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Geographic variation in mating signals is of interest to evolutionary biologists because the consequences of spatial divergence may lead to behavioral discrimination, assortative mating, and speciation. Birdsong is a mating signal of songbirds, and geographic variation in the form of small-scale dialects or large-scale regiolects has been documented in many species. We studied macrogeographic variation in song of the MacGillivray's Warbler (Geothlypis tolmiei) to determine the pattern of song variation in this species. Hypotheses used to explain the evolution of song divergence were also examined. We found extensive individual variation in the cultural units and physical parameters of song that overwhelmed differences among populations. We did not find dialects in the breeding range but did find a pattern of clinal variation with song differences increasing with increasing geographic distances among populations. Hypotheses that explain patterns of song divergence in other species did not apply to MacGillivray's Warblers. Selection for novel songs that facilitates individual recognition may be important in this species that breeds in extremely dense vegetation. Extensive individual variation among male tutors within and among populations may also inhibit dialect formation and perpetuate song diversity in future generations. [ABSTRACT FROM AUTHOR]

We describe the isolation of 10 microsatellite loci with tetranucleotide repeat motifs from the Orange-crowned Warbler ( Oreothlypis celata) by using an enrichment protocol. All 10 loci were variable across two sampled populations (Alaska, California Channel Islands); the number of alleles ranged from 2-23, and observed heterozygosity ranged from 0.333-1.000. We tested the utility of these loci across an additional 13 parulid species, spanning the evolutionary and ecological diversity of the Parulidae. Nine of our 10 primer pairs were successfully PCR-amplified across at least 12 species, with the remaining locus being amplified across 9 parulid species. We expect the identified loci to be of particular use in studies of phylogeography, determination of cryptic species boundaries, hybrid zone dynamics, and paternity assignment across New World warblers. [ABSTRACT FROM AUTHOR]

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.

Geographic variation in song may reduce or eliminate the ability of some populations to recognize each other as conspecifics, possibly leading to assortative mating, reproductive isolation, and speciation. Song playback experiments, used to evaluate the significance of geographic variation in song, have been particularly useful in discovering divergence among previously unknown populations of sibling species. In this study, I report the results of song playback to male Mourning Warblers (Geothlypis Philadelphia) from populations throughout the breeding range and discuss the implications for population divergence. Four regions in the breeding range contain unique song types or regiolects: western, eastern, Nova Scotia, and Newfoundland. Results of reciprocal song playback experiments showed that males from the western and Newfoundland regiolects respond more aggressively to songs in their own regiolect than those in the other regiolects. Interior populations, i.e., eastern and Nova Scotia regions, showed little or no difference in aggressive response toward their own versus other regiolects. This pattern may be due to a combination of geographic proximity of populations belonging to different regiolects, song learning, experience, and contact during migration. Song discrimination by populations from the western Prairie Provinces and Newfoundland is consistent with the existence of at least partial reproductive isolation at the geographic extremes of the breeding range. [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]

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]

Abstract: The avian genera Oporornis and Geothlypis are thought to represent a single lineage of closely related New World wood-warbler (AOU Family Parulidae) species. Phylogenetic relationships within this assemblage have not yet been addressed using molecular genetic methods. We used sequence data from three mitochondrial (mtDNA) genes (cytochrome b, ND2, and control region) to reconstruct an hypothesis of relationships for this group. Our ingroup sampling included 34 individuals representing all currently recognized Oporornis (4 spp.) and Geothlypis (9 spp.) species. Our results indicate that Geothlypis is paraphyletic with respect to Oporornis formosus. The four members of Oporornis do not form a clade but instead comprise a grade at the base of the Oporornis–Geothlypis topology. Two species within Geothlypis are polyphyletic. The Costa Rican form of G. aequinoctialis is embedded within the Neotropical G. semiflava complex, and the widespread North American form G. trichas consists of at least two groups, each having a closer affinity to other Geothlypis species than with each other. Five Geothlypis species differ from one another on average by about 2% uncorrected (cytochrome b) divergence, indicating a rapid and recent radiation within this genus. Our phylogenetic hypothesis for this assemblage indicates that morphological characters such as size and plumage brightness that have traditionally defined relationships with Geothlypis are not concordant with molecular data. Most members of Geothlypis are sedentary whereas all members of Oporornis are long-distance Nearctic migrants. Our topology suggests that Geothlypis is derived from a migrant, Oporornis-like ancestor that ceased migration and established itself as a sedentary breeding population in the Neotropics. We speculate that an ecological switch from forested to more open habitats at this time led to range expansion and diversification in this new lineage. [Copyright &y& Elsevier]

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]

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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]

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]