Background: Invasive plants are associated with the decline of native plant richness, but the imp... more Background: Invasive plants are associated with the decline of native plant richness, but the impact of removal of invasives on native plant richness is often unknown. Aims: We investigated whether the presence of the introduced plant Centaurea solstitialis (Asteraceae) was correlated with reduced native plant richness; whether rain in late spring, when C. solstitialis is virtually the only plant actively growing, increased its cover; and whether native species richness increased following the control of C. solstitialis. Methods: From 2011 to 2017 in a grassland in Sonoma County, California, USA, we treated 20 1-m 2 plots in C. solstitialis-invaded patches with chemical and mechanical removal. We monitored cover of all plants in those plots, plus 20 invaded untreated and 20 uninvaded plots, for a total of 60 plots in two blocks. Results: Native plant richness was lower in invaded than in non-invaded plots. More late spring rainfall resulted in greater C. solstitialis cover in the following year. Native species richness in the six years after initial removal was slightly higher in removal plots than in untreated control plots. Conclusions: Centaurea solstitialis removal alone results in modest benefits for native plant species richness. Managing this invasive requires more resources in years with more late spring rainfall.
Latitudinal clines in sex ratio during the nonbreeding season occur in some shorebirds of the Sco... more Latitudinal clines in sex ratio during the nonbreeding season occur in some shorebirds of the Scolopacidae. We compared populations of nonbreeding Dunlin (Calidris alpina pacifica) from two latitudes along the Pacific flyway: the Fraser River Delta, British Columbia, and Bolinas Lagoon, California, to determine whether, and to what degree, they exhibited sex ratios consistent with a latitudinal cline. Dunlin are plumage monomorphic, so we used a maximum likelihood model to estimate overall and monthly sex ratios for each population based on culmen length distributions. Sex ratios in the Fraser River Delta were corrected for sex differences in habitat use. Monthly sex ratios were similar at the two sites but varied throughout the winter, likely reflecting differences in seasonal movement patterns between the sexes. Both populations showed an overall bias toward males (Fraser ϭ 61% males, Bolinas ϭ 65% males). Since there is no evidence to support the possibility of a skew toward males in C. a. pacifica as a whole, our data are consistent with some form of latitudinal cline in the sex ratio of C. a. pacifica. However, additional data from the Oregon coast, southern California, and Mexico are required to resolve this question. We also tested the hypothesis that mean body size within each sex is larger at the higher-latitude site (Fraser River Delta), but this did not appear to be the case.
Worldwide, shorebird populations are declining. Our objectives were to examine abundance trends o... more Worldwide, shorebird populations are declining. Our objectives were to examine abundance trends of shorebirds regularly wintering at Tomales Bay, Marin County, California, accounting for the local effects of rainfall, raptors, and the restoration of part of the bay to tidal wetlands. From November 1989 to February 2019, we conducted 177 comprehensive winter shorebird surveys of Tomales Bay; we averaged 5.7 ± 0.9 (mean ± SD) winter surveys per year. In 30 yr, we counted 1,215,821 shorebirds of 31 species. We used generalized linear models and multi-model inference to evaluate trends in shorebird abundance while accounting for local sources of variation. We conducted separate analyses for 14 species seen in at least 20 of the 30 yr of monitoring and for all shorebird species combined. During the study, the abundance of all species combined declined 66% (52% in the North Bay and 81% in the South Bay) with the most rapid decline in the first 10 yr of monitoring. Of 13 species for which ...
Background: Invasive plants are associated with the decline of native plant richness, but the imp... more Background: Invasive plants are associated with the decline of native plant richness, but the impact of removal of invasives on native plant richness is often unknown. Aims: We investigated whether the presence of the introduced plant Centaurea solstitialis (Asteraceae) was correlated with reduced native plant richness; whether rain in late spring, when C. solstitialis is virtually the only plant actively growing, increased its cover; and whether native species richness increased following the control of C. solstitialis. Methods: From 2011 to 2017 in a grassland in Sonoma County, California, USA, we treated 20 1-m 2 plots in C. solstitialis-invaded patches with chemical and mechanical removal. We monitored cover of all plants in those plots, plus 20 invaded untreated and 20 uninvaded plots, for a total of 60 plots in two blocks. Results: Native plant richness was lower in invaded than in non-invaded plots. More late spring rainfall resulted in greater C. solstitialis cover in the following year. Native species richness in the six years after initial removal was slightly higher in removal plots than in untreated control plots. Conclusions: Centaurea solstitialis removal alone results in modest benefits for native plant species richness. Managing this invasive requires more resources in years with more late spring rainfall.
BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting... more BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research.
Places where migrant birds stop to rest, drink, and eat at are often described as either stopover... more Places where migrant birds stop to rest, drink, and eat at are often described as either stopover or staging sites. Attempts have been made to differentiate between these two terms but they are frequently used interchangeably. Some authors have equated staging sites with sites that attract large concentrations (many thousands) of birds, a definition that others have expanded to include long stopover durations and significant rates of refueling on predictable, abundant prey. It has also been suggested that birds using staging sites are those that employ a jumping strategy during migration. I argue that while all sites where birds rest and feed during migration are stopover sites, further classification of stopover sites is of ecological and conservation value. I propose that sites with abundant, predictable food resources where birds prepare for an energetic challenge (usually a long flight over a barrier such as an ocean or a desert) requiring substantial fuel stores and physiological changes without which significant fitness costs are incurred are most appropriately described as staging sites.
Movement by animals to obtain resources and avoid predation often depends on natural cycles, and ... more Movement by animals to obtain resources and avoid predation often depends on natural cycles, and human alteration of the landscape may disrupt or enhance the utility of different habitats or resources to animals through the phases of these cycles. We studied habitat selection by GPS/accelerometer-tagged great egrets (Ardea alba) foraging in areas with shellfish aquaculture infrastructure and adjacent natural wetlands, while accounting for tide-based changes in water depth. We used integrated step selection analysis to test the prediction that egrets would express stronger selection for natural wetlands (eelgrass, tidal marsh, and other tidal wetlands) than for shellfish aquaculture areas. We also evaluated differences in foraging behavior among shellfish aquaculture areas and natural wetlands by comparing speed travelled (estimated from distance between GPS locations) and energy expended (Overall Dynamic Body Acceleration) while foraging. We found evidence for stronger overall habit...
Availability of wetlands with low salinities during the breeding season can influence waterfowl r... more Availability of wetlands with low salinities during the breeding season can influence waterfowl reproductive success and population recruitment. Salinities as low as 2 ppt (3.6 mScm–1) can impair duckling growth and influence behavior, with mortality occurring above 9 ppt (14.8 mScm–1). We used satellite imagery to quantify the amount of available water, and sampled surface water salinity at Grizzly Island, in the brackish Suisun Marsh, at three time-periods during waterfowl breeding (April, May, July) over 4 years (2016–2019). More water was available and salinity was lower during wetter years (2017, 2019) than during drier years (2016, 2018), and the amount of water in wetlands decreased 73%–86% from April to July. Across all time-periods and years, the majority (64%–100%) of wetland habitat area had salinities above what has been shown to negatively affect ducklings (> 2 ppt), and up to 42% of wetland area had salinities associated with duckling mortality (> 9 ppt). During ...
SUMMARYWe investigated the influence of changes in weather associated with winter storms on mass ... more SUMMARYWe investigated the influence of changes in weather associated with winter storms on mass balance, activity and food consumption in captive dunlin (Calidris alpina) held in outdoor aviaries, and compared the aviary results with weather-related body mass differences in free-living dunlin collected at Bolinas Lagoon, California. Captive birds fed ad libitum increased their body mass at higher wind speeds and lower temperatures, suggesting regulation of energy stores, whereas free-living birds exhibited patterns suggesting thermoregulatory limits on body mass regulation. Daily energy expenditure in aviary dunlin was 2.85 kJ g d–1, or 2.8× basal metabolic rate (BMR), with thermostatic costs averaging 59 % of daily expenditure. Slight but significant increases in body mass and energy expenditure in captive birds on rainy days, adjusted for possible external water mass, suggested rainfall as a proximate cue in regulating daily body mass. Body mass changes under artificial rainfall ...
Extensive habitat loss and degradation have resulted in decreases in populations of tidal marsh b... more Extensive habitat loss and degradation have resulted in decreases in populations of tidal marsh breeding birds in the San Francisco Estuary in the past 150 years. We conducted point count surveys and nest monitoring in tidal marsh habitat at China Camp State Park from 1996 through 2007 to assess bird abundance, species richness and reproductive success over time. We found overall species richness at China Camp to be significantly lower than that of other San Pablo Bay tidal marshes, but also to be increasing during the study period. We present relative density indices and confirm breeding for three focal species that are of conservation concern: San Pablo song sparrow (Melospiza melodia samuelis), California black rail (Laterallus jamaicensis coturniculus), and California clapper rail (Rallus longirostris obsoletus). Song sparrows were observed at higher densities at China Camp than at other San Pablo Bay sites. There was no apparent trend in song sparrow density during the study period at China Camp, in contrast with the rest of San Pablo Bay, which displayed a significant decline. We determined song sparrow nest survival probability using the method described by Mayfield (1975) and found that nest survival at China Camp varied markedly among years, from >30% in 1996 to 6% in 2006, with no discernible trend. The main causes of nest failure were predation and tidal flooding. Song sparrow nests were found predominantly in gumplant (Grindelia stricta) and pickleweed (Sarcocornia pacifica) and less commonly in saltgrass (Distichlis spicata). Clapper rails nested exclusively in pickleweed and black rail nests were found mainly in gumplant and less commonly in saltgrass. China Camp's expansive ancient marsh supports endemic and bird species of conservation concern, while serving as a reference site for tidal marsh studies in San Francisco Bay. The long-term monitoring of tidal marsh bird breeding parameters at China Camp has the potential to provide early detection of declining population trends before local populations become imperiled.
We observed two patterns of residency. Wintering birds in 1995 arrived on 17 November (median) an... more We observed two patterns of residency. Wintering birds in 1995 arrived on 17 November (median) and departed on 17 March (median), with length of stay of 120.0 ± 4.2 d; and in 1996 arrived on 12 October (median) and departed on 8 March (median), with length of stay of 146.9 + 4.3 d. Transient birds in 1995 arrived on 7 December (median) and departed on 17 February (median), with stays of 33.7 ± 4.3 d; and in 1996 arrived on 23 October (median) and departed on 3 December (median), with stays of 33.7 + 4.1 d. Residence time was independent of sighting effort. Both wintering birds and transients exhibited site fidelity between years. Both categories were independent with respect to age, trapping month, or year. The mid-season departures were not correlated with either age or the banding period. Older birds were more likely to depart earlier and switch their residency pattern from wintering to transient. While the ecological significance of variation in residency patterns remains unknown, evidence from this and previous studies suggest that such variation may be relatively common, with important implications for studies of shorebird populations and conservation strategies. CRONOLOGIA MIGRATORIA Y FIDELIDAD DE CALIDRIS MAURI NOMADAS E INVERNANTES EN ESTERO PUNTA BANDA, MEXICO Sinopsis.-Calidris mauri es uno de los playeros mas abundantes en el noroeste de Mexico, sin embargo, se conoce poco de su ecologia durante el invierno en este pais. Estudiamos los patrones de residencia de machos de C. mauri durante los inviernos
The emergence of highly pathogenic avian influenza (HPAI) H5N1 has elevated concerns about wild b... more The emergence of highly pathogenic avian influenza (HPAI) H5N1 has elevated concerns about wild birds as virus hosts; however, little is known about the ecological and epidemiological factors of transmission by shorebirds. Here we summarize results for 2,773 shorebirds that were live-trapped on the Pacific coast of the United States during 2006-2007 and tested for avian influenza virus using real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and virus isolation. As was the case throughout North America, HPAI H5N1 was not detected in shorebirds during this interval. Contrary to other wild bird groups, most notably waterfowl, the prevalence of even low pathogenicity virus among shorebirds in our study areas in California, Washington, and Alaska was extremely low (0.5%). Virus was detected by RT-PCR from four different species, including, Dunlin (Calidris alpina ; N = 3), Western Sandpiper (C. mauri ; N = 8), Long-billed Dowitcher (Limnodromus scolopaceus ; N = 1), and American Avocet (Recurvirostra americana ; N = 1), with the detections in the latter three constituting the first published records for these birds. Based on studies in the eastern United States, we expected, but did not detect (H 1 = 1.6, P = 0.21) elevated avian influenza prevalence among shorebirds during spring migration. Diagnostic tests, which were designed to evaluate testing and sampling methods, indicated poor functioning of traditional virus isolation methods and no improvement in detection likelihood by collecting oropharyngeal swabs in addition to cloacal swab samples for low pathogenicity viruses (Z 1 = 0.7, P = 0.48).
Take-down policy If you believe that this document breaches copyright please contact us providing... more Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Our understanding of migratory birds' year-round ecology and evolution remains patchy despite rec... more Our understanding of migratory birds' year-round ecology and evolution remains patchy despite recent fundamental advances. Periodic reviews focus future research and inform conservation and management; here, we take advantage of our combined experiences working on Western Hemisphere avian migration systems to highlight recent lessons and critical gaps in knowledge. Among topics discussed are: (1) The pipeline from pure to applied researchers leaves room for improvement. (2) Population limitation and regulation includes both seasonal and between-season interactions. (3) The study of movements of small-bodied species remains a major research frontier. (4) We must increase our understanding of population connectivity. (5) With few exceptions, population regulation has barely been investigated. (6) We have increasingly integrated landscape configuration of habitats, large-scale habitat disturbances, and habitat quality impacts into models of seasonal and overall demographic success. (7) The post-breeding season (late summer for latitudinal migrants) is increasingly appreciated for its impacts on demography. (8) We recognize the diverse ways that avian brood parasites, nest predators, and food availability affect demography. (9) Source-sink and meta-population models help us understand migratory avian distributions among fragmented habitats. (10) Advances in modeling have improved estimates of annual survival and fecundity, but for few species. (11) Populations can be limited by ecological conditions in winter, but habitat needs are poorly known for most species at this time. (12) Migration tends to occupy broad spatial fronts that may change seasonally or when migrants cross major barriers. (13)
Background: Invasive plants are associated with the decline of native plant richness, but the imp... more Background: Invasive plants are associated with the decline of native plant richness, but the impact of removal of invasives on native plant richness is often unknown. Aims: We investigated whether the presence of the introduced plant Centaurea solstitialis (Asteraceae) was correlated with reduced native plant richness; whether rain in late spring, when C. solstitialis is virtually the only plant actively growing, increased its cover; and whether native species richness increased following the control of C. solstitialis. Methods: From 2011 to 2017 in a grassland in Sonoma County, California, USA, we treated 20 1-m 2 plots in C. solstitialis-invaded patches with chemical and mechanical removal. We monitored cover of all plants in those plots, plus 20 invaded untreated and 20 uninvaded plots, for a total of 60 plots in two blocks. Results: Native plant richness was lower in invaded than in non-invaded plots. More late spring rainfall resulted in greater C. solstitialis cover in the following year. Native species richness in the six years after initial removal was slightly higher in removal plots than in untreated control plots. Conclusions: Centaurea solstitialis removal alone results in modest benefits for native plant species richness. Managing this invasive requires more resources in years with more late spring rainfall.
Latitudinal clines in sex ratio during the nonbreeding season occur in some shorebirds of the Sco... more Latitudinal clines in sex ratio during the nonbreeding season occur in some shorebirds of the Scolopacidae. We compared populations of nonbreeding Dunlin (Calidris alpina pacifica) from two latitudes along the Pacific flyway: the Fraser River Delta, British Columbia, and Bolinas Lagoon, California, to determine whether, and to what degree, they exhibited sex ratios consistent with a latitudinal cline. Dunlin are plumage monomorphic, so we used a maximum likelihood model to estimate overall and monthly sex ratios for each population based on culmen length distributions. Sex ratios in the Fraser River Delta were corrected for sex differences in habitat use. Monthly sex ratios were similar at the two sites but varied throughout the winter, likely reflecting differences in seasonal movement patterns between the sexes. Both populations showed an overall bias toward males (Fraser ϭ 61% males, Bolinas ϭ 65% males). Since there is no evidence to support the possibility of a skew toward males in C. a. pacifica as a whole, our data are consistent with some form of latitudinal cline in the sex ratio of C. a. pacifica. However, additional data from the Oregon coast, southern California, and Mexico are required to resolve this question. We also tested the hypothesis that mean body size within each sex is larger at the higher-latitude site (Fraser River Delta), but this did not appear to be the case.
Worldwide, shorebird populations are declining. Our objectives were to examine abundance trends o... more Worldwide, shorebird populations are declining. Our objectives were to examine abundance trends of shorebirds regularly wintering at Tomales Bay, Marin County, California, accounting for the local effects of rainfall, raptors, and the restoration of part of the bay to tidal wetlands. From November 1989 to February 2019, we conducted 177 comprehensive winter shorebird surveys of Tomales Bay; we averaged 5.7 ± 0.9 (mean ± SD) winter surveys per year. In 30 yr, we counted 1,215,821 shorebirds of 31 species. We used generalized linear models and multi-model inference to evaluate trends in shorebird abundance while accounting for local sources of variation. We conducted separate analyses for 14 species seen in at least 20 of the 30 yr of monitoring and for all shorebird species combined. During the study, the abundance of all species combined declined 66% (52% in the North Bay and 81% in the South Bay) with the most rapid decline in the first 10 yr of monitoring. Of 13 species for which ...
Background: Invasive plants are associated with the decline of native plant richness, but the imp... more Background: Invasive plants are associated with the decline of native plant richness, but the impact of removal of invasives on native plant richness is often unknown. Aims: We investigated whether the presence of the introduced plant Centaurea solstitialis (Asteraceae) was correlated with reduced native plant richness; whether rain in late spring, when C. solstitialis is virtually the only plant actively growing, increased its cover; and whether native species richness increased following the control of C. solstitialis. Methods: From 2011 to 2017 in a grassland in Sonoma County, California, USA, we treated 20 1-m 2 plots in C. solstitialis-invaded patches with chemical and mechanical removal. We monitored cover of all plants in those plots, plus 20 invaded untreated and 20 uninvaded plots, for a total of 60 plots in two blocks. Results: Native plant richness was lower in invaded than in non-invaded plots. More late spring rainfall resulted in greater C. solstitialis cover in the following year. Native species richness in the six years after initial removal was slightly higher in removal plots than in untreated control plots. Conclusions: Centaurea solstitialis removal alone results in modest benefits for native plant species richness. Managing this invasive requires more resources in years with more late spring rainfall.
BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting... more BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research.
Places where migrant birds stop to rest, drink, and eat at are often described as either stopover... more Places where migrant birds stop to rest, drink, and eat at are often described as either stopover or staging sites. Attempts have been made to differentiate between these two terms but they are frequently used interchangeably. Some authors have equated staging sites with sites that attract large concentrations (many thousands) of birds, a definition that others have expanded to include long stopover durations and significant rates of refueling on predictable, abundant prey. It has also been suggested that birds using staging sites are those that employ a jumping strategy during migration. I argue that while all sites where birds rest and feed during migration are stopover sites, further classification of stopover sites is of ecological and conservation value. I propose that sites with abundant, predictable food resources where birds prepare for an energetic challenge (usually a long flight over a barrier such as an ocean or a desert) requiring substantial fuel stores and physiological changes without which significant fitness costs are incurred are most appropriately described as staging sites.
Movement by animals to obtain resources and avoid predation often depends on natural cycles, and ... more Movement by animals to obtain resources and avoid predation often depends on natural cycles, and human alteration of the landscape may disrupt or enhance the utility of different habitats or resources to animals through the phases of these cycles. We studied habitat selection by GPS/accelerometer-tagged great egrets (Ardea alba) foraging in areas with shellfish aquaculture infrastructure and adjacent natural wetlands, while accounting for tide-based changes in water depth. We used integrated step selection analysis to test the prediction that egrets would express stronger selection for natural wetlands (eelgrass, tidal marsh, and other tidal wetlands) than for shellfish aquaculture areas. We also evaluated differences in foraging behavior among shellfish aquaculture areas and natural wetlands by comparing speed travelled (estimated from distance between GPS locations) and energy expended (Overall Dynamic Body Acceleration) while foraging. We found evidence for stronger overall habit...
Availability of wetlands with low salinities during the breeding season can influence waterfowl r... more Availability of wetlands with low salinities during the breeding season can influence waterfowl reproductive success and population recruitment. Salinities as low as 2 ppt (3.6 mScm–1) can impair duckling growth and influence behavior, with mortality occurring above 9 ppt (14.8 mScm–1). We used satellite imagery to quantify the amount of available water, and sampled surface water salinity at Grizzly Island, in the brackish Suisun Marsh, at three time-periods during waterfowl breeding (April, May, July) over 4 years (2016–2019). More water was available and salinity was lower during wetter years (2017, 2019) than during drier years (2016, 2018), and the amount of water in wetlands decreased 73%–86% from April to July. Across all time-periods and years, the majority (64%–100%) of wetland habitat area had salinities above what has been shown to negatively affect ducklings (> 2 ppt), and up to 42% of wetland area had salinities associated with duckling mortality (> 9 ppt). During ...
SUMMARYWe investigated the influence of changes in weather associated with winter storms on mass ... more SUMMARYWe investigated the influence of changes in weather associated with winter storms on mass balance, activity and food consumption in captive dunlin (Calidris alpina) held in outdoor aviaries, and compared the aviary results with weather-related body mass differences in free-living dunlin collected at Bolinas Lagoon, California. Captive birds fed ad libitum increased their body mass at higher wind speeds and lower temperatures, suggesting regulation of energy stores, whereas free-living birds exhibited patterns suggesting thermoregulatory limits on body mass regulation. Daily energy expenditure in aviary dunlin was 2.85 kJ g d–1, or 2.8× basal metabolic rate (BMR), with thermostatic costs averaging 59 % of daily expenditure. Slight but significant increases in body mass and energy expenditure in captive birds on rainy days, adjusted for possible external water mass, suggested rainfall as a proximate cue in regulating daily body mass. Body mass changes under artificial rainfall ...
Extensive habitat loss and degradation have resulted in decreases in populations of tidal marsh b... more Extensive habitat loss and degradation have resulted in decreases in populations of tidal marsh breeding birds in the San Francisco Estuary in the past 150 years. We conducted point count surveys and nest monitoring in tidal marsh habitat at China Camp State Park from 1996 through 2007 to assess bird abundance, species richness and reproductive success over time. We found overall species richness at China Camp to be significantly lower than that of other San Pablo Bay tidal marshes, but also to be increasing during the study period. We present relative density indices and confirm breeding for three focal species that are of conservation concern: San Pablo song sparrow (Melospiza melodia samuelis), California black rail (Laterallus jamaicensis coturniculus), and California clapper rail (Rallus longirostris obsoletus). Song sparrows were observed at higher densities at China Camp than at other San Pablo Bay sites. There was no apparent trend in song sparrow density during the study period at China Camp, in contrast with the rest of San Pablo Bay, which displayed a significant decline. We determined song sparrow nest survival probability using the method described by Mayfield (1975) and found that nest survival at China Camp varied markedly among years, from >30% in 1996 to 6% in 2006, with no discernible trend. The main causes of nest failure were predation and tidal flooding. Song sparrow nests were found predominantly in gumplant (Grindelia stricta) and pickleweed (Sarcocornia pacifica) and less commonly in saltgrass (Distichlis spicata). Clapper rails nested exclusively in pickleweed and black rail nests were found mainly in gumplant and less commonly in saltgrass. China Camp's expansive ancient marsh supports endemic and bird species of conservation concern, while serving as a reference site for tidal marsh studies in San Francisco Bay. The long-term monitoring of tidal marsh bird breeding parameters at China Camp has the potential to provide early detection of declining population trends before local populations become imperiled.
We observed two patterns of residency. Wintering birds in 1995 arrived on 17 November (median) an... more We observed two patterns of residency. Wintering birds in 1995 arrived on 17 November (median) and departed on 17 March (median), with length of stay of 120.0 ± 4.2 d; and in 1996 arrived on 12 October (median) and departed on 8 March (median), with length of stay of 146.9 + 4.3 d. Transient birds in 1995 arrived on 7 December (median) and departed on 17 February (median), with stays of 33.7 ± 4.3 d; and in 1996 arrived on 23 October (median) and departed on 3 December (median), with stays of 33.7 + 4.1 d. Residence time was independent of sighting effort. Both wintering birds and transients exhibited site fidelity between years. Both categories were independent with respect to age, trapping month, or year. The mid-season departures were not correlated with either age or the banding period. Older birds were more likely to depart earlier and switch their residency pattern from wintering to transient. While the ecological significance of variation in residency patterns remains unknown, evidence from this and previous studies suggest that such variation may be relatively common, with important implications for studies of shorebird populations and conservation strategies. CRONOLOGIA MIGRATORIA Y FIDELIDAD DE CALIDRIS MAURI NOMADAS E INVERNANTES EN ESTERO PUNTA BANDA, MEXICO Sinopsis.-Calidris mauri es uno de los playeros mas abundantes en el noroeste de Mexico, sin embargo, se conoce poco de su ecologia durante el invierno en este pais. Estudiamos los patrones de residencia de machos de C. mauri durante los inviernos
The emergence of highly pathogenic avian influenza (HPAI) H5N1 has elevated concerns about wild b... more The emergence of highly pathogenic avian influenza (HPAI) H5N1 has elevated concerns about wild birds as virus hosts; however, little is known about the ecological and epidemiological factors of transmission by shorebirds. Here we summarize results for 2,773 shorebirds that were live-trapped on the Pacific coast of the United States during 2006-2007 and tested for avian influenza virus using real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and virus isolation. As was the case throughout North America, HPAI H5N1 was not detected in shorebirds during this interval. Contrary to other wild bird groups, most notably waterfowl, the prevalence of even low pathogenicity virus among shorebirds in our study areas in California, Washington, and Alaska was extremely low (0.5%). Virus was detected by RT-PCR from four different species, including, Dunlin (Calidris alpina ; N = 3), Western Sandpiper (C. mauri ; N = 8), Long-billed Dowitcher (Limnodromus scolopaceus ; N = 1), and American Avocet (Recurvirostra americana ; N = 1), with the detections in the latter three constituting the first published records for these birds. Based on studies in the eastern United States, we expected, but did not detect (H 1 = 1.6, P = 0.21) elevated avian influenza prevalence among shorebirds during spring migration. Diagnostic tests, which were designed to evaluate testing and sampling methods, indicated poor functioning of traditional virus isolation methods and no improvement in detection likelihood by collecting oropharyngeal swabs in addition to cloacal swab samples for low pathogenicity viruses (Z 1 = 0.7, P = 0.48).
Take-down policy If you believe that this document breaches copyright please contact us providing... more Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Our understanding of migratory birds' year-round ecology and evolution remains patchy despite rec... more Our understanding of migratory birds' year-round ecology and evolution remains patchy despite recent fundamental advances. Periodic reviews focus future research and inform conservation and management; here, we take advantage of our combined experiences working on Western Hemisphere avian migration systems to highlight recent lessons and critical gaps in knowledge. Among topics discussed are: (1) The pipeline from pure to applied researchers leaves room for improvement. (2) Population limitation and regulation includes both seasonal and between-season interactions. (3) The study of movements of small-bodied species remains a major research frontier. (4) We must increase our understanding of population connectivity. (5) With few exceptions, population regulation has barely been investigated. (6) We have increasingly integrated landscape configuration of habitats, large-scale habitat disturbances, and habitat quality impacts into models of seasonal and overall demographic success. (7) The post-breeding season (late summer for latitudinal migrants) is increasingly appreciated for its impacts on demography. (8) We recognize the diverse ways that avian brood parasites, nest predators, and food availability affect demography. (9) Source-sink and meta-population models help us understand migratory avian distributions among fragmented habitats. (10) Advances in modeling have improved estimates of annual survival and fecundity, but for few species. (11) Populations can be limited by ecological conditions in winter, but habitat needs are poorly known for most species at this time. (12) Migration tends to occupy broad spatial fronts that may change seasonally or when migrants cross major barriers. (13)
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