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Gustavo J Fernandez - One of the best experts on this subject based on the ideXlab platform.
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range contraction in the pampas Meadowlark sturnella defilippii in the southern pampas grasslands of argentina
Oryx, 2004Co-Authors: Fabian M Gabelli, Gustavo J Fernandez, Gabriela Posse, Valentina Ferretti, Eugenio Coconier, Hernan J Gavieiro, Paulo E Llambias, Pablo I Pelaez, Maria L Valles, Pablo L. TubaroAbstract:The Vulnerable Pampas Meadowlark Sturn- ella defilippii (Family Icteridae) is a Neotropical grassland bird that suffered a severe population reduction and range contraction during the 20th century. Formerly dis- tributed across most of the pampas grasslands, it is now confined to the southern tip of its original range. There are small groups of wintering birds in southern Brazil, a small reproductive population in eastern Uruguay, and the main reproductive population occurs on the southern pampas grasslands of Argentina. In this paper we report the results of an extensive field survey of these southern pampas grasslands, carried out to estimate the pampas Meadowlark's population size and to iden- tify the factors potentially responsible for its range con- traction. During the 1999 breeding season we surveyed a total of 296 sample locations (transects, randomly selected points, and sites checked for nesting site re-occupation).We found 66 reproductive groups of pampas Meadowlarks. The minimum population size and extent of occurrence were estimated to be 28,000 individuals and 4,810 km 2 , respectively. This value repre- sents a range contraction of c. 30% compared to that estimated in a study carried out between 1992 and 1996. Pampas Meadowlarks re-occupied natural grassland sites for nesting that were used in previous breeding seasons when these sites remained undisturbed. Habitat transformation appears to be the main factor causing the range contraction of the pampas Meadowlark. We suggest that long-term monitoring of this population and its preferred habitat, the natural grasslands, is required in order to ensure the conservation of this species.
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bird habitat relationship for the declining pampas Meadowlark populations in the southern pampas grasslands
Biological Conservation, 2004Co-Authors: Gustavo J Fernandez, Gabriela Posse, Valentina Ferretti, Fabian M GabelliAbstract:During the past century, the Pampas Meadowlark Sturnella defilippii underwent a severe population drop and now, it is confined mostly to southern Pampas grasslands. We analyzed the habitat and landscape characteristics associated to the presence of reproductive groups of Pampas Meadowlarks in this area. During the 1999 breeding season, we surveyed 89 randomly stratified selected points where we noted the presence/absence of Pampas Meadowlarks. For each point we estimated seven habitat variables related to vegetation cover and six landscape variables derived from different maps. We found 11 groups of displaying males, nine of them on natural grassland plots. Multivariate analyses indicate that field type and vegetation cover are the main factors associated to the presence of Pampas Meadowlark. Reproductive groups were found preferentially at natural grasslands with high vegetation cover. Habitat loss and intensive grazing of fields appear to be the main factors associated to their sharp population decline and distribution retraction.
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Bird–habitat relationship for the declining Pampas Meadowlark populations in the southern Pampas grasslands
Biological Conservation, 2003Co-Authors: Gustavo J Fernandez, Gabriela Posse, Valentina Ferretti, Fabian M GabelliAbstract:During the past century, the Pampas Meadowlark Sturnella defilippii underwent a severe population drop and now, it is confined mostly to southern Pampas grasslands. We analyzed the habitat and landscape characteristics associated to the presence of reproductive groups of Pampas Meadowlarks in this area. During the 1999 breeding season, we surveyed 89 randomly stratified selected points where we noted the presence/absence of Pampas Meadowlarks. For each point we estimated seven habitat variables related to vegetation cover and six landscape variables derived from different maps. We found 11 groups of displaying males, nine of them on natural grassland plots. Multivariate analyses indicate that field type and vegetation cover are the main factors associated to the presence of Pampas Meadowlark. Reproductive groups were found preferentially at natural grasslands with high vegetation cover. Habitat loss and intensive grazing of fields appear to be the main factors associated to their sharp population decline and distribution retraction.
Fabian M Gabelli - One of the best experts on this subject based on the ideXlab platform.
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range contraction in the pampas Meadowlark sturnella defilippii in the southern pampas grasslands of argentina
Oryx, 2004Co-Authors: Fabian M Gabelli, Gustavo J Fernandez, Gabriela Posse, Valentina Ferretti, Eugenio Coconier, Hernan J Gavieiro, Paulo E Llambias, Pablo I Pelaez, Maria L Valles, Pablo L. TubaroAbstract:The Vulnerable Pampas Meadowlark Sturn- ella defilippii (Family Icteridae) is a Neotropical grassland bird that suffered a severe population reduction and range contraction during the 20th century. Formerly dis- tributed across most of the pampas grasslands, it is now confined to the southern tip of its original range. There are small groups of wintering birds in southern Brazil, a small reproductive population in eastern Uruguay, and the main reproductive population occurs on the southern pampas grasslands of Argentina. In this paper we report the results of an extensive field survey of these southern pampas grasslands, carried out to estimate the pampas Meadowlark's population size and to iden- tify the factors potentially responsible for its range con- traction. During the 1999 breeding season we surveyed a total of 296 sample locations (transects, randomly selected points, and sites checked for nesting site re-occupation).We found 66 reproductive groups of pampas Meadowlarks. The minimum population size and extent of occurrence were estimated to be 28,000 individuals and 4,810 km 2 , respectively. This value repre- sents a range contraction of c. 30% compared to that estimated in a study carried out between 1992 and 1996. Pampas Meadowlarks re-occupied natural grassland sites for nesting that were used in previous breeding seasons when these sites remained undisturbed. Habitat transformation appears to be the main factor causing the range contraction of the pampas Meadowlark. We suggest that long-term monitoring of this population and its preferred habitat, the natural grasslands, is required in order to ensure the conservation of this species.
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bird habitat relationship for the declining pampas Meadowlark populations in the southern pampas grasslands
Biological Conservation, 2004Co-Authors: Gustavo J Fernandez, Gabriela Posse, Valentina Ferretti, Fabian M GabelliAbstract:During the past century, the Pampas Meadowlark Sturnella defilippii underwent a severe population drop and now, it is confined mostly to southern Pampas grasslands. We analyzed the habitat and landscape characteristics associated to the presence of reproductive groups of Pampas Meadowlarks in this area. During the 1999 breeding season, we surveyed 89 randomly stratified selected points where we noted the presence/absence of Pampas Meadowlarks. For each point we estimated seven habitat variables related to vegetation cover and six landscape variables derived from different maps. We found 11 groups of displaying males, nine of them on natural grassland plots. Multivariate analyses indicate that field type and vegetation cover are the main factors associated to the presence of Pampas Meadowlark. Reproductive groups were found preferentially at natural grasslands with high vegetation cover. Habitat loss and intensive grazing of fields appear to be the main factors associated to their sharp population decline and distribution retraction.
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Bird–habitat relationship for the declining Pampas Meadowlark populations in the southern Pampas grasslands
Biological Conservation, 2003Co-Authors: Gustavo J Fernandez, Gabriela Posse, Valentina Ferretti, Fabian M GabelliAbstract:During the past century, the Pampas Meadowlark Sturnella defilippii underwent a severe population drop and now, it is confined mostly to southern Pampas grasslands. We analyzed the habitat and landscape characteristics associated to the presence of reproductive groups of Pampas Meadowlarks in this area. During the 1999 breeding season, we surveyed 89 randomly stratified selected points where we noted the presence/absence of Pampas Meadowlarks. For each point we estimated seven habitat variables related to vegetation cover and six landscape variables derived from different maps. We found 11 groups of displaying males, nine of them on natural grassland plots. Multivariate analyses indicate that field type and vegetation cover are the main factors associated to the presence of Pampas Meadowlark. Reproductive groups were found preferentially at natural grasslands with high vegetation cover. Habitat loss and intensive grazing of fields appear to be the main factors associated to their sharp population decline and distribution retraction.
Richard E. Warner - One of the best experts on this subject based on the ideXlab platform.
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POSTFLEDGING MOVEMENTS AND SURVIVAL OF JUVENILE EASTERN MeadowlarkS (STURNELLA MAGNA) IN ILLINOIS
The Auk, 2004Co-Authors: Eric L. Kershner, Jeffery W. Walk, Richard E. WarnerAbstract:Abstract The postfledging period is the least-studied stage of avian life cycles. Survival during this period has crucial effects on population dynamics. Survival of fledged young may be influenced by dispersal from their nest sites, because juveniles must cope with the hazards of novel environments. To better understand this important life stage, we used radiotelemetry techniques to study postfledging movements and survival of 50 juvenile Eastern Meadowlarks (Sturnella magna) at Prairie Ridge State Natural Area in Jasper County, Illinois, in 1999 and 2000. Juveniles began to move away from the nesting area in the third week after fledging. Most juveniles moved only 1–5 km from their birth site by the end of the study (90 days). Juvenile survival for the first 90 days after fledging was estimated as 56–69%. Mortality was greatest during the first week of the postfledging period, likely because of high rates of predation. Juvenile Meadowlarks are flightless at fledging and thus are vulnerable to predators....
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Postfledging Movements and Survival of Juvenile Eastern Meadowlarks (Sturnella Magna) in Illinois
The Auk, 2004Co-Authors: Eric L. Kershner, Jeffery W. Walk, Richard E. WarnerAbstract:Abstract The postfledging period is the least-studied stage of avian life cycles. Survival during this period has crucial effects on population dynamics. Survival of fledged young may be influenced by dispersal from their nest sites, because juveniles must cope with the hazards of novel environments. To better understand this important life stage, we used radiotelemetry techniques to study postfledging movements and survival of 50 juvenile Eastern Meadowlarks (Sturnella magna) at Prairie Ridge State Natural Area in Jasper County, Illinois, in 1999 and 2000. Juveniles began to move away from the nesting area in the third week after fledging. Most juveniles moved only 1–5 km from their birth site by the end of the study (90 days). Juvenile survival for the first 90 days after fledging was estimated as 56–69%. Mortality was greatest during the first week of the postfledging period, likely because of high rates of predation. Juvenile Meadowlarks are flightless at fledging and thus are vulnerable to predators. We did not observe a second peak of mortality, as other studies have shown, at independence or when juveniles began to move away from their nest areas. The present study suggests that immediate postfledging movements may not be related to dispersal to future breeding sites, but rather occur in response to immediate needs for food resources and security from predators. Furthermore, the data suggest that presumed mortality patterns and estimated levels of juvenile survival are suspect; that interspecific variability of juvenile survival and postfledging movements may be considerable; and that detailed, longer-duration field studies are necessary to elucidate this important demographic period.
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Breeding-Season Decisions, Renesting, and Annual Fecundity of Female Eastern Meadowlarks (Sturnella Magna) in Southeastern Illinois
The Auk, 2004Co-Authors: Eric L. Kershner, Jeffery W. Walk, Richard E. WarnerAbstract:Abstract Annual fecundity is a demographic parameter that is elemental to population biology, but accurate measures of fecundity are rarely obtained. We used radiotelemetry to follow female Eastern Meadowlarks (Sturnella magna) throughout the 1999-2000 breeding seasons in southeastern Illinois to estimate their annual fecundity and assess if the outcome of initial nesting attempts affected site selection for subsequent nests. Thirty-four females built 52 nests (1.53 ± 0.12 nests female−1), but only 21 females (62%) fledged young. Only 44% of females renested at the study site, and more females (53%) emigrated after successfully fledging young from an initial nest than after failing in their first attempt (21%). Nest-site characteristics were similar between successful and failed nests for both initial and subsequent attempts. Females that failed during first attempts did not change nest characteristics for renests. Given that few females were double-brooded and that unsuccessful females did not persistently renest, annual fecundity for females nesting at the study site was between 1.27 ± 0.38 and 1.36 ± 0.37 female young year−1. On the basis of our fecundity measure, we estimated that annual adult survival of 59–61% was necessary for maintenance of a stable population (λ = 1.0). Failure of most females to attempt to raise two broods suggests that double brooding carries substantial costs for Meadowlarks.
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BREEDING-SEASON DECISIONS, RENESTING, AND ANNUAL FECUNDITY OF FEMALE EASTERN MeadowlarkS (STURNELLA MAGNA) IN SOUTHEASTERN ILLINOIS
The Auk, 2004Co-Authors: Eric L. Kershner, Jeffery W. Walk, Richard E. WarnerAbstract:Abstract Annual fecundity is a demographic parameter that is elemental to population biology, but accurate measures of fecundity are rarely obtained. We used radiotelemetry to follow female Eastern Meadowlarks (Sturnella magna) throughout the 1999-2000 breeding seasons in southeastern Illinois to estimate their annual fecundity and assess if the outcome of initial nesting attempts affected site selection for subsequent nests. Thirty-four females built 52 nests (1.53 ± 0.12 nests female−1), but only 21 females (62%) fledged young. Only 44% of females renested at the study site, and more females (53%) emigrated after successfully fledging young from an initial nest than after failing in their first attempt (21%). Nest-site characteristics were similar between successful and failed nests for both initial and subsequent attempts. Females that failed during first attempts did not change nest characteristics for renests. Given that few females were double-brooded and that unsuccessful females did not persistent...
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Grassland management for the conservation of songbirds in the Midwestern USA
Biological Conservation, 2000Co-Authors: Jeffery W. Walk, Richard E. WarnerAbstract:We monitored breeding eastern Meadowlarks, dickcissels, Henslow's sparrows, grasshopper sparrows and field sparrows using strip transect surveys in 1995 and 1996. The 473-ha study area was an array of 3-ha management units of burned, mowed, hayed, grazed and undisturbed (>1 year) cool- and warm-season grasses and annual weeds. Management units grouped by habitat type (management regime and grass type) had different (P
Valentina Ferretti - One of the best experts on this subject based on the ideXlab platform.
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range contraction in the pampas Meadowlark sturnella defilippii in the southern pampas grasslands of argentina
Oryx, 2004Co-Authors: Fabian M Gabelli, Gustavo J Fernandez, Gabriela Posse, Valentina Ferretti, Eugenio Coconier, Hernan J Gavieiro, Paulo E Llambias, Pablo I Pelaez, Maria L Valles, Pablo L. TubaroAbstract:The Vulnerable Pampas Meadowlark Sturn- ella defilippii (Family Icteridae) is a Neotropical grassland bird that suffered a severe population reduction and range contraction during the 20th century. Formerly dis- tributed across most of the pampas grasslands, it is now confined to the southern tip of its original range. There are small groups of wintering birds in southern Brazil, a small reproductive population in eastern Uruguay, and the main reproductive population occurs on the southern pampas grasslands of Argentina. In this paper we report the results of an extensive field survey of these southern pampas grasslands, carried out to estimate the pampas Meadowlark's population size and to iden- tify the factors potentially responsible for its range con- traction. During the 1999 breeding season we surveyed a total of 296 sample locations (transects, randomly selected points, and sites checked for nesting site re-occupation).We found 66 reproductive groups of pampas Meadowlarks. The minimum population size and extent of occurrence were estimated to be 28,000 individuals and 4,810 km 2 , respectively. This value repre- sents a range contraction of c. 30% compared to that estimated in a study carried out between 1992 and 1996. Pampas Meadowlarks re-occupied natural grassland sites for nesting that were used in previous breeding seasons when these sites remained undisturbed. Habitat transformation appears to be the main factor causing the range contraction of the pampas Meadowlark. We suggest that long-term monitoring of this population and its preferred habitat, the natural grasslands, is required in order to ensure the conservation of this species.
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bird habitat relationship for the declining pampas Meadowlark populations in the southern pampas grasslands
Biological Conservation, 2004Co-Authors: Gustavo J Fernandez, Gabriela Posse, Valentina Ferretti, Fabian M GabelliAbstract:During the past century, the Pampas Meadowlark Sturnella defilippii underwent a severe population drop and now, it is confined mostly to southern Pampas grasslands. We analyzed the habitat and landscape characteristics associated to the presence of reproductive groups of Pampas Meadowlarks in this area. During the 1999 breeding season, we surveyed 89 randomly stratified selected points where we noted the presence/absence of Pampas Meadowlarks. For each point we estimated seven habitat variables related to vegetation cover and six landscape variables derived from different maps. We found 11 groups of displaying males, nine of them on natural grassland plots. Multivariate analyses indicate that field type and vegetation cover are the main factors associated to the presence of Pampas Meadowlark. Reproductive groups were found preferentially at natural grasslands with high vegetation cover. Habitat loss and intensive grazing of fields appear to be the main factors associated to their sharp population decline and distribution retraction.
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Bird–habitat relationship for the declining Pampas Meadowlark populations in the southern Pampas grasslands
Biological Conservation, 2003Co-Authors: Gustavo J Fernandez, Gabriela Posse, Valentina Ferretti, Fabian M GabelliAbstract:During the past century, the Pampas Meadowlark Sturnella defilippii underwent a severe population drop and now, it is confined mostly to southern Pampas grasslands. We analyzed the habitat and landscape characteristics associated to the presence of reproductive groups of Pampas Meadowlarks in this area. During the 1999 breeding season, we surveyed 89 randomly stratified selected points where we noted the presence/absence of Pampas Meadowlarks. For each point we estimated seven habitat variables related to vegetation cover and six landscape variables derived from different maps. We found 11 groups of displaying males, nine of them on natural grassland plots. Multivariate analyses indicate that field type and vegetation cover are the main factors associated to the presence of Pampas Meadowlark. Reproductive groups were found preferentially at natural grasslands with high vegetation cover. Habitat loss and intensive grazing of fields appear to be the main factors associated to their sharp population decline and distribution retraction.
Gabriela Posse - One of the best experts on this subject based on the ideXlab platform.
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range contraction in the pampas Meadowlark sturnella defilippii in the southern pampas grasslands of argentina
Oryx, 2004Co-Authors: Fabian M Gabelli, Gustavo J Fernandez, Gabriela Posse, Valentina Ferretti, Eugenio Coconier, Hernan J Gavieiro, Paulo E Llambias, Pablo I Pelaez, Maria L Valles, Pablo L. TubaroAbstract:The Vulnerable Pampas Meadowlark Sturn- ella defilippii (Family Icteridae) is a Neotropical grassland bird that suffered a severe population reduction and range contraction during the 20th century. Formerly dis- tributed across most of the pampas grasslands, it is now confined to the southern tip of its original range. There are small groups of wintering birds in southern Brazil, a small reproductive population in eastern Uruguay, and the main reproductive population occurs on the southern pampas grasslands of Argentina. In this paper we report the results of an extensive field survey of these southern pampas grasslands, carried out to estimate the pampas Meadowlark's population size and to iden- tify the factors potentially responsible for its range con- traction. During the 1999 breeding season we surveyed a total of 296 sample locations (transects, randomly selected points, and sites checked for nesting site re-occupation).We found 66 reproductive groups of pampas Meadowlarks. The minimum population size and extent of occurrence were estimated to be 28,000 individuals and 4,810 km 2 , respectively. This value repre- sents a range contraction of c. 30% compared to that estimated in a study carried out between 1992 and 1996. Pampas Meadowlarks re-occupied natural grassland sites for nesting that were used in previous breeding seasons when these sites remained undisturbed. Habitat transformation appears to be the main factor causing the range contraction of the pampas Meadowlark. We suggest that long-term monitoring of this population and its preferred habitat, the natural grasslands, is required in order to ensure the conservation of this species.
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bird habitat relationship for the declining pampas Meadowlark populations in the southern pampas grasslands
Biological Conservation, 2004Co-Authors: Gustavo J Fernandez, Gabriela Posse, Valentina Ferretti, Fabian M GabelliAbstract:During the past century, the Pampas Meadowlark Sturnella defilippii underwent a severe population drop and now, it is confined mostly to southern Pampas grasslands. We analyzed the habitat and landscape characteristics associated to the presence of reproductive groups of Pampas Meadowlarks in this area. During the 1999 breeding season, we surveyed 89 randomly stratified selected points where we noted the presence/absence of Pampas Meadowlarks. For each point we estimated seven habitat variables related to vegetation cover and six landscape variables derived from different maps. We found 11 groups of displaying males, nine of them on natural grassland plots. Multivariate analyses indicate that field type and vegetation cover are the main factors associated to the presence of Pampas Meadowlark. Reproductive groups were found preferentially at natural grasslands with high vegetation cover. Habitat loss and intensive grazing of fields appear to be the main factors associated to their sharp population decline and distribution retraction.
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Bird–habitat relationship for the declining Pampas Meadowlark populations in the southern Pampas grasslands
Biological Conservation, 2003Co-Authors: Gustavo J Fernandez, Gabriela Posse, Valentina Ferretti, Fabian M GabelliAbstract:During the past century, the Pampas Meadowlark Sturnella defilippii underwent a severe population drop and now, it is confined mostly to southern Pampas grasslands. We analyzed the habitat and landscape characteristics associated to the presence of reproductive groups of Pampas Meadowlarks in this area. During the 1999 breeding season, we surveyed 89 randomly stratified selected points where we noted the presence/absence of Pampas Meadowlarks. For each point we estimated seven habitat variables related to vegetation cover and six landscape variables derived from different maps. We found 11 groups of displaying males, nine of them on natural grassland plots. Multivariate analyses indicate that field type and vegetation cover are the main factors associated to the presence of Pampas Meadowlark. Reproductive groups were found preferentially at natural grasslands with high vegetation cover. Habitat loss and intensive grazing of fields appear to be the main factors associated to their sharp population decline and distribution retraction.