Search citation statements
Paper Sections
Citation Types
Year Published
Publication Types
Relationship
Authors
Journals
ABSTRACT. Since the 1940s, populations of Gray Vireos (Vireo vicinior) in California have collapsed, presumably because of parasitism by Brown-headed Cowbirds (Molothrus ater). In 2012 and 2013, we studied the vireo's nesting ecology to assess factors affecting two of California's largest remaining populations in the chaparral of San Diego County. Nest success was extremely low, with a model-averaged probability of nest survival of only 0.08 (N = 95). More nest failures were due to predation (83%) than to cowbird parasitism (13%). Video-recording at 30 nests revealed that California Scrub-Jays (Aphelocoma californica) were the most common nest predator (67%). Of eight variables tested, height of shrubs surrounding the nest had the strongest negative influence on nest survival, but was more strongly correlated with cowbird parasitism than with jay predation. Despite frequent renesting, seasonal productivity was well below the level required to sustain a population, especially in northern San Diego County where we found no Gray Vireos at six of seven sites where they had been present from 1997 to 2001 and where cowbird parasitism was more frequent. The vireo's continuing range collapse contrasts with recent climate-change models predicting a range expansion, highlighting the importance of demographic studies. Low nest success is likely contributing to population declines in California, and the additive effect of cowbird parasitism suppresses productivity. Conservation of Gray Vireos in California will likely require development of alternative approaches to cowbird and scrub-jay control appropriate to sites widely scattered in rugged chaparral.RESUMEN. Bajo exito reproductivo de Vireo vicinior en una poblaci on de California en declive Desde la d ecada de 1940, las poblaciones de Vireo vicinior en California se han desplomado, presuntamente por el parasitismo por Molothrus ater. En 2012 y 2013, estudiamos la ecolog ıa de anidaci on de Vireo vicinior, con el objetivo de determinar los factores que afectan las dos poblaciones m as grandes de California en el chaparral del condado de San Diego. El exito reproductivo fue extremadamente bajo, con una probabilidad promedio de supervivencia del nido de solo 0.08 (N = 95). La mayor cantidad fracasos de nidos fue producto de depredaci on (83%) y no de parasitismo por Molothrus ater (13%). Grabaciones de 30 nidos revelaron que el depredador m as com un fue Aphelocoma californica (67%). De las ocho variables evaluadas, la altura de los arbustos alrededor del nido tuvo la influencia negativa m as fuerte sobre la supervivencia del nido, sin embargo, estuvo m as fuertemente correlacionada con el parasitismo por parte de Molothrus ater que por la depredaci on por parte de Aphelocoma californica. A pesar de los intentos frecuentes de re-anidaci on, la productividad estacional fue considerablemente menor al nivel requerido para sostener una poblaci on, especialmente en el norte del condado de San Diego, donde no encontramos Vireo vicinior en seis de las siete localidades donde hab ...
ABSTRACT. Since the 1940s, populations of Gray Vireos (Vireo vicinior) in California have collapsed, presumably because of parasitism by Brown-headed Cowbirds (Molothrus ater). In 2012 and 2013, we studied the vireo's nesting ecology to assess factors affecting two of California's largest remaining populations in the chaparral of San Diego County. Nest success was extremely low, with a model-averaged probability of nest survival of only 0.08 (N = 95). More nest failures were due to predation (83%) than to cowbird parasitism (13%). Video-recording at 30 nests revealed that California Scrub-Jays (Aphelocoma californica) were the most common nest predator (67%). Of eight variables tested, height of shrubs surrounding the nest had the strongest negative influence on nest survival, but was more strongly correlated with cowbird parasitism than with jay predation. Despite frequent renesting, seasonal productivity was well below the level required to sustain a population, especially in northern San Diego County where we found no Gray Vireos at six of seven sites where they had been present from 1997 to 2001 and where cowbird parasitism was more frequent. The vireo's continuing range collapse contrasts with recent climate-change models predicting a range expansion, highlighting the importance of demographic studies. Low nest success is likely contributing to population declines in California, and the additive effect of cowbird parasitism suppresses productivity. Conservation of Gray Vireos in California will likely require development of alternative approaches to cowbird and scrub-jay control appropriate to sites widely scattered in rugged chaparral.RESUMEN. Bajo exito reproductivo de Vireo vicinior en una poblaci on de California en declive Desde la d ecada de 1940, las poblaciones de Vireo vicinior en California se han desplomado, presuntamente por el parasitismo por Molothrus ater. En 2012 y 2013, estudiamos la ecolog ıa de anidaci on de Vireo vicinior, con el objetivo de determinar los factores que afectan las dos poblaciones m as grandes de California en el chaparral del condado de San Diego. El exito reproductivo fue extremadamente bajo, con una probabilidad promedio de supervivencia del nido de solo 0.08 (N = 95). La mayor cantidad fracasos de nidos fue producto de depredaci on (83%) y no de parasitismo por Molothrus ater (13%). Grabaciones de 30 nidos revelaron que el depredador m as com un fue Aphelocoma californica (67%). De las ocho variables evaluadas, la altura de los arbustos alrededor del nido tuvo la influencia negativa m as fuerte sobre la supervivencia del nido, sin embargo, estuvo m as fuertemente correlacionada con el parasitismo por parte de Molothrus ater que por la depredaci on por parte de Aphelocoma californica. A pesar de los intentos frecuentes de re-anidaci on, la productividad estacional fue considerablemente menor al nivel requerido para sostener una poblaci on, especialmente en el norte del condado de San Diego, donde no encontramos Vireo vicinior en seis de las siete localidades donde hab ...
There are many gaps in our understanding of Gray Vireo (Vireo vicinior) life history especially as it relates to nesting ecology. Our objective was to determine habitat features selected by Gray Vireos for nesting to improve management strategies for breeding populations. We searched for Gray Vireo nests on Kirtland Air Force Base in Albuquerque, New Mexico from 2016 to 2017. We estimated Gray Vireo nest-site selection at the tree level, the surrounding vegetation, and at two broader scales corresponding to selection within territories. Nest-site selection was estimated for 99 Gray Vireo nests. For tree-level selection, we compared characteristics of nesting trees with mean characteristics from groups of six randomly selected one-seed junipers (Juniperus monosperma) within a 25m radius. We also compared overall vegetation characteristics at the 25-m scale for nesting plots and 66 randomly selected plots. Broadscale cover proportions of nest sites and random points were estimated at 50-and 100-m radius spatial scales using a geographic information system. Gray Vireos selected nesting trees that were taller and wider than other adjacent junipers. Selection of vegetation characteristics surrounding nests showed a similar pattern, where Gray Vireos nested in areas where junipers were taller, wider, and had greater foliage density than was randomly available. Broad-scale analyses suggested that Gray Vireos selected nest sites in areas with higher proportions of junipers at low elevations (< 1954 m), and lower proportions of junipers in higher elevations (> 1954 m); however, juniper proportions at nest sites consistently ranged from 15 to 30% of available cover. Gray Vireos also tended to select areas with less pinyon pine than what was randomly available at the 100-m radius scale. Future management strategies should provide large patches of old-growth juniper to optimize Gray Vireo nesting habitat. Analyse multiéchelle de la sélection du site de nidification du Viréo gris (Vireo vicinior) dans le centre du Nouveau-Mexique RÉSUMÉ. Notre compréhension du cycle biologique du Viréo gris (Vireo vicinior) est incomplète, particulièrement en ce qui a trait à l'écologie de nidification. Notre objectif était de déterminer les caractéristiques d'habitat recherchées par les Viréos gris durant la nidification afin d'améliorer les stratégies d'aménagement destinées aux populations nicheuses. Nous avons cherché des nids de viréos sur la base des forces aériennes de Kirtland à Albuquerque, au Nouveau-Mexique, en 2016 et 2017. Nous avons évalué la sélection des sites de nidification des viréos à l'échelle de l'arbre, de la végétation environnante et à deux autres échelles plus grandes à l'intérieur des territoires des oiseaux. Nous avons analysé la sélection du site de 99 nids de Viréos gris. En matière de sélection à l'échelle de l'arbre, nous avons comparé les caractéristiques des arbres abritant un nid avec les caractéristiques moyennes de groupes de six genévriers monospermes (Juniperus monosperma) tirés aléatoirement dans un ray...
The Gray Vireo (Vireo vicinior; hereafter “vireo”) is a little-studied songbird with small breeding and wintering ranges. Because of uncertainty about vireo populations, conservationists are concerned about the future of this species. The goal of the present study was to provide new data on the ecology of the vireo to help determine its conservation status. During May and June 2001, I studied breeding habitat selection by vireos on the Colorado Plateau in northern Arizona and southern Utah. I surveyed for vireos and collected vegetation data on 31 transects in pinyon-juniper (Pinus edulis-Juniperus spp.) woodlands throughout this region. Estimated density of vireos was 0.064 ± 0.011 (mean ± SE) birds ha−1. Analysis at two scales showed that the vireo’s primary habitat preference was for areas where junipers predominate over pinyon pine. Vireos also preferred areas with some shrub cover, and they increased with the prevalence of sagebrush (Artemisia tridentata) among shrubs. Additionally, vireos were more common at lower elevations, an effect that was largely independent of vegetation characters. Habitats preferred by vireos are widespread in the southwestern United States and may be increasing in extent as woodlands expand into grasslands and shrublands. On the basis of these results, I suggest that vireo populations are relatively safe, at least for the short term. Additional data on vireo demography are needed to ensure the long-term conservation of this species. Abundancia y Preferencias de Hábitat de Vireo vicinior en la Planicie de Colorado
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.