Background/Question/Methods The San Francisco Bay estuary provides critical habitat for over one ... more Background/Question/Methods The San Francisco Bay estuary provides critical habitat for over one million waterbirds annually. Although the landscape has been altered for well over a century by increasing levels of urbanization, and by the historic establishment of evaporator ponds for salt production, it remains heavily used by waterbirds. The area also hosts the west coast’s largest tidal wetlands restoration project; the South Bay Salt Pond Restoration Project is implementing a plan to convert thousands of acres of salt ponds into tidal and managed wetland habitat. While the restoration to tidal marsh will increase habitat for many species, it also will reduce the overall habitat available for waterbirds. Through adaptive management, the Project is committed to maintaining historic levels of waterbirds in this landscape. To inform these efforts, the USFWS, San Francisco Bay Bird Observatory, USGS and UC Davis partnered to assess changes in bird population abundance and community c...
Proceedings of the Royal Society B: Biological Sciences
Bar-headed geese are renowned for migratory flights at extremely high altitudes over the world... more Bar-headed geese are renowned for migratory flights at extremely high altitudes over the world's tallest mountains, the Himalayas, where partial pressure of oxygen is dramatically reduced while flight costs, in terms of rate of oxygen consumption, are greatly increased. Such a mismatch is paradoxical, and it is not clear why geese might fly higher than is absolutely necessary. In addition, direct empirical measurements of high-altitude flight are lacking. We test whether migrating bar-headed geese actually minimize flight altitude and make use of favourable winds to reduce flight costs. By tracking 91 geese, we show that these birds typically travel through the valleys of the Himalayas and not over the summits. We report maximum flight altitudes of 7290 m and 6540 m for southbound and northbound geese, respectively, but with 95 per cent of locations received from less than 5489 m. Geese travelled along a route that was 112 km longer than the great circle (shortest distance) rout...
The physiological and biomechanical requirements of flight at very high altitude have been the su... more The physiological and biomechanical requirements of flight at very high altitude have been the subject of much interest. Here, we uncover steep relations between (i) heart rate and wingbeat frequency and (ii) estimated metabolic power and wingbeat frequency in migratory bar-headed geese. Flight costs increase more rapidly than anticipated as air density declines, overturning prevailing expectations that all birds should maintain high-altitude flight when traversing mountainous regions. Instead, a “roller coaster” strategy, which involves shadowing the underlying terrain and often discarding large altitude gains even if it necessitates recouping lost height later in the same flight, is shown to be energetically advantageous for this species during Himalayan flights. Rare examples of rapid ascent or descent unaccompanied by marked changes in flight effort were presumably attributable to orographic updrafts and downdrafts, but had negligible overall effect on migration costs.
Identifying movement routes and stopover sites is necessary for developing effective management a... more Identifying movement routes and stopover sites is necessary for developing effective management and conservation strategies for migratory animals. In the case of migratory birds, a collection of migration routes, known as a flyway, is often hundreds to thousands of kilometers long and can extend across political boundaries. Flyways encompass the entire geographic range between the breeding and non-breeding areas of a population, species, or a group of species, and they provide spatial frameworks for management and conservation across international borders. Existing flyway maps are largely qualitative accounts based on band returns and survey data rather than observed movement routes. In this study, we use satellite and GPS telemetry data and dynamic Brownian bridge movement models to build upon existing maps and describe waterfowl space use probabilistically in the Central Asian and East Asian-Australasian Flyways. Our approach provided new information on migratory routes that was n...
CRAIG R. ELY*1, ANTHONY D. FOX2, RAY T. ALISAUSKAS3, ALEXANDER ANDREEV4, ROBERT G. BROMLEY5, AG D... more CRAIG R. ELY*1, ANTHONY D. FOX2, RAY T. ALISAUSKAS3, ALEXANDER ANDREEV4, ROBERT G. BROMLEY5, AG DEGTYAREV6, BARWOLT EBBINGE7, EN GURTOVAYA8, RICHARD KERBES3, ALEXANDER V. KONDRATYEV9, IGOR KOSTIN10, ARSENI V. ...
The South Bay Salt Pond (SBSP) Restoration Project plans to restore 50-90% of the salt ponds to t... more The South Bay Salt Pond (SBSP) Restoration Project plans to restore 50-90% of the salt ponds to tidal marsh to reverse the loss (>80%) of tidal marsh within the San Francisco Bay Estuary. While the restored tidal marsh habitats will benefit many animals, a goal of the SBSP Restoration Project is to maintain current migratory and breeding populations of birds
The California gull (Larus californicus) population in San Francisco Bay has increased from <2... more The California gull (Larus californicus) population in San Francisco Bay has increased from <200 in 1982 to >46,800 in 2008, and may be negatively affecting nesting waterbirds through harassment, encroachment on nesting sites, and predation on eggs and chicks. The California gull colony at Pond A6 is the largest (>26,000) and is expected to be displaced when this salt pond
Background/Question/Methods The San Francisco Bay estuary provides critical habitat for over one ... more Background/Question/Methods The San Francisco Bay estuary provides critical habitat for over one million waterbirds annually. Although the landscape has been altered for well over a century by increasing levels of urbanization, and by the historic establishment of evaporator ponds for salt production, it remains heavily used by waterbirds. The area also hosts the west coast’s largest tidal wetlands restoration project; the South Bay Salt Pond Restoration Project is implementing a plan to convert thousands of acres of salt ponds into tidal and managed wetland habitat. While the restoration to tidal marsh will increase habitat for many species, it also will reduce the overall habitat available for waterbirds. Through adaptive management, the Project is committed to maintaining historic levels of waterbirds in this landscape. To inform these efforts, the USFWS, San Francisco Bay Bird Observatory, USGS and UC Davis partnered to assess changes in bird population abundance and community c...
Proceedings of the Royal Society B: Biological Sciences
Bar-headed geese are renowned for migratory flights at extremely high altitudes over the world... more Bar-headed geese are renowned for migratory flights at extremely high altitudes over the world's tallest mountains, the Himalayas, where partial pressure of oxygen is dramatically reduced while flight costs, in terms of rate of oxygen consumption, are greatly increased. Such a mismatch is paradoxical, and it is not clear why geese might fly higher than is absolutely necessary. In addition, direct empirical measurements of high-altitude flight are lacking. We test whether migrating bar-headed geese actually minimize flight altitude and make use of favourable winds to reduce flight costs. By tracking 91 geese, we show that these birds typically travel through the valleys of the Himalayas and not over the summits. We report maximum flight altitudes of 7290 m and 6540 m for southbound and northbound geese, respectively, but with 95 per cent of locations received from less than 5489 m. Geese travelled along a route that was 112 km longer than the great circle (shortest distance) rout...
The physiological and biomechanical requirements of flight at very high altitude have been the su... more The physiological and biomechanical requirements of flight at very high altitude have been the subject of much interest. Here, we uncover steep relations between (i) heart rate and wingbeat frequency and (ii) estimated metabolic power and wingbeat frequency in migratory bar-headed geese. Flight costs increase more rapidly than anticipated as air density declines, overturning prevailing expectations that all birds should maintain high-altitude flight when traversing mountainous regions. Instead, a “roller coaster” strategy, which involves shadowing the underlying terrain and often discarding large altitude gains even if it necessitates recouping lost height later in the same flight, is shown to be energetically advantageous for this species during Himalayan flights. Rare examples of rapid ascent or descent unaccompanied by marked changes in flight effort were presumably attributable to orographic updrafts and downdrafts, but had negligible overall effect on migration costs.
Identifying movement routes and stopover sites is necessary for developing effective management a... more Identifying movement routes and stopover sites is necessary for developing effective management and conservation strategies for migratory animals. In the case of migratory birds, a collection of migration routes, known as a flyway, is often hundreds to thousands of kilometers long and can extend across political boundaries. Flyways encompass the entire geographic range between the breeding and non-breeding areas of a population, species, or a group of species, and they provide spatial frameworks for management and conservation across international borders. Existing flyway maps are largely qualitative accounts based on band returns and survey data rather than observed movement routes. In this study, we use satellite and GPS telemetry data and dynamic Brownian bridge movement models to build upon existing maps and describe waterfowl space use probabilistically in the Central Asian and East Asian-Australasian Flyways. Our approach provided new information on migratory routes that was n...
CRAIG R. ELY*1, ANTHONY D. FOX2, RAY T. ALISAUSKAS3, ALEXANDER ANDREEV4, ROBERT G. BROMLEY5, AG D... more CRAIG R. ELY*1, ANTHONY D. FOX2, RAY T. ALISAUSKAS3, ALEXANDER ANDREEV4, ROBERT G. BROMLEY5, AG DEGTYAREV6, BARWOLT EBBINGE7, EN GURTOVAYA8, RICHARD KERBES3, ALEXANDER V. KONDRATYEV9, IGOR KOSTIN10, ARSENI V. ...
The South Bay Salt Pond (SBSP) Restoration Project plans to restore 50-90% of the salt ponds to t... more The South Bay Salt Pond (SBSP) Restoration Project plans to restore 50-90% of the salt ponds to tidal marsh to reverse the loss (>80%) of tidal marsh within the San Francisco Bay Estuary. While the restored tidal marsh habitats will benefit many animals, a goal of the SBSP Restoration Project is to maintain current migratory and breeding populations of birds
The California gull (Larus californicus) population in San Francisco Bay has increased from <2... more The California gull (Larus californicus) population in San Francisco Bay has increased from <200 in 1982 to >46,800 in 2008, and may be negatively affecting nesting waterbirds through harassment, encroachment on nesting sites, and predation on eggs and chicks. The California gull colony at Pond A6 is the largest (>26,000) and is expected to be displaced when this salt pond
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