Annual Data and Model-based Estimates of Pacific Black Brant Age Ratios
Pacific brant are an Arctic-breeding sea goose that stage and feed on seagrasses during the non-breeding season in coastal areas of Alaska. Brant are an important subsistence and sport harvest species and the focus of several population surveys by state and federal agencies. Each fall the entire population stages during migration in Izembek Lagoon, Alaska, presenting a unique opportunity to survey the proportion of young and derive and index of annual productivity.
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(Credit: Jeff Wasley, USGS)
Since 1963, the USGS and U.S. Fish and Wildlife Service have conducted surveys to record the number of juvenile (i.e., first-year birds) and adult (i.e., birds ≥ 2 years old) Pacific brant (Branta bernicla nigricans) and estimate the age ratio (number of juvenile birds compared to total birds aged) for the overall population. This fall age ratio estimate is the only measure of annual productivity for the entire population and a potential index of recruitment (i.e., number of young produced per female) given that most first-year mortality in Pacific brant occurs between hatch and migration to Izembek. USGS recently published model-based age ratio estimates through 2015 suggesting a slow decline in brant productivity (Ward et al. 2018). However, age ratios have improved in recent years and although they vary widely, general trends appear stable.
To provide up-to-date information for managers, USGS will publish age ratio data and model-based age ratio estimates annually on this site - data are currently available through 2023.
Data
Data Download | Metadata | Version History
Citation: Patil, V.P., Amundson, C.L., Ward, D.H., Williams, A.R., 2020, Data and model-based estimates from Black brant (Branta bernicla nigricans) fall age ratio surveys at Izembek Lagoon, Alaska (ver 5.0, December 2023): U.S. Geological Survey data release, https://doi.org/10.5066/P9QIJIU2
(Credit: Vijay Patil, USGS)
Below are other science projects associated with this project.
Waterfowl Research
Ecosystems Analytics
Pacific brant are an Arctic-breeding sea goose that stage and feed on seagrasses during the non-breeding season in coastal areas of Alaska. Brant are an important subsistence and sport harvest species and the focus of several population surveys by state and federal agencies. Each fall the entire population stages during migration in Izembek Lagoon, Alaska, presenting a unique opportunity to survey the proportion of young and derive and index of annual productivity.
Return to Ecosystems >> Terrestrial Ecosystems >> Waterfowl Research
(Credit: Jeff Wasley, USGS)
Since 1963, the USGS and U.S. Fish and Wildlife Service have conducted surveys to record the number of juvenile (i.e., first-year birds) and adult (i.e., birds ≥ 2 years old) Pacific brant (Branta bernicla nigricans) and estimate the age ratio (number of juvenile birds compared to total birds aged) for the overall population. This fall age ratio estimate is the only measure of annual productivity for the entire population and a potential index of recruitment (i.e., number of young produced per female) given that most first-year mortality in Pacific brant occurs between hatch and migration to Izembek. USGS recently published model-based age ratio estimates through 2015 suggesting a slow decline in brant productivity (Ward et al. 2018). However, age ratios have improved in recent years and although they vary widely, general trends appear stable.
To provide up-to-date information for managers, USGS will publish age ratio data and model-based age ratio estimates annually on this site - data are currently available through 2023.
Data
Data Download | Metadata | Version History
Citation: Patil, V.P., Amundson, C.L., Ward, D.H., Williams, A.R., 2020, Data and model-based estimates from Black brant (Branta bernicla nigricans) fall age ratio surveys at Izembek Lagoon, Alaska (ver 5.0, December 2023): U.S. Geological Survey data release, https://doi.org/10.5066/P9QIJIU2
(Credit: Vijay Patil, USGS)
Below are other science projects associated with this project.