Among white-bellied glossy swiftlets of the Collocalia group, A. R. Wallace was first to recognise the Makassar Strait, separating Borneo and Sulawesi, as a geographical barrier between different phenotypes: plain-tailed to the west and spot-tailed to the east. Other morphological characters used to define species within the group have been blue or green gloss to the dorsal plumage, and the presence or absence of a single minute tufted feather on the hallux. The value of these characters as taxonomic markers is now known to be unreliable due to the discovery of phenotypically mixed populations east of the Makassar Strait, from North Maluku province, I ndonesia, through Papua New Guinea to New Ireland. We combine field observations of plumage characters with genetic evidence to establish taxonomy of Collocalia group swiftlets. Sequencing specific mitochondrial genes (Cytb and ND2), the nuclear-encoded Fib gene, and a subset of mitochondrial genomes provided data for phylogenetic analysis. Genetic divergence of c.4.7% is observed between two Collocalia clades either side of the Makassar Strait: the plain-tailed C. affinis cyanoptila sampled at Fraser's Hill, Peninsular Malaysia, and a phenotypically mixed population of C. esculenta spilura from North Maluku, Indonesia. Each population formed high-affinity genetic clades, within which divergence was <0.5%. These findings are consistent with geographic but not phenotypic separation between populations. We therefore conclude taxonomy based on these plumage features in glossy swiftlets of the Collocaliini is unreliable.

A revision of large extinct members of Strigidae described from Quaternary cave deposits in Cuba here reduces the number of valid taxa from five to three. Ornimegalonyx oteroiArredondo, 1958a, is the only valid species of the four previously described in the genus. The type series of Bubo osvaldoiArredondo & Olson, 1994, is revealed to be a composite, comprising two different species in the genera Bubo Duméril, 1805, and OrnimegalonyxArredondo, 1958a, with the latter described herein as a new, diminutive species.

The case for recognising Bahama Nuthatch Sitta insularis as a species separate from Brown-headed Nuthatch S. pusilla has been made several times since 2004, based on plumage, morphometrics, voice and genetic distance, but only one of four world lists currently accepts it as such. We assembled three new sets of recordings and recently published evidence on playback responses. We found that S. insularis has at least five vocalisations that are homologous to but always much higher pitched (by 2–3 kHz) than those of S. pusilla, such that the main calls of the latter are strikingly different from those of the former, and playback studies all suggest a consistently weak response in one species to the calls of the other. Moreover, genetic divergence of insularis from mainland pusilla is greater than that of another Bahamian taxon, Bahama Warbler Setophaga flavescens, recently accepted by all world lists as a species, from mainland Yellow-throated Warbler S. dominica. Taken together with the notably larger bill of Sitta insularis, these factors reinforce the case for treating Bahama Nuthatch as a (regrettably now almost certainly extinct) species.

One of us (SMH) surveyed the Ninigo and Hermit Islands (27 January–13 February and 2–14 October 2019), providing the first observations of birds on these islands for c.50 years. KDB collated data from the unpublished diaries of W. F. Coultas, a member of the Whitney South Sea Expedition, including observations from the nearby Kaniet and Sae Islands. Four new landbirds, in addition to six new shorebirds and five new seabirds, were added to the list of birds for these poorly known islands, bringing the total list to 59 species. We also document significant extensions of the known breeding ranges of Brown Noddy Anous stolidus, Black Noddy A. minutus and Red-footed Booby Sula sula. The biological importance of the West Melanesian Trench is further emphasised by our seabird observations.

New Guinea's mountains consist today of the high Central Range, plus ten isolated lower outlying ranges. But during Pleistocene periods of low sea level, when New Guinea's current shallow continental shelf was exposed as dry land, the main island included further outliers that subsequently became cut off as land-bridge islands as rising sea levels submerged the shelf connecting them to New Guinea. We surveyed the upland avifauna of Yapen, the highest of those land-bridge islands. Yapen supports 26 upland species. That number is higher than on nearby oceanic islands of similar elevation, because Yapen in contrast to oceanic islands could acquire species overland during the Pleistocene. However, that number is much lower than on New Guinea's outliers of similar elevation, due to extinctions of many of Yapen's populations following its isolation as an island.

Of New Guinea's 193 upland species, some are much more widely distributed on the ten outliers than the rest. Yapen's upland species, and those of the other land-bridge islands, are a small subset of those successful colonists of mainland outliers. Part of the explanation for differential success is that only species whose elevational floors lie well below the summits of the outliers and of Yapen are likely to have survived on or colonised those mountains, all much lower than New Guinea's Central Range. For the remainder, we infer that more than half of Yapen's former upland populations have gone extinct since Yapen's isolation. For those species with poor ability to disperse overwater, abundance is a predictor of survival and continued presence on Yapen—as expected from the inverse relationship between extinction risk and population size.

We identify half-a-dozen mechanisms for colonisation by upland species: dispersal overwater when Yapen was an island; regular post-breeding descent to the lowlands; irregular straggling to the lowlands; dispersal through flat lowlands; dispersal over hill bridges; and dispersal during cool Pleistocene phases, when some current upland species had lowland populations. Relict sets of those mostly vanished Pleistocene lowland populations survive on three remnant fragments of southern New Guinea's former Arafura platform: on the Aru Islands, New Guinea's Fly River bulge, and the northern tip of Australia's Cape York Peninsula.

Compared to the outlying mountain ranges of New Guinea and surrounding islands, the known avifauna of Yapen Island numbers fewer upland species than expected, perhaps reflecting reduced coverage by ornithologists. In particular, the eastern portion of Yapen's uplands remained ornithologically unexplored until September 2019, when a seven-day expedition reached an elevation of 1,315 m, and documented three new species for the island. Two (Black-eared Catbird Ailuroedus melanotis and Yellow-legged Flyrobin Kempiella griseoceps) are widespread across the other outlying ranges and were therefore expected to occur on Yapen, whereas the third (Dimorphic Jewel-babbler Ptilorrhoa geislerorum) concerns a presumably isolated population of a species otherwise known from south-east New Guinea.

Maranhão Hermit Phaethornis maranhaoensis is endemic to Brazil, where it occurs in the states of Piauí, Maranhão, Tocantins, Pará, Mato Grosso and Goiás. Nothing has been published concerning its breeding biology. We present the first descriptions of the nest, eggs and nestlings of P. maranhaoensis, with data on nestling development. We found four nests in the understorey of closed-canopy forest in eastern Maranhão. All four nests were attached to the undersides of babaçu palm fronds (Attalea speciosa), and were constructed of plant material and moss, bound together with spider webs. Nests are similar to those of other Phaethornis, conical and attached to the tip of the frond. They were sited at a mean height of 71.5 ± 21.3 cm above ground, and were 23.6 ± 1.8 cm in height, with an external diameter of 41.7 ± 2.7 mm, internal diameter 18.4 ± 3.7 mm, and the incubation chamber was 24.5 ± 3.1 mm deep (n = 4). Eggs are white and elliptical, measuring 11.9 ± 0.2 × 7.8 ± 0.1 mm, with a mean mass of 0.4 ± 0.05 g (n = 4). Our observations indicate that the species' breeding season occupies November–April.

The western and trans-Andean populations of Striped Woodhaunter Automolus subulatus are sometimes considered separate species. We discuss previously published data on the nesting of Striped Woodhaunter and present novel information concerning the nest, eggs, nestlings and parental care of western A. s virgatus and trans-Andean A. s. subulatus. Nest placement and architecture of the two populations are similar to each other and to other Automolus species. However, Striped Woodhaunter build shorter nest tunnels than other related species and genera. All similarities in nest design, nestbuilding behaviour and parental care presented herein support the genetic clade including Automolus, Thripadectes and Clibanornis, but do not differentiate between the subspecies of Striped Woodhaunter. More studies are required about adult attendance and nest design within this clade, taking into account more samples across the species' range.