Wintering Reed Bunting Emberiza schoeniclus in Lubuskie voivodeship, Poland

Male birds sing to find a mate or to defend a territory. Their songs are known to be highly species-specific, but males may additionally show high levels of song individuality. Differences in song features have been shown to code for male quality and/or motivational states. Quantifying differences and similarities in the singing of males may broaden the general understanding of avian song and pairing systems. Here, we investigated the song of an Eastern German population of Reed Buntings (Emberiza schoeniclus), a species with a medium-sized song repertoire and extraordinary high extra-pair young rates (up to 55 %). Using a computed template-recognition algorithm, we analysed songs of 11 males focussing on individual variation in song composition and use. To determine the degree of song sharing among males, we compared two different measurements of song similarity (DICE coefficient and coefficient of compositional similarity; CCS). We found that males sing highly individual with respect to most analysed parameters. On average, males shared 62 % of their syllable type repertoire with at least one other male. However, taking song use into account, the overall degree of song sharing was low to moderate for both similarity measures, and average DICE values were higher than the CCS values. Additionally, we found that the closer the male territories were to each other, the higher the proportion of song sharing tended to be. We discuss the implications of our findings for the function of song in the Reed Bunting.

Cover photo: Singing Reed Bunting Emberiza schoeniclus at Årnestangen, Nordre Øyeren nature reserve. Photo: Øyvind Hagen. The Reed Bunting Emberiza schoeniclus is considered the most common of the five species of Emberiza buntings breeding in Norway and is currently listed as a species of Least Concern. However, a complete census of territorial male Reed Buntings conducted in the Nordre Øyeren nature reserve in 2019 showed a decline in the local breeding population of 67% compared to the last counts completed 40 years ago. Censuses were conducted in 1976 and 1981 in the same area and with the same methods. Analyses of citizen science data from the Norwegian Biodiversity Information Centre also show a similar decreasing trend (-66%) for the Reed Bunting breeding population in Nordre Øyeren from 1976 to 2019. Moreover, image analyses of the census maps show that that the number and density of Reed Bunting territories have decreased locally and probably has done so since early 1980s. Interestingly, a subset of localities within the survey area still have the same territory densities as the 1976 and 1981 censuses. We suggest that changes in habitat, vegetation and farming practice, especially grazing, could be the underlying cause of variation in bird numbers. Our results indicate a negative population trend for the Reed Bunting locally, a tendency that is also observed regionally in the Nordic countries. Taken together, local and regional declines raise concerns about the conservation status of the Reed Bunting in Norway.

Migrating species and populations are affected by conditions existing across large geographical scales. The degree to which populations mix at stop-over sites and wintering grounds is variable and can involve important fitness consequences. Thus, the link between breeding and wintering grounds and seasonal shifts in population structure are important to understand population demographics, local adaption and diversification patterns. This work aims to infer migration patterns and population connectivity in the Reed Bunting (Emberiza schoeniclus) community of a Ramsar-designated wetland, Lake Neusiedl, Seewinkel, Austria. Stable isotope markers (hydrogen, δ2H, carbon, δ13C) in feathers were analyzed to assign individuals to a specific breeding or natal area. Based on the geographic assignment, birds were compared with respect to their ecomorphological traits and their habitat selection (large reed bed versus more open habitat at shore of an alkaline lake) during winter to assess potential ecological differences and possibly associated morphological divergence. Stable isotope data revealed that the local Reed Bunting community undergoes seasonal changes in population structure. Three different populations that vary in their δ2H signature and to some extent in morphological characteristics as well as in δ13C values were identified. Indications for differential migration related to age and/or sex were additionally found, since males and females as well as first-year birds and adults showed remarkable differences in their traits and feather isotope values. δ2H values diverged significantly between these groups in both age and sex classes and birds with highest feather δ2H values were considered to represent the local breeding population at Lake Neusiedl and possibly also Reed Buntings from close surroundings. Moreover, this group had the highest δ13C values in first-year individuals as well as in adults. In both sex classes, the assignment of Reed Buntings to different populations was ultimately possible due to differences in bill shape with residents being characterized by more massive bills than individuals belonging to populations visiting the study area only during migration or for wintering. During winter, beak shape and feather δ2H and δ13C values differed significantly between birds caught in the reed stand of Lake Neusiedl and those captured near the salt pan, hence, indicating differential habitat selection among co-occurring populations during winter. These findings suggest that morphological attributes, such as bill shape and size as well as linked adaptations to different food sources play a decisive role for niche segregation among wintering populations. The results provide evidence that different populations mix during migration and during winter at Lake Neusiedl and the extent to which they are specialized to a specific habitat varied.

Capsule Oilseed Rape was the preferred breeding season habitat for Reed Buntings on arable farmland and reduced this species' dependence on wet features. Aims To identify preferred breeding season habitats for Reed Buntings on arable farmland and factors influencing the attractiveness of Oilseed Rape. Methods Summer usage of arable fields by nesting and foraging farmland birds was assessed from a random sample of arable fields in Nottinghamshire, England. Generalized linear models were used to identify habitat and landscape predictors of Reed Bunting breeding density and of foraging by other farmland birds. Results Occupancy rates and densities of Reed Buntings were approximately four times greater in Oilseed Rape fields than in cereals or set-aside. Reed Buntings commonly nested in Oilseed Rape fields more than 100 m from wet features, but the same was not true of cereals or set-aside fields. Usage of Oilseed Rape by farmland birds was promoted by weediness, bare patches and nearby wet features, and reduced by grass margins, tall field boundaries and electricity pylons. Conclusions Oilseed Rape is one of the most important breeding season habitats for Reed Buntings in lowland Britain, providing a relatively rich source of seed and invertebrate food and possibly protection from nest predators. Breeding in Oilseed Rape reduces the dependence of Reed Buntings on nearby wet features.

BackgroundThe dynamics and structure of many bird communities are changing due to the global warming and changes in the land use and management. The Ebro Valley constitutes one of the chief wintering areas for several passerine species in Iberia, and the reed beds spread across this Valley concentrate huge numbers of birds that use them to roost, while the surrounding agricultural areas serve as main foraging habitats. The aims of this work are (1) to quantify how variable a non-breeding passerine bird community associated to a reed bed area in the Ebro Valley is, and, (2) to test for the effect of weather on possible annual fluctuations in species’ proportions at a regional/local scale.MethodsWe used for that ringing data collected at Badina de Escudera lagoon (Navarra) over a 12-year period.ResultsThough, overall, the assemblage did not vary strongly among years (most similarity values were > 0.8), we still found a significant linear effect of year on the proportion of captures of Reed Buntings (Emberiza schoeniclus), i.e., the dominant species detected in our passerine community. The increasing loss of weight of Reed Buntings in the community was due to a progressive decrease in its abundance.ConclusionsThe structure and diversity of passerine community in Badina Escudera was not influenced by meteorological conditions at a local scale, suggesting that local weather would not have an impact on numbers of Reed Buntings in winter.

The morphology of the reproductive organs of both male and female Reed Buntings (Emberiza schoeniclus) are described in relation to the high level of sperm competition exhibited by the species as a result of extra-pair copulation behavior. In males, the volume of the cloacal protuberance in relation to body weight was 26.7 mm 3 g -1 , which is relatively large for a socially monogamous passerine. The weight of the testes was 23% greater than that expected for a bird of comparable size, and the spermatozoa were among the longest recorded for any avian species (mean length = 291 μm). The morphology of the female tract also showed adaptations associated with a high level of sperm competition: the sperm storage tubules were extremely long (mean length = 865 μm).

Reactions of Willow Warblers Phylloscopus trochilus, Reed Buntings Emberiza schoeniclus, Blackcaps Sylvia atricapilla and Bluethroats Luscinia svecica, towards mimetic model Cuckoo Cuculus canorus eggs were tested by exchanging one of their eggs for a model plastic egg. Reactions of Willow Warblers, Reed Buntings and Bluethroats towards a foreign conspecific egg were also tested. Some Willow Warblers were also tested with Great Tit Parus major eggs. The Willow Warblers, Reed Buntings and Blackcaps rejected mimetic model eggs at a high rate (90-100%), while the Bluethroats showed a lower (but not statistically significant) rejection rate (63%). The Willow Warblers and the Bluethroats accepted conspecific eggs, but the Reed Buntings rejected some of these eggs (3 of 8 trials). Great Tit eggs, which resemble Willow Warbler eggs in colour and pattern but are bigger (although considerably smaller than Cuckoo eggs), were rejected in 5 of 6 trials. The responses of the above species towards mimetic model eggs were similar to those previously reported for non-mimetic eggs. This behaviour pattern is important in providing an explanation for their present status as only rare hosts of the Cuckoo.

Capsule Site fidelity and territory settlement is probably limited by the occupancy of suitable sites by males and the high mortality in females. Aim To investigate the relationship between territory settlement and site fidelity in Reed Buntings. Methods Two hundred and seventy Reed Buntings were colour‐ringed at five fishponds in South Bohemia, the Czech Republic, in 2000–2009. Model selection was used to test the effect of individual covariates (sex, age, weight and body measurements) on apparent survival and recapture probabilities. Results There is a correlation between territory settlement and site fidelity. Older males were more frequently re‐sighted in the study area during the year of ringing. Moreover, males were more frequently recovered in subsequent breeding seasons. An effect of body measurements as well as body weight did not appear evident. An effect of breeding performance in previous seasons on site fidelity was not found. Conclusion There is a connection between territory settlement and site fidelity in the early‐arriving Reed Buntings. Site fidelity and territory settlement is probably limited by the occupancy of suitable sites by males and the high mortality in females most likely caused by the extended breeding season in the study area. Moreover, territory settlement, and marginally, site fidelity is associated with the previous experience of males. Forming pre‐breeding flocks probably provides an addition of nutrition reserves after spring arrival. High competition between males and lack of suitable breeding habitats, owing to occupancy by older residents, indicated the crucial importance of small fragmented wetlands to this species in this study area.

Song represents one of the possible key factors influencing the interaction among songbird populations and can affect their evolution. We studied the effect of song differences between morphologically different subspecies of the reed bunting (Emberiza schoeniclus) on the territorial behaviour of males of the Mediterranean subspecies E. s. intermedia. Twenty males were presented with playback of different songs belonging to either their own or to the foreign subspecies, northern European E. s. schoeniclus, and their response behaviour was recorded. Both treatments elicited an aggressive approach to the loudspeaker, but the response to the foreign playback was slightly weaker. We conclude that the response of intermedia males seems close to that expected if the members of a demographically inferior subspecies need to defend resources from another, more abundant, subspecies. However, the hypothesis of song as an effective barrier between subspecies in territorial defence cannot be excluded.

Lowland Farmland Birds III: Delivering Solutions in an Uncertain World. A report on the BOU’s Annual Conference held at the University of Leicester, 31 March–2 April 2009

In birds, females are generally assumed to determine whether extra-pair copulations occur, and thus most studies on extra-pair paternity (EPP) have focussed on female preference for male traits, whereas female traits have been largely neglected. However, the occurrence of EPP is likely to be a result of behavioural interactions (e.g., mate guarding by the social male and escaping mate guarding by the female), and may be related to individual experience, which is expected to increase with age. We investigated the effect of age on levels of EPP in reed buntings Emberiza schoeniclus, a socially monogamous passerine with extremely high levels of extra-pair young (more than 50% of offspring). In broods of older males the rate of cuckoldry declined, which is in agreement with our previous finding that older males are more successful, either through female choice or through male experience. In contrast, older females tended to increase the level of extra-pair paternity in their broods. When including the age of the partner, we found that young males, but not old males, were cuckolded more by old females than by young females. The increase in EPP with female age is not likely to be due to disassortative mating with respect to age, an increased capacity of older females to raise a brood without male help, nor a male preference for older females. With age, males nor females changed their share in parental effort. We suggest that with increase in age, females become more choosy when selecting the male that sires their offspring, or alternatively, become more experienced at circumventing paternity assurance tactics of young males.

Summary 1. The reed bunting Emberiza schoeniclus is one of a suite of granivorous farmland bird species that suffered a major population decline in Britain during the late 1970s and early 1980s. Extensive monitoring data indicate a large increase in the abundance of reed buntings between 1963 and 1975, followed by a decline of 58% on farmland and 66% along linear waterways during the period 1975–83. Since 1983 numbers have remained relatively stable in both habitats. 2. During the population decline, breeding numbers declined rapidly on arable and mixed farms, but remained relatively stable on pastoral farms. The decline on farmland was greater in northern Britain than in the south‐east. 3. Extensive nest recording indicated that breeding performance was higher during the period of population decline (2·74 young per nesting attempt) than during the preceding period of population increase (2·65) or the recent period of population stability (2·17). 4. Minimum survival during the first year of life (estimated from mark–recapture data) declined during the 1970s and early 1980s, and increased strongly during the 1990s. The trend in first‐year survival was independent of a weak positive relationship with winter temperature. Although there was evidence of a similar temporal trend in adult survival, this disappeared when winter temperature was taken into account. 5. A demographic model indicated that the timing and magnitude of the observed changes in first‐year survival and adult survival were each sufficient alone to account for the observed changes in the abundance of reed buntings during the period 1969–87. A reduction in over‐winter survival was probably the main demographic cause of the reed bunting population decline, although loss of breeding habitat and a recent reduction in breeding performance may also have influenced numbers. 6. During winter reed buntings feed mainly on small grass and weed seeds. The observed declines in abundance and survival rates coincide with the widespread introduction of a range of efficient herbicides and the loss of winter stubbles from British farmland. Our findings are therefore consistent with the hypothesis that the decline of the British reed bunting population was caused primarily by a reduction in food availability outside the breeding season. Changes in agricultural practices that increase the abundance of small weed and grass seed on farmland during winter are likely to allow at least a partial recovery of the British reed bunting population.

In passerine birds morphological differentiation in bill size within species is not commonly observed. Bill size is usually associated with a trophic niche, and strong differences in it may reflect the process of genetic differentiation and, possibly, speciation. We used both mitochondrial DNA (mtDNA) and nuclear microsatellites to study genetic variation between two subspecies of reed bunting, Emberiza schoeniclus schoeniclus and E.s. intermedia, along their distributional boundary in western Europe. These two subspecies are characterized by a high dimorphism in bill size and, although breeding populations of the two subspecies are found very close to each other in northern Italy, apparently no interbreeding occurs. The observed morphological pattern between the two subspecies may be maintained by geographically varying selective forces or, alternatively, may be the result of a long geographical separation followed by a secondary contact. MtDNA sequences of cytochrome b and ND5 (515 bp) showed little variation and did not discriminate between the two subspecies, indicating a divergence time of less than 500 000 years. The analysis of four microsatellite loci suggested a clear, although weak, degree of genetic differentiation in the large- and small-billed populations, as indicated by FST and RST values and genetic distances. The correlation between bill size and genetic distance between populations remained significant after accounting for the geographical distances between sampling localities. Altogether, these results indicate a very recent genetic differentiation between the two bill morphs and suggest that a strong selection for large bills in the southern part of the breeding range is probably involved in maintaining the geographical differentiation of this species.

Extra‐pair paternity (EPP) is common in many socially monogamous birds, but large variations in frequency of EPP are found both between and within species. Local ecological factors can affect the costs and benefits of extra‐pair mating behaviour, and may therefore influence the chance that individuals engage in extra‐pair copulations (EPCs). We investigated the effect of weather conditions during the peak fertile period of the female on the levels of EPP in reed buntingsEmberiza schoeniclus. The reed bunting is a socially monogamous passerine, with extremely high levels of EPP (50% of offspring in 80% of broods). We found that higher daily minimum temperatures and more rainfall during the peak fertile period were associated with lower proportions of EPP. As during adverse weather conditions individuals have to invest more in self maintenance, we suggest that during long periods of rain the extra‐pair mating behaviour of all individuals will be restricted, leading to lower proportions of EPP. During cold mornings, time‐consuming activities such as mate guarding are likely to be more strongly affected than less time‐consuming activities such as EPCs, leading to higher proportions of EPP.

The two main functions of bird song are territory defence and mate attraction. Considerable progress has been made in understanding how species adjust the use of songs to serve these and other (presumed) functions of bird song, but the striking variety of singing behavior observable in wild birds remains enigmatic. Some species make do with simple songs and small repertoires, while others show large, complex repertoires and still others have evolved several distinct singing styles. In most species with distinct singing styles, however, the functions of singing styles are poorly understood. Two distinct singing styles (type I and II, respectively) have long been known in the reed bunting Emberiza schoeniclus, while a new third one has recently been reported to exist. We first quantitatively investigated the evidence for the existence of three singing styles. Then, we tested predictions of the mate attraction hypothesis, the mate guarding hypothesis and the territory defence hypothesis by examining the relations between singing style use with social and temporal factors. Cluster and discriminant analyses supported the existence of three (instead of two) singing styles, which could be differentiated based on four variables referring to song structure and complexity. Use of singing styles was related to male mating status (consistent with the mate attraction hypothesis), but not to female breeding stage (no support for the mate guarding hypothesis). Finally, use of singing styles differed in relation to time of day, with the dawn chorus of paired reed buntings consisting almost exclusively of songs of the recently discovered type III singing style and daytime singing primarily consisting of songs of long‐known type I (in unpaired males) or II singing styles (in paired males). Our findings suggest that one singing style (type I) primarily serves to attract a social mate, although an additional territorial function of this singing style cannot be dismissed. The function(s) of the other two singing styles, both only sung by paired males, are not related to attraction of a social mate or to the own female's fertility, but appear to be important in the context of territory defence and extra‐pair matings.