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#           Annual Data and Model-based Estimates of Pacific Black Brant Age Ratios      

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      By Alaska Science Center      December 22, 2023    

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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**

View Media Details

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** [84KB] | 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

 

 

 

View Media Details

 

### Izembek Lagoon in Izembek NWR

### Contacts

#### Vijay P Patil, Ph.D.

##### Wildlife Biologist

Alaska Science Center

vpatil@usgs.gov

907-786-7178

### Explore Search

                      - Birds
                      - Waterfowl
                      - Biology
                      - Ecosystems
                      - Pacific brant
                      - Arctic-breeding sea goose
                      - Seagrasses

View All **

Below are other science projects associated with this project.

link

November 3, 2023

####                 Waterfowl Research              

Ecosystems Mission Area, Land Management Research Program, Species Management Research Program, Alaska Science Center

link

November 3, 2023

####   Waterfowl Research

Learn More

link

October 27, 2023

####                 Ecosystems Analytics              

Alaska Science Center

link

October 27, 2023

####   Ecosystems Analytics

Learn More

Below are publications associated with this project.

April 24, 2019

####                 Monitoring annual trends in abundance of eelgrass (Zostera marina) at Izembek National Wildlife Refuge, Alaska, 2018              

Ecosystems Mission Area, Alaska Science Center

February 1, 2018

####                 Long‐term trends in fall age ratios of black brant              

Ecosystems Mission Area, Alaska Science Center

January 1, 2009

####                 Change in abundance of Pacific brant wintering in Alaska: Evidence of a climate warming effect?              

Ecosystems Mission Area, Alaska Science Center

January 1, 1997

####                 Distribution and stability of eelgrass beds at Izembek Lagoon, Alaska              

Ecosystems Mission Area, Earth Resources Observation and Science (EROS) Center , Alaska Science Center

January 1, 1989

####                 Autumn use of Izembek Lagoon, Alaska, by brant from different breeding areas              

Ecosystems Mission Area, Alaska Science Center

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**

View Media Details

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** [84KB] | 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

 

 

 

View Media Details

 

### Izembek Lagoon in Izembek NWR

### Contacts

#### Vijay P Patil, Ph.D.

##### Wildlife Biologist

Alaska Science Center

vpatil@usgs.gov

907-786-7178

### Explore Search

                      - Birds
                      - Waterfowl
                      - Biology
                      - Ecosystems
                      - Pacific brant
                      - Arctic-breeding sea goose
                      - Seagrasses

View All **

Below are other science projects associated with this project.

link

November 3, 2023

####                 Waterfowl Research              

Ecosystems Mission Area, Land Management Research Program, Species Management Research Program, Alaska Science Center

link

November 3, 2023

####   Waterfowl Research

Learn More

link

October 27, 2023

####                 Ecosystems Analytics              

Alaska Science Center

link

October 27, 2023

####   Ecosystems Analytics

Learn More

Below are publications associated with this project.

April 24, 2019

####                 Monitoring annual trends in abundance of eelgrass (Zostera marina) at Izembek National Wildlife Refuge, Alaska, 2018              

Ecosystems Mission Area, Alaska Science Center

February 1, 2018

####                 Long‐term trends in fall age ratios of black brant              

Ecosystems Mission Area, Alaska Science Center

January 1, 2009

####                 Change in abundance of Pacific brant wintering in Alaska: Evidence of a climate warming effect?              

Ecosystems Mission Area, Alaska Science Center

January 1, 1997

####                 Distribution and stability of eelgrass beds at Izembek Lagoon, Alaska              

Ecosystems Mission Area, Earth Resources Observation and Science (EROS) Center , Alaska Science Center

January 1, 1989

####                 Autumn use of Izembek Lagoon, Alaska, by brant from different breeding areas              

Ecosystems Mission Area, Alaska Science Center