Population Of Warblers Research Articles

Extracting historical population trends using archival ringing data—an example: the globally threatened Aquatic Warbler

Understanding how animal population size changes over time is one of the key means to identify threats and facilitate the successful implementation of conservation measures. The globally endangered Aquatic Warbler has undergone a major decline throughout its range. While in the first half of the 20th century, it was still an abundant species across major parts of Central and Western Europe, over the last century the size of its European population is considered to have declined by more than 90 %. However, little is known of the historical changes in its population size. Here we model the past population size of the Aquatic Warbler using historical ringing records of European ringing schemes and population monitoring software (TRends for Indices and Monitoring). We found that during the short 30-year period between 1950 and 1980 the European Aquatic Warbler population underwent a dramatic 95 % decline. According to this model, the population has recently been stable, no further decline was observed between 1980 and the late 1990s.

Climatic Influences on Survival of Migratory African Reed WarblersAcrocephalus baeticatusin South Africa

The focus of most research on the influence of recent climate change on birds has been on the northern hemisphere. Climate change has been different in the southern hemisphere, prohibiting extrapolation from northern research findings — and inference regarding future climate change — to species living there. We investigated the correlation between climatic conditions and survival of a migratory population of African Reed Warblers Acrocephlaus baeticatus in Paarl, South Africa. We used temperature and rainfall in its breeding area, and Normalized Difference Vegetation Index (NDVI) in its wintering area, Central Africa around the Congo Basin. We fitted capture-mark-recapture models for open populations to a 12-year ringing dataset (1998–2010). After accounting for transience — this species exhibits high breeding site fidelity — with a ‘Time-Since-Marking’ model we found a mean survival probability of 0.79 ± 0.04 SE. Rainfall and NDVI did not influence survival in this dataset. Mean temperature (Aug–Apr) had...

No Association between Personality and Candidate Gene Polymorphisms in a Wild Bird Population.

Consistency of between-individual differences in behaviour or personality is a phenomenon in populations that can have ecological consequences and evolutionary potential. One way that behaviour can evolve is to have a genetic basis. Identifying the molecular genetic basis of personality could therefore provide insight into how and why such variation is maintained, particularly in natural populations. Previously identified candidate genes for personality in birds include the dopamine receptor D4 (DRD4), and serotonin transporter (SERT). Studies of wild bird populations have shown that exploratory and bold behaviours are associated with polymorphisms in both DRD4 and SERT. Here we tested for polymorphisms in DRD4 and SERT in the Seychelles warbler (Acrocephalus sechellensis) population on Cousin Island, Seychelles, and then investigated correlations between personality and polymorphisms in these genes. We found no genetic variation in DRD4, but identified four polymorphisms in SERT that clustered into five haplotypes. There was no correlation between bold or exploratory behaviours and SERT polymorphisms/haplotypes. The null result was not due to lack of power, and indicates that there was no association between these behaviours and variation in the candidate genes tested in this population. These null findings provide important data to facilitate representative future meta-analyses on candidate personality genes.

Isotopic (δ2Hf) evidence of “loop migration” and use of the Gulf of Maine Flyway by both western and eastern breeding populations of Blackpoll Warblers

Isotopic (δ²H_f) evidence of “loop migration” and use of the Gulf of Maine Flyway by both western and eastern breeding populations of Blackpoll Warblers

A proxy of social mate choice in prairie warblers is correlated with consistent, rapid, low-pitched singing

In songbirds, female mate choice may be influ- enced by how well a male performs his songs. Performing songs well may be especially difficult if it requires maximiz- ingmultipleaspectsofperformancesimultaneously.Wethere- fore hypothesized that, in a population of prairie warblers, the males most attractive to females would be those with superior performance in more than one facet of singing. We tested this prediction by comparing different aspects of song perfor- mance, as well as different combinations of these aspects, to determine which were the best predictors of first-egg date, which we took to be a proxy for social mate choice. We found thatfirst-egg datewasbestpredicted bya combination ofsong performance traits that included consistent performance, rapid rate, and low pitch. Female preference for males capable of physically challenging song performance may have contribut- ed to the evolution of acoustically complex vocalizations in oscine songbirds, because if complex sounds are more difficult to perform, they may be favored by selection for signal reliability.

Selection and evolutionary potential of spring arrival phenology in males and females of a migratory songbird

The timing of annual life-history events affects survival and reproduction of all organisms. A changing environment can perturb phenological adaptations and an important question is if populations can evolve fast enough to track the environmental changes. Yet, little is known about selection and evolutionary potential of traits determining the timing of crucial annual events. Migratory species, which travel between different climatic regions, are particularly affected by global environmental changes. To increase our understanding of evolutionary potential and selection of timing traits, we investigated the quantitative genetics of arrival date at the breeding ground using a multigenerational pedigree of a natural great reed warbler (Acrocephalus arundinaceus) population. We found significant heritability of 16.4% for arrival date and directional selection for earlier arrival in both sexes acting through reproductive success, but not through lifespan. Mean arrival date advanced with 6 days over 20 years, which is in exact accordance with our predicted evolutionary response based on the breeder's equation. However, this phenotypic change is unlikely to be caused by microevolution, because selection seems mainly to act on the nongenetic component of the trait. Furthermore, demographical changes could also not account for the advancing arrival date. Instead, a strong correlation between spring temperatures and population mean arrival date suggests that phenotypic plasticity best explains the advancement of arrival date in our study population. Our study dissects the evolutionary and environmental forces that shape timing traits and thereby increases knowledge of how populations cope with rapidly changing environments.

The influence of climatic conditions in breeding grounds and migratory flyways on a subalpine Norwegian Willow Warbler (Phylloscopus trochilus) population

Many European-breeding bird species wintering south of the Sahel region in Africa have been reported to be in decline since the 1970s. However, most studies focus on conditions local to the breeding sites as determinants of population change, despite the potential influence on populations during migration and over-wintering. To investigate the relative importance of climate at the breeding site and during migration and overwintering periods, we studied a Fennoscandian Willow Warbler (Phylloscopus trochilus) population that has been monitored in its subalpine breeding grounds in Norway over the last 45 years (1967-2011). The long-term trend for our population follows a quadratic trend, showing a marked period of decline after the late 1960s, followed by some increase during the last two decades. The most parsimonious model of the annual change in the Willow Warbler population is obtained by combining the mean June temperature and the Sahel spring index. The annual rate of change in the Willow Warbler population was positively related to summer temperatures on the breeding grounds and positively related to Sahel precipitation, although the statistical support is not very strong. Our study shows that climatic conditions at different stages of the annual cycle have influence on the population change. However, the on-going habitat changes in tropical Africa most likely have negatively affected on the overall population size of the Willow Warbler. This habitat loss may prevent many long-distance migratory bird species from returning to their former population peaks, even though the impact from the recent Sahelian drought may have culminated.

The influence of phenology on double-brooding and polygyny incidence in the Sedge Warbler Acrocephalus schoenobaenus

There is growing evidence that the fitness of birds in temperate zones depends strongly on the match between the timing of breeding and local phenology. We have analysed data collected from a 15-year study on a Sedge Warbler (Acrocephalus schoenobaenus) population in its natural habitat. The highly skewed distribution of arrival dates of males indicated that they competed intensely to be the earliest arrivals. The distribution of mating dates, unlike arrival dates, was not skewed, rather it formed a bell-shaped distribution. Because females arrived much later, they could not base their mating choices on the arrival dates of males. Females, however, could use male song repertoire, a trait we found to be correlated with male arrival date. Double-brooded females mated early in the season, exactly within the peak of mating date distribution. Polygynous females, on the other hand, mated later in the season, choosing high-quality older males which had arrived significantly earlier. Male territory quality did not differ between double-brooded and polygynous females, nor did the quality of the territories occupied by an individual female change during her lifetime. Although longer lifespan and double-brooding influenced a female’s fitness over the course of her lifetime, polygyny had no significant effect. We conclude that Sedge Warbler females do not compete for territorial resources, but they do prefer to mate with high-quality early-arriving males. Polygyny is an effective strategy used by females to compensate for their late arrival and breeding onset, since they pair with high-quality males.

A quantitative PCR protocol for detecting specific Haemoproteus lineages: molecular characterization of blood parasites in a Sedge Warbler population from southern Poland

AbstractIn evolutionary studies, blood parasites in avian populations are commonly used as a model of host–parasite interactions. The effect of mixed infections on avian hosts has recently drawn more interest, but the effects of infection with multiple blood parasites and specific parasite lineages are poorly known. A protocol for reliable detection and quantification of lineages is essential to this type of research. Here, we present a newly developed quantitative PCR (qPCR) assay using SYBR Green I to assess the infection intensity of SW1 and SW3 Haemoproteus belopolskyi lineages in a Sedge Warbler (Acrocephalus schoenobaenus) population from southern Poland. These Haemoproteus lineages are not specific to the Sedge Warbler, so the proposed protocol should prove useful for many avian malaria studies. The assay is based on nucleotide primers designed to amplify a fragment of the cytochrome b gene, allowing the two avian malaria lineages to be differentiated. Using this assay, specific host–parasite interactions can be identified and the impact of mixed infections on a host population can be assessed. Most of the parasitized birds in our study were in a low-intensity, chronic phase of infection. In those with mixed SW1/SW3 infections, we detected significantly higher parasitemia caused by the SW3 lineage, whose prevalence was underestimated by the commonly used method, nested PCR. The prevalence of avian malaria parasites in the studied population as estimated by nested PCR was 61 % and did not differ between years, though the prevalence of the SW1 lineage showed significant annual variation. Altogether, two Haemoproteus and five Plasmodium lineages were detected. The two Haemoproteus lineages (SW1, SW3) were most prevalent in the population and comprised 93 % of all infections. We detected significantly higher haemoparasite prevalence and intensity in males, which were sampled immediately after arrival from wintering grounds, suggesting decreased immunoprotection as a result of adaptive resource allocation during migration.

Divergence of vocal culture among isolated alpine habitats is inconsistent among three Oscine species

Divergence in song culture has been well documented among isolated bird populations. Montane populations separated by unsuitable lower-elevation habitats thus appear to be excellent candidates for cultural divergence, and existing data support this conjecture. To explore the generality of this phenomenon, we investigated song sharing patterns in songbird species breeding in isolated alpine life zones in the Rocky Mountains of Colorado. We recorded songs of American Pipits (Anthus rubescens alticola), Wilson’s Warblers (Cardellina pusilla pileolata), and White-crowned Sparrows (Zonotrichia leucophrys leucophrys) across 19 sites among 6 mountain ranges. We used spectrographic cross-correlation to calculate song similarity coefficients between individuals within and among populations. White-crowned Sparrows exhibited significantly elevated song sharing within isolated mountain ranges, but Wilson’s Warbler and the American Pipit did not. Cluster analyses showed that White-crowned Sparrow songs diverged among alpine fragments but were generally similar among sites within contiguous alpine habitat within mountain ranges. There was no such clustering within American Pipit or Wilson’s Warbler populations. Song similarity declined with distance between sites within contiguous alpine habitat in White-crowned Sparrows but not in American Pipits or Wilson’s Warblers. Our results provide convincing evidence for the existence of geographically structured vocal culture in White-crowned Sparrow populations in Colorado, and this geographic pattern may be explained by clinal variation rather than by a mosaic pattern of divergence among isolated alpine fragments.

Agonistic behaviors between Chestnut-sided (Setophaga pensylvanica) and Golden-winged (Vermivora chrysoptera) warblers are unlikely a result of plumage misidentification

Plumage coloration within species is often a signal of competitive ability and can influence territorial aggression between males. Agonistic interactions among males of different co-occurring species could result from misidentification (misdirected conspecific aggression). Reflectance spectrometry of plumage coupled with models of avian vision can be used to infer whether plumage color differences can be distinguished by birds. Here we investigate crown coloration similarity as a potential explanation for aggression between the imperiled Golden-winged Warbler (Vermivora chrysoptera) and the comparatively abundant Chestnut-sided Warbler (Setophaga pensylvanica). Because the yellow crown coloration of the two species appears identical to humans, we hypothesized that misidentification of heterospecifics as conspecifics could escalate agonistic interactions. Using museum study skins, we tested whether the yellow crown coloration of the two species should be distinguishable to the birds. Spectral reflectance data demonstrate that plumage color differs between the two species and avian vision models suggest these color differences should be easily discriminated. Thus, we conclude that plumage coloration similarity between these wood warblers is unlikely to cause misidentification of heterospecifics as conspecifics and may just be a result of phylogenic constraint. As populations of Golden-winged Warblers are experiencing accelerating declines, research focusing on the role interspecific competition plays on reduced productivity and survival is warranted.

A phylogeographic break and bioacoustic intraspecific differentiation in the Buff-barred Warbler (Phylloscopus pulcher) (Aves: Passeriformes, Phylloscopidae)

According to current taxonomy only three out of 27 Sinohimalayan leaf warbler species (Phylloscopidae) are considered genetically uniform across their entire breeding range along the Southeastern margin of the Qinghai-Tibetan Plateau, the Buff-barred Warbler (Phylloscopus pulcher) being one of them. Because marked differentiation among Himalayan and Chinese populations has been recently demonstrated for a number of Phylloscopus species (or sister species) we investigated the intraspecific variation of a mitochondrial gene, songs and morphology of P. pulcher in a phylogeographic approach. We sequenced a fragment of the mitochondrial cytochrome b, reconstructed haplotype networks and analyzed DNA polymorphism among Himalayan and Chinese populations. We measured time and frequency parameters of two distinct song types and analyzed among population-differentiation in a principal component analysis and a discriminant analysis. We also compared measurements of body size dimensions taken from museum specimens. The mitochondrial haplotype network (cytb) was divided into two distinct clusters corresponding to geographic origin of samples. Pairwise genetic distances among Himalayan and Chinese mtDNA lineages account for 1.3% which coincides with Pleistocene lineage separation at roughly 650,000 years ago. Genetic diversity is slightly higher in the Chinese part of the species’ range with respect to haplotype and nucleotide diversity while the less diversified Himalayan population lineage shows signs of recent range expansion. The vocal repertoire of P. pulcher comprises two distinct verse types that are combined with short interspersed click notes to long continuous song displays. Trill verse types showed significant differences among regions in almost all measured frequency and time parameters: Chinese males displayed more rapid and more broad-banded trills at a lower pitch. In contrast, warbling verse types showed a distinctively different structure among regions: Himalayan songs consisted of repeated syllables while Chinese songs comprised repetitions of single, long and strongly modulated elements. Subtle morphological differences among specimens from the two study regions could only be confirmed for plumage coloration but not for metric characters. Based on the genetic and bioacoustic distinctiveness of Chinese Buff-barred Warbler populations, we recommend that the name Phylloscopus pulcher vegetus Bangs, 1913 should be re-validated for this taxon.

Partitioning the sources of demographic variation reveals density-dependent nest predation in an island bird population.

Ecological factors often shape demography through multiple mechanisms, making it difficult to identify the sources of demographic variation. In particular, conspecific density can influence both the strength of competition and the predation rate, but density-dependent competition has received more attention, particularly among terrestrial vertebrates and in island populations. A better understanding of how both competition and predation contribute to density-dependent variation in fecundity can be gained by partitioning the effects of density on offspring number from its effects on reproductive failure, while also evaluating how biotic and abiotic factors jointly shape demography. We examined the effects of population density and precipitation on fecundity, nest survival, and adult survival in an insular population of orange-crowned warblers (Oreothlypis celata) that breeds at high densities and exhibits a suite of traits suggesting strong intraspecific competition. Breeding density had a negative influence on fecundity, but it acted by increasing the probability of reproductive failure through nest predation, rather than through competition, which was predicted to reduce the number of offspring produced by successful individuals. Our results demonstrate that density-dependent nest predation can underlie the relationship between population density and fecundity even in a high-density, insular population where intraspecific competition should be strong.

Wind speed during migration influences the survival, timing of breeding, and productivity of a neotropical migrant, Setophaga petechia.

Over the course of the annual cycle, migratory bird populations can be impacted by environmental conditions in regions separated by thousands of kilometers. We examine how climatic conditions during discrete periods of the annual cycle influence the demography of a nearctic-neotropical migrant population of yellow warblers (Setophaga petechia), that breed in western Canada and overwinter in Mexico. We demonstrate that wind conditions during spring migration are the best predictor of apparent annual adult survival, male arrival date, female clutch initiation date and, via these timing effects, annual productivity. We find little evidence that conditions during the wintering period influence breeding phenology and apparent annual survival. Our study emphasizes the importance of climatic conditions experienced by migrants during the migratory period and indicates that geography may play a role in which period most strongly impacts migrant populations.

Improving Aquatic Warbler Population Assessments by Accounting for Imperfect Detection

Monitoring programs designed to assess changes in population size over time need to account for imperfect detection and provide estimates of precision around annual abundance estimates. Especially for species dependent on conservation management, robust monitoring is essential to evaluate the effectiveness of management. Many bird species of temperate grasslands depend on specific conservation management to maintain suitable breeding habitat. One such species is the Aquatic Warbler (Acrocephalus paludicola), which breeds in open fen mires in Central Europe. Aquatic Warbler populations have so far been assessed using a complete survey that aims to enumerate all singing males over a large area. Because this approach provides no estimate of precision and does not account for observation error, detecting moderate population changes is challenging. From 2011 to 2013 we trialled a new line transect sampling monitoring design in the Biebrza valley, Poland, to estimate abundance of singing male Aquatic Warblers. We surveyed Aquatic Warblers repeatedly along 50 randomly placed 1-km transects, and used binomial mixture models to estimate abundances per transect. The repeated line transect sampling required 150 observer days, and thus less effort than the traditional ‘full count’ approach (175 observer days). Aquatic Warbler abundance was highest at intermediate water levels, and detection probability varied between years and was influenced by vegetation height. A power analysis indicated that our line transect sampling design had a power of 68% to detect a 20% population change over 10 years, whereas raw count data had a 9% power to detect the same trend. Thus, by accounting for imperfect detection we increased the power to detect population changes. We recommend to adopt the repeated line transect sampling approach for monitoring Aquatic Warblers in Poland and in other important breeding areas to monitor changes in population size and the effects of habitat management.

Habitat type and ambient temperature contribute to bill morphology

Avian bills are iconic structures for the study of ecology and evolution, with hypotheses about the morphological structure of bills dating back to Darwin. Several ecological and physiological hypotheses have been developed to explain the evolution of the morphology of bill shape. Here, we test some of these hypotheses such as the role of habitat, ambient temperature, body size, intraspecific competition, and ecological release on the evolution of bill morphology. Bill morphology and tarsus length were measured from museum specimens of yellow warblers, and grouped by habitat type, sex, and subspecies. We calculated the mean maximum daily temperature for the month of July, the hottest month for breeding specimens at each collecting location. Analysis of covariance models predicted total bill surface area as a function of sex, habitat type, body size, and temperature, and model selection techniques were used to select the best model. Habitat, mangrove forests compared with inland habitats, and climate had the largest effects on bill size. Coastal wetland habitats and island populations of yellow warblers had similar bill morphology, both of which are larger than mainland inland populations. Temperate but not tropical subspecies exhibited sexual dimorphism in bill morphology. Overall, this study provides evidence that multiple environmental factors, such as temperature and habitat, contribute to the evolution of bill morphology.

Phaeomelanin- and carotenoid-based pigmentation reflect oxidative status in two populations of the yellow warbler (Setophaga petechia)

Carotenoid- and phaeomelanin-based sexual pigmentation may signal a capacity to maintain oxidative balance and viability. However, diverse empirical results leave the association between pigmentation and oxidative stress (OS) unclear. We assessed the hypothesis that population-specific levels of oxidative challenge, or strategies for managing OS, affect relationships between sexual pigmentation and OS. Specifically, intense oxidative challenge in migratory, temperate breeding birds might enhance correlations between pigmentation and OS relative to allied tropical breeders, since quality-based differences in OS may arise only under intense oxidative challenge. Alternatively, in temperate breeders with intense within-season reproductive effort, high-quality birds may invest in reproduction over oxidative balance, dampening negative correlations between pigmentation and OS. To assess these alternatives, we compared prenesting relationships between pigmentation and OS in a migratory, Californian population of yellow warblers (Setophaga petechia brewsteri) and in a resident, Mexican population (Setophaga petechia bryanti, “mangrove warblers”). Yellow warblers displayed higher OS than mangrove warblers. However, year of capture and sex had bigger influences on correlations between pigmentation and OS than population. Males with more intense melanin pigmentation had lower OS among mangrove warblers and yellow warblers captured in 2011, but not among yellow warblers captured in 2012. In females only, lower OS levels were associated with more colorful carotenoid pigmentation. Results suggest that both phaeomelanin- and carotenoid-based pigmentation have the potential to correlate with OS levels, but that the signaling potential of pigmentation may shift with inter-annual variation in environmental conditions and display sex-specific dynamics.

Model-Based Selection of Areas for the Restoration of Acrocephalus paludicola Habitats in NE Germany

The global Aquatic Warbler (Acrocephalus paludicola, Vieillot, 1817) population has suffered a major decline due to the large-scale destruction of its natural habitat (fen mires). The species is at risk of extinction, especially in NE Germany/NW Poland. In this study, we developed habitat suitability models based on satellite and environmental data to identify potential areas for habitat restoration on which further surveys and planning should be focused. To create a reliable model, we used all Aquatic Warbler presences in the study area since 1990 as well as additional potentially suitable habitats identified in the field. We combined the presence/absence regression tree algorithm Cubist with the presence-only algorithm Maxent since both commonly outperform other algorithms. To integrate the separate model results, we present a new way to create a metamodel using the initial model results as variables. Additionally, a histogram approach was applied to further reduce the final search area to the most promising sites. Accuracy increased when using both remote sensing and environmental data. It was highest for the integrated metamodel (Cohen's Kappa of 0.4, P<0.001). The final result of this study supports the selection of the most promising sites for Aquatic Warbler habitat restoration.

Inferences about population dynamics from count data using multistate models: a comparison to capture–recapture approaches

Wildlife populations consist of individuals that contribute disproportionately to growth and viability. Understanding a population's spatial and temporal dynamics requires estimates of abundance and demographic rates that account for this heterogeneity. Estimating these quantities can be difficult, requiring years of intensive data collection. Often, this is accomplished through the capture and recapture of individual animals, which is generally only feasible at a limited number of locations. In contrast, N-mixture models allow for the estimation of abundance, and spatial variation in abundance, from count data alone. We extend recently developed multistate, open population N-mixture models, which can additionally estimate demographic rates based on an organism's life history characteristics. In our extension, we develop an approach to account for the case where not all individuals can be assigned to a state during sampling. Using only state-specific count data, we show how our model can be used to estimate local population abundance, as well as density-dependent recruitment rates and state-specific survival. We apply our model to a population of black-throated blue warblers (Setophaga caerulescens) that have been surveyed for 25 years on their breeding grounds at the Hubbard Brook Experimental Forest in New Hampshire, USA. The intensive data collection efforts allow us to compare our estimates to estimates derived from capture–recapture data. Our model performed well in estimating population abundance and density-dependent rates of annual recruitment/immigration. Estimates of local carrying capacity and per capita recruitment of yearlings were consistent with those published in other studies. However, our model moderately underestimated annual survival probability of yearling and adult females and severely underestimates survival probabilities for both of these male stages. The most accurate and precise estimates will necessarily require some amount of intensive data collection efforts (such as capture–recapture). Integrated population models that combine data from both intensive and extensive sources are likely to be the most efficient approach for estimating demographic rates at large spatial and temporal scales.

Reproductive success and habitat characteristics of Golden-winged Warblers in high-elevation pasturelands

The Golden-winged Warbler (Vermivora chrysoptera) is one of the most rapidly declining vertebrate species in the Appalachian Mountains. It is the subject of extensive range-wide research and conservation action. However, little is known about this species' breeding ecology in high-elevation pasturelands, a breeding habitat with conservation potential considering the U.S. Natural Resource Conservation Service's Working Lands for Wildlife program targeting private lands in the Appalachian Mountains. We located 100 nests of Golden-winged Warblers in pastures in and around the Monongahela National Forest in West Virginia during 2008–2012. Daily nest survival rate (mean ± SE = 0.962 ± 0.006), clutch size (4.5 ± 0.1), and number of young fledged per nest attempt (2.0 ± 0.2) and successful nest (4.0 ± 0.1) fell within the range of values reported in other parts of the species' range and were not significantly affected by year or the presence/absence of cattle grazing. Classification tree analysis revealed that nests were in denser vegetation (≥52%) and closer to forest edges (<36.0 m) and shrubs (<7.0 cm) than random locations within the male's territory. Successful nests had significantly more woody cover (≥9%) within 1 m than failed nests. Our results suggest that cattle grazing at 1.2–2.4 ha of forage/animal unit with periodic mowing can create and maintain these characteristics without interfering with the nesting of Golden-winged Warblers. High-elevation pasturelands may provide a refuge for remaining populations of Golden-winged Warblers in this region.