that several orders of birds, besides those previously reported, have a large, well-organized ION, including: hummingbirds, woodpeckers, coots and allies, and kingfishers. At the other end of the spectrum, parrots, herons, waterfowl, owls and diurnal raptors have relatively small ION volumes. ION also appears to be absent or unrecognizable is several taxa, including one of the basal avian groups, the tinamous, which suggests that the ION may have evolved only in the more modern group of birds, Neognathae. Finally, we demonstrate that evolutionary changes in the relative size and the cytoarchitectonic organization of ION have occurred largely independent of phylogeny. The large relative size of the ION in orders with very different lifestyles and feeding behaviors suggest there is no clear association with pecking behavior or predator detection. Instead, our results suggest that the ION is more complex and enlarged in birds that have eyes that are emmetropic in some parts of the visual field and myopic in others. We therefore posit that the ION is involved in switching attention between two parts of the retina i.e. from an emmetropic to a myopic part of the retina.     

Mitochondrial and nuclear DNA sequences support a Cretaceous origin of Columbiformes and a dispersal-driven radiation in the Paleocene

Phylogenetic relationships among genera of pigeons and doves (Aves, Columbiformes) have not been fully resolved because of limited sampling of taxa and characters in previous studies. We therefore sequenced multiple nuclear and mitochondrial DNA genes totaling over 9000 bp from 33 of 41 genera plus 8 outgroup taxa, and, together with sequences from 5 other pigeon genera retrieved from GenBank, recovered a strong phylogenetic hypothesis for the Columbiformes. Three major clades were recovered with the combined data set, comprising the basally branching New World pigeons and allies (clade A) that are sister to Neotropical ground doves (clade B), and the Afro-Eurasian and Australasian taxa (clade C). None of these clades supports the monophyly of current families and subfamilies. The extinct, flightless dodo and solitaires (Raphidae) were embedded within pigeons and doves (Columbidae) in clade C, and monophyly of the subfamily Columbinae was refuted because the remaining subfamilies were nested within it. Divergence times estimated using a Bayesian framework suggest that Columbiformes diverged from outgroups such as Apodiformes and Caprimulgiformes in the Cretaceous before the mass extinction that marks the end of this period. Bayesian and maximum likelihood inferences of ancestral areas, accounting for phylogenetic uncertainty and divergence times, respectively, favor an ancient origin of Columbiformes in the Neotropical portion of what was then Gondwana. The radiation of modern genera of Columbiformes started in the Early Eocene to the Middle Miocene, as previously estimated for other avian groups such as ratites, tinamous, galliform birds, penguins, shorebirds, parrots, passerine birds, and toucans. Multiple dispersals of more derived Columbiformes between Australasian and Afro-Eurasian regions are required to explain current distributions.     

An assessment of the diversity of early Miocene Scolopaci (Aves,Charadriiformes) from Saint‐Gérand‐le‐Puy (Allier,France)

Abstract: ‘Totanus’lartetianus, Elorius paludicola and ‘Tringa’gracilis are the three scolopacid birds from the early Miocene of Saint‐Gérand‐le‐Puy described by the French palaeontologist Milne‐Edwards in the 19th century. Since then, no revision of these taxa has been performed. Our re‐examination revealed that not much of the material originally assigned to ‘Totanus’lartetianus can be retained within the species. Presumably plesiomorphic features of the humerus – and potentially the coracoid we attributed to this taxon – indicate that it is misplaced in the extant scolopacid genus and may not even belong to the Scolopacidae (sandpipers and allies), and we therefore place it in the new genus Scolopacimilis. Comparisons of the material assigned to Elorius paludicola and ‘Tringa’gracilis show that they are morphologically similar, both exhibiting distinct scolopacid anatomical features. The latter, however, cannot be referred to the extant taxon Tringa and is classified into the new genus Parvelorius. We further introduce three new species, ?Elorius limosoides sp. nov., and ?Parvelorius calidris sp. nov., which we have tentatively assigned to the extinct scolopacid genera Elorius and Parvelorius, respectively, and Becassius charadriioides gen. et. sp. nov., which, together with Scolopacimilis, display a morphology uncharacteristic for extant Scolopaci. For the first time we have assigned skulls to some of the postcranial elements described in this study. The presence of at least six species of Scolopaci from the early Miocene considerably increases the number of members of the group known from this time.     

Temporal and environmental influences on the vocal behaviour of a nocturnal bird

Temporal and environmental variation in vocal activity can provide information on avian behaviour and call function not available to short‐term experimental studies. Inter‐sexual differences in this variation can provide insight into selection effects. Yet factors influencing vocal behaviour have not been assessed in many birds, even those monitored by acoustic methods. This applies to the New Zealand kiwi (Apterygidae), for which call censuses are used extensively in conservation monitoring, yet which have poorly understood acoustic ecology. We investigated little spotted kiwi Apteryx owenii vocal behaviour over 3 yr, measuring influences on vocal activity in both sexes from time of night, season, weather conditions and lunar cycle. We tested hypotheses that call rate variation reflects call function, foraging efficiency, historic predation risk and variability in sound transmission, and that there are inter‐sexual differences in call function. Significant seasonal variation showed that vocalisations were important in kiwi reproduction, and inter‐sexual synchronisation of call rates indicated that contact, pair‐bonding or resource defence were key functions. All weather variables significantly affected call rates, with elevated calling during increased humidity and ground moisture indicating a relation between vocal activity and foraging conditions. A significant decrease in calling activity on cloudy nights, combined with no moonlight effect, suggests an impact of light pollution in this species. These influences on vocal activity provide insight into kiwi call function, have direct consequences for conservation monitoring of kiwi, and have wider implications in understanding vocal behaviour in a range of nocturnal birds.     

Bone growth marks reveal protracted growth in New Zealand kiwi (Aves,Apterygidae)

The presence of bone growth marks reflecting annual rhythms in the cortical bone of non-avian tetrapods is now established as a general phenomenon. In contrast, ornithurines (the theropod group including modern birds and their closest relatives) usually grow rapidly in less than a year, such that no annual rhythms are expressed in bone cortices, except scarce growth marks restricted to the outer cortical layer. So far, cyclical growth in modern birds has been restricted to the Eocene Diatryma, the extant parrot Amazona amazonica and the extinct New Zealand (NZ) moa (Dinornithidae). Here we show the presence of lines of arrested growth in the long bones of the living NZ kiwi (Apteryx spp., Apterygidae). Kiwis take 5–6 years to reach full adult body size, which indicates a delayed maturity and a slow reproductive cycle. Protracted growth probably evolved convergently in moa and kiwi sometime since the Middle Miocene, owing to the severe climatic cooling in the southwest Pacific and the absence of mammalian predators.     

Environmental influences on the orientation of free-flying nocturnal bird migrants

Autumn nocturnal bird migration was investigated using radar and visual observations. Multivariate analyses assessed the influence of environmental variables on orientation. Two categories of birds were distinguished: (1) shorebirds and waterfowl migrating in flocks; and (2) passerine birds flying singly. These two classes of migrants employ different orientation mechanisms. Landbirds selectively flew with the wind, regardless of its direction or speed or whether the skies were clear or overcast. Shorebirds and waterfowl flew in directions independent of wind in light or moderate winds. The accuracy of passerine orientation was not correlated with any of the variables examined. The passerine orientation observed cannot be accounted for by stellar orientation, but is explicable via orientation on the basis of wind direction.     

Evidence for an auditory fovea in the New Zealand kiwi (Apteryx mantelli)

Kiwi are rare and strictly protected birds of iconic status in New Zealand. Yet, perhaps due to their unusual, nocturnal lifestyle, surprisingly little is known about their behaviour or physiology. In the present study, we exploited known correlations between morphology and physiology in the avian inner ear and brainstem to predict the frequency range of best hearing in the North Island brown kiwi. The mechanosensitive hair bundles of the sensory hair cells in the basilar papilla showed the typical change from tall bundles with few stereovilli to short bundles with many stereovilli along the apical-to-basal tonotopic axis. In contrast to most birds, however, the change was considerably less in the basal half of the epithelium. Dendritic lengths in the brainstem nucleus laminaris also showed the typical change along the tonotopic axis. However, as in the basilar papilla, the change was much less pronounced in the presumed high-frequency regions. Together, these morphological data suggest a fovea-like overrepresentation of a narrow high-frequency band in kiwi. Based on known correlations of hair-cell microanatomy and physiological responses in other birds, a specific prediction for the frequency representation along the basilar papilla of the kiwi was derived. The predicted overrepresentation of approximately 4-6 kHz matches potentially salient frequency bands of kiwi vocalisations and may thus be an adaptation to a nocturnal lifestyle in which auditory communication plays a dominant role.     

A phylogenetic analysis of basal Anseriformes, the fossil Presbyornis, and the interordinal relationships of waterfowl

A phylogenetic analysis of 123 morphological characters of basal waterfowl (Aves: Anseriformes) and other selected avian orders confirmed that the screamers (Anhimae: Anhitn-idae) are the sister-group of other waterfowl (Anseres), and that the magpie goose (Anseranatidae: Anseranas semipalmata) is the sister group of other modern waterfowl exclusive of screamers (Anatidae sensu stricto). The analysis also supports the traditional hypothesis of the gallinaceous birds (Galliformes) as the sister group of the Anseriformes. Presbyornis, a fossil from the early Eocene of Wyoming and averred by Olson & Feduccia as showing that the Anseriformes were derived from shorebirds (Charadriiformes), was found to represent the sister group of the Anatidae. Associated hypotheses by Olson & Feduccia concerning the implications of Presbyornis for the phylogenetic relationships of flamingos (Phoenicopteriformes), the position of the Anhimidae within the waterfowl, relationships among modern Anatidae, and a plausible evolutionary scenario for waterfowl also are rejected. Analyses revealed that cranial characters were critical to the establishment of the Galliformes as the sister group of the Anseriformes; exclusion of the Anhimidae, especially in combination with Anseranas, also undermined the support for this inference. Placement of Presbyornis as the sister group of the Anatidae casts doubt on the role suggested by Feduccia of ‘transitional shorebirds' in the origin of modern avian orders, and calls into question the concept of ‘fossil mosaics’. The phylogenetic hypothesis is used to reconstruct an evolutionary scenario for selected ecomorphological characters in the galliform-anseriform transition, to predict the most parsimonious states of these characters for Presbyornis, and to propose a phylogenetic classification of the higher-order taxa of waterfowl. This re-examination of Presbyornis also is used to exemplify the fundamental methodological shortcomings of the intuitive approach to the reconstruction of phylogenetic relationships.     

Influenza in migratory birds and evidence of limited intercontinental virus exchange

Migratory waterfowl of the world are the natural reservoirs of influenza viruses of all known subtypes. However, it is unknown whether these waterfowl perpetuate highly pathogenic (HP) H5 and H7 avian influenza viruses. Here we report influenza virus surveillance from 2001 to 2006 in wild ducks in Alberta, Canada, and in shorebirds and gulls at Delaware Bay (New Jersey), United States, and examine the frequency of exchange of influenza viruses between the Eurasian and American virus clades, or superfamilies. Influenza viruses belonging to each of the subtypes H1 through H13 and N1 through N9 were detected in these waterfowl, but H14 and H15 were not found. Viruses of the HP Asian H5N1 subtypes were not detected, and serologic studies in adult mallard ducks provided no evidence of their circulation. The recently described H16 subtype of influenza viruses was detected in American shorebirds and gulls but not in ducks. We also found an unusual cluster of H7N3 influenza viruses in shorebirds and gulls that was able to replicate well in chickens and kill chicken embryos. Genetic analysis of 6,767 avian influenza gene segments and 248 complete avian influenza viruses supported the notion that the exchange of entire influenza viruses between the Eurasian and American clades does not occur frequently. Overall, the available evidence does not support the perpetuation of HP H5N1 influenza in migratory birds and suggests that the introduction of HP Asian H5N1 to the Americas by migratory birds is likely to be a rare event.     

Is the occurrence of avian influenza virus in Charadriiformes species and location dependent?

Birds in the order Charadriiformes were sampled at multiple sites in the eastern half of the continental USA, as well as at Argentina, Chile, and Bermuda, during 1999-2005, and tested for avian influenza virus (AIV). Of more than 9,400 birds sampled, AIV virus was isolated from 290 birds. Although Ruddy Turnstones (Arenaria interpres) comprised just 25% of birds sampled, they accounted for 87% of isolates. Only eight AIV isolations were made from birds at four locations outside of the Delaware Bay, USA, region; six of these were from gulls (Laridae). At Delaware Bay, AIV isolations were predominated by hemagglutinin (HA) subtype H10, but subtype diversity varied each year. These results suggest that AIV infection among shorebirds (Scolopacidae) may be localized, species specific, and highly variable in relation to AIV subtype diversity.     

Anatomical specializations for nocturnality in a critically endangered parrot, the Kakapo (Strigops habroptilus)

The shift from a diurnal to nocturnal lifestyle in vertebrates is generally associated with either enhanced visual sensitivity or a decreased reliance on vision. Within birds, most studies have focused on differences in the visual system across all birds with respect to nocturnality-diurnality. The critically endangered Kakapo (Strigops habroptilus), a parrot endemic to New Zealand, is an example of a species that has evolved a nocturnal lifestyle in an otherwise diurnal lineage, but nothing is known about its' visual system. Here, we provide a detailed morphological analysis of the orbits, brain, eye, and retina of the Kakapo and comparisons with other birds. Morphometric analyses revealed that the Kakapo's orbits are significantly more convergent than other parrots, suggesting an increased binocular overlap in the visual field. The Kakapo exhibits an eye shape that is consistent with other nocturnal birds, including owls and nightjars, but is also within the range of the diurnal parrots. With respect to the brain, the Kakapo has a significantly smaller optic nerve and tectofugal visual pathway. Specifically, the optic tectum, nucleus rotundus and entopallium were significantly reduced in relative size compared to other parrots. There was no apparent reduction to the thalamofugal visual pathway. Finally, the retinal morphology of the Kakapo is similar to that of both diurnal and nocturnal birds, suggesting a retina that is specialised for a crepuscular niche. Overall, this suggests that the Kakapo has enhanced light sensitivity, poor visual acuity and a larger binocular field than other parrots. We conclude that the Kakapo possesses a visual system unlike that of either strictly nocturnal or diurnal birds and therefore does not adhere to the traditional view of the evolution of nocturnality in birds.