Data and Model-Based Estimates from Black Brant (Branta bernicla nigricans) Fall Age Ratio Surveys at Izembek Lagoon, Alaska
Dates
Publication Date
2020-03-02
Start Date
1963
End Date
2023
Last Revision
2023-12-22
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.
Summary
These data are in two tables relating to fall age ratios (number of juvenile birds : total birds aged) of Black Brant (Branta bernicla nigricans) staging in Izembek Lagoon, Alaska, since 1963. The first table is observation data for the age classes of Black Brant during surveys, and associated survey characteristics. The second table contains model-based estimates of age ratios by year along with Standard Error (SE), and 95% Bayesian credible intervals around estimates. Version History: First release: March 2020 Revised: December 2020 (ver. 2.0) Revised: December 2021 (ver. 3.0) Revised: January 2023 (ver. 4.0) Revised: December 2023 (ver. 5.0)
Summary
These data are in two tables relating to fall age ratios (number of juvenile birds : total birds aged) of Black Brant (Branta bernicla nigricans) staging in Izembek Lagoon, Alaska, since 1963. The first table is observation data for the age classes of Black Brant during surveys, and associated survey characteristics. The second table contains model-based estimates of age ratios by year along with Standard Error (SE), and 95% Bayesian credible intervals around estimates.
Version History:
First release: March 2020
Revised: December 2020 (ver. 2.0)
Revised: December 2021 (ver. 3.0)
Revised: January 2023 (ver. 4.0)
Revised: December 2023 (ver. 5.0)
Ward, D.H., Amundson, C.L., Stehn, R.A., Dau, C.P., 2018. Long-term trends in fall age ratios of Black Brant. Journal of Wildlife Management 82(2):362-373, https://doi.org/10.1002/jwmg.21388
Each fall, the entire population of Black Brant stages during fall migration in Izembek Lagoon, Alaska. Since 1963, surveys have been conducted to record the number of juvenile (i.e., first-year birds) and adult (i.e., birds at lease 2 years old) brant and estimate the age ratio (number of juvenile birds : total birds aged) for the overall population. The fall age ratio estimate is the first measure of annual productivity for the entire population and is a potential index of recruitment given that most first-year mortality in brant occurs between the time of hatch and the migration to Izembek Lagoon.
