Journal of Avian Biology

I examined a total of 27,581 images of 6.345 individuals from the Cornell Lab of Ornithologys Macaulay Library to clarify conflicting reports on molt and plumage strategies in eight species of hummingbirds that breed or have bred primarily in the southwestern United States. Fixed replacement sequences from two nodes among primaries and two nodes among secondaries were found without exception, conforming to the findings of previous studies. I concluded that the preformative molt is limited to partial in three species, partial to incomplete in three species, partial to complete in one species, and complete in one species. These molt strategies could be interpreted as having differentiated through synapomorphy, with species between currently recognized clades varying in the extent of their preformative molts; however, given the plastic nature of molt strategies, I predict that this variation will be shaped more by environmental factors than by synapomorphy. Results of this study additionally clarify molt terminology in Trochilidae as based on homologies and establish new criteria for age determinations. The Macaulay Library clearly provides an important resource for the investigation of avian molts and plumages. The results of a validation exercise that I conducted indicate that banders and field ornithologists with a wide range of previous experience can collect accurate data in this manner. I present a road map for such studies and suggest many other questions on avian molt that can also be investigated, including how timing of molts vary geographically and by habitat and how remigial replacement sequences proceed in little-known bird families. I encourage contributors to the Macaulay Library to take and upload images of birds in molt or in worn plumages.

Understanding how migratory birds balance energetic costs of movement with wintering benefits requires quantifying their energy expenditure across the full annual cycle. Here, we present a novel approach to reconstruct annual energy budget from multi-sensor geolocator data on atmospheric pressure and activity. We apply this method to tracking data of Eurasian Wrynecks from a European breeding population exhibiting striking variation in migration distance: short-distance migration to southern Europe, medium-distance to northern Africa, and long-distance to sub-Saharan Africa. Long-distance migrants had 21-26% lower annual energy expenditure than shorter-distance migrants, primarily due to reduced thermoregulation costs during boreal winter. However, they faced extreme physiological demands during migration, with daily energy expenditure exceeding 9.5 times basal metabolic rate. Since 1950, climate warming has progressively reduced winter thermoregulation demands disproportionately benefiting and potentially promoting shorter-distance strategies. These results reveal shifting energetic trade-offs under climate change, potentially driving evolution of migration patterns.

Rapid environmental change caused by humans has become a major concern for wildlife conservationists. But phenotypic and evolutionary responses of species to such change may often be swift enough to prevent their collapse. Several North American bird species living in boreal forests now have more pointed wings (a proxy for sustained ight efficiency), than they had a century ago. This remarkable pattern has been hypothesized as resulting from selective pressures favoring colonization of isolated habitat. Additionally, aerodynamics predict that heavier birds can achieve faster ight, a further advantage for exploring isolated habitats. We tested whether birds establishing territories in isolated areas have more pointed wings and are heavier than con-specifics found in more densely populated areas. Wing shapes of wild-caught adults from 21 passerine bird species did not generally support this prediction. However individuals with large body mass relative to their species were found more frequently in isolated habitats. Our results offer partial support for the isolation hypothesis at the landscape scale. We encourage further work at coarser, regional, scales to further examine whether wing shape and body mass evolutionarily respond to habitat isolation.

The physiology of tropical birds is poorly understood, particularly in how it relates to local climate and changes between seasons. This is particularly true of tropical montane species, which may have sensitive thermal tolerances to local microclimates. We studied metabolic rates (using open flow respirometry), body mass and haemoglobin concentrations of five sedentary Mesoamerican songbirds between the summer and winter at two elevations (1550 m and 1950 m, respectively). We asked whether there were uniform seasonal shifts in physiological traits across species, and whether higher elevation species displayed evidence for cold tolerance. Seasonal shifts in metabolic rates differed between the three species for which data were collected. Basal metabolic rates in one species - black-headed nightingalethrushes Catharus mexicanus - were up-regulated in summer (~19% increase of winter metabolism), however two other species displayed no seasonal regulation. No species exhibited shifts in haemoglobin concentrations across season or across elevation, whereas body mass in two species was significantly higher in the summer. One species restricted to higher elevations - ruddy-capped nightingale-thrushes C. frantzii - displayed physiological traits indicative of cold-tolerance. Although only summer data were available for this species (C. frantzii), metabolic rates were constant across temperatures tested (5-34{degrees}C) and haemoglobin concentrations were significantly higher compared to the other four species. Our results suggest that seasonal acclimatisation in physiological traits is variable between species and appear unrelated to changes in local climate. As such, the distinct physiological traits observed in ruddy-capped nightingale-thrushes likely relate to historic isolation and conserved physiological traits rather than contemporary climatic adaption.

Many organisms time reproduction to photoperiod, a constant from year to year. Predicting how anthropogenic change will influence future timing demands greater knowledge of the current role of photoperiod. We held two closely related bird populations in a common environment. One population is resident; the other winters in sympatry with the resident population but migrates north prior to reproducing. We increased photoperiod gradually and measured preparation for migration and reproduction, using feather stable isotopes to estimate breeding latitude. We predicted population differences in the minimum stimulatory day length to elicit a response (CPP, critical photoperiod) and co-variation between CPP and distance migrated. We found clear population differences in CPP and greater CPP in longer distance migrants. We conclude that current geographic variation in reproductive timing has a genetic or early developmental basis and recommend that future research focus on how anthropogenic changes will interact with CPP to adjust timing of reproduction and migration.

Climate warming and forest fragmentation threaten tropical biodiversity by altering microclimates and narrowing the range of temperatures within which species can maintain optimal physiological performance. We investigated the thermoregulatory capacities of five forest-dependent bird species from the Taita Hills (Kenya), a montane biodiversity hotspot experiencing severe habitat loss. Using respirometry, we measured resting metabolic rate (RMR) across a range of temperatures to determine thermoneutral zone (TNZ) limits, quantified evaporative water loss (EWL), evaporative heat loss (EHL), and metabolic heat production (MHP) as proxies of cooling capacity, and estimated heat tolerance limits (HTLs). Contrary to expectations of a classical TNZ pattern, RMR-temperature relationships were predominantly V-shaped, suggesting the absence, or marked narrowness, of a TNZ. In contrast, HTL clearly increased with body mass, with larger species tolerating higher temperatures. Evaporative cooling efficiency remained weak across all species (EHL/MHP < 1), indicating limited capacity to dissipate metabolic heat. Compared with global data, the Taita Hills species exhibited low critical temperatures and narrow thermal ranges, consistent with specialisation to the stable microclimates of tropical montane forests. Our findings suggest that small-bodied, forest-dependent tropical birds function within narrow thermal margins, which may make them especially vulnerable to rising temperatures and the microclimatic changes associated with climate change and forest fragmentation.

Initial descriptions of avian subspecies were based on expert opinions of geographic variation in phenotypes and are inherently subjective. Although best practices for subspecies delimitation continue to be debated, reassessing subspecies limits with current, quantitative methods is important toward refining and improving taxonomic treatments. Plumage coloration is the basis of many subspecies diagnoses, but is potentially problematic because of the historical lack of quantitative methods to quantify color. Recently developed methods, such as colorimetry, provide repeatable measurements of color variation that can be used to reassess subspecies limits. In this study, we reassess color variation among subspecies of the Oregon Dark-eyed Junco (Junco hyemalis [oreganus Group]) complex, in which differences in back and hood color were established as diagnostic characters. We measured back and hood brightness and hue in 206 museum specimens among five Oregon Dark-eyed Junco subspecies using a colorimeter. We then compared mean measurements among subspecies and conducted a discriminant function analysis to assess how well dorsal color predicted subspecies. Our data correctly classified only 67.9% of males and 82.5% of females to their presumed subspecies. Furthermore, no adjacent subspecies pairs passed the "75% rule" due to extensive overlap in plumage characters. Thus, back color alone is not as effective in diagnosing Oregon Dark-eyed Junco subspecies as originally described, suggesting a possible taxonomic revision. Specifically, similarity in phenotypic and genetic data suggests that some combination of thurberi, montanus, and shufeldti may be lumped to recognize broad, clinal variation in dorsal color alongside clinal variation in other phenotypes and extensive gene flow.

Polar and sub-polar animals evolved to thrive in cold climates and may thus be particularly vulnerable to rising temperatures associated with climate change. Penguins may be especially vulnerable due to their dual habitat, alternating between foraging in cold waters and breeding/moulting on an increasingly warm land. Here, we characterized heat stress occurrence in breeding king penguins through behavioural observations (e.g. panting occurrence) and body temperature measurements. We observed that behavioural signs of heat stress are frequent in king penguins breeding in the sub-Antarctic region (> 20% of observations at mid-day), and that subcutaneous temperatures increase under high heat load, especially in penguins showing behavioural signs of heat stress. Subcutaneous and core body temperatures were moderately correlated and both increased with heat load. Yet, their responses were not parallel since core body temperature is markedly less sensitive to heat load than subcutaneous temperature. Air temperature alone was a poor predictor of heat stress occurrence, whereas the combination of high solar radiation, low wind speed and high air temperatures provided the strongest predictive power. Finally, reproductive failures were more likely to occur on warmer days, suggesting that heat stress may have significant sublethal effects that could ultimately affect population dynamics. O_FIG O_LINKSMALLFIG WIDTH=150 HEIGHT=200 SRC="FIGDIR/small/611977v2_ufig1.gif" ALT="Figure 1"> View larger version (95K): org.highwire.dtl.DTLVardef@f2c985org.highwire.dtl.DTLVardef@18c4688org.highwire.dtl.DTLVardef@6a99dforg.highwire.dtl.DTLVardef@9c32fa_HPS_FORMAT_FIGEXP M_FIG C_FIG

Migration is a well-described behavioural strategy that allows species to track variation in resources and climatic conditions by moving in response to seasonality. A common form is elevational migration, an annual short-distance movement undertaken by many mountain bird species globally. While studies show that the timing of migration may relate to food availability, the mechanisms determining which species migrate remain unclear. Our study investigated if the degree of dietary specialization explains why some high-elevation bird species in seasonal environments migrate downslope for the winter while others remain resident at high altitudes despite the apparent scarcity of their preferred food resources. We mist-netted birds along a 2300-m elevational gradient in the Eastern Himalaya and collected blood and faecal samples from 261 individual birds belonging to 18 species of high-elevation residents (ten) and elevational migrants (eight) in their breeding and wintering ranges. Using stable isotope ratios of carbon and nitrogen in whole blood and faecal DNA metabarcoding, we compared their seasonal trophic levels and dietary niches. Nitrogen isotope ratios showed that residents had a substantially lower trophic position in the winter compared to summer (-0.35 [-0.52, -0.17]), whereas migrants had a slightly higher trophic position in the winter (0.15 [-0.02, 0.32]). This trophic shift in residents was likely due to a decrease in insectivory and an increase in frugivory in the winter. The frequency of key insect orders (Lepidoptera, Hemiptera, and Coleoptera) declined by 20-35% in their winter diets alongside an increase in fruit, particularly from the family Polygonaceae (0.33 [0.18, 0.46]). Additionally, compared with residents, migrants showed greater overlap in their dietary niches between summer and winter (98% vs 80%). Because arthropod abundances in the Himalayas peak at high elevations in the summer and decline in the winter, we suggest that elevational migrants are likely dietary specialists that track resources, while high-elevation residents are dietary generalists that supplement their winter diet with fruit and nectar because of the scarcity of arthropods. These findings indicate that a species dietary specialization is linked to its migratory behaviour, providing a potential mechanistic explanation for how different species solve the challenge of seasonal resource limitation.

AO_SCPLOWBSTRACTC_SCPLOWConspecific attraction has often been hypothesized as a mechanism that could facilitate migration and territory acquisition. We studied conspecific attraction by songbirds during spring migration between 2019 and 2025 at the Dunes of Tadoussac, Quebec, Canada. This location is known to produce spectacular migration events with thousands of passerine birds flying at close range from the observers. We recorded sequences of individual birds moving just over the ground in a [~]20 m wide corridor along the edge of the St. Lawrence estuary. We also conducted hourly counts to detect conspecific clusters at a coarser temporal scale. Birds were much more likely to be following conspecifics at close range than other species, as evidenced by randomization tests, after accounting for species composition and abundance during each specific migration event. Conspecific sequences were mostly of two individuals, but much larger sequences occurred, up to 103 consecutive individuals of the same species. We found no evidence of leading species, i.e. species that were more likely to lead, rather than follow, another species. Hourly species counts were often much more variable than expected from a random (Poisson) process, at least in the case of Tennessee and Magnolia Warblers, providing evidence for conspecific attraction at a coarser temporal scale. This study provides the first detailed evidence of conspecific attraction with passerine birds during migration.

Many different physiological changes have been observed in wild waterfowl during the flightless stage of wing moult, including a loss of body mass. Previously we established that captive barnacle geese (Branta leucopsis) underwent this characteristic decrease in body mass during their wing moult, even though they had unlimited and unrestricted access to food. In the present study we aimed to determine if this body mass loss during moult comprised mainly a reduction in fat stores, and to ascertain if the captive geese undergo pre-migratory and pre-winter fattening over a similar temporal scale to their wild conspecifics. The non-destructive technique of deuterium oxide isotope dilution was employed to provide repeated measurements of estimated fat deposition from a captive flock of fourteen barnacle geese. Birds were injected with deuterium oxide at 7 distinct intervals for one annual cycle. During the flightless period of the moult, body fat decreased by approximately 40% from the pre-moult value. During late-September and early October, body fat reached its highest point in the annual cycle, both as an absolute value and as a percentage of total body mass. We propose that while the energetic cost of wing moult is not the ultimate cause of fat loss in moulting barnacle geese, the approximate 212 g of fat catabolised during moult would provide sufficient energy to cover the cost of the replacement of the flight feathers, estimated to be 6384 kJ, over an approximate 42 day period. We conclude that the previously recorded increase in metabolism during moult in the geese, led to the use of endogenous fat reserves because the birds reduced rather than increased their food intake rates owing to the increased risk of predation when flightless. We also conclude that captive barnacle geese do undergo pre-winter and pre-migratory fattening, providing further evidence of the innate nature of these fat deposition cycles.Competing Interest StatementThe authors have declared no competing interest.View Full Text

Birds maintain some of the highest body temperatures (Tb) among endothermic animals. Often deemed a selective advantage for heat tolerance, high Tb also limits the capacity to increase Tb before reaching lethal levels. Recent thermal modelling suggests that sustained effort in Arctic birds might be restricted at mild air temperatures (Ta) during energetically demanding life history stages, which may force reductions in activity to avoid overheating, with expected negative impacts on reproductive performance. Consequently, understanding how Arctic birds will cope with increasing Ta has become an urgent concern. We examined within-individual changes in Tb in response to an experimental increase in activity in outdoor captive Arctic cold-specialised snow buntings (Plectrophenax nivalis), exposed to naturally varying Ta from -15 to 36 {degrees}C. Calm buntings exhibited a modal Tb range from 39.9 - 42.6 {degrees}C. However, we detected a dramatic increase in Tb within minutes of shifting birds to active flight, with strong evidence for a positive effect of Ta on Tb (slope = 0.04 {degrees}C/{degrees}C). Importantly, by Ta of 9 {degrees}C, flying buntings were already generating Tb [&ge;] 45{degrees}C, approaching the upper thermal limits of organismal performance (i.e., Tb = 45 - 47 {degrees}C). Under scenarios of elevated Tb, buntings must increase rates of evaporative water loss and/or reduce activity to avoid overheating. With known limited evaporative heat dissipation capacities, we argue buntings operating at peak energy levels will increasingly rely on behavioral thermoregulatory strategies (i.e., reducing activity) to regulate Tb, at the potential detriment to nestling growth and survival.

Many animals have camouflage appearances that correspond to the habitat where they live, termed phenotype-environment matching. However, this has generally been tested in only a limited number of systems and natural settings, and often not to the relevant vision of key receivers (predators) across different spatial scales. Here, we measured the plumage attributes and putative camouflage used by ground-nesting bird species specialist to particular biomes, specifically tropical rainforest, taiga forest, dry forest, grassland, desert, and tundra from museum specimens. Digital photography and image analysis were used to quantify colour patterns to models of predator vision to understand how different colour patterns may correspond with biome type. With this information, we next created bird models that were photographed in situ in the Valdivian temperate rainforest and Patagonian grassland biomes of Chile to quantify the extent to which plumage coloration and pattern traits provide effective camouflage at different spatial scales. In general, we find that specialist ground-nesting birds express a phenotype that better matches the substrate composition and vegetation structure across large spatial scales of their own biome. This study reveals how animal camouflage works across biomes, relative to the visual system of raptor predators, and at the appropriate distance at which detection may occur.

The evolution of eye coloration in mammals and its potential ecological significance remain understudied. Evidence from anthropoid primates suggests that photoprotective demands are crucial determinants of pigmentation in the peri-iridal tissues, which encompass the conjunctiva and portions of the sclera peripheral to the iris. However, it is unclear to what extent these findings can be generalized. Here, we quantify peri-iridal brightness in a photographic sample of 62 terrestrial non-primate mammal species (n = 930). Phylogenetically-controlled analyses revealed significant effects of eye size as well as ecology on ocular pigmentation. Peri-iridal brightness exhibits a notable phylogenetic signal, correlates negatively with eye size and hence exposure to UV light, and is more pronounced in nocturnal species. Significant interspecific effects of latitude on peri-iridal brightness were not recovered, but tentative evidence for non-negligible impacts of this variable at the intraspecific level were found. Overall, these results align with and help to contextualize findings on primates and suggest that photoprotective demands importantly shape ocular appearance across the mammalian radiation. Furthermore, they have implications for hypotheses tying eye pigmentation chiefly to gaze signaling and provide a broad evolutionary framework for the emergence of human eye appearance.

Flight feather vanes are the primary aerodynamic surface of the avian wing. Because loading varies across the wing, vane macrostructure should co-vary with local mechanical demands, yet comparative data on how barb and barbule traits change among remiges and between vane surfaces remain scarce. We quantified barb density, barbule density, barb angle, barb length, and vane width on both vanes at three measurement positions along the rachis of all remiges in four species with contrasting flight modes (white stork, common buzzard, house sparrow, pygmy cormorant), generating over 40,000 measurements across 15 response variables from 992 feathers of 41 individuals. Two complementary generalised additive models characterised variation along the spanwise, inter-vane, and longitudinal axes, and compared outer primaries, inner primaries, and secondaries as functional wing regions. Feather macrostructure varied along all three axes and outer primaries represent the most distinctive region, with lower leading-vane barb density, reduced barb angles, and vane width asymmetry two to three times higher than in inner primaries or secondaries. House sparrow exhibited the densest vane architecture and the highest vane width asymmetry, whereas the low wing-beat frequency species showed complex nonlinear spanwise patterns undetectable by single-feather sampling. Pygmy cormorant barbule density was 39-53% lower than in all other species, matching its wettable plumage strategy. Longitudinal gradients in barb density and barb angle (22-31% decline) were conserved across species. The avian wing is thus functionally regionalised at the macrostructural level, with vane architecture reflecting both aerodynamic and ecological pressures. Summary statementFine-scale vane measurements across all remiges in four species show macrostructural regionalisation of the avian wing, with outer primaries showing the most distinctive vane architecture.

Animal coloration has diverse functions such as camouflage, communication, thermoregulation, protection from UV damage and more, and can be shaped by environmental selective pressures. Some climactic selective pressures are strong enough to produce consistent patterns in many species across large-scale geographic gradients. One pattern in endothermic animals is Glogers rule, which predicts that populations in hot, humid areas will be darker than those in cool, dry areas. This pattern has been demonstrated in several species across latitudinal gradients and is expected to relate to the selective effects of both local thermoregulatory pressures and humidity. However, shortwave radiation from sunlight extends beyond the visible spectrum [400-700 nm] into the near-infrared; thus, thermal pressures often result in changes in surface reflectance characteristics beyond the visible [e.g., 700-2500 nm]. Further, heat exchange with the environment extends into the mid-infrared, including MIR heat loss through the atmospheric transmission window [7.5 - 14 um]. Here, we examine both UV-NIR absorption and MIR emittance in five species of birds that have been shown to follow, or not follow, Glogers rule. We show that NIR absorption varies by species and population in ways that correspond to their habitat and thermoregulatory strategies. MIR emittance, by contrast, was very stable across both species and populations but differed across populations of Northern Bobwhites. We conclude by highlighting the importance of extending coloration research into the NIR and MIR. Further consideration of infrared radiation is necessary for a complete view of animals phenotypic diversity and possible responses to thermal challenge.

Birds and mammals are shrinking and shapeshifting as global temperatures rise. Ecogeographic rules predict that such changes should ease heat stress by increasing surface-area-to-volume ratios, and thus, the capacity for heat exchange. This has led to the hypothesis that body size reductions are driven by thermoregulatory selection or adaptive plasticity, although recent syntheses point to more complex, multifactorial causes. Crucially, recent theoretical models predict that thermoregulatory benefits of smaller body size only emerge at extreme deviations from average phenotypes. Here, we exploit agricultural selection in Japanese quail to directly test this hypothesis, using three breeds spanning extreme differences in body mass, surface area, and relative appendage lengths. Evaporative cooling capacity and the scope for evaporative water loss broadly followed allometric predictions when contrasting small and larger breeds. As expected, this allowed the smallest breed to tolerate higher air temperatures. However, differences in heat tolerance limits between breeds were consistently much smaller than predicted. Additionally, the breadth of thermoneutral zones overlapped in full, and upper critical temperatures were remarkably similar, between breeds. Together, these results show that heat tolerance is only weakly linked to surface-area-to-volume relationships and cannot be explained by size alone. Thus, although smaller bodies may modestly enhance heat dissipation when size variation in a population is substantial, our findings suggest that recent body size reductions and morphological shifts are unlikely to be driven primarily by thermoregulatory benefits.

Most of our knowledge on hole-nesting birds, including plumage colouration (an important component of visual signalling), comes from studies on populations breeding in human-provided nestboxes. However, as demonstrated in comparative studies, multiple parameters, such as cavity dimensions and microclimatic conditions, differ between natural and artificial cavities. Despite this, no study so far examined the impact of cavity type on plumage colouration to verify whether extrapolation of results from birds growing in nestboxes is justified. Here, we examined the impact of cavity type - natural cavities vs. nestboxes - on the carotenoid-based colouration of blue tit (Cyanistes caeruleus) and great tit (Parus major) nestlings. We found clear differences in plumage colouration depending on the type of cavity in which the birds developed. Our study adds to the growing body of evidence confirming that varying properties of natural cavities and nestboxes might influence nestling physiology, leading to phenotypic differences in the long-term.

Inferring the environmental selection pressures responsible for phenotypic variation is a challenge in adaptation studies as traits often have multiple functions and are shaped by complex selection regimes. We provide experimental evidence that morphology of the multifunctional avian bill is related to climate, not foraging efficiency, in song sparrows (Melospiza melodia) on the California Channel Islands. Our research builds on a study in song sparrow museum specimens that demonstrated a positive correlation between bill surface area and maximum temperature, suggesting a greater demand for dry heat dissipation in hotter, xeric environments. We sampled contemporary sparrow populations across three climatically distinct islands to test the alternate hypotheses that song sparrow bill morphology is either a product of vegetative differences with functional consequences for foraging efficiency or related to maximum temperature and, consequently, important for thermoregulation. Measurements of >500 live individuals indicated a significant, positive relationship between maximum temperature and bill surface area when correcting for body size. In contrast, maximum bite force, seed extraction time, and vegetation on breeding territories (a proxy for food resources) were not significantly associated with bill dimensions. While we cannot exclude the influence of foraging ability and diet on bill morphology, our results are consistent with the hypothesis that variation in song sparrows need for thermoregulatory capacity across the northern Channel Islands selects for divergence in bill surface area. SUMMARY STATEMENTIsland song sparrow bill differences are correlated with climate, not vegetation, and experimental evidence finds no functional effect on foraging efficiency. This suggests many factors shape this multifunctional trait.

Polytypic species with large ranges may harbor unrecognized diversity because taxonomy ranks populations differing subtly in plumage as subspecies. The Ruddy Foliage-gleaner (Clibanornis rubiginosus) exemplifies this problem. It ranges from Mexico to Brazil, with 15 subspecies, and forms a non-monophyletic complex with two congeners, yet its songs had not been compared. We measured ten spectral and temporal variables on 104 recordings covering 14 of 15 subspecies. Bayesian linear mixed models showed three song groups: eight subspecies west of the Andes share a single-note song, whereas Amazonian and Guianan populations add a short introductory note and sing longer, lower-pitched songs. Within this group, watkinsorum sings the lowest-pitched and longest song and is phylogenetically closer to C. cinnamomeigula than to its Amazonian neighbors. The third group is C. cinnamomeigula alone, a white-eyed taxon in an otherwise dark-eyed group. Its high-pitched, vibrato song resembles none other in the genus. One-note and two-note songs differ in kind without intermediates, and every two-note taxon sequenced to date falls in one clade, so C. rubiginosus is paraphyletic. We recognize four species, C. rubiginosus sensu stricto, C. cinnamomeigula, C. watkinsorum, and C. obscurus. This raises Clibanornis from five species to eight and divides its only polytypic species.