Songbird Species Research Articles

Exposure of passerine birds to brodifacoum during management of Norway rats on farms

The exposure of non-target wildlife to anticoagulant compounds used for rodent control is a well-known phenomenon. Exposure can be primary when non-target species consume bait or secondary via uptake of poisoned animals by mammalian and avian predators. However, nothing is known about the exposure patterns in passerine birds that are commonly present on farms where rodent control is conducted.We used liquid chromatography coupled with tandem mass spectrometry to screen for residues of anticoagulant rodenticides (ARs) in liver tissue of passerine birds that were present during rodent control with a product containing brodifacoum (BR). The 222 birds of 13 species were bycatch of rodent snap trapping in 2011–2013 on 11 livestock farms run synchronously with baiting.During baiting, ARs were detected in about 30% of birds; 28% carried BR. In liver tissue of 54 birds that carried BR, concentrations ranged from 4 to 7809 ng/g (mean 490 ± 169 ng/g). Among common bird species with AR residues, BR was most prevalent in robins (Erithacus rubecula) (44%) and dunnocks (Prunella modularis) (41%). Mean BR concentration was highest in great tits (Parus major) (902 ± 405 ng/g). The occurrence and concentrations of BR residues were about 30% higher in birds collected close to bait stations compared to birds collected further away.The results demonstrate that several ground feeding songbird species are exposed to ARs used on farms. If BR was present in liver tissue, concentrations were variable, which may imply a combination of primary and secondary exposure of songbirds. Exposure was mostly restricted to the immediate surroundings of farms where bait was used, which might limit the transfer to the wider environment. Efforts should be made to reduce the access for birds to AR bait to prevent high exposure.

High responsiveness of auditory neurons to specific combination of acoustic features in female songbirds.

Zebra finch (Taeniopygia guttata) is a songbird species in which males sing their unique songs to attract females who then select their preferred male. Acoustic features in the songs of individual males are important features for female auditory perception. While the male of this species is a classic model of vocal production, it has been little known about auditory processing in female. In the higher auditory brain regions, the caudomedial mesopallium (CMM) and nidopallium (NCM) contribute to female's sound recognition, we, therefore, extracted acoustic features that induce neural activities with high detection power on both regions in female finches. A multiple linear regression analysis revealed that neurons were sensitive to mean frequency and Wiener entropy. In addition, we performed an experiment with modified artificial songs and harmonic songs to directly investigate neural responsiveness for deriving further evidence for the contribution of these two acoustic features. Finally, we illustrated a specific ratio combining these two acoustic features that showed highest sensitivity to neural responsiveness, and we found that properties of sensitivity are different between CMM and NCM. Our results indicate that the mixture of the two acoustic features with the specific ratio is important in the higher auditory regions of female songbirds, and these two regions have differences in encoding for sensitivity to these acoustic features.

Do Female Songbirds Avoid a Mammalian Nest Predator When Selecting Their Nest Site?

Perceived predation risk can elicit strong behavioral responses in potential prey. During nest building, songbirds exhibit anti-predator behaviors under experimental conditions. Here, we hypothesized that females of two ground-nesting songbird species, the Ovenbird (Seiurus aurocapilla) and the Hermit Thrush (Catharus guttatus), would use naturally available cues of predation risk when selecting their nest site, thereby avoiding activity hotspots of Eastern Chipmunks (Tamias striatus), a predator on songbird nests and fledglings. Chipmunks are highly vocal, thus providing cues of their presence. We mapped chipmunk detections and songbird nests over four successive years in study plots located in mature deciduous forest of New Brunswick, Canada. Chipmunk activity varied by an order of magnitude among study plots and years. Nests were built further away from chipmunk detections than expected by chance in some, but not all, plot-year combinations. When comparing study plots, the proportion of nests built within hotspots of chipmunk activity was four times lower in the two plots where chipmunk activity was highest. Yet, we did not find clear evidence that chipmunk avoidance provided fitness benefits, possibly because this behavior procured little protection at high chipmunk densities. The persistence of this avoidance behavior in our focal species of ground-nesting songbirds might be linked to the benefits it procures at intermediate chipmunk densities.

Budgerigars have complex sleep structure similar to that of mammals.

Birds and mammals share specialized forms of sleep including slow wave sleep (SWS) and rapid eye movement sleep (REM), raising the question of why and how specialized sleep evolved. Extensive prior studies concluded that avian sleep lacked many features characteristic of mammalian sleep, and therefore that specialized sleep must have evolved independently in birds and mammals. This has been challenged by evidence of more complex sleep in multiple songbird species. To extend this analysis beyond songbirds, we examined a species of parrot, the sister taxon to songbirds. We implanted adult budgerigars (Melopsittacus undulatus) with electroencephalogram (EEG) and electrooculogram (EOG) electrodes to evaluate sleep architecture, and video monitored birds during sleep. Sleep was scored with manual and automated techniques, including automated detection of slow waves and eye movements. This can help define a new standard for how to score sleep in birds. Budgerigars exhibited consolidated sleep, a pattern also observed in songbirds, and many mammalian species, including humans. We found that REM constituted 26.5% of total sleep, comparable to humans and an order of magnitude greater than previously reported. Although we observed no spindles, we found a clear state of intermediate sleep (IS) similar to non-REM (NREM) stage 2. Across the night, SWS decreased and REM increased, as observed in mammals and songbirds. Slow wave activity (SWA) fluctuated with a 29-min ultradian rhythm, indicating a tendency to move systematically through sleep states as observed in other species with consolidated sleep. These results are at variance with numerous older sleep studies, including for budgerigars. Here, we demonstrated that lighting conditions used in the prior budgerigar study-and commonly used in older bird studies-dramatically disrupted budgerigar sleep structure, explaining the prior results. Thus, it is likely that more complex sleep has been overlooked in a broad range of bird species. The similarities in sleep architecture observed in mammals, songbirds, and now budgerigars, alongside recent work in reptiles and basal birds, provide support for the hypothesis that a common amniote ancestor possessed the precursors that gave rise to REM and SWS at one or more loci in the parallel evolution of sleep in higher vertebrates. We discuss this hypothesis in terms of the common plan of forebrain organization shared by reptiles, birds, and mammals.

Effects of a Bacterial Infection on Mitochondrial Function and Oxidative Stress in a Songbird.

AbstractAs a major physiological mechanism involved in cellular renewal and repair, immune function is vital to the body's capacity to support tissue maintenance and organismal survival. Because immune defenses can be energetically expensive, the activities of metabolically active organs, such as the liver, are predicted to increase during infection by most pathogens. However, some pathogens are immunosuppressive, which might reduce the metabolic capacities of select organs to suppress immune response. Mycoplasma gallisepticum (MG) is a well-known immunosuppressive bacterium that infects domestic chickens and turkeys as well as songbirds. In the house finch (Haemorhous mexicanus), which is the primary host for MG among songbird species, MG infects both the respiratory system and the conjunctiva of the eye, causing conspicuous swelling. To study the effect of a systemic bacterial infection on cellular respiration and oxidative damage in the house finch, we measured mitochondrial respiration, mitochondrial membrane potential, reactive oxygen species production, and oxidative damage in the livers of house finches that were wild caught and either infected with MG, as indicated by genetic screening for the pathogen, or free of MG infection. We observed that MG-infected house finches showed significantly lower oxidative lipid and protein damage in liver tissue compared with their uninfected counterparts. Moreover, using complex II substrates, we documented a nonsignificant trend for lower state 3 respiration of liver mitochondria in MG-infected house finches compared with uninfected house finches (). These results are consistent with the hypothesis that MG suppresses organ function in susceptible hosts.

Parental benefits and offspring costs reflect parent–offspring conflict over the age of fledging among songbirds

Parent-offspring conflict has explained a variety of ecological phenomena across animal taxa, but its role in mediating when songbirds fledge remains controversial. Specifically, ecologists have long debated the influence of songbird parents on the age of fledging: Do parents manipulate offspring into fledging to optimize their own fitness or do offspring choose when to leave? To provide greater insight into parent-offspring conflict over fledging age in songbirds, we compared nesting and postfledging survival rates across 18 species from eight studies in the continental United States. For 12 species (67%), we found that fledging transitions offspring from comparatively safe nesting environments to more dangerous postfledging ones, resulting in a postfledging bottleneck. This raises an important question: as past research shows that offspring would benefit-improve postfledging survival-by staying in the nest longer: Why then do they fledge so early? Our findings suggest that parents manipulate offspring into fledging early for their own benefit, but at the cost of survival for each individual offspring, reflecting parent-offspring conflict. Early fledging incurred, on average, a 13.6% postfledging survival cost for each individual offspring, but parents benefitted through a 14.0% increase in the likelihood of raising at least one offspring to independence. These parental benefits were uneven across species-driven by an interaction between nest mortality risk and brood size-and predicted the age of fledging among species. Collectively, our results suggest that parent-offspring conflict and associated parental benefits explain variation in fledging age among songbird species and why postfledging bottlenecks occur.

Categorical Auditory Working Memory in Crows.

SummaryThe ability to group sensory data into behaviorally meaningful classes and to maintain these perceptual categories active in working memory is key to intelligent behavior. Here, we show that carrion crows, highly vocal and cognitively advanced corvid songbirds, possess categorical auditory working memory. The crows were trained in a delayed match-to-category task that required them to flexibly match remembered sounds based on the upward or downward shift of the sounds' frequency modulation. After training, the crows instantaneously classified novel sounds into the correct auditory categories. The crows showed sharp category boundaries as a function of the relative frequency interval of the modulation. In addition, the crows generalized frequency-modulated sounds within a category and correctly classified novel sounds kept in working memory irrespective of other acoustic features of the sound. This suggests that crows can form and actively memorize auditory perceptual categories in the service of cognitive control of their goal-directed behaviors.

Inferring spatial patterns of mercury exposure in migratory boreal songbirds: Combining feather mercury and stable isotope (δ2H) measurements

Migratory songbirds breeding in the Canadian Boreal forest are exposed to mercury (Hg), a potent neurotoxin that impairs avian health, however, the degree of exposure depends on many factors. As breeding grounds are geographically remote and vast, the measurement of Hg in individual birds is impractical particularly at large spatial scales. Here, we present a Canada-wide dataset of nearly 2000 migratory songbirds that were used to assess summer Hg exposure of 15 songbird species sampled during fall migration. We measured Hg concentrations in tail feathers and related those to dietary guild, geographic capture location, age, sex and probable breeding ground locations using feather δ2H. Overall mean (±SE) feather Hg concentration was 1.49 ± 0.03 μg/g (N = 1946): however, a clear geographic gradient in feather Hg concentrations emerged being highest in East and lowest in West. Dietary guild was the next strongest predictor of feather Hg with insectivorous songbirds in Eastern Canada at particular risk due to Hg exposure on summer breeding grounds. This broad-scale assessment of Hg exposure in migratory songbirds in Canada can be used to guide future studies on finer-scale determinants of Hg exposure in birds.

A hierarchy of compass systems in migratory birds

Migratory birds use several different sources of orientation information. They have at least three compass systems based on different cues: the sun and polarized light, the stars and their constellations, and the geomagnetic field. The concurrent information obtained from these three compasses is redundant, therefore the compasses need to have a hierarchy and must be calibrated relative to each other. One of the compasses should dominate the others, or some orientation cue should be used to calibrate the remaining compass systems. Results of experiments on a variety of songbird species demonstrate that while astronomical cues calibrate the magnetic compass during the pre-migratory period, strategies used during the migratory period are more diverse. In the present review, we analyze the results of all crucial cue-conflict studies, mostly performed in nocturnal songbird migrants; we also try to understand why some migratory species calibrate their magnetic compass on sunset cues while others use the geomagnetic field or stars as a primary cue source, and we examine why the previous hypothesis could not explain the findings of all cue-conflict experiments.

Post-fledging Golden-winged Warblers require forests with multiple stand developmental stages

Abstract Our understanding of songbird habitat needs during the breeding season stems largely from studies of nest success. However, growing evidence shows that nesting habitat and post-fledging habitat often differ. Management guidelines for declining species need to be reevaluated and updated to account for habitat shifts that may occur across the full breeding cycle. The Golden-winged Warbler (Vermivora chrysoptera) is a declining songbird species for which best management practices (BMPs) are based overwhelmingly on nesting habitat. We studied stand-scale habitat selection by fledgling Golden-winged Warblers during May–July, 2014–2017, in 2 landscapes (2 yr of data for each landscape), 200 km apart in Pennsylvania. Across 4 yr, we radio-tagged and tracked 156 fledglings. We used discrete-choice models to evaluate habitat selection during 2 post-fledging time periods (days 1–5, days 6–28). Fledglings used a variety of cover types, but most telemetry relocations (i.e. 85%) occurred in forest in the stand initiation stage, stem exclusion stage, or mature forest upland. Fledglings primarily selected stand initiation forest during the first 5 days, but preferred habitats differed between regions during days 6–28 post-fledging. Fledglings in one landscape favored stands in the stem exclusion stage while fledglings in the other landscape continued to select stands in the initiation stage. Fledglings moved greater distances as they aged and dispersed ~750 m by day 28 post-fledging. These findings suggest the need to update Golden-winged Warbler BMPs to account for the broader habitat needs of fledglings during the breeding season. In addition, these results indicate that regional studies of habitat requirements can help guide management of dynamic forest landscapes for birds.

Ultraviolet-reflective film applied to windows reduces the likelihood of collisions for two species of songbird.

Perhaps a billion birds die annually from colliding with residential and commercial windows. Therefore, there is a societal need to develop technologies that reduce window collisions by birds. Many current window films that are applied to the external surface of windows have human-visible patterns that are not esthetically preferable. BirdShades have developed a short wavelength (ultraviolet) reflective film that appears as a slight tint to the human eye but should be highly visible to many bird species that see in this spectral range. We performed flight tunnel tests of whether the BirdShades external window film reduced the likelihood that two species of song bird (zebra finch, Taeniopygia guttata and brown-headed cowbird, Molothrus ater) collide with windows during daylight. We paid particular attention to simulate the lighting conditions that birds will experience while flying during the day. Our results indicate a 75–90% reduction in the likelihood of collision with BirdShades-treated compared with control windows, in forced choice trials. In more ecologically relevant comparison between trials where all windows were either treated or control windows, the estimated reduction in probability of collision was 30–50%. Further, both bird species slow their flight by approximately 25% when approaching windows treated with the BirdShades film, thereby reducing the force of collisions if they were to happen. Therefore, we conclude that the BirdShades external window film will be effective in reducing the risk of and damage caused to populations and property by birds’ collision with windows. As this ultraviolet-reflective film has no human-visible patterning to it, the product might be an esthetically more acceptable low cost solution to reducing bird-window collisions. Further, we call for testing of other mitigation technologies in lighting and ecological conditions that are more similar to what birds experience in real human-built environments and make suggestions for testing standards to assess collision-reducing technologies.

Effects of breeding and molt activity on songbird site fidelity

AbstractThe prebasic molt is a perilous period for songbirds, characterized by heightened energetic demands and vulnerability to predators. Given these vulnerabilities, songbirds are under selective pressure to locate and use quality habitat during the prebasic molt, potentially resulting in site fidelity between years. In this study, we aimed to determine how differences in breeding and molting activity affected site fidelity for a diversity of species at the landscape scale. To accomplish our objective, we used 31 yr of banding data from northern California and southern Oregon for 16 species of songbirds with Cormack-Jolly-Seber analyses and weighted linear regression models to assess the effects of molting and breeding activity on the probability of a species returning to a site in subsequent years. Despite substantial variation in site use for breeding and/or molting, each study species had at least some locations that were used for both breeding and molting. Captured breeding birds (n = 18,574) were much more common than molting birds (n = 7,622). Breeding activity was positively correlated with higher site fidelity for 10 of the 16 species, while we found little evidence of a relationship between molting activity and site fidelity. Only the Dark-eyed Junco (Junco hyemalis) showed increased site fidelity with increased presence of molt activity. It is likely that a shifting mosaic of food resources during the post-breeding period drives dynamic movements of songbirds in search of the necessary resources to successfully complete their annual molt.

Rhythm: Similar Structure in Birdsong and Music Gives Neuroethological Insight

Analysis of the rhythm structure of the songs of two songbird species and corpora of human music finds compelling similarities in rhythm categories and the effects of tempo. This gives insight into the neuroethological basis of song and music production.

Mercury delays cerebellar development in a model songbird species, the zebra finch.

Mercury exposure can disrupt development of the cerebellum, part of the brain essential for coordination of movement through a complex environment, including flight. In precocial birds, such as fowl, the cerebellum develops embryonically, and the chick is capable of leaving the nest within hours of hatching. However, most birds, including all songbirds, are altricial, and spend weeks in the nest between hatching and fledging. The objective of this study was to describe the normal development of the cerebellum in a model altricial songbird so as to determine the effect of exposure to mercury on cerebellar maturation. Adult zebra finch (Taeniopygia guttata) pairs were fed either a control diet, or a diet augmented with one of four treatment-levels of methylmercury (0.3-2.4 μg/g wet weight), and their offspring, the subjects of this study, were fed the same diet by parents. We documented, for the first time, the schedule of cerebellar development in an altricial bird, and compared stages of development among methylmercury-exposed groups. For all treatments of methylmercury, the age of completion of cellular migration was later than for control zebra finches, indicating a delay in cerebellar maturation. Displaced (heterotopic) Purkinje neurons, a pathology typical of methylmercury exposure in developing vertebrate brains, were more numerous in methylmercury-exposed birds, and persisted at least until the age of independence. Delays in maturation of the cerebellum could delay fledging in altricial bird species, with potential serious implications for the fitness of exposed individuals, as predation rates in the nest are often very high.

Development syndromes in New World temperate and tropical songbirds.

We studied avian development in 49 to 153 species of temperate and tropical New World passerine birds to determine how growth rates, and incubation and nestling periods, varied in relation to other life-history traits. We collected growth data and generated unbiased mass and tarsus growth rate estimates (mass n = 92 species, tarsus n = 49 species), and measured incubation period (n = 151) and nestling period (n = 153), which we analyzed with respect to region, egg mass, adult mass, clutch size, parental care type, nest type, daily nest predation rate (DMR), and nest height. We investigated covariation of life-history and natural-history attributes with the four development traits after controlling for phylogeny. Species in our lowland tropical sample grew 20% (incubation period), 25% (mass growth rate), and 26% (tarsus growth rate) more slowly than in our temperate sample. Nestling period did not vary with respect to latitude, which suggests that tropical songbirds fledge in a less well-developed state than temperate species. Suboscine species typically exhibited slower embryonic and post-embryonic growth than oscine passerines regardless of their breeding region. This pattern of slow development in tropical species could reflect phylogenetic effects based on unknown physiological attributes. Time-dependent nest mortality was unrelated to nestling mass growth rate, tarsus growth rate, and incubation period, but was significantly associated with nestling period. This suggests that nest predation, the predominant cause of nest loss in songbirds, does not exert strong selection on physiologically constrained traits, such as embryonic and post-embryonic growth, among our samples of temperate and lowland tropical songbird species. Nestling period, which is evolutionarily more labile than growth rate, was significantly shorter in birds exposed to higher rates of nest loss and nesting at lower heights, among other traits. Differences in life-history variation across latitudes provide insight into how unique ecological characteristics of each region influence physiological processes of passerines, and thus, how they can shape the evolution of life histories. While development traits clearly vary with respect to latitude, trait distributions overlap broadly. Life-history and natural history associations differ for each development trait, which suggests that unique selective pressures or constraints influence the evolution of each trait.

Quantifying Long-Term Bird Population Responses to Simulated Harvest Plans and Cumulative Effects of Disturbance

There is interest in linking outputs from land use simulators to bird species distribution models to project how boreal birds will respond to cumulative effects of caribou (Rangifer tarandus) conservation, harvest, fire, and energy-sector development in Alberta. Our hypotheses were: 1) species associated with older mixed-wood stands would decline more if harvest was shifted away from areas used by caribou to areas with more mixed-wood; and 2) species associated with older forests would be more negatively affected by the combined effects of harvest, fire, and non-forestry footprint than by harvest alone. We used vegetation data from two harvest scenarios produced in Patchworks as inputs for density models of 20 boreal forest songbird and woodpecker species in Alberta. We projected abundance of these species over 50 years under: 1) two scenarios created in Patchworks, without fire but with and without deferral of timber harvest within a caribou conservation zone on lands tenured to Alberta-Pacific Forest Industries Inc.; 2) a scenario with fire but no human footprint; and 3) five scenarios in ALCES Online, in which habitat was affected by Patchworks harvest locations, fire (1-2 × current rate), and energy sector development (present or absent; with or without seismic line reclamation to improve caribou habitat). In the Patchworks scenarios, we found similar projected numbers of each bird species over time, whether harvest deferral occurred or not. Both harvest plans increased habitat and numbers for most species associated with older forests over 50 years, while most species associated with younger forests declined in both harvest plans, because average projected forest age increased over 50 years. Fire and other footprint generally reduced relative amount of habitat for species associated with older forests, which still increased over time, while other species responded positively or less negatively to fire. Seismic restoration created habitat for three-quarters of species that responded negatively to energy sector development over 50 years. As projections depended on whether just harvest, fire or all footprints were analyzed, multiple human impacts over time beyond harvest should be considered in conservation and land use planning based on long-term predictions about wildlife in anthropogenic landscapes.

Glucose Concentrations in Closely Related Titmice (Baeolophus) Species Linked to Regional Habitat Differences Across an Avian Hybrid Zone

Aims:We used physiological data, in conjunction with habitat information, to elucidate the interactions between two hybridizing songbirds within a hybrid zone.Background:Hybrid zones are ideal regions to examine a variety of ecological, behavior, and evolutionary processes. In addition to genetics, behavior, and morphology, physiological differences may impact hybrid fitness, genetic introgression, and even the stability of a hybrid zone.Objective:To assess physiological differences in hybridizing species, we investigated selected venous blood analytes in two species of songbirds hybridizing along the Balcones Escarpment in central Texas.Methods:Using a portable blood analyzer, we assayed blood samples from Black-crested Titmouse (Baeolophus atricristatus) and Tufted Titmouse (B. bicolor) individuals along a longitudinal transect that included the contact zone. Ecologically, this transect varies from higher elevation semi-arid regions on the Balcones Escarpment (and west across the Edwards Plateau) to lower elevation mesic forests east of the escarpment.Results:As expected, several blood analytes differed with age, sex, and sedative administration; however, we observed relatively increased blood glucose concentrations in Black-crested Titmice, which occupy the semi-arid habitats of west Texas. Furthermore, glucose concentrations were further elevated following rainfall events. Blood glucose concentrations often increase during stressful conditions and or related to changes in diet.Conclusion:We suspect that Black-crested Titmice have relatively increased blood glucose concentrations as a product of living in a semi-arid environment that causes chronic stress from unpredictable food and water resources. The link between rainfall and glucose may be a result of the increased and greater diversity of food availability after rainfall. Although further research is needed, we suspect that habitat differences and associated lack of physiological adaptations may be a limiting factor in westward range expansion in the more aggressive Tufted Titmice.

Intrinsic Markers Reveal Breeding Origin and Geographically-Structured Migration Timing of Two Songbird Species at a Coastal Stopover Site

AbstractWe used stable hydrogen isotope markers to identify geographic provenance of Blackpoll Warblers (Setophaga striata) and Red-eyed Vireos (Vireo olivaceus) passing through a coastal stopover area in the Gulf of Maine on fall migration, and supplemented δ2 H signatures from feathers with wing length data as an additional proxy for migration origin, since geographic size variation has been documented for this species. We captured migrant blackpolls with putative origins from as close as the Adirondacks, New Brunswick, and northwestern Maine, and potentially as far as Alaska. We captured vireos with putative origins from as close as Maine and Nova Scotia, and potentially as far as British Columbia and Alberta. We found a significant relationship between blackpoll wing length and capture date indicating that birds with longer wings– and thus likely from more western and northern breeding regions – passed through the capture site earlier in the season than more local breeders. In contrast, vireos from more distant breeding latitudes passed through the capture site later in the season. These results demonstrate that mid-coast Maine serves as a catchment area for both Blackpoll Warblers, and Red-eyed Vireos, and provides some evidence that connectivity between breeding areas and stopover sites may be strong for blackpolls; however, additional study linking breeding and stopover sites across the migratory range of both species is necessary to understand more fully how strong connectivity is between breeding and stopover areas for these species.

Stopover Duration and Body Mass Change of Two Siberian Songbird Species at a Refuelling Site in the Russian Far East

Long-distance bird migration is often characterized by a number of flight bouts interspersed with intermittent stopover periods for re-fuelling. However, little is known about the stopover ecology of songbirds migrating along the East Asian flyway. The aim of this study was to estimate the minimum stopover duration and body mass change during stopover of Red-flanked Bluetail Tarsiger cyanurus and Yellow-browed Warbler Phylloscopus inornatus based on 6,073 ringed and 502 re-captured birds during spring and autumn migration in the Russian Far East. For Red-flanked Bluetail the minimum stopover duration averaged 3.4 days in autumn and 1.7 days in spring, while for Yellow-browed Warbler it was 3.2 days in autumn and 2.1 days in spring. Significant differences in stopover duration were found between seasons, but not between the two species. The body mass of Red-flanked Bluetails significantly increased during stopover in spring and autumn, but no significant body mass changes were detected in Yellow-browed Warblers. The shorter minimum stopover duration of both species in spring may indicate a faster migration than in autumn, suggesting a time-minimizing strategy in spring to reach the breeding grounds as fast as possible.

Neurotelemetry Reveals Putative Predictive Activity in HVC during Call-Based Vocal Communications in Zebra Finches.

Premotor predictions facilitate vocal interactions. Here, we study such mechanisms in the forebrain nucleus HVC (proper name), a cortex-like sensorimotor area of songbirds, otherwise known for being essential for singing in zebra finches. To study the role of the HVC in calling interactions between male and female mates, we used wireless telemetric systems for simultaneous measurement of neuronal activity of male zebra finches and vocalizations of males and females that freely interact with each other. In a non-social context, male HVC neurons displayed stereotypic premotor activity in relation to active calling and showed auditory-evoked activity to hearing of played-back female calls. In a social context, HVC neurons displayed auditory-evoked activity to hearing of female calls only if that neuron showed activity preceding the upcoming female calls. We hypothesize that this activity preceding the auditory-evoked activity in the male HVC represents a neural correlate of behavioral anticipation, predictive activity that helps to coordinate vocal communication between social partners.SIGNIFICANCE STATEMENT Most social-living vertebrates produce large numbers of calls per day, and the calls have prominent roles in social interactions. Here, we show neuronal mechanisms that are active during call-based vocal communication of zebra finches, a highly social songbird species. HVC, a forebrain nucleus known for its importance in control of learned vocalizations of songbirds, displays predictive activity that may enable the male to adjust his own calling pattern to produce very fast sequences of male female call exchanges.