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Yellow Warblers (yellow + warbler)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Temporal fluctuation in abundance of Brown-headed Cowbirds and their hosts in riparian habitat in the Okanagan Valley, British Columbia, Canada

JOURNAL OF FIELD ORNITHOLOGY, Issue 4 2006
Tawna C. Morgan
ABSTRACT We tested the hypothesis that the abundance of Brown-headed Cowbirds (Molothrus ater) and their hosts, as well as parasitism rates, changed between 1992,1993 and 2001,2003 in riparian habitats in the Okanagan Valley, British Columbia, Canada, where riparian habitat has been reduced in area by more than 85% over the past 60 years. Cowbird abundance declined from a mean of 2.1 and 1.9 individuals per census plot in 1992 and 1993, respectively, to 0.66 individuals per plot in 2001,2002. The mean number of potential host individuals per census plot was also lower in 2001,2002 (5.5) than in 1992 (7.0) and 1993 (7.8). Although the percentage of Yellow Warbler (Dendroica petechia) nests parasitized declined (77% in 1992,1993 to 50% in 2002,2003), Yellow Warblers and Song Sparrows (Melospiza melodia) in the Okanagan Valley continue to be parasitized at high rates and have low nesting success. Host species and the distance of nests from the edge of nest patches were the strongest predictors of both nest success and parasitism, indicating the importance of large continuous patches of shrubs that allow nests to be located further from edges. SINOPSIS Se expuso a pruebas la hipótesis de la abundancia de tordos (Molothrus ater) y sus huespedes y como la tasa de parasitismo cambiaron durante el 1992,1993 y el 2001,2002 en un hábitat ripario en el valle Okanagan, Columbia Británica, Canada. En dicha localidad el hábitat ripario se redujo en un 85% en los últimos 60 años. La abundancia de tordos se redujo en un promedio de 2.1 y 1.9 de individuos/censo en 1992 y 1992, respectivamente, a 0.66 individuos en 2001,2002. El número promedio de hospederos potenciales por localidad censada (5.5) fue menor para el mismo periodo en comparación con el 1992 (7.0) y el 1993 (7.8). Aunque el porcentaje de nidos parasitados (77% en el 1992,1993 a 50% en 2002,2003) en Dendroica petechia, se redujo, tanto la especie como Melospiza melodia, tuvieron un alto grado de parasitismo y un bajo éxito de anidamiento. Tanto las especies hospederas y la distancia del nido al borde del parcho de anidamiento resultaron ser los elementos de predicción más fuertes con respecto al parasitismo y el éxito de anidamiento. Esto es un indicativo claro de la importancia de parchos de arbustos amplios y contínuos, que permitan el anidamiento lejos del borde. [source]

Phylogeography and genetic structure of northern populations of the yellow warbler (Dendroica petechia)

MOLECULAR ECOLOGY, Issue 6 2000
Emmanuel Milot
Abstract Phylogeographic patterns of intraspecific variation can provide insights into the population-level processes responsible for speciation and yield information useful for conservation purposes. To examine phylogeography and population structure in a migratory passerine bird at both continental and regional geographical scales, we analysed 344 bp of mitochondrial DNA (mtDNA) control region sequence from 155 yellow warblers (Dendroica petechia) collected from seven locations across Canada and from Alaska. There is a major subdivision between eastern (Manitoba to Newfoundland) and western (Alaska and British Columbia) populations which appears to have developed during the recent Pleistocene. Some localities within these two regions also differ significantly in their genetic composition, suggesting further subdivision on a regional geographical scale. Eastern and western birds form distinct phylogeographic entities and the clustering of all western haplotypes with two eastern haplotypes suggests that the western haplotypes may be derived from an eastern lineage. Analyses based on coalescent models support this explanation for the origin of western haplotypes. These results are consistent with important features of Mengel's model of warbler diversification. From a conservation perspective they also suggest that individual populations of migrant birds may form demographically isolated management units on a smaller scale than previously appreciated. [source]

Variation in Vocal Performance in the Songs of a Wood-Warbler: Evidence for the Function of Distinct Singing Modes

ETHOLOGY, Issue 7 2004
Martin D. Beebee
Male North American wood-warblers (family Parulidae) subdivide their song repertoires into two different categories, or modes, of singing (first and second category songs). These two modes are thought to be specialized for interacting with females and males, although the data are inconclusive. I conducted an acoustic analysis of the song types used by yellow warblers (Dendroica petechia) for type I (first category) and type II (second category) singing to ask whether there are consistent structural differences between them which could provide insight into how they might function as separate signals. I found that type I songs are performed closer to the upper boundary of a song performance limit, measured in terms of the difficulty of production, compared with type II songs. By contrast, the performance of specific song types did not depend on whether they were used for type I singing vs. type II singing by different males. In addition, type I songs had a greater amplitude increase across the first two syllables compared with type II songs. There was no relationship between the performance of type I or type II songs and male condition. These results suggest that wood-warblers might subdivide their song repertoire into distinct categories to highlight the relative vocal performance of their songs. [source]