Avian Taxa Research Articles

A primitive grebe (Aves, Podicipedidae) from the Miocene of Eastern Siberia (Lake Baikal, Olkhon Island)

A small grebe, Miobaptus huzhiricus sp. nov., is described from the uppermost Lower Miocene–lower Middle Miocene of Olkhon Island (Lake Baikal; Tagai locality). This fossil grebe differs from all extant representatives of the family in several morphological features, which indicate a stem position of the genus Miobaptus in the phylogenetic tree of Podicipediformes. This Asian record of the genus Miobaptus, which was initially described from the Lower Miocene of Central Europe, is evidence of wide distribution of at least some genera of water birds in the Burdigalian of Eurasia. A review of the Miocene and Pliocene fossil record of Podicipedidae is provided. The previously undescribed grebe from the Middle Miocene of the Steinheim locality in Germany is also referred to the genus Miobaptus, although it possesses more derived morphology compared to M. huzhiricus. The genus Miobaptus partially bridges the morphological gap between Podicipedidae and other avian taxa, for example, Palaelodidae. Early evolution of Podicipedidae is discussed.

Behaviorally Induced Camouflage: A New Mechanism of Avian Egg Protection.

When animals potentially occupy diverse microhabitats, how can camouflage be achieved? Here we combine descriptive and experimental methods to uncover a novel form of phenotypic plasticity in the camouflage of bird eggs that may be present in other avian taxa. Soil from the bare substrate adheres to the blue-footed booby's (Sula nebouxii's) pale eggs, which parents manipulate both under and on top of their webs. Analysis of digital images confirmed that dirtiness increases progressively during the first 16 days of the incubation period, making eggs more similar to the nest substrate. Observations of 3,668 single-egg clutches showed that the probability of egg loss declines progressively over the same time frame and then remains low for the rest of the 41-day incubation period. An experiment showed that when chicken eggs are soiled and exposed in artificial booby nests, they are less likely to be taken by Heermann's gulls (Larus heermanni) than clean eggs.

Turnover rates of stable isotopes in avian blood and toenails: Implications for dietary and migration studies

Most stable isotope (SI) applications in avian ecology are based on the analysis of feathers and blood, whereas toenails are much less used. These structures grow slowly and continuously, thus integrating information over comparatively longer periods which may be useful for migration connectivity studies, while avoiding some of the difficulties posed by incomplete information on feather molt.In spite of this, interpretation of data from toenails is limited by lack of accurate figures on their turnover rates and discrimination values. To improve our understanding of SI ratios in toenails and surpass these drawbacks we measured the change in carbon (δ13C) and nitrogen (δ15N) SI ratios in plasma, red blood cells and toenails of captive dunlins Calidris alpina after a controlled diet switch. Discrimination values were estimated by comparing isotopic values at the end of the experiment with those of artificial food. We also estimated toenail growth rates in this species.Toenails showed much lower SI turnover rates than blood components, with half-lives of 27days and 35days for δ13C and δ15N, respectively. Isotopic ratios in toenails reached equilibrium with the new diet after 100–120days, roughly coinciding with the duration of toenail replacement.The discrimination values of 2.74±0.68‰ for δ13C and 4.06±0.27‰ for δ15N found for toenails are higher than those of both blood components. These values are also higher than most published values for blood in other avian species, but similar to those previously reported for feathers which, like toenails, are metabolically inert after synthesis and are mainly composed of keratin.This study highlights the potential role of toenails as sources of SI data for ecological studies, particularly to determine geographic origin of birds migrating between isotopically distinct environments. Indeed, their long turnover rates might allow for the detection of SI signals from the wintering or breeding ranges, by sampling individuals at their staging sites. Isotopic turnover in toenails follow their replacement rates, and these seem to be rather similar across several avian taxa. Thus, the turnover rates described here may potentially be used to interpret SI data for other birds.

Avian remains from the Upper Pleistocene (MIS3) site of Aguilón P-7, south of the Ebro River, Spain

Aves are represented by abundant fossil remains in Quaternary sites. Birds are well adapted to the environment they inhabit, so they make very good paleoenvironmental indicators for Quaternary sites. Here we analyse the avian remains from the Late Pleistocene (probably MIS3) site of Aguilón P-7 (AGP-7). The Pleistocene sediments fill up a shallow cave, which is located in the Zaragozan part of the Iberian Range, 55 km south of the city of Zaragoza. We have for the first time provided a taxonomic and taphonomic study of the avian assemblage of AGP-7, as well as a preliminary paleoenvironmental analysis based on these data. Nine avian taxa have been identified: Galliformes indet., Lagopus sp., Aquila chrysaetos, Gyps fulvus, Passeridae indet., Anthus sp., Prunella modularis,Sturnus cf. unicolor and Corvus monedula. The taphonomic analysis did not provide conclusive information. However, it suggests an accumulation of uneaten food remains by diurnal birds of prey. The identified taxa currently inhabit the Iberian Peninsula, populating woodland environments with rocky areas. They are found in areas with an oceanic climate, in contrast to the Mediterranean climate that now prevails in Aguilón.

Neural FoxP2 and FoxP1 expression in the budgerigar, an avian species with adult vocal learning

Vocal learning underlies acquisition of both language in humans and vocal signals in some avian taxa. These bird groups and humans exhibit convergent developmental phases and associated brain pathways for vocal communication. The transcription factor FoxP2 plays critical roles in vocal learning in humans and songbirds. Another member of the forkhead box gene family, FoxP1 also shows high expression in brain areas involved in vocal learning and production. Here, we investigate FoxP2 and FoxP1 mRNA and protein in adult male budgerigars (Melopsittacus undulatus), a parrot species that exhibits vocal learning as both juveniles and adults. To examine these molecules in adult vocal learners, we compared their expression patterns in the budgerigar striatal nucleus involved in vocal learning, magnocellular nucleus of the medial striatum (MMSt), across birds with different vocal states, such as vocalizing to a female (directed), vocalizing alone (undirected), and non-vocalizing. We found that both FoxP2 mRNA and protein expressions were consistently lower in MMSt than in the adjacent striatum regardless of the vocal states, whereas previous work has shown that songbirds exhibit down-regulation in the homologous region, Area X, only after singing alone. In contrast, FoxP1 levels were high in MMSt compared to the adjacent striatum in all groups. Taken together these results strengthen the general hypothesis that FoxP2 and FoxP1 have specialized expression in vocal nuclei across a range of taxa, and suggest that the adult vocal plasticity seen in budgerigars may be a product of persistent down-regulation of FoxP2 in MMSt.

Genomic resources for the endangered Hawaiian honeycreepers.

BackgroundThe Hawaiian honeycreepers are an avian adaptive radiation containing many endangered and extinct species. They display a dramatic range of phenotypic variation and are a model system for studies of evolution, conservation, disease dynamics and population genetics. Development of a genome-scale resources for this group would augment the quality of research focusing on Hawaiian honeycreepers and facilitate comparative avian genomic research.ResultsWe assembled the genome sequence of a Hawaii amakihi (Hemignathus virens),and identified ~3.9 million single nucleotide polymorphisms (SNPs) in the genome. Using the amakihi genome as a reference, we also identified ~156,000 SNPs in RAD tag (restriction site associated DNA) sequencing of five honeycreeper species (palila [Loxioides bailleui], Nihoa finch [Telespiza ultima], iiwi [Vestiaria coccinea], apapane [Himatione sanguinea], and amakihi). SNPs are distributed throughout the amakihi genome, and the individual sequenced shows several large regions of low heterozygosity on chromosomes 1, 5, 6, 8 and 11. SNPs from RAD tag sequencing were also found throughout the genome but were found to be more densely located on microchromosomes, apparently a result of differential distribution of the particular site recognized by restriction enzyme BseXI.ConclusionsThe amakihi genome sequence will be useful for comparative avian genomics research and provides a significant resource for studies in such areas as disease ecology, evolution, and conservation genetics. The genome sequences will enable mapping of transcriptome data for honeycreepers and comparison of gene sequences between avian taxa. Researchers will be able to use the large number of SNP markers to genotype honeycreepers in regions of interest or across the whole genome. There are enough markers to enable use of methods such as genome-wide association studies (GWAS) that will allow researchers to make connections between phenotypic diversity of honeycreepers and specific genetic variants. Genome-wide markers will also help resolve phylogenetic and population genetic questions in honeycreepers.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-1098) contains supplementary material, which is available to authorized users.

Zebra finch mates use their forebrain song system in unlearned call communication.

Unlearned calls are produced by all birds whereas learned songs are only found in three avian taxa, most notably in songbirds. The neural basis for song learning and production is formed by interconnected song nuclei: the song control system. In addition to song, zebra finches produce large numbers of soft, unlearned calls, among which “stack” calls are uttered frequently. To determine unequivocally the calls produced by each member of a group, we mounted miniature wireless microphones on each zebra finch. We find that group living paired males and females communicate using bilateral stack calling. To investigate the role of the song control system in call-based male female communication, we recorded the electrical activity in a premotor nucleus of the song control system in freely behaving male birds. The unique combination of acoustic monitoring together with wireless brain recording of individual zebra finches in groups shows that the neuronal activity of the song system correlates with the production of unlearned stack calls. The results suggest that the song system evolved from a brain circuit controlling simple unlearned calls to a system capable of producing acoustically rich, learned vocalizations.

A critical season approach to Allen's rule: bill size declines with winter temperature in a cold temperate environment

AbstractAimBill size is positively correlated with average air temperature in several avian taxa. The conventional explanation for this pattern is that the poorly insulated surface area of the bill functions to dissipate excess heat in hot climates or retain heat in cold climates (Allen's rule). We hypothesize that the applicability of Allen's rule depends upon the season of critical thermal stress, which may vary by location and species. We previously found that bill size increases with high summer temperature in song sparrows (Melospiza melodia) of California, supporting the hypothesis that larger bills are an adaptation to release dry heat and minimize evaporative water loss in a hot, dry environment. Song sparrows in eastern North America face a different climatic regime, in which summers are warm but moist, and winters are cold. We predicted that this climate region would select for smaller bills to minimize heat loss.LocationFrom coastal Delaware and Maryland to the Allegheny Plateau of the eastern USA.MethodsWe measured body size and bill morphology of 274 song sparrow individuals across a climatic gradient and geographical gradient. We used linear regression models to test for effects of geographical location and 30‐year means of minimum winter and maximum summer temperatures and annual rainfall on bill size.ResultsBill size was best predicted by, and positively correlated with, cold winter temperatures and distance from the Atlantic coast. Body size did not change substantially with distance from the coast, indicating that the pattern of bill size was not a result of allometry. Coastal birds had bills larger than predicted by a linear effect of minimum temperature.Main conclusionsCollectively, these results support the hypothesis that variation in bill size reflects selection for winter heat retention rather than for summer heat dissipation. Bill size may be shaped by physiological responses to regional climates, and the season of critical thermal stress may vary geographically, even on relatively small spatial scales.

Vocal behaviour of the island-endemic Cozumel Wren (Troglodytes aedon beani): song structure, repertoires, and song sharing

Documenting the diversity of vocal behaviour across different avian taxa is key to understanding the ecology and evolution of complex behaviours. Unique to Cozumel Island in the Mexican Caribbean Sea, the Cozumel Wren (Troglodytes aedon beani) provides an opportunity to investigate how isolation influences complex cultural traits. Most aspects of the biology, natural history, and taxonomy of Cozumel Wrens are unknown. In an attempt to better understand the Cozumel Wren’s biology, we provide the first description of the songs and the vocal behaviour of this island-endemic bird. Based on more than 700 h of recordings, including more than 36,000 songs, we describe the fine structural characteristics of male Cozumel Wrens songs, and explore patterns of repertoire organization and song sharing. Cozumel Wrens sing songs composed of highly variable syllables, with prominent trills at the end of each song. Each bird has a limited repertoire of songs, which they create by recombining a restricted number of syllable and trill types. They repeat a song type several times before switching to a different one, with some variation in the number of times they repeat specific elements. Cozumel Wrens share more song types with neighbours than distant individuals. Syllable sharing, however, is equivalent between neighbours and distant individuals. Our results provide important data for future research on the ecology, evolution, and behaviour of this island-endemic songbird, and for helping to clarify the taxonomic status of Cozumel Wrens.

Limited Phylogeographic Signal in Sex-Linked and Autosomal Loci Despite Geographically, Ecologically, and Phenotypically Concordant Structure of mtDNA Variation in the Holarctic Avian Genus Eremophila

Phylogeographic studies of Holarctic birds are challenging because they involve vast geographic scale, complex glacial history, extensive phenotypic variation, and heterogeneous taxonomic treatment across countries, all of which require large sample sizes. Knowledge about the quality of phylogeographic information provided by different loci is crucial for study design. We use sequences of one mtDNA gene, one sex-linked intron, and one autosomal intron to elucidate large scale phylogeographic patterns in the Holarctic lark genus Eremophila. The mtDNA ND2 gene identified six geographically, ecologically, and phenotypically concordant clades in the Palearctic that diverged in the Early - Middle Pleistocene and suggested paraphyly of the horned lark (E. alpestris) with respect to the Temminck's lark (E. bilopha). In the Nearctic, ND2 identified five subclades which diverged in the Late Pleistocene. They overlapped geographically and were not concordant phenotypically or ecologically. Nuclear alleles provided little information on geographic structuring of genetic variation in horned larks beyond supporting the monophyly of Eremophila and paraphyly of the horned lark. Multilocus species trees based on two nuclear or all three loci provided poor support for haplogroups identified by mtDNA. The node ages calculated using mtDNA were consistent with the available paleontological data, whereas individual nuclear loci and multilocus species trees appeared to underestimate node ages. We argue that mtDNA is capable of discovering independent evolutionary units within avian taxa and can provide a reasonable phylogeographic hypothesis when geographic scale, geologic history, and phenotypic variation in the study system are too complex for proposing reasonable a priori hypotheses required for multilocus methods. Finally, we suggest splitting the currently recognized horned lark into five Palearctic and one Nearctic species.

Earliest and first Northern Hemispheric hoatzin fossils substantiate Old World origin of a “Neotropic endemic”

The recent identification of hoatzins (Opisthocomiformes) in the Miocene of Africa showed part of the evolution of these birds, which are now only found in South America, to have taken place outside the Neotropic region. Here, we describe a new fossil species from the late Eocene of France, which constitutes the earliest fossil record of hoatzins and the first one from the Northern Hemisphere. Protoazin parisiensis gen. et sp. nov. is more closely related to South American Opisthocomiformes than the African taxon Namibiavis and substantiates an Old World origin of hoatzins, as well as a relictual distribution of the single extant species. Although recognition of hoatzins in Europe may challenge their presumed transatlantic dispersal, there are still no North American fossils in support of an alternative, Northern Hemispheric, dispersal route. In addition to Opisthocomiformes, other avian taxa are known from the Cenozoic of Europe, the extant representatives of which are only found in South America. Recognition of hoatzins in the early Cenozoic of Europe is of particular significance because Opisthocomiformes have a fossil record in sub-Saharan Africa, which supports the hypothesis that extinction of at least some of these "South American" groups outside the Neotropic region was not primarily due to climatic factors.

First diagnosable non-sphenisciform bird from the early Paleocene of New Zealand

A new avian taxon from the early Paleocene Waipara Greensand in Canterbury, New Zealand, is described. The holotype of Australornis lovei, gen. et sp. nov. includes wing and pectoral girdle bones, which exhibit distinctive morphologies. Notable features are a very long crista deltopectoralis, a craniocaudally flattened shaft, and a large tuberculum dorsale of the humerus, as well as a ridge-like caudal surface of the proximal ulna. Although a well-founded assignment of the new species to any of the extant higher-level taxa is not possible, key morphological features of stem group Sphenisciformes (penguins) are absent in A. lovei. Other than penguins, the holotype of A. lovei represents one of the most significant records of a marine Paleocene bird from the Southern Hemisphere, and contributes to the emerging view that Neoaves were already diversified in the earliest Paleogene.Australornishttp://zoobank.org/urn:lsid:zoobank.org:act:DBD4F0B3-CDB4-40DA-AEC7-44D0F88AB944Australornis loveihttp://zoobank.org/urn:lsid:zoobank.org:act:D5CE55DD-12EF-46AB-A7D7-E36D0B0C73BF

Evidence is required to address potential albatross mortality in the New South Wales Ocean Trawl fishery.

To examine the current management of trawl fisheries is important to ensure albatross mortality is not being overlooked. By-catch of albatrosses in trawl fisheries occurs cryptically, which has hindered the development of conservation policy. The implementation of tasked seabird observer programmes in trawl fisheries, nevertheless, has shown that albatross mortality can happen at threatening levels. Consequently, mitigation measures have been developed and adopted in some trawl fisheries. Despite this, some trawl fisheries lack clear policy in relation to albatross mortality. In this context, I investigated the management of potential albatross mortality in a state trawl fishery, the New South Wales Ocean Trawl, in Australia. I conducted a literature search and addressed a set of questions to the responsible management agency through questions on notice at the State Parliament of New South Wales to understand albatross interactions from a policy standpoint. My results indicate that current policy neither encompasses albatross mortality nor is evidence-based. However, the combination of characteristics of this fishery and its overlap with albatross occurrence, along with the reported albatross mortality from other trawl fisheries, may warrant the need to collect empirical evidence on potential albatross interactions. Hence, the responsible management agency should take action according to legal obligations. In this scenario, I recommend the implementation of a tasked seabird observer programme, collection of baseline data, and adoption of adaptive management by the examined fishery. As uncertainty can hamper conservation efforts because management actions require evidence, it is imperative to fill current information gaps in this fishery. Additionally, an improved understanding of albatross mortality from individual trawl fisheries across different fisheries management jurisdictions will enable the prioritization of conservation efforts of this avian taxon in an international and multi-gear fishing context.

The first enantiornithine bird from the Upper Cretaceous of China

ABSTRACT A new Late Cretaceous avian taxon, Parvavis chuxiongensis, gen. et sp. nov., is reported here based on an incomplete skeleton from Upper Cretaceous lake deposits in Yunnan Province, southern China. A phylogenetic analysis of 32 taxa and 242 morphological characters resulted in three most parsimonious trees, the strict consensus tree of which places Parvavis chuxiongensis within Enantiornithes. Histological study shows that the bones of Parvavis were composed of parallel-fibered bone tissue without lines of arrested growth, and indicated that growth rate had slowed but had not stopped at any stage prior to death. The bones also lack the rough surface texture seen in juvenile birds. Therefore, the new bird was probably close to adult body size at the time of death. However, the specimen is surprisingly small, highlighting the wide range of body sizes in Upper Cretaceous enantiornithines. The new specimen also represents both the first known bird from the Upper Cretaceous of China and the first Mesozoic bird from the south of China, and thus extends the temporal and geographic range of Mesozoic birds in China. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

Tracking Changing Environments: Innovators Are Fast, but Not Flexible Learners

Behavioural innovations are increasingly thought to provide a rich source of phenotypic plasticity and evolutionary change. Innovation propensity shows substantial variation across avian taxa and provides an adaptive mechanism by which behaviour is flexibly adjusted to changing environmental conditions. Here, we tested for the first time the prediction that inter-individual variation in innovation propensity is equally a measure of behavioural flexibility. We used Indian mynas, Sturnus tristis, a highly successful worldwide invader. Results revealed that mynas that solved an extractive foraging task more quickly learnt to discriminate between a cue that predicted food, and one that did not more quickly. However, fast innovators were slower to change their behaviour when the significance of the food cues changed. This unexpected finding appears at odds with the well-established view that avian taxa with larger brains relative to their body size, and therefore greater neural processing power, are both faster, and more flexible learners. We speculate that the existence of this relationship across taxa can be reconciled with its absence within species by assuming that fast, innovative learners and non innovative, slow, flexible learners constitute two separate individual strategies, which are both underpinned by enhanced neural processing power. This idea is consistent with the recent proposal that individuals may differ consistently in ‘cognitive style’, differentially trading off speed against accuracy in cognitive tasks.

The biparental care hypothesis for the evolution of monogamy: experimental evidence in an amphibian

Selection for biparental care is considered to be an important factor favoring the evolution of monogamy if the value of exclusive cooperation in care for mutual offspring outweighs the benefits of polygamy for either sex. Support for this hypothesis has come primarily through parent removal experiments in avian taxa. We tested this hypothesis in the first known example of a socially and genetically monogamous amphibian, the mimic poison frog (Ranitomeya imitator). Biparental care in R. imitator is characterized by egg attendance, tadpole transport, and feeding of tadpoles with unfertilized trophic eggs. Using a male removal experiment, we found lower tadpole growth and lower survival for widowed females compared with control families. We demonstrate that in addition to egg attendance and tadpole transport, male parental care is critical for offspring survival throughout larval development. Previous research has shown the importance of female trophic egg provisioning of tadpoles in R. imitator. This, coupled with the results of the present study demonstrating the adaptive value of male care, supports the hypothesis that selection for biparental care has driven the evolution of monogamy in an amphibian.

New specimens of the early Eocene bird Vastanavis and the interrelationships of stem group Psittaciformes

We describe new skeletal elements of Vastanavis from the early Eocene Cambay Shale Formation of western India, including a small coracoid that represents an unnamed new species, and comment on the relationships between this avian taxon and the recently described Avolatavis from the early Eocene Green River Formation in North America. Like the previously described ones, the new Vastanavis bones resemble those of the late Eocene Quercypsittidae, thus strengthening psittaciform affinities of the Indian taxon. Vastanavis differs from Avolatavis in the presence of a crista medianoplantaris on the tarsometatarsus and in claw morphology, but a fossil from the early Eocene London Clay, which was previously assigned to Vastanavidae, closely resembles Avolatavis in these features and all other osteological aspects. We show that most branches in a recent phylogeny of stem group Psittaciformes collapse after modification of a single erroneous character scoring for Vastanavis. We further describe a morphologically distinctive distal humerus of a small bird resembling the stem group nyctibiid Paraprefica, which was discovered in the most recent excavation in Vastan Lignite Mine.

Interspecific Parental Care by a Wood Thrush (Hylocichla mustelina) at a Nest of the Veery (Catharus fuscescens)

Abstract Reports of interspecific parental behavior are rare but widespread among avian taxa. We present the first known case of interspecific parental care by a Wood Thrush (Hylocichla mustelina) at a nest of the Veery (Catharus fuscescens), documented by video at a long-term study site in northern Delaware, USA. We provide data on nest chronology, quantify parental behavior, and describe a copulation event between the Wood Thrush and the female Veery that was captured on video. Despite incurring no obvious fitness benefit, the Wood Thrush provided significant and prolonged nestling care including more feeding attempts and sanitation maneuvers than either Veery. We propose that these observations are a consequence of the normal adaptive behavior of the recipient species.

The Influence of Study Species Selection on Estimates of Pesticide Exposure in Free-Ranging Birds

Field studies of pesticide effects on birds often utilize indicator species with the purpose of extrapolating to other avian taxa. Little guidance exists for choosing indicator species to monitor the presence and/or effects of contaminants that are labile in the environment or body, but are acutely toxic, such as anticholinesterase (anti-ChE) insecticides. Use of an indicator species that does not represent maximum exposure and/or effects could lead to inaccurate risk estimates. Our objective was to test the relevance of a priori selection of indicator species for a study on pesticide exposure to birds inhabiting fruit orchards. We used total plasma ChE activity and ChE reactivation to describe the variability in anti-ChE pesticide exposure among avian species in two conventionally managed fruit orchards. Of seven species included in statistical analyses, the less common species, chipping sparrow (Spizella passerina), showed the greatest percentage of exposed individuals and the greatest ChE depression, whereas the two most common species, American robins (Turdus migratorius) and gray catbirds (Dumatella carolinensis), did not show significant exposure. Due to their lower abundance, chipping sparrows would have been an unlikely choice for study. Our results show that selection of indicator species using traditionally accepted criteria such as abundance and ease of collection may not identify species that are at greatest risk. Our efforts also demonstrate the usefulness of conducting multiple-species pilot studies prior to initiating detailed studies on pesticide effects. A study such as ours can help focus research and resources on study species that are most appropriate.

Differences in δ13C and δ15N values between feathers and blood of seabird chicks: implications for non-invasive isotopic investigations

Blood and feathers are the most targeted tissues for isotopic investigations in avian ecology, primarily because they can be easily and non-destructively sampled on live individuals. Comparing blood and feather isotopic ratios can provide valuable information on dietary shifts, trophic specialization and migration patterns, but it requires a good knowledge of the isotopic differences between the two tissues. Here, δ13C and δ15N values of whole blood (in blood cells of a few species) and simultaneously grown body feathers were measured in seabird chicks to quantify the tissue-related isotopic differences. Seabirds include 27 populations of 22 wild species that were sampled in 2000–2008, and a review of the literature added 8 groups (including adult birds) to the analysis. The use of a large data set that overall encompasses wide δ13C and δ15N ranges allowed us to depict for the first time accurate relationships between blood and feather isotopic ratios across avian taxa. Blood was impoverished in 13C and generally in 15N compared with feathers. Both mean δ13C and δ15N values of feathers and blood were highly positively and linearly related [feather δ13C = 0.972 (±0.020) blood δ13C + 0.962 (±0.414), and feather δ15N = 1.014 (±0.056) blood + 0.447 (±0.665), respectively; both P < 0.0001]. The regressions should be applied to mathematically correct feather or whole blood δ13C and δ15N values when comparing isotopic ratios within and between ecological studies on birds.