Small Passerine Birds Research Articles

The prenatal assimilation of minerals and metals in nestlings of a small passerine bird

Although certain metals can reach their highest concentrations in tissues of newly hatched nestlings, their sources have yet to be fully elucidated. Evidence for the differentiation of body reserves, including some chemical elements, during avian embryonic life and early post-hatching period is limited mostly to studies on poultry. Here, we present novel findings on the bioaccumulation and egg-to-nestling transfer of 10 minerals and metals, including non-essential potentially toxic chemical elements (Cu, Ni Cd, Pb, Zn, Ag, Mg, Fe, Co and Ca) in the tissues of the gastrointestinal tract (GT), whole body (WB) and carcass (CA) of nestlings of a small passerine bird, the Eurasian Reed Warbler Acrocephalus scirpaceus, breeding in an intensively fertilized fishpond habitat. Our findings show that concentrations of metals that are relevant to contaminated systems (Cu, Ni, Cd, Pb, Zn, Fe and Co) are the highest in GT tissues across all the nestling age classes examined (from hatching to day 9 of life). The important question emerged from our findings: why the hatchlings were characterized by higher metal concentrations in GT, WB and CA compared to older nestlings. We suggest that the prenatal accumulation of chemical elements assimilated from egg contents, and their subsequent utilization for building various tissues/internal organs by the growing embryo, is a reasonable explanation for this finding. More specifically, the potential functional mechanism explaining the highest concentrations of some trace metals in hatchlings seems to be associated with an extremely high rate of utilization of residual yolk metal resources that survived from the embryonic until the post-natal period. On the basis of our own work and literature data, we identified a presumable significant discrepancy in the actual rate of egg-to-nestling and egg-to-embryo metal transfer due to the eggshell being ignored (a commonly occurrence), and only the egg contents being treated as the basic repository of chemical elements for developing embryos. Much more research is needed on the prenatal assimilation and subsequent accumulation of chemical elements in a developing avian embryo, representing both the transition from near-to-hatching embryos to hatchlings, and then to older nestlings.

The flashy escape: support for dynamic flash coloration as anti-predator defence.

Dynamic flash coloration is a type of antipredator coloration where intermittently appearing colour patterns in moving animals misdirect predator attacks by obscuring the precise location and trajectory of the moving prey. Birds and butterflies with differing dorsoventral wing coloration or iridescent surface structures may potentially benefit from such effects. However, we lack an understanding of what makes for an effective dynamic flash colour design and how much it benefits the carrier. Here, we test the effect of colour flashing using small passerine birds preying upon colourful, moving, virtual 'prey' stimuli on a touchscreen. We show that at fast speeds, green-to-blue flashing colour patterns can reduce the likelihood of pecks hitting the target, induce greater error in targeting accuracy and increase the number of pecks at a stimulus relative to similarly coloured non-flashing targets. Our results support the idea that dynamic flash coloration can deflect predatory attacks at fast speeds, but the effect may be the opposite when moving slowly.

Rolling with the punches—How competition shapes the morphology of small passerines on small islands

AbstractAimWallacea is a global biodiversity hotspot and Sulawesi is the largest island in this region, notable for a high proportion of endemic species. The Wakatobi archipelago, off the southeastern peninsular arm of Sulawesi, is home to several endemic bird species. Although islands are known to influence the morphology of their resident species, competitive interactions also exert strong influences on morphology. Here, we consider the contributions of both islands and competitors on two morphological traits of two bird species in a small passerine guild found on the Wakatobi islands.LocationWakatobi archipelago, Sulawesi Tenggara, Indonesia.TaxonWakatobi White‐eye (Zosterops flavissimus) and Wakatobi Sunbird (Cinnyris infrenatus).MethodsWorking with morphological measures (from netting studies), population density metrics (from transect surveys) and fundamental data from islands (area, distance from mainland and elevation), we investigated (by means of multiple linear regression) which terms best explained variation in the body size and bill size of two small passerine birds endemic to the Wakatobi islands.ResultsBoth island metrics and competitor presence/density were useful in describing the variation in body size of both bird species. However, only competitor presence/density was useful in describing variation in bill size of the birds. The best models describing variation in these traits included terms representing both interspecific and intraspecific competition.Main ConclusionsOur findings indicate that simple island metrics may be useful in predicting some of the variation in some functional traits of island species. However, in this example, simple island metrics were insufficient to explain the full variation in body size of endemic birds across the Wakatobi archipelago and were of no use in predicting the variation in their bill size. As bill morphology frequently dictates diet and feeding niche, it is a trait which may determine population divergence and speciation. If simple island metrics fail to describe such diversification, it is surely important to capture that information in other ways.

Extra-pair paternity in the Wood Warbler (Phylloscopus sibilatrix) in Central Russia

Extra-pair paternity is widespread in passerine birds. The number of extra-pair young (EPY) varies among different species and populations of the same species. We tested if it is a case for a small passerine bird with poly-territorial behaviour, the Wood Warbler (Phylloscopus sibilatrix). The results are based on the microsatellite analysis of seven loci and revealed a high level of EPY in Central Russia population of Wood Warbler (EPY in 41% of all nests, 16 of 39 nests; 25% of all young were EPY, 52 of 212 young). We did not find relationship between relatedness among mates in the pair and the presence of EPY. There was no difference in heterozygosity and body mass between EPY and within pair young (WPY). Possible causes of extra-pair paternity are discussed.

Complete Mitochondrial Genome and Phylogenetic Analysis of Tarsiger indicus (Aves: Passeriformes: Muscicapidae).

Tarsiger indicus (Vieillot, 1817), the White-browed Bush Robin, is a small passerine bird widely distributed in Asian countries. Here, we successfully sequenced its mitogenome using the Illumina Novaseq 6000 platform (Illumina, San Diego, CA, USA) for PE 2 × 150 bp sequencing. Combined with other published mitogenomes, we conducted the first comprehensive comparative mitogenome analysis of Muscicapidae birds and reconstructed the phylogenetic relationships between Muscicapidae and related groups. The T. indicus mitogenome was 16,723 bp in size, and it possessed the typical avian mitogenome structure and organization. Most PCGs of T. indicus were initiated strictly with the typical start codon ATG, while COX1 and ND2 were started with GTG. RSCU statistics showed that CUA, CGA, and GCC were relatively high frequency in the T. indicus mitogenome. T. cyanurus and T. indicus shared very similar mitogenomic features. All 13 PCGs of Muscicapidae mitogenomes had experienced purifying selection. Specifically, ATP8 had the highest rate of evolution (0.13296), whereas COX1 had the lowest (0.01373). The monophylies of Muscicapidae, Turdidae, and Paradoxornithidae were strongly supported. The clade of ((Muscicapidae + Turdidae) + Sturnidae) in Passeriformes was supported by both Bayesian Inference and Maximum likelihood analyses. The latest taxonomic status of many passerine birds with complex taxonomic histories were also supported. For example, Monticola gularis, T. indicus, and T. cyanurus were allocated to Turdidae in other literature; our phylogenetic topologies clearly supported their membership in Muscicapidae; Paradoxornis heudei, Suthora webbiana, S. nipalensis, and S. fulvifrons were formerly classified into Muscicapidae; we supported their membership in Paradoxornithidae; Culicicapa ceylonensis was originally classified as a member of Muscicapidae; our results are consistent with a position in Stenostiridae. Our study enriches the genetic data of T. indicus and provides new insights into the molecular phylogeny and evolution of passerine birds.

Development and parentage analysis of SNP markers for Chestnut-vented Nuthatch (Sitta nagaensis) based on ddRAD-seq data

Extra-pair paternity (EPP) is commonly found in socially monogamous birds, especially in small passerine birds, and there are interspecific and intraspecific variations in the extent of EPP. The Chestnut-vented Nuthatch (Sitta nagaensis) is a socially monogamous passerine bird, and verifying whether this species has EPP relies on parentage testing—S. nagaensis is not known to have EPP. In this study, we developed SNP markers of this species that are informative for parentage analysis from double digest restriction site-associated DNA sequencing (ddRAD-seq) data. A panel consisting of 50 SNP markers, with a mean heterozygosity of 0.343, was used to resolve 95% of nestlings to fathers. The combined exclusion probabilities for the first parent and second parent were 0.991 and 0.9999, respectively. This panel of SNP markers is a powerful tool for parentage assignments in S. nagaensis. In addition, we found that three offspring (7.9%) from three nests (23.1%) were the result of extra-pair fertilization out of 38 offspring in 13 nests. Our study provided information on parentage analysis that has not been reported before in S. nagaensis. It also supplemented the understudied EPP behavior of birds in Asia, contributing to a general understanding of the EPP behaviors of birds.

Estimating mortality of small passerine birds colliding with wind turbines

As demand for renewable energy is rising, wind power development is rapidly growing worldwide. In its wake, conflicts arise over land use changes converting pristine nature into industrial power plants and its associated adverse biodiversity effects, crowned by one of the most obvious and deadly consequences: bird collisions. Most post-construction studies report low levels of avian mortality, but the majority of these studies are conducted primarily on larger birds. However, the diversity and abundance of small passerine birds are rarely reflected in the carcass surveys, although they in numeric proportion to their abundances should be the most numerous. The assumption that surveys find all carcasses seems thus rarely fulfilled and passerine mortality is likely to be grossly underestimated. We therefore designed an experiment with dummy birds to estimate mortality of small-bodied passerines and other small-bodied birds during post-construction surveys, tested in a medium-sized wind farm in western Norway. The wind farm was surveyed weekly during the migration periods by carcass survey teams using trained dogs to find killed birds. The dogs in the carcass surveys were more successful in locating the large than the small dummy birds (60–200 g), where they found 74% of the large dummy birds. Detecting the smaller category (5–24 g) was more demanding and the dogs only found 17% of the small dummy birds. Correcting the post-construction carcass survey outcome with the results from the experiment leads to an almost fourfold increase in estimated mortality rates, largely due to the low detection rate of the smallest category. The detection rates will naturally vary between wind farms, depending on the specific habitat characteristics, the efficiency of the carcass surveys and the search intervals. Thus, implementing a simple experiment with dummy birds to future post-construction surveys will produce more accurate estimates of the wind turbine mortality rates, and thus improve our understanding of the biodiversity effects of conforming to a more sustainable future.

Biophysical models accurately characterize the thermal energetics of a small invasive passerine bird

Effective management of invasive species requires accurate predictions of their invasion potential in different environments. By considering species' physiological tolerances and requirements, biophysical mechanistic models can potentially deliver accurate predictions of where introduced species are likely to establish. Here, we evaluate biophysical model predictions of energy use by comparing them to experimentally obtained energy expenditure (EE) and thermoneutral zones (TNZs) for the common waxbill Estrilda astrild, a small-bodied avian invader. We show that biophysical models accurately predict TNZ and EE and that they perform better than traditional time-energy budget methods. Sensitivity analyses indicate that body temperature, metabolic rate, and feather characteristics were the most influential traits affecting model accuracy. This evaluation of common waxbill energetics represents a crucial step toward improved parameterization of biophysical models, eventually enabling accurate predictions of invasion risk for small (sub)tropical passerines.

Sex-specific selective effect of winter weather on morphological traits in a small passerine bird

Harsh environmental conditions often impose strong selection on the phenotype of natural populations through impacts on their fitness. For overwintering birds, winter is an important period for survival because the weather conditions in winter is usually severer than in other seasons and birds often suffer more thermoregulation costs while food is in short supply. Thus, the selective effect of weather conditions on phenotype in winter is expected to be strong. In this study, we examined the relationship of overwinter survival of Silver-throated Tits (Aegithalos glaucogularis) with their morphological traits under different levels of winter conditions (winters with and without snowstorms) to explore the differential selective effect of winter weather on their morphology. We found that regardless of whether the winter experienced a snowstorm, the female Silver-throated Tits with a smaller bill surface area or smaller bill depth and a smaller surface area:volume ratio were more likely to survive during the winter, which supported the hypothesis of selection for heat retention. Furthermore, the females with a smaller body length survived better than the larger females, indicating that the lesser food requirements for smaller body sizes may confer advantages during the winter when food availability was reduced. In addition, in agreement with the finding in many short-lived birds that survival rate increases with the increase of age, older (≥2-year-old) female Silver-throated Tits had higher overwinter survival than 1-year-old females. However, we did not find any correlation of morphological traits and age with survival in male Silver-throated Tits. These results illustrate differential selective effects of winter weather on female and male Silver-throated Tits and contribute to the knowledge of sex-specific selection on the phenotype of natural populations.

Seasonal acclimatization and temperature acclimation in small passerine birds is achieved via metabolic adjustments

Temperature and other environmental factors play an integral role in the metabolic adjustments of animals and drive a series of morphological, physiological, and behavioral adaptions essential to survival. However, it is not clear how the capacity of an organism for temperature acclimation translates into seasonal acclimatization to maintain survival. Basal metabolic rate (BMR), evaporative water loss (EWL), and energy budget were measured in the Chinese Hwamei (Garrulax canorus) following winter and summer acclimatization, and in those acclimatized to 15 ​°C (cold) and 35 ​°C (warm) under laboratory conditions for 28 days. In addition to the above indicators, internal organ masses, as well as state 4 respiration and cytochrome c oxidase (COX) activity were also measured for the liver, skeletal muscle, heart, and kidney. Both winter-acclimatized and cold-acclimated birds exhibited significantly higher BMR, EWL, and energy budget, as well as organ masses, state 4 respiration, and COX activity compared with the summer-acclimatized and warm-acclimated birds. This indicated that the Chinese Hwamei could adapt to seasonal or just temperature changes through some physiological and biochemical thermogenic adjustments, which would be beneficial to cope with natural environmental changes. A general linear model showed that body mass, BMR, GEI, state 4 respiration in the liver and kidney, and COX activity in the skeletal muscle, liver, and kidney were significantly affected by temperature and acclimation. A positive correlation was observed between BMR and each of the other parameters (body mass, EWL, energy budget, heart dry mass, kidney dry mass, state 4 respiration) in the muscle, heart, and kidney and also between BMR and COX activity in the muscle and kidney. The results suggested that similar to seasonal acclimatization, Chinese Hwameis subjected to temperature acclimation also exhibited significant differences in metabolism-related physiological and biochemical parameters, depending on the temperature. The data also supported the prediction that metabolic adjustment might be the primary means by which small birds meet the energetic challenges triggered by cold conditions.

Питание беркута на средней Лене, Якутия, Россия

Presented data on the Golden Eagle (Aquila chrysaetos) diet is based on the analysis of 291 pellets and 233 food remains found in or under nests and perches. Data was also obtained based on visual information. Small rodents were identified by teeth structure, birds – by femur and humerus sizes. If possible, species was determined by mammal hairs and bird feathers found in pellets or food remains. Information on the Golden Eagle diet was obtained between 2006 and 2023 in three administrative areas of Yakutia (Khangalassky and Namsky districts, administrative area of the city of Yakutsk) located in the basin of the middle reaches of Lena (Middle Lena). The study area has a wide and complexly terraced valley, 70% of which is covered by taiga with combination of coniferous (larch, spruce, pine) and small-leaved (willow, birch) forests, meadows, and agricultural land. The Middle Lena is characterized by an extremely continental climate and a short summer: average temperature in January is -43.2°, in June – +18,0°, frostfree period lasts 95 days. Previously Golden Eagle nested throughout the taiga of Yakutia, and until the early 1960s was a common species in the Middle Lena (Vorobiev, 1963). Since the 1970s–1980s a sharp decrease in its abundance was recorded, and since the 1990s it has become extremely rare (Solomonov, Larionov, 1976; Borisov, 1987; Isaev et al., 2020). According to our observations, since the beginning of the 2000s there was a gradual increase in the number of Golden Eagle and the emergence of breeding territories in areas where Golden Eagles were absent for a long-time during breeding period. Today, 33 Golden Eagle nests are known in the Middle Lena, breeding occurred in 11 of them. The Golden Eagle arrival is usually observed from the second decade of March to the first decade of April. Golden Eagle lays eggs in April, nestlings hatch in May and depart from nests in September–October. Research by Yu.V. Labutin (1992) shows that in the 1970s–1980s, the main food source for Golden Eagle in Central Yakutia was Mountain Hare (89%); according to G.P. Larionov et al., 1991, in the 1980s–1990s this species accounted for 37.7% of prey. It should be noted that in the beginning-middle of the 20th century, Mountain Hare was one of the most common species in Central Yakutia, and in years of its peak abundance – massive commercial species, as almost 850,000 hare skins were harvested then. A steady downward trend in the number of species has begun from the 1970s, the population size has decreased, mainly due to the anthropogenic factor (Solomonov, 1975). Since 2000s, hare hunting has ceased due to its low numbers in the region. Accounting that has been carried out in Central Yakutia in 2008–2018 showed that the number of species is very low – 0.2–0.3 individuals/10 km of the route (Sedalishchev, Odnokurtsev, 2022). As shown by the recent data, 11 mammal and 29 bird species are found in the Golden Eagle diet in Central Yakutia, and Long-Tailed Ground Squirrel has become its main prey. The predominance of Ground Squirrels in the diet suggests that, due to an increase in hare abundance, Golden Eagle switched to species with higher population density. The diet of Golden Eagle changes depending on the season. The greatest prey variety is observed in spring; eagles feed on young Roe Deer, Ground Squirrels, less often – hare, sable, etc. There are also reports of Golden Eagles attacking exhausted adult Roe Deer in early spring. It is worth noting that, judging by the survey data, Golden Eagles were often observed near fallen horses. While horse hairs were found in only one of the examined pellets, it confirmed Golden Eagle feeding on horse meat. From the beginning of June, Golden Eagle switch to its main prey, the Long-Tailed Ground Squirrel, occasionally feeding on small mammals and passerine birds. Interestingly, insects are sometimes found in pellets collected in Golden Eagle nests.

Short-term night lighting disrupts lipid and glucose metabolism in Zebra Finches: Implication for urban stopover birds

Night lighting has been shown to affect wild animals. To date, the effects of night lighting on the metabolic homeostasis of birds that spend short time in urban environments remain unclear. Using model bird species Zebra Finch (Taeniopygia guttata), we investigated the effects of short-term night lighting on liver transcriptome, blood glucose, triglyceride, and thyroxine (T4 and T3) levels in birds exposed to two different night lighting duration periods (three days and six days). After three days of night lighting exposure, the expression of genes involved in fat synthesis in the liver was upregulated while the expression of genes involved in fatty acid oxidation and triglyceride decomposition was downregulated. There was also a reduction in blood triglyceride, glucose, and T3 concentrations. However, after six days of night lighting, the expression of genes associated with fatty acid decomposition and hyperglycemia in the liver was upregulated, while the expression of genes involved in fat synthesis was downregulated. Simultaneously, blood glucose levels and T3 concentration increased. These findings indicate that short-term exposure to night lighting can disrupt the lipid and glucose metabolism of small passerine birds, and longer stopovers in urban area with intense night lighting may cause birds to consume more lipid energy.

Draft genome assemblies of four manakins

Manakins are a family of small suboscine passerine birds characterized by their elaborate courtship displays, non-monogamous mating system, and sexual dimorphism. This family has served as a good model for the study of sexual selection. Here we present genome assemblies of four manakin species, including Cryptopipo holochlora, Dixiphia pipra (also known as Pseudopipra pipra), Machaeropterus deliciosus and Masius chrysopterus, generated by Single-tube Long Fragment Read (stLFR) technology. The assembled genome sizes ranged from 1.10 Gb to 1.19 Gb, with average scaffold N50 of 29 Mb and contig N50 of 169 Kb. On average, 12,055 protein-coding genes were annotated in the genomes, and 9.79% of the genomes were annotated as repetitive elements. We further identified 75 Mb of Z-linked sequences in manakins, containing 585 to 751 genes and an ~600 Kb pseudoautosomal region (PAR). One notable finding from these Z-linked sequences is that a possible Z-to-autosome/PAR reversal could have occurred in M. chrysopterus. These de novo genomes will contribute to a deeper understanding of evolutionary history and sexual selection in manakins.

Breathing in the Cold: Seasonal Changes in the Ventilatory Pattern in a Small Boreal Passerine Bird

Small passerine birds in the north need to take advantage of several behavioral and physiological mechanisms to maintain energy balance during the winter characterized by low food supply, low ambient temperatures, and short days. Here we test if the breathing pattern of a non-migratory species, the great tit (Parus major), show seasonal variation that could help the species keeping a positive energy balance in the winter. To this aim, we measured oxygen consumption and ventilatory variables (tidal volume and respiratory frequency) in summer- and winter-acclimatized great tits exposed to ambient temperatures between –15 and 30°C. Winter-acclimatized great tits had a higher resting metabolic rate and a different breathing pattern compared to the summer-acclimatized birds. During the winter the great tits utilized a breathing pattern, consisting of an increased respiratory frequency to tidal volume ratio compared to summer-acclimatized birds at all temperatures. The higher oxygen uptake and the altered breathing pattern in the winter-acclimatized tits resulted in a higher lung oxygen extraction. However, during acute cold exposure neither the winter- nor summer-acclimatized great tits increased the oxygen extraction at low ambient temperature. The higher lung oxygen extraction in the winter-acclimatized tits implies that the birds will save on the minute ventilation, which reduces the evaporative water loss through respiration. The daily water loss saved can be more than 1 g of water per day. This is a substantial saving corresponding to a saving in evaporative heat loss corresponding to between 4 and 8% of the resting metabolic rate. This might be significant in keeping an energy balance, and the altered breathing pattern in the winter, ensuring an increased oxygen extraction, may therefore represents an additional physiological mechanism making it possible for small passerine birds to survive the northern winter.

Plumage and Fat Condition Scores as Well-Being Assessment Indicators in a Small Passerine Bird, the Zebra Finch (Taeniopygia guttata).

The well-being of animals kept by humans in laboratories, farms, or as pets should always be of the highest importance, and a prerequisite for this is adequate housing. To assess the potential indicators for animal well-being, ideally simple, non-invasive, and reliable methods are necessary. Here, we propose a novel plumage scoring system for small songbirds, using the example of the Zebra Finch, and examine its reliability in comparison with a well-known body condition index, that is, the fat score. We used up to five different observers of different experience levels to assess inter- and intra-observer reliability of the proposed plumage score and also the fat score. We found substantial inter-observer reliability for the proposed novel plumage score, and lower inter-observer reliability for the fat score, which seems to require more training of observers. The intra-observer reliability of the experienced observer who trained the others also showed a very strong reliability for the plumage score and for the fat score. Thus, we conclude that our proposed novel plumage score is a simple, reliable, and non-invasive way to estimate an important indicator of captive Zebra Finches' well-being. Furthermore, the plumage score can be reliably taught to other observers. The plumage score, maybe in combination with the fat score, may be an important tool to reliably assess well-being on a regular basis in captive populations in zoos, laboratories, or pet stocks.

Терморегуляция и уровень метаболизма у мелких воробьиных птиц Якутии в зимний период

The data on basal metabolism and thermoregulatory responses in small passerine birds in the winter, in the temperature range natural for Yakutsk, have been analysed. Common redpoll Acanthis flammea (Linnaeus, 1758), Eurasian tree sparrow Passer montanus (Linnaeus, 1758), and Eurasian bullfinch Pyrrhula pyrrhula (Linnaeus, 1758) were researched. In Common redpoll, the minimal metabolism rates (about 3.1 ml O2/g · h) were reported in ambient temperatures between 10 °C and 20 °C. At temperatures going down from 20 °C to -30 °C, oxygen consumption doubled at a rate of 0.06 ml O2/g · h per 1 °C. In the Eurasian tree sparrow, the growth of metabolism began at the temperature decreasing to 10 °C and continued to temperatures going down to -25 °C — -30 °C. With the ambient temperature from decreasing from -20 °C to -30 °C, the metabolic rate was increasing by 0.06 ml O2/g · h per 1 °C. The Eurasian bullfinch had a significantly higher level of minimal metabolism than the Eurasian tree sparrow, while the maximum metabolic levels were close in absolute values. The rate of metabolic growth in bullfinch was half as high as in Common redpoll and Eurasian tree sparrow.

Diverse single-stranded DNA viruses identified in New Zealand (Aotearoa) South Island robin (Petroica australis) fecal samples

The South Island robin (Petroica australis) is a small passerine bird endemic to New Zealand (Aotearoa). Although its population has declined recently and it is considered ‘at risk,’ little research has been done to identify viruses in this species. This study aimed to survey the diversity of single-stranded DNA viruses associated with South Island robins in a small, isolated population on Nukuwaiata Island. In total, 108 DNA viruses were identified from pooled fecal samples collected from 38 individual robins sampled. These viruses belong to the Circoviridae (n = 10), Genomoviridae (n = 12), and Microviridae (n = 73) families. A number of genomes that belong to the phylum Cressdnaviricota but are otherwise unclassified (n = 13) were also identified. These results greatly expand the known viral diversity associated with South Island robins, and we identify a novel group of viruses most closely related genomoviruses.

First microsatellite markers for the European Robin (Erithacus rubecula) and their application in analysis of parentage and genetic diversity

The European Robin is a small passerine bird associated with woodlands of Eurasia and North Africa. Despite being relatively widespread and common, little is known of the species’ breeding biology and genetic diversity. We used Next Generation Sequencing (NGS) to develop and characterize microsatellite markers for the European Robin, designing three multiplex panels to amplify 14 microsatellite loci. The level of polymorphism and its value for assessing parentage and genetic structure was estimated based on 119 individuals, including seven full families and 69 unrelated individuals form Poland’s Białowieża Primaeval Forest and an additional location in Portugal. All markers appeared to be highly variable. Analysis at the family level confirmed a Mendelian manner of inheritance in the investigated loci. Genetic data also revealed evidence for extra-pair paternity in one family. The set of markers that we developed are proven to be valuable for analysis of the breeding biology and population genetics of the European Robin.

Assortative mating for between-patch dispersal status in a wild bird population: Exploring the role of direct and indirect underlying mechanisms.

Previous studies have reported functional integration between dispersal and other phenotypic traits allowing individuals to alleviate dispersal costs, and such associations can affect dispersal evolution in return. In sexually reproducing species, assortative mating according to dispersal can shape the maintenance of such trait associations. Despite the potentially crucial consequences of dispersal in natural populations, assortative mating for dispersal and its underlying mechanisms remain largely unexplored. Here, we assessed assortative mating for between-patch dispersal status in a fragmented population of a small passerine bird, the collared flycatcher, and explored whether such assortative mating could result from (i) direct mate choice based on dispersal-related behavioural (aggressiveness and boldness) and morphological traits (tarsus and wing length), (ii) biased mating due to spatio-temporal heterogeneity in the distribution of dispersal phenotypes and/or (iii) post-mating adjustment of dispersal phenotype or dispersal-related traits. We found intrinsic assortative mating (i.e. positive among-pair correlation) for current dispersal status (in the year of mating) but not for natal dispersal status, even though we could not exclude it due to limited power. We also found assortative mating for boldness and age category (yearlings vs. older adults), and the probability for pair members to be assorted for current dispersal status was higher when both pair members were of similar boldness score and of the same age compared with mixed-age pairs. Mate choice based on boldness and age thus appears as a possible mechanism underlying assortative mating for dispersal status. Our analyses however remained correlative, and only an experimental manipulation of these traits could allow inferring causal links. Non-random mating for dispersal-related traits may affect the evolution of dispersal syndromes in this population. More work is nevertheless needed to fully assess the evolutionary implications of age- and behaviour-based assortative mating for dispersal.

A songbird adjusts its heart rate and body temperature in response to season and fluctuating daily conditions.

In a seasonal world, organisms are continuously adjusting physiological processes relative to local environmental conditions. Owing to their limited heat and fat storage capacities, small animals, such as songbirds, must rapidly modulate their metabolism in response to weather extremes and changing seasons to ensure survival. As a consequence of previous technical limitations, most of our existing knowledge about how animals respond to changing environmental conditions comes from laboratory studies or field studies over short temporal scales. Here, we expanded beyond previous studies by outfitting 71 free-ranging Eurasian blackbirds (Turdus merula) with novel heart rate and body temperature loggers coupled with radio transmitters, and followed individuals in the wild from autumn to spring. Across seasons, blackbirds thermoconformed at night, i.e. their body temperature decreased with decreasing ambient temperature, but not so during daytime. By contrast, during all seasons blackbirds increased their heart rate when ambient temperatures became colder. However, the temperature setpoint at which heart rate was increased differed between seasons and between day and night. In our study, blackbirds showed an overall seasonal reduction in mean heart rate of 108 beats min-1 (21%) as well as a 1.2°C decrease in nighttime body temperature. Episodes of hypometabolism during cold periods likely allow the birds to save energy and, thus, help offset the increased energetic costs during the winter when also confronted with lower resource availability. Our data highlight that, similar to larger non-hibernating mammals and birds, small passerine birds such as Eurasian blackbirds not only adjust their heart rate and body temperature on daily timescales, but also exhibit pronounced seasonal changes in both that are modulated by local environmental conditions such as temperature. This article is part of the theme issue 'Measuring physiology in free-living animals (Part I)'.