Search

The first record of the Common Yellowthroat, the 2nd North American passerine observed in Switzerland, was the most significant event of 2022. The first Swiss observation of the Moltoni's Warbler in Ticino was more anticipated. The 2nd record of Blue-cheeked Bee-eater, the 3rd record of wild Saker, Pacific Golden Plover and Dusky Warbler have been reported. The 4th to 7th records of Bonelli's Eagle were revealed by the GPS positions of their transmitters (none were observed in the field). An unprecedented influx of Pallas's Leaf Warbler produced the 5th to 7th records in our country and an invasion of young European Rollers occurred at the end of summer with at least 51 individuals. The 12th Terek Sandpiper for Switzerland (the 1st since 1875 on the shores of Lake Geneva) and the 11th Great Spotted Cuckoo (the last dated from 2010) were observed. Finally, two new colonies of Pallid Swift were discovered outside Ticino, in Brig and Geneva, and the 9th breeding record of Subalpine Warbler was recorded. In 2022, the CAvS examined 384 cases (59 % from German-speaking Switzerland, 39 % from French-speaking Switzerland and 9 % from Ticino), concerning 108 species. A total of 306 cases (80 %) relating to 81 species were approved; 39 related to previous years and 4 remain outstanding. At the end of 2022, the Swiss list included 428 species in categories A, B (wild birds) and C (introduced birds), of which 421 have been observed since 1900; 6 species remain in category D (birds of doubtful origin). At the end of 2022, the Swiss list comprised 428 species in categories A, B (birds of wild origin) and C (introduced species), 421 of which have been recorded since 1900. Six species of uncertain origin remain in category D (doubtful origin). In the text, the three figures after the German and scientific names refer to the number of records/individuals, 1900-1999, 2000-2021 and in 2022, respectively. The species are listed systematically, and within species records are listed in chronological order. Detailed information is given as follows: location, date(s), number of individuals (one individual if not specified), age and sex if known, available documentation (photographs, video, audio recordings, skins) and in brackets the name(s) of the observer(s). [ABSTRACT FROM AUTHOR]

Belding's Yellowthroat (Geothlypis beldingi) is an endangered species endemic to the southern half of the Baja California Peninsula. There are no current estimates of the species' population, crucial to scientifically based management for its conservation. Therefore, we assessed the species' population at one of its major sites, the oasis of San Ignacio. During the reproductive season, the density of birds reached around 17 individuals per hectare, representing an estimated total population of about 250 birds. Previous estimates of the abundance of Belding's Yellowthroat are inconsistent, emphasizing the need for a re-evaluation with more robust methods. In addition, we recorded a significant decrease in the number of males of the species immediately after the reproductive season, which suggests that these birds may disperse immediately after the breeding season, possibly to avoid competition with their conspecifics. If so, this has important implications for this bird's spatial population structure. [ABSTRACT FROM AUTHOR]

In the past few years, miniature light-level geolocators have been developed for tracking wild bird species that were previously too small to track during their full annual cycle. Geolocators offer an exciting opportunity to study the full annual cycle for many species. However, the potential detrimental effects of carrying geolocators are still poorly understood, especially for small-bodied birds. Here, we deployed light-level geolocators on common yellowthroat warblers (Geothlypis trichas). Over two years, we monitored return rates and neighborhood demography for 40 warblers carrying a geolocator and 20 reference birds that did not carry a geolocator. We compared the two groups with long-term data from 108 unmanipulated birds breeding at the same location in previous and subsequent years. Overall, we found that individuals carrying a geolocator were less likely to return to the study site in the following year (21% to 33% returned, depending on inclusion criteria) than either contemporaneous controls (55%) or long-term controls (55%). Among birds marked with geolocators, we also detected viability selection for greater wing length, whereas this pattern was not present in control birds. Finally, in each year after geolocator deployment, inexperienced breeders colonized vacant territories and this demographic effect persisted for two years after deployment. Sexual selection and ornamentation are strongly age-dependent in this system, and behavioral data collected after geolocator deployment is likely to differ systematically from natural conditions. Clearly geolocators will continue to be useful tools, but we suggest that future studies should carefully consider the potential for biased returns and the ecological validity of behavioral data collected from geolocator marked populations. [ABSTRACT FROM AUTHOR]

Genes of the major histocompatibility complex (MHC) are a critical part of the adaptive immune response, and the most polymorphic genes in the vertebrate genome, especially in passerine birds. This diversity is thought to be influenced by exposure to pathogens which can vary in relation to numerous factors. Migratory behaviour may be a particularly important trait to consider because migratory birds are exposed to a greater number of different pathogens and parasites at both breeding (i.e. temperate) and overwintering (i.e. tropical and subtropical) areas, as well as at stopover sites during migration. Thus, migrants are predicted to have greater MHC diversity than residents. We compared MHC variation, at both class I and II, and levels of haemosporidian infection between one resident and two migratory populations of the common yellowthroat (Geothlypis trichas). We found that residents were less likely to be infected with haemosporidian parasites and had lower MHC diversity at class I; however, variation at MHC class II was greater in residents than migrants, contrary to our prediction. These patterns were not likely to be caused by differences in population demography as genomewide heterozygosity (based on 9225 single nucleotide polymorphisms) was high in all three populations and not correlated with MHC variation. Our different results for MHC class I and II suggest that studies of immune gene variation in relation to life history need to consider that there could be different selection pressures arising from intracellular (class I) and extracellular (class II) pathogens in different populations. [ABSTRACT FROM AUTHOR]

The Hamilton-Zuk hypothesis predicts that ornament expression is a signal of the ability of individuals to resist parasite infection. Thus, across a population (i.e. between-individuals) more ornamented individuals should have lower levels of parasitism. Numerous studies have tested this prediction and the results are mixed. One reason for these conflicting results may be that many studies have examined this relationship at the between-individual level, which may be affected by confounding factors such as selective mortality. Using within-subject centering we examined the relationship between male ornamentation and avian blood parasites at both the between- and within-individual levels. These relationships focus on differences in genetically-based resistance to parasites and the trade-off in resource allocation between parasite resistance and ornament expression within an individual, respectively. We studied male common yellowthroats Geothlypis trichas, which have two plumage ornaments, a yellow, carotenoid-based bib (throat and chest) and a black, melanin-based facial mask. Surprisingly, within-individuals, an increase in parasitism between years was associated with an increase in mask size and, potentially, greater concentration of carotenoids in the yellow feathers. This suggests that males may be able to tolerate an increase in parasitism and still increase ornament expression. In contrast, ornamentation was not related to parasitism at the between-individual level. Thus, our study revealed relationships between ornaments and parasitism at the within-individual level that were not present at the between-individual level. Our results highlight the importance of examining both within- and between-individual relationships as correlations between variables, such as ornaments and parasites, may depend on the level of analysis (i.e. within- or between-individuals). [ABSTRACT FROM AUTHOR]

Although the selective loss of individuals susceptible to disease can favor the evolution of female preference for older males, the interrelationship between age, infection, longevity, and mating success remains poorly characterized in natural populations. In a longitudinal study of 61 male common yellowthroats ( Geothlypis trichas), we found that the probability of infection with hematozoa increased as males aged from 1 to 5 years. Despite a significant, negative association between infection and longevity that partially masked age-effects, the odds that a male was infected with Trypanosoma, Plasmodium, or Leucocytozoon increased 71-212% per year. Nearly 75% of males in their first breeding season were either uninfected or infected with only a single parasite, while 50% of older males were infected with at least two parasites and 16% were infected with all three. No males escaped infection after their second breeding season. Older males were also more likely to sire extra-pair young (EPY) and, as a consequence, infection with multiple parasites was associated with a fourfold increase in the odds of producing EPY. Unlike younger males, 80% of the oldest males had a history of either surviving chronic infection or recovering. Combined with previous work showing higher diversity at the major histocompatibility complex among older males, our results suggest that the song and plumage traits that signal male age in common yellowthroats also, perforce, signal resistance to parasites. By preferring older males, females may obtain good genes for disease resistance even in the absence of any effect of infection on male ornamentation. [ABSTRACT FROM AUTHOR]

Telomere dynamics in natural populations have been linked to survival, reproduction, and energetic investment. Given their putative role in mediating life-history trade-offs, telomeres are also a likely candidate for maintaining honesty in sexually selected signals; few studies to date, however, have demonstrated a correlation between sexual signals and telomere dynamics. Here, we show that plumage coloration in male common yellowthroats ( Geothlypis trichas) is correlated with both relative telomere length and with the rate of telomere loss between years. Elevated antioxidant capacity is also associated with reduced telomere loss, but only among older males. Previous work in this population has demonstrated that males with brighter plumage are in better condition, have higher reproductive success, and are more likely to survive over winter. Thus, the signal attribute associated with mate choice in this system also conveys reliable information about telomere dynamics. At present, it is unclear whether telomere maintenance plays a causal role in maintaining signal honesty or whether the correlation arises due to underlying variation in individual resources or genotypes. We suggest that subsequent work should consider the possibility that fundamental trade-offs between signal investment and cell-level processes that influence aging and reproductive senescence may provide a foundation for understanding the maintenance of sexual signal honesty. [ABSTRACT FROM AUTHOR]

Male ornaments are hypothesized to signal the ability of males to produce an effective immune response without extensive oxidative stress and damage to DNA., We examined this hypothesis in male common yellowthroats ( Geothlypis trichas), which have two ornaments, a black (eumelanin-based) facial mask and a yellow (carotenoid-based) bib. In our study population, only the black mask is sexually selected., As predicted by the oxidative stress hypothesis, males with larger black masks were more resistant to oxidative stress, as measured by an in vitro assay of the resistance of erythrocytes to haemolysis by free radicals. Furthermore, males with larger masks also tended to have lower levels of glutathione, which was predicted because glutathione inhibits eumelanin production. In contrast, mask size was not related to absolute levels of oxidative stress measured in the plasma., Although the yellow bib is not under sexual selection in our population, males with larger bibs and feathers with greater carotenoid chroma had lower levels of oxidative stress., The oxidative stress hypothesis was first proposed for carotenoid-based ornaments. However, our results suggest that, even in the same individuals, carotenoid and eumelanin-based plumage ornaments may both signal the ability of males to resist or manage oxidative stress. [ABSTRACT FROM AUTHOR]

Measures of bird song that capture aspects of motor performance, such as consistency, have become a major focus in understanding sexual selection on song. Despite accumulating evidence that consistency is related to reproductive success in many species, the relative importance of male-male interactions and female-male interactions is still unclear. We studied the function and flexibility of song consistency and song rate in common yellowthroat warblers ( Geothlypis trichas). A previous study of this population found that song consistency-measured as the amount of variability within a bout of songs-was positively correlated with the likelihood of siring extrapair young. In this study, we conducted two experiments aimed at testing (1) the role of song consistency and rate in mediating male-male and male-female interactions and (2) whether song effort is flexibly adjusted to changes in social context. In the first experiment, we simulated a male territorial intrusion with song playbacks that varied in consistency and rate; focal males responded aggressively to playbacks, but their response did not differ with playback consistency or rate. In the second experiment, we presented focal males with a taxidermic female mount and female vocalizations; focal males approached the speaker, but continued to sing and did not perform the aggressive rattle vocalization observed during male encounters. Immediately after the simulated female encounter, focal males increased in song consistency. Taken together, our results are most consistent with the hypothesis that song consistency in common yellowthroats is primarily a female-directed signal that is actively adjusted in response to rapidly changing social conditions. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Entomologist is the property of Cambridge University Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Although some comparative studies of oscine songbirds have found that long-distance migration is positively correlated with elaborate songs, an analysis of singing by species in the genus Geothlypis (Parulidae) found no evidence of such a correlation. The migratory species in the genus sing relatively simple songs, whereas the singing of nonmigratory species varies; some species have simple songs, and others have more elaborate songs. Elaborate songs are found in the nonmigratory species G. semiflava, G. aequinoctialis, and G. poliocephala. For example, in Costa Rican populations of these species, songs are longer, contain more notes, have greater note-type diversity, and (in G. semiflava and G. aequinoctialis) have more phrase types than the songs of the migratory Geothlypis species. However, in other nonmigratory species (G. nelsoni, G. flavovelata, G. speciosa, and G. rostrata), the duration, note count, and note-type diversity of songs are similar to those of the migratory species. Thus, there seems to be no consistent relationship between migration and song elaboration in Geothlypis. In accordance with this inconsistency, ancestralcharacter- state reconstruction showed that evolutionary loss of migratory behavior was associated with increased song elaboration in some clades within the genus, but not in others. Overall, song variation in wood-warblers (Geothlypis) provides no support for the hypothesis that long-distance migration favors the evolution of elaborate songs. [ABSTRACT FROM AUTHOR]

The article presents a study on the use of eye coloration in determining the age of Common Yellowthroat (Geothlypis trichas). The eye color of 300 birds was identified and compared with other known aging criteria such as skull ossification, preformative molt and shape of rectrices. It was found that the retrix shape, molt and wear can be used as complementary characteristics in age determination and changes in eye color must be observed in different species within different age categories.

Physiological mechanisms underlying migration remain poorly understood, but recent attention has focused on the role of the glucocorticoid hormone corticosterone (CORT) as a key endocrine regulator of migration. The migration-modulation hypothesis (MMH) proposes that baseline plasma CORT levels are elevated in migratory birds to facilitate hyperphagia and lipogenesis and that further elevation of CORT in response to acute stress is suppressed. Consequently, CORT may be a poor indicator of individual condition or environmental variation in migratory birds. We tested the MMH by measuring baseline and stress-induced CORT in common yellowthroats (Geothlypis trichas) during fall migration over 2 consecutive years in the Revelstoke Reach drawdown zone, a migratory stopover site affected by local hydroelectric operations. Birds had low baseline CORT at initial capture (<5 ng/mL) and then showed a robust stress response, with CORT increasing to ca. 50 ng/mL within 10-20 min. Our data therefore do not support the MMH. Baseline CORT did not vary with body mass, time of capture, Julian day, or year, suggesting that variable flooding regimes did not affect baseline CORT. Individual variation in the rate of increase in CORT was correlated with Julian day, being higher later in the migration period. Our data suggest that plasma CORT can be a useful metric in migration studies. [ABSTRACT FROM AUTHOR]

The article discusses records of parasitic mites found and taken from perching birds Passeriformes, that include an Indigo Bunting Passerina cyanea, a Black-and-white Warbler Mniotilta varia, and a Common Yellowthroat Geothlypis trichas, on Vaca Key, Florida between April to May 2013. Parasitic mites discussed include Amerodectes mites Proctophyllodidae, Trouessartia mites Trouessartiidae, and Mesalgoides sp., a psoroptoidid mite Psoroptoididae.

Understanding the relationships of bird abundance to vegetation and the surrounding landscape would help to guide meadow restoration for wildlife habitat. I examined the relationship between bird abundance and vegetation structure and the composition of the surrounding landscape in southeastern Pennsylvania in 2011 and 2012 by using regression models. The relationship between abundance and habitat characteristics varied among species. Common yellowthroats and red-winged blackbirds were more abundant in meadows with tall, dense grasses, while eastern meadowlarks were more abundant in shorter, sparser meadows. Field sparrow abundance was positively related to the amount of woody vegetation in a meadow. The habitat surrounding a survey point also explained bird abundances, with bobolinks and meadowlarks more common in meadows surrounded by grasslands and common yellowthroats more abundant in meadows surrounded by forest. Restoration of meadows in landscapes containing a high proportion of grassland habitats should target eastern meadowlarks and bobolinks by restoring shorter, sparser vegetation. Meadow restorations in forested areas should target other species such as field sparrows or common yellowthroats. Strategic planning of meadow restoration based on the surrounding landscape composition and species-specific vegetation structure requirements should be used to increase the probability of a successful habitat restoration. [ABSTRACT FROM AUTHOR]

Females often possess ornaments that appear smaller and duller than homologous traits in males. These ornaments may arise as nonfunctional by-products of sexual selection in males and cause negative viability or fecundity selection in females in proportion to the cost of their production and maintenance. Alternatively, female ornaments may function as signals of quality that are maintained by sexual or social selection. In a 4-year study of 83 female common yellowthroats ( Geothlypis trichas) and their 222 young, we found strong viability and fecundity selection on the yellow bib, a carotenoid-based plumage ornament that is a target of sexual selection in males. Females with larger bibs were older, larger and more fecund than females with smaller bibs. However, bib size positively covaried with bib total brightness and carotenoid chroma, aspects of bib coloration that were under negative viability and fecundity selection. Females with more colourful bibs laid fewer eggs in their first clutch, were more likely to suffer total brood loss due to predation and were less likely to return to the study area. Selection against bib coloration limits the value of bib size as a quality indicator in females and may constrain the elaboration of bib attributes in males. [ABSTRACT FROM AUTHOR]

The Common Yellowthroat (Geothlypis trichas) exhibits widespread geographic variation in plumage, morphology, migratory behavior, and song. In addition, researchers recently found evidence that the Common Yellowthroat has three genetically distinct groups across its North American range: eastern, western, and southwestern. These groups are more genetically similar to other Geothlypis species than to each other, which suggests relatively long-term isolation. I hypothesized that geographic variation in song behavior should reflect these genetic differences. To test this hypothesis, I examined spatial patterns of variation in both note types and acoustic characteristics of song. Consistent with the hypothesis, I found significant differences among the three groups, particularly in frequency measures, internote duration, notes per phrase, and note elaborateness. Within the eastern and western groups, I also found significant song differences among historically recognized subspecies. When comparing western and eastern subspecies, I found different latitudinal trends, even though subspecies found at similar latitudes that exhibit similar migratory behavior might be expected to have similar song characteristics. Two possible explanations for this lack of convergence are (1) stochastic changes in song in isolated populations and (2) nonlatitudinal dissimilarities in habitat, including transmission properties or effects on morphological evolution, that drive song divergence. Without excluding other explanations, I found evidence of an effect of morphological divergence: Subspecies with larger bills sang songs with lower frequencies. Overall, the geographic variation in the songs of the Common Yellowthroat demonstrates that multiple evolutionary processes interact to shape birdsong, and that the importance of each of these processes and their interactions varies among populations. [ABSTRACT FROM AUTHOR]

The article presents a report from the U.S. Geological Survey (USGS) Patuxent Wildlife Research Center for the fall of 2013. Topics covered include the retirement of the Laurel and Lakeshore Estates backyard stations because of declining agility, the absence of an Atlantic hurricane entering the Gulf of Mexico or the Atlantic coast of North America, and the recapturing of a banded Common Yellowthroat by bander Aaron Given.

Birds are expected to select nest sites that maximize their reproductive success. In some settings, particularly in human-modified landscapes, birds may make maladaptive choices based on unreliable cues. We studied nest-site selection and the factors that influence reproductive success of Common Yellowthroats (Geothlypis trichas) in managed switchgrass (Panicum virgatum) grasslands in Iowa. We compared vegetation variables at 115 nest sites and corresponding random points. Conditional logistic regression was used to relate nest success, brood parasitism, and number of young fledged per successful nest to vegetation characteristics. Common Yellowthroats selected nest sites with denser and more senescent vegetation, and more forb cover compared with random points. Nest success, however, was negatively related to forb cover. Brood parasitism was not well-explained by any variables. Number of young fledged was positively related to the proportion of senescent vegetation. Selection of nest sites with denser vegetation and more senescent vegetation is consistent with variables reported in the literature and emphasizes the importance of nonharvested areas for Common Yellowthroats in switchgrass fields. Maladaptive preference for nest sites with more forbs could have negative consequences for Common Yellowthroat populations if the pattern we saw persists or applies to other settings. [ABSTRACT FROM AUTHOR]

Habitat fragmentation is particularly severe in the Lower Rio Grande Valley (LRGV) of Texas, where greater than 90% of the native wetland habitat has been replaced by agriculture and urban development. The Brownsville Common Yellowthroat (Geothlypis trichas insperata), a rare subspecies of the Common Yellow-throat restricted to this area, is a good model for studying the effects of this extensive fragmentation on avian genetics and ecology. In this study, three hypotheses addressing genetics and habitat fragmentation were tested: (1) the density of Brownsville Yellowthroats is greatest along the Rio Grande rather than away from the river; (2) individuals found on or near the Rio Grande are more closely related than individuals farther away; and (3) a source-sink metapopulation model is the best fit to describe the population dynamics of the subspecies. We used 15 microsatellites to examine the genetic diversity of 128 individuals from Cameron and Hidalgo Counties (Texas) sampled during 2008-2009. The densities of yellowthroats at sites near the Rio Grande were not significantly different from densities at sites farther from the river. Genetic analysis indicated that individuals were as related to each other as would be expected in distant relatives and indicated the presence of a single, admixed population. The results suggest that the Brownsville Common Yellowthroat is able to move freely among isolated habitat patches and that wetlands along the Rio Grande do not act as an exclusive corridor for this species. [ABSTRACT FROM AUTHOR]

Hamilton and Zuk proposed that females choose mates based on ornaments whose expression is dependent on their genetically based resistance to parasites. The major histocompatibility complex (MHC) plays an important role in pathogen recognition and is a good candidate for testing the relationships between immune genes and both ornament expression and parasite resistance. We tested the hypothesis that female common yellowthroats prefer to mate with more ornamented males, because it is a signal of their MHC-based resistance to parasites and likelihood of survival. In this species, females prefer males that have larger black facial masks as extrapair mates. Using pyrosequencing, we found that mask size was positively related to the number of different MHC class II alleles, as predicted if greater variation at the MHC allows for the recognition of a greater variety of pathogens. Furthermore, males with more MHC class II alleles had greater apparent survival, and resistance to malaria infection was associated with the presence of a particular MHC class II allele. Thus, extrapair mating may provide female warblers with immunity genes that are related to parasite resistance, survival, and the expression of a male ornament, consistent with good genes models of sexual selection. [ABSTRACT FROM AUTHOR]

Females are thought to gain better-quality genes for their offspring by mating with particular males. Genes of the major histocompatibility complex (MHC) play a critical role in adaptive immunity, and several studies have examined female mate choice in relation to MHC variation. In common yellowthroats, females prefer males that have larger black facial masks, an ornament associated with MHC variation, immune function and condition. Here we also tested whether mating patterns are directly correlated with MHC diversity or similarity. Using pyrosequencing, we found that the presence of extra-pair young in the brood was not related to male MHC diversity or similarity between the female and her within-pair mate. Furthermore, extra-pair sires did not differ in overall diversity from males they cuckolded, or in their similarity to the female. MHC diversity is extremely high in this species, and it may limit the ability of females to assess MHC variation in males. Thus, mating may be based on ornaments, such as mask size, which are better indicators of overall male health and genetic quality. [ABSTRACT FROM AUTHOR]

A mated female was observed singing in a color-banded population of Common Yellowthroats (Geothlypis trichas) in New York State in 2011. This female continued to sing, often concurrently with her mate, for ~1 week, at which time she completed nest construction and was not observed singing for the remainder of the season. Her song did not resemble any normal Common Yellowthroat song or vocalization. No previous publications have described female song in this species; common explanations for female song in other species include abnormally high testosterone levels, development of male-like characteristics with age, and increased territory defense demands at high densities. We found little support for any of these hypotheses, as our singing female was within the normal range for breeding density, testosterone, morphology, ornamentation, and several physiological parameters. We did not know the age of our female and could not discount old age as a cause of singing; however, other known-age, old females in the population were not observed singing. The potential explanations for singing seem inadequate in this case and the female may have been anomalous in some dimension that we did not measure, or a combination of factors may have contributed to the behavior. Alternatively, female song may be functional but only used in rarely observed social situations in this species. [ABSTRACT FROM AUTHOR]

The article explores a few records of ectoparasites from the Common Yellowthroat from Vaca Key in Marathon, Monroe County, Florida. The bird discovered dead on September 30, 2010 was found harboring several hundred feather mites, whereas the bird discovered on October 3, 2010 had only about a dozen feather mites. The specimen was examined under a dissecting microscope.

The article discusses oxidative damage to erythrocyte DNA in the common yellowthroat (Geothlypis trichas), a sexually dichromatic warbler bird in which sexual selection favors components of the male's yellow bib. Single-cell gel electrophoresis was used to explore the hypothesis that carotenoid-based sexual ornaments are reliable signals of male quality. Results suggest that carotenoid-based ornaments can convey information about oxidative stress (OXS) to prospective mates.

The name “Mary-Land Yellow-Throat” coined by James Petiver in 1702 was subsequently applied to the bird now known as the common yellowthroat, Geothlypis trichas, and the term “yellowthroat”, ultimately derivable from Petiver, is now used as a generic term for all nine species of the warbler genus Geothlypis (Parulidae). Re-examination of Petiver's illustration shows that his bird cannot have been a Geothlypis warbler and was almost certainly the yellow-throated warbler, Dendroica dominica. [ABSTRACT FROM AUTHOR]

The major histocompatibility complex (MHC) is characterized by a birth and death model of evolution involving gene duplication, diversification, loss of function, and deletion. As a result, gene number varies across taxa. Birds have between one and 7 confirmed MHC class II B genes, and the greatest diversity appears to occur in passerines. We used multiple primer sets on both genomic DNA (gDNA) and complementary DNA (cDNA) to characterize the range of class II B genes present in a passerine, the common yellowthroat (Geothlypis trichas). We confirmed 39 exon 2 sequences from gDNA in a single individual, indicating the presence of at least 20 class II B loci. From a second individual, we recovered 16 cDNA sequences belonging to at least 8 transcribed loci. Phylogenetic analysis showed that common yellowthroat sequences fell into subgroups consisting of classical loci, as well as at least 4 different clusters of sequences with reduced sequence variability that may represent pseudogenes or nonclassical loci. Data from 2 additional common yellowthroats demonstrated high interindividual variability. Our results reveal that some passerines possess an extraordinary diversity of MHC gene duplications, including both classical and nonclassical loci. [ABSTRACT FROM PUBLISHER]

In many animals, sexual selection has resulted in complex signaling systems in which males advertise aspects of their phenotypic or genetic quality through elaborate ornamentation and display behaviors. Different ornaments might convey different information or be directed at different receivers, but they might also be redundant signals of quality that function reliably at different times (ages) or in different contexts. We explored sexual selection and age- and condition-dependent signaling in the common yellowthroat ( Geothlypis trichas), a sexually dichromatic warbler with two prominent plumage ornaments—a melanin-based, black facial “mask” and carotenoid-based, UV-yellow “bib.” In a three-year study, variance among males in the number of social (Mw) and extra-pair (Me) mates generated strong sexual selection on mask and bib attributes. Some traits (mask size, bib yellow brightness) were correlated with male age and did not experience selection beyond age-related increases in Mw and Me. Other traits showed age-specific (bib size) or age-reversed (ultraviolet brightness) patterns of selection that paralleled changes in the information-content of each ornament. The components of male fitness generating selection in young versus old males were distinct, reflecting different sources of variation in male fertilization success. Age- and context-dependent changes in the strength, direction, and target of selection may help explain the maintenance of multiple ornaments in this and other species. [ABSTRACT FROM AUTHOR]

1. Female preferences for particular male ornaments may shift between populations as a consequence of ecological differences that change the reliability and detectability of the ornament, but few studies have examined how ornaments function in different populations. 2. We examined the signalling function of male plumage ornaments in a warbler, the common yellowthroat ( Geothlypis trichas), breeding in New York (NY) and Wisconsin (WI), USA. Males have two prominent ornaments: a black facial mask pigmented with melanin and a yellow bib pigmented by carotenoids. Previous studies in WI indicate that the size of the mask, and not the bib, is primarily related to female choice and male reproductive success. In NY, however, the pattern is reversed and attributes of the bib (size and colour), and not the mask, are the target of sexual selection. 3. We found that brightness of the yellow bib was the best signal of humoral immunity (immunoglobulin G) in NY and mask size was the best signal in WI, after controlling for breeding experience and capture date. Thus, similar aspects of male quality appeared to be signalled by different ornaments in different populations. 4. There was no difference between populations in the level of plasma carotenoids or the prevalence of malarial parasites, which may affect the costs and benefits of choosing males with particular ornaments in each location. 5. Even though females in different populations prefer different ornaments produced by different types of pigments, these ornaments appear to be signalling similar aspects of male quality. Our results caution against inferring the function of particular ornaments based simply on their type of pigment. [ABSTRACT FROM AUTHOR]

Our current understanding of migration routes of many birds is limited and researchers have employed various methods to determine migratory patterns. Recently, parasites have been used to track migratory birds. The objective of this study was to determine whether haemosporidian parasite lineages detect significant geographic structure in common yellowthroats (Geothlypis trichas). We examined liver tissue or blood from 552 birds sampled from multiple locations throughout the continental United States, southern Canada, and the Bahamas. We found a 52.7% overall prevalence of haematozoan infection. We identified 86.1% of these infections to genus: 81% were Plasmodium; 5% were Haemoproteus; and 0.1% were Leucocytozoon. There were significant differences in the prevalence of different parasite genera among regions (χ² = 36.82, P < 0.0001) and in the proportion of Plasmodium infections versus other parasites among regions (χ² = 35.52, P < 0.0001). Sequence information identified three Haemoproteus lineages, two Leucocytozoon lineages, and thirteen Plasmodium lineages. Due to the low number of Haemoproteus and Leucocytozoon, only Plasmodium lineages were used in the geographic comparison of lineages. Six Plasmodium lineages were found in eight or more birds and the prevalence of these varied significantly among regions (χ² = 172.33, P < 0.0001). Additionally, 45 juvenile birds were sampled to determine what parasites could be obtained in the breeding grounds and we found only one lineage. In conclusion, parasite lineages show some geographic structure, with some lineages being more geographically specific than others, but are not useful for determining migratory connectivity in this species. [ABSTRACT FROM AUTHOR]

Abstract: Numerous studies have explored the influence of forest management on avian communities empirically, but uncertainty about causal relationships between landscape patterns and temporal dynamics of bird communities calls into question how observed historical patterns can be projected into the future, particularly to assess consequences of differing management alternatives. We used the Habplan harvest scheduler to project forest conditions under several management scenarios mapped at 5-year time steps over a 40-year time span. We used empirical models of overall avian richness, richness of selected guilds, and probability of presence for selected species to predict avian community characteristics for each of the mapped landscapes generated for each 5-year time step for each management scenario. We then used time series analyses to quantify relationships between changes in avian community characteristics and management-induced changes to forest landscapes over time. Our models of avian community and species characteristics indicated habitat associations at multiple spatial scales, although landscape-level measures of habitat were generally more important than stand-level measures. Our projections showed overall avian richness, richness of Neotropical migrants, and the presence of Blue-gray Gnatcatchers and Eastern Wood-pewees varied little among management scenarios, corresponding closely to broad, overall landscape changes over time. By contrast, richness of canopy nesters, richness of cavity nesters, richness of scrub-successional associates, and the presence of Common Yellowthroats showed high temporal variability among management scenarios, likely corresponding to short-term, fine-scale changes in the landscape. Predicted temporal variability of both interior-forest and early successional birds was low in the unharvested landscape relative to that in the harvested landscape. Our results also suggested that early successional species can be sensitive to both availability and connectivity of habitat on the landscape. To increase or maintain the avian diversity, our projections indicate that forest managers need to consider landscape-scale configuration of stands, maintaining a spatially heterogeneous distribution of age classes. Our findings suggest which measures of richness or species presence may be appropriate indicators for monitoring effects of forest management on avian communities, depending on management objectives. [Copyright &y& Elsevier]

Copyright of Journal of Field Ornithology is the property of Resilience Alliance and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

When the reproductive value of sons differs from that of daughters, selection will favor broods biased toward the sex that can provide greater fitness benefits. In species where female choice is based on male ornamentation, females mated to highly ornamented males may experience a reproductive advantage by skewing the brood sex ratio toward sons. In the Common Yellowthroat (Geothlypis trichas), males with larger black facial masks are more likely to gain a social mate and sire extrapair young and, as a result, have increased seasonal reproductive success. Females mated to larger-masked males could benefit if they produced more sons. Given that largermasked males are preferred as extrapair sires, females may also benefit by producing more extrapair sons. We tested these hypotheses during a five-year study of Common Yellowthroats in Wisconsin. Contrary to our predictions, females did not produce more sons when mated to males with larger masks, and extrapair young were not more likely to be male. However, sons were more likely to be sired by males with longer tarsi, which suggests that females may respond to male body size rather than to male ornament size. [ABSTRACT FROM AUTHOR]

Male ornaments may be signals of direct or indirect benefits to females that mate with those males. One important direct benefit to females is the level of male parental assistance they receive when provisioning young. Three main hypotheses attempt to explain the relationship between male ornament size and parental care. The good parent hypothesis predicts that males with larger ornaments will provide more care, while the differential allocation and trade-off hypotheses predict that they will provide less care. We examined the relationship between male ornamentation and parental care in two populations of common yellowthroats, Geothlypis trichas, in which the sexually selected male ornament differs. More ornamented males provided less parental care in both populations, contrary to the good parent hypothesis. However, females did not feed their nestlings more frequently when mated with more ornamented males, which is an additional prediction of the differential allocation hypothesis. Our results are most consistent with the trade-off hypothesis, which suggests that more ornamented males provide less care because they spend relatively more of their effort in pursuing extrapair mates or defending their territories from other males. [Copyright &y& Elsevier]

Despite numerous studies of extrapair paternity in birds, little is known about the behaviours that males and females use to seek (or avoid) extrapair copulations. We used radiotelemetry to examine the extraterritorial movements of both male and female common yellowthroats, Geothlypis trichas, in relation to male ornaments, particularly the black facial mask. We found that many males (62%) and females (47%) forayed, and they primarily visited the territories of immediate neighbours (91%). Parentage analyses revealed that the majority of extrapair sires were neighbours (80%) who typically had larger facial masks than the male that they cuckolded. Females only forayed during their fertile period, and they directed most of their forays to territories of males with larger masks than their own social mate. In contrast, males directed most of their forays to territories where the female was fertile and the resident male had a smaller mask than their own. The relatively short foray distances of birds may be partly responsible for the wide distribution of extrapair fertilizations among males in the population (45% of males). If this is a general pattern among species, then the effect of extrapair mating on sexual selection is likely to be weaker than currently thought. [Copyright &y& Elsevier]

Melanin-based ornaments often function as signals in male–male competition, whereas carotenoid-based ornaments appear to be important in female mate choice. This difference in function is thought to occur because carotenoid pigments are more costly to produce than melanins and are thus more reliable indicators of male quality. We examined the role of melanin- and carotenoid-based ornaments in male–male competition and female choice in the common yellowthroat Geothlypis trichas, a sexually dichromatic passerine. Males display a black facial mask produced by melanin pigmentation and a bright yellow bib (throat, breast and belly) produced by carotenoid pigmentation. In controlled aviary experiments, mask size was the best predictor of both male–male competition and female mate choice, and, therefore, mask size may be regarded as an ornament of dual function. These dual functions may help to maintain the reliability of mask size as an indicator of male quality, despite the potentially low cost of production. The size of the bib was unrelated to male–male competition or female choice, but there was a tendency for females to prefer males with more colourful bibs. We propose that the black mask is important in competition for territories with other males and for attracting females. Our results highlight the need for more studies of the mechanisms of sexual selection in species with ornaments composed of different pigment types. [ABSTRACT FROM AUTHOR]

The U.S. Department of Agriculture (USDA) under its Continuous Enrollment Conservation Reserve Program (CRP) has actively promoted establishment of conservation buffers. Although these programs are intended to benefit wildlife in addition to protecting soil and water resources, benefits to grassland birds may be compromised by narrow widths, presence of woody vegetation, and high predation pressure. During 2001 and 2002, we surveyed breeding grassland birds and searched for nests in 33 CRP filter strips that varied in planting mixture (cool-season vs. warm-season grasses) and adjacent edge type (non-wooded vs. wooded). The most abundant species in filter strips were red-winged blackbird (Agelaius phoeniceus), dickcissel (Spiza americana), song sparrow (Melospiza melodia), and common yellowthroat (Geothlypis trichas). Relative abundances of birds and nests were similar between cool-season and warm-season planting mixtures. Dickcissels and red-winged blackbirds and their nests were relatively less abundant at wooded than non-wooded sites. Our nest success estimates generally were low in all treatments, and nest success varied little with the variables we studied. Predation was the major cause of nest failure; 62% of all nests were depredated. Although the most common birds using filter strips are generalists, filter strips also have potential to provide breeding habitat for some species of management concern. [ABSTRACT FROM AUTHOR]

Although Common Yellowthroats (Geothlypis trichas) are Nearctic-Neotropical migrants that are common breeders across the United States and Canada, very little has been published about the migration and stopover ecology of this species. We used spring migration banding records of Common Yellowthroats from 1992-2001 on Appledore Island, Maine, to investigate potential sexual and age-related differences in migration timing and stopover ecology of this species. Arrival dates of males were significantly earlier than arrival dates of females during spring, with mean male arrival five days earlier than female arrival. Also, after-second-year (ASY) birds arrived significantly earlier than second-year (SY) birds within each sex. Males also were significantly heavier than females upon arrival on Appledore. During spring migration, 5.0% of males and 4.2% of females were recaptured at least one day after initial capture, resulting in a mean stopover length of approximately three days for both sexes. We found no significant difference in the mean minimum stopover length nor the rate of mass change between the sexes based on recaptured individuals. Furthermore, we found no significant differences in stopover ecology between age groups within either sex. Both sexes significantly increased mass during stopover, both as calculated from recaptured individuals and as estimated by regression of condition (mass × 100/wing chord) over time. Results of this study confirmed differential migration among Common Yellowthroats, which is consistent with previous studies of passerine migration ecology. Lack of differences in stopover ecology between the sexes or between age groups suggests that earlier arrival of males than females and of ASY birds than SY birds may be due to an earlier onset of migration rather than increased migration speed. [ABSTRACT FROM AUTHOR]