Songbird Species Research Articles

Female preference for artificial song dialects in the zebra finch (Taeniopygia guttata)

AbstractBirdsong is culturally transmitted, and geographical variations of song have been found in several songbird species. There is evidence that such dialects contribute to reproductive isolation through variation in female preference. In the wild, there is no report of consistent dialects in populations of zebra finches. However, under laboratory conditions, we were able to artificially create different colony‐wide song dialects. In this species, song plays a crucial role in mate choice and the importance of both subadult and adult song experience in shaping song preferences has been well documented. Therefore, we expected females to prefer songs corresponding to their colony's dialect. We measured this preference using an operant test: females could either trigger a song corresponding to their Colony Song Type (CST) sang by an unfamiliar individual, or another conspecific song, corresponding to a Non‐Colony Song Type (N‐CST). Most females preferred the CST over the N‐CST, supporting the idea that zebra finch females exhibit a preference for songs similar to their colony's song. It also reveals that song dialects matter to female zebra finches. It has been proposed that song could be used as an affiliative signal in highly social species. Therefore, preferring the colony dialect could be the consequence of a sexual preference, but also of a social preference. We discuss the potential role of song dialects in the context of social learning.

First description of the structure and geographic patterns in the songs of the Connecticut Warbler (Oporornis agilis)

Geographic variation in song characteristics within songbird species has the potential to reveal some of the complex interactions between ecology and behavior. The Connecticut Warbler (Oporornis agilis) is an uncommon and little studied Neotropical migratory wood warbler that breeds across the southern boreal forest in North America. The song of the Connecticut Warbler has remained poorly described and, prior to our study, no detailed spectrographic analysis exists. We document 20 distinct song variants in this species, based on differences in the structure and sequence of notes within repeated phrases, from across the breeding range. One song type, distributed across the entire breeding range, represented 36% of our samples. Preliminary evidence suggests a lack of geographic structure and no evidence of dialects or regiolects in the song types of this species. Our results highlight a unique distribution in song types within the Oporornis–Geothlypis complex, providing a baseline for future studies of geographic variation in this, and related, species.

Investigating Behavioral Responses to Mirrors and the Mark Test in Adult Male Zebra Finches and House Crows.

Earlier evidence suggests that besides humans, some species of mammals and birds demonstrate visual self-recognition, assessed by the controversial “mark” test. Whereas, there are high levels of inter-individual differences amongst a single species, some species such as macaques and pigeons which do not spontaneously demonstrate mirror self-recognition (MSR) can be trained to do so. We were surprised to discover that despite being widely used as a model system for avian research, the performance of zebra finches (Taenopygia guttata) on the mark test had not been studied earlier. Additionally, we studied the behavioral responses of another species of passerine songbirds (Indian house crows; Corvus splendens) to a mirror and the MSR mark test. Although a small number of adult male zebra finches appeared to display heightened responses toward the mark while observing their reflections, we could not rule out the possibility that these were a part of general grooming rather than specific to the mark. Furthermore, none of the house crows demonstrated mark-directed behavior or increased self-exploratory behaviors when facing mirrors. Our study suggests that self-directed behaviors need to be tested more rigorously in adult male zebra finches while facing their reflections and these findings need to be replicated in a larger population, given the high degree of variability in mirror-directed behaviors.

Song theme sharing in the Grey-crowned Warbler Phylloscopus tephrocephalus

ABSTRACT In many songbird species, individuals sing multiple song types, some of which are shared between neighbours. Individuals may also share transitions between different song types, which leads to sharing sequencies of several (usually few) song types. Song themes, i.e. groups of song types that are consistently delivered in close succession, were identified in song sequences of several bird species. Detailed data on song theme sharing are still lacking. Here, we examined patterns of repertoire sharing in the Grey-crowned Warbler Phylloscopus tephrocephalus. Males of this species had repertoires of 29–42 song types that were divided into shorter song themes of up to 10–15 song types each. Each of the 13 studied males shared 81.6–100% of his repertoire as well as several song themes with other males. These themes recombined in different ways leading to the fact that exact song sequencing varied between individuals. That is why males shared much less transition types than song types in our study. Therefore, the analysis of song theme sharing may provide more careful description of sharing above the level of song type than the analysis of song sequence sharing alone.

Migratory connectivity then and now: a northward shift in breeding origins of a long-distance migratory bird wintering in the tropics.

Temporal variation in the connectivity of populations of migratory animals has not been widely documented, despite having important repercussions for population ecology and conservation. Because the long-distance movements of migratory animals link ecologically distinct and geographically distant areas of the world, changes in the abundance and migratory patterns of species may reflect differential drivers of demographic trends acting over various spatial scales. Using stable hydrogen isotope analyses (δ2H) of feathers from historical museum specimens and contemporary samples obtained in the field, we provide evidence for an approximately 600 km northward shift over 45 years in the breeding origin of a species of songbird of major conservation concern (blackpoll warbler, Setophaga striata) wintering in the foothills of the eastern Andes of Colombia. Our finding mirrors predictions of range shifts for boreal-breeding species under warming climate scenarios and habitat loss in the temperate zone, and underscores likely drivers of widespread declines in populations of migratory birds. Our work also highlights the value of natural history collections to document the effects of global change on biodiversity.

Trade‐offs in expressed major histocompatibility complex diversity seen on a macroevolutionary scale among songbirds

To survive organisms must defend themselves against pathogens. Classical Major Histocompatibility Complex (MHC) genes play a key role in pathogen defense by encoding molecules involved in pathogen recognition. MHC diversity influences the variety of pathogens individuals can recognize and respond to and has consequently been a popular genetic marker for disease resistance in ecology and evolution. However, MHC diversity is predominantly estimated using genomic DNA (gDNA) with little knowledge of expressed diversity. This limits our ability to interpret the adaptive significance of variation in MHC diversity, especially in species with very many MHC genes, such as songbirds. Here we address this issue using phylogenetic comparative analyses of the number of MHC class I alleles (MHC-I diversity) in gDNA and complementary DNA (cDNA), i.e. expressed alleles, across thirteen songbird species. We propose three theoretical relationships that could be expected between genomic and expressed MHC-I diversity on a macro-evolutionary scale and test which of these are best supported. In doing so, we show that significantly fewer MHC-I alleles than the number available are expressed, suggesting that optimal MHC-I diversity could be achieved by modulating gene expression. Understanding the relationship between genomic and expressed MHC-I diversity is essential for interpreting variation in MHC diversity in an evolutionary context. This article is protected by copyright. All rights reserved.

East Asian buntings: Ongoing illegal trade and encouraging conservation responses

AbstractThe dramatic decline in the once superabundant Yellow‐breasted Bunting Emberiza aureola, a widely distributed Eurasian songbird, triggered worldwide media interest. Five years after the initial publication, we set out to give an update on the status of this critically endangered species, the conservation actions that followed, and the lessons that can be learned from this exceptional case for the conservation of migratory land birds in Asia and beyond. While there are signs of possible population recovery in the Yellow‐breasted Bunting, other migratory songbird species were recently observed to be trapped in huge numbers, which could lead to further declines. We argue that the Yellow‐breasted Bunting can be used as a flagship species to promote the conservation of East Asian land bird migrants.

Auditory perception of self and others in zebra finches: evidence from an operant discrimination task.

Vocal communication is essential for social interactions in many animal species. For this purpose, an animal has to perceive vocal signals of conspecifics and is often also required to discriminate conspecifics. The capacity to discriminate conspecifics is particularly important in social species in which individuals interact repeatedly. In addition, auditory perception of self plays an important role for vocal learners. A vocal learner has to memorise vocalisations of conspecifics and to subsequently modify its own vocalisations in order to match the memorised vocalisations. Here, we investigated auditory perception of self and others in zebra finches (Taeniopygia guttata), a highly gregarious songbird species and vocal learner. We used laboratory colonies in which founder males had been previously trained to produce the same song type. This resulted in artificial dialects in the song of founders and their offspring. We investigated whether those birds would be able to discriminate between familiar and unfamiliar conspecifics based on song. Furthermore, we examined whether they would classify their own song as familiar or unfamiliar. We found that birds were able to discriminate between songs of familiar versus unfamiliar conspecifics, despite the fact that all songs were imitations of the same song type. This suggests that such discrimination is possible even based on songs with a high acoustic similarity. None of the subjects classified their own song as unfamiliar. Three out of eight males classified their own song as familiar. Thus zebra finches might recognise their own song. Further experiments are needed to confirm such self-recognition.

An inexpensive, 3D‐printable breast muscle meter for field ornithologists

The size of the pectoral muscle is an important component of body condition in birds and has been linked to indices of fitness and migratory performance. Bauchinger et al. (2011. Journal of Ornithology 152: 507–514) developed, calibrated, and validated an aluminum “muscle meter” device that estimates the size of pectoral muscles noninvasively. To make this tool more widely available, we created a CAD model from 3D‐scan data of the aluminum muscle meter that can be 3D‐printed in durable plastic for ~ $30 USD. We tested this device on seven species of songbirds in Jamaica, The Bahamas, Cameroon, Equatorial Guinea, and Michigan. We demonstrate that the breast muscle meter measurements are (1) repeatable among users, (2) correlated with a four‐category visual breast muscle scoring system, and (3) correlated with scaled mass index (an index of body condition). Muscle scores from our device outperformed the traditional four‐category muscle scoring system in predicting scaled mass index. Finally, with our device, we quantified the increasing breast muscle size of American Redstarts (Setophaga ruticilla) from March through May as they prepared for spring migration. Given the precision of the 3D‐scanning hardware used to generate our 3D image for printing, we produced a plastic muscle meter that is as precise and useful as the aluminum original, but more cost‐effective and widely available.

11ß hydroxysteroid dehydrogenases regulate circulating glucocorticoids but not central gene expression

Regulation of glucocorticoids (GCs), important mediators of physiology and behavior at rest and during stress, is multi-faceted and dynamic. The 11ß hydroxysteroid dehydrogenases 11ß-HSD1 and 11ß-HSD2 catalyze the regeneration and inactivation of GCs, respectively, and provide peripheral and central control over GC actions in mammals. While these enzymes have only recently been investigated in just two songbird species, central expression patterns suggest that they may function differently in birds and mammals, and little is known about how peripheral expression regulates circulating GCs. In this study, we utilized the 11ß-HSD inhibitor carbenoxolone (CBX) to probe the functional effects of 11ß-HSD activity on circulating GCs and central GC-dependent gene expression in the adult zebra finch (Taeniopygia guttata). Peripheral CBX injection produced a marked increase in baseline GCs 60 min after injection, suggestive of a dominant role for 11ß-HSD2 in regulating circulating GCs. In the adult zebra finch brain, where 11ß-HSD2 but not 11ß-HSD1 is expressed, co-incubation of micro-dissected brain regions with CBX and stress-level GCs had no impact on expression of several GC-dependent genes. These results suggest that peripheral 11ß-HSD2 attenuates circulating GCs, whereas central 11ß-HSD2 has little impact on gene expression. Instead, rapid 11ß-HSD2-based regulation of local GC levels might fine-tune membrane GC actions in brain. These results provide new insights into the dynamics of GC secretion and action in this important model organism.

A songbird strategically modifies its blinking behavior when viewing human faces.

Even though blinking is necessary to maintain clear vision in many species, blinking is likely costly because it temporarily impairs vision. Given this cost, individuals can strategically modify their blinking behavior to minimize information loss. We tested whether a songbird species modifies its blinking behavior when viewing potential threats (human faces). We recorded the blinking behavior of captive great-tailed grackles (Quiscalus mexicanus) before, during, and after they viewed human face stimuli or control stimuli (tree bark as well as scrambled versions of human faces and tree bark). We found that the birds inhibited their blinking behavior the most when viewing human faces versus controls. In addition, they inhibited their blinking behavior more when viewing human faces that were directed rather than averted. Furthermore, when viewing the human faces, their blinking behavior was modified based on reactivity. These results suggest that a songbird can strategically modify its blinking behavior based on its perceived level of risk.

Territorial males do not discriminate between local and novel plumage phenotypes in a tropical songbird species complex: implications for the role of social selection in trait evolution

Whether novel traits involved in animal communication are favored or not by social selection depends on how receivers respond to them. If alternative traits arise at different locations or the same traits are perceived differently, then populations may diverge even when occupying similar environments. Aggressiveness towards bearers of novel versus familiar traits is informative about how male-male competition may drive phenotypic evolution, yet few studies have tested the function of signaling traits in social selection across populations. We assessed the role of a black pectoral band during territorial contests in two allopatric species of Neotropical passerine birds in the genus Arremon either having or lacking this plumage trait. Field experiments using taxidermic mounts and playback of conspecific songs revealed that males of both species were equally aggressive towards phenotypes bearing or lacking a pectoral band. Although evaluating physiological and social costs of bearing alternative traits and assessing female preferences is required to further examine the roles of social and sexual mechanisms in the evolution of plumage and geographic variation, our results indicate that social selection via male-male interactions is an unlikely driver of phenotypic divergence among populations of Arremon. Social selection via intrasexual competition for resources may drive phenotypic divergence and population differentation in animals, but few studies have tested predictions of this hypothesis by examining how alternative traits varying geographically are perceived in contexts of male-male competition. We assessed the behavioral response of territorial males in two species of Neotropical songbirds to taxidermic mounts having or lacking a black pectoral band, a geographically variable plumage trait. Irrespective of their own phenotype, males of both species were similarly aggressive to potential intruders bearing or lacking the pectoral band. In contrast with work suggesting male-male interactions may mediate trait evolution, our results indicate that pectoral bands in this system are unlikely targets of social selection via contests in which males compete for territories, and call for studies assessing long-term costs of bearing alternative traits or female choice as selective forces driving phenotypic evolution.

Discrimination of natural acoustic variation in vocal signals

Studies of acoustic communication often focus on the categories and units of vocalizations, but subtle variation also occurs in how these signals are uttered. In human speech, it is not only phonemes and words that carry information but also the timbre, intonation, and stress of how speech sounds are delivered (often referred to as “paralinguistic content”). In non-human animals, variation across utterances of vocal signals also carries behaviorally relevant information across taxa. However, the discriminability of these cues has been rarely tested in a psychophysical paradigm. Here, we focus on acoustic communication in the zebra finch (Taeniopygia guttata), a songbird species in which the male produces a single stereotyped motif repeatedly in song bouts. These motif renditions, like the song repetitions of many birds, sound very similar to the casual human listener. In this study, we show that zebra finches can easily discriminate between the renditions, even at the level of single song syllables, much as humans can discriminate renditions of speech sounds. These results support the notion that sensitivity to fine acoustic details may be a primary channel of information in zebra finch song, as well as a shared, foundational property of vocal communication systems across species.

A regional-scale study of associations between farmland birds and linear woody networks of hedgerows and trees

Farmland birds have declined throughout Europe over recent decades. Many farmland songbirds are associated with linear woody features on field boundaries, such as hedgerows and tree lines. Previous studies have assessed songbird associations with specific hedgerow and tree characteristics, and their landscape context, but large-scale assessments have been limited by difficulties in mapping linear woody networks over large extents, particularly their height structure. We used a high-resolution lidar model of the complete network of linear woody features in southwest England (9424 km2), summarising linear feature lengths by height class. Associations were tested between heights of linear woody features and the abundance of 22 farmland birds, using bird survey data summarised for 1446 near-contiguous tetrads, and a weighted version of the phi coefficient of association. Land cover mapping defined tetrads as grassland, mixed or arable farmland.Results showed that the linear woody network was dominated by features corresponding to managed hedgerows (1.5–2.9 m tall, 42−47% of the network by land cover type), followed by tree lines (≥ 6.0 m, 28–35 %). All songbird species had statistically significant, but weak, associations with combinations of land cover and height class of linear woody features, although land cover appeared to be the dominant factor. Many species showed more positive associations with linear woody features on arable farmland than on grassland, particularly for taller hedgerows and tree lines. The results suggest that land-use diversification may benefit some farmland songbirds, such as introducing pockets of arable farming in landscapes dominated by intensively managed grassland. Diverse heights in the linear woody network, incorporating tall hedgerows and trees, would also likely benefit a range of songbird species. The study demonstrates the significant potential of lidar in characterising the structure of linear woody features at the landscape scale, facilitating detailed analyses of wildlife habitat associations and landscape ecology.

Grazer density and songbird counts in a restored conservation area.

Grazing by large herbivores is increasingly used as a management tool in European nature reserves. The aim is usually to support an open but heterogeneous habitat and its corresponding plant and animal communities. Previous studies showed that birds may profit from grazing but that the effect varies among bird species. Such studies often compared bird counts among grazed areas with different stocking rates of herbivores. Here, we investigated how space use of Konik horses and Highland cattle is related to bird counts in a recently restored conservation area with a year-round natural grazing management. We equipped five horses and five cattle with GPS collars and correlated the density of their GPS positions on the grazed area with the density of bird observations from winter through the breeding season. We found that in the songbirds of our study site, both the overall density of bird individuals and the number of species increased with increasing density of GPS positions of grazers. Correlations of bird density with horse density were similar to correlations with cattle density. Of the eight most common songbird species observed in our study area, the Eurasian Skylark and the Common Starling had the clearest positive correlations with grazer density, while the Blackbird showed a negative correlation. Skylarks and Starlings in our study area thus seem to profit from year-round natural grazing by a mixed group of horses and cattle.

Fuel loads of Neotropical migrant songbirds on autumn passage through the Darién region of Colombia: Influence of migratory distance, route, ENSO, age and body size

AbstractAvailable energy stores determine stopover length, migration speed and likely survival in migrating birds. We measured energy stores by estimating fuel load in 11 species of Neotropical migrant songbirds in the Darién of Colombia over five years. We evaluated 1) whether individuals flying further from breeding origin arrived with smaller fuel loads, 2) if the ENSO (El Niño-Southern Oscillation) cycle affected fuel load and 3) if species known to migrate mostly overwater arrived with less fuel relative to those migrating overland. Breeding origin, inferred from feather δ2H values, only had a significant positive effect on fuel load in Swainson’s Thrush (Catharus ustulatus). Veery (Catharus fuscescens) and Swainson’s thrush had higher and lower fuel loads, respectively, in El Niño years. Multi-species mixed-effects models revealed support for larger fuel loads in larger-bodied species and in species taking overwater routes, contrary to our prediction. Across species, we found no support for common effects of breeding origin or ENSO on fuel loads, in contrast to community-wide effects of migration route and body-size. In general, the variables considered here explained little of the variance in fuel loads, suggesting that inter-individual differences likely have a greater impact than broad-scale factors in our study system.

Species turnover in forest bird communities on Fiordland islands following predator eradications

Recent advances in the control of mammalian predators have begun to reveal interspecific competition as a key driver in the structure of New Zealand forest bird communities once predation pressure is reduced. We present evidence that, when at high densities, South Island robins (Petroica australis) may be responsible for declines in a suite of smaller native and introduced songbird species. Bird surveys undertaken on 47 islands in Breaksea Sound and Dusky Sound, Fiordland, during 1974 to 1986, were repeated on the same islands in 2016 or 2019. During the first block of surveys, Norway rats (Rattus norvegicus) were present on two islands, and stoats (Mustela erminea) were known or presumed to regularly reach 43 of the remaining islands. The rats were eradicated in 1986 and 1988, and stoats have been controlled to zero density since 2001 on all 28 of the islands surveyed in Dusky Sound, and since 2008 on 12 of 19 islands surveyed in Breaksea Sound. Bird species that apparently benefited from pest mammal eradications included South Island robin (Petroica australis) and kākā (Nestor meridionalis), both of which are endemic. Species recorded less often after the eradications included tomtit (Petroica macrocephala), grey warbler (Gerygone igata), silvereye (Zosterops lateralis), dunnock (Prunella modularis), and chaffinch (Fringilla coelebs) – a mixture of endemic, native, and introduced species. We hypothesise that these five species have been outcompeted or displaced by the now widespread and abundant South Island robin, probably through aggressive interactions.

Threats to an undescribed songbird species in Indonesia

Threats to an undescribed songbird species in Indonesia

The First Record of Horned Lark from Jigme Khesar Strict Nature Reserve – A New Record for Bhutan

The Horned Lark (Eremophila alpestris) even though a widespread songbird species had not been recorded from Bhutan. The bird was observed in Jigme Khesar Strict Nature Reserve in a recent trip to Gakiling, Haa. With this new record, the number of bird species found in Bhutan has increased to 739 species.

Interspecific aggression and defence of extra nest sites in two species of songbirds

AbstractInterspecific competition is expected when two species share resource needs. For example, secondary cavity‐nesting birds may compete vigorously for suitable nest sites both within and among species. However, little is known of whether monogamous species defend more than one nest site on their territory after breeding has begun, and in particular whether they are aggressive against other species. Defending extra nest sites may be adaptive because they may be used for renesting after a failure or to produce a second brood. We studied interactions between a monogamous, resident bird, the great tit Parus major and a migrant, the pied flycatcher Ficedula hypoleuca, providing nest boxes in woodlands in Norway. Agonistic behaviours may be subtle and easily overlooked so we experimentally placed caged male pied flycatchers near nests of great tits and at a dyad of empty nest boxes erected in the territory 25 m away. We filmed interactions between species at 21 sites in the egg‐laying period of the tit, and at 26 nest sites during incubation. Male great tits showed aggression towards the caged flycatcher both at their own nest box and at the nest boxes erected at a distance. We manipulated the external appearance of the nest boxes with painted designs around the entrances but the intensity of aggression at the empty nest boxes did not depend on whether those boxes matched the nest box with the tit nest and was not correlated with tit clutch size. Neither was the intensity of display activity at each nest box by the flycatchers that settled associated with these variables. The results are discussed in relation to hypotheses for nest site choice involving interspecific social learning and aggression.