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Mid-winter Waterfowl Survey

PURPOSE
Some species of ducks, geese, and swans are not presently monitored during the spring and summer on breeding areas because they are either difficult to survey using airplanes or they nest in remote and inaccessible Arctic areas. Abundance indices for some of these species are obtained from surveys on wintering areas. The Mid-winter Waterfowl Survey is a nationwide effort to survey waterfowl in major concentration areas. The Mid-winter Survey is a primary source of information on population trends for some species. This survey also is useful in documenting the distribution of waterfowl on their wintering grounds and in assessing habitat use.

PROCEDURES
Survey design and field procedures are determined by individual states. The Mid-winter Survey is, today, conducted primarily by fixed-wing aircraft, although some states use helicopters and/or conduct counts from automobile or boat in certain areas. The Mid-winter Survey is known as a “cruise” survey, in that specific sampling procedures are not defined. Instead, an aerial crew determines the best and most practical means to conduct a complete count of all waterfowl within a predefined unit area. The exact means of coverage may vary from year to year, however, the objective is to obtain a complete count of all waterfowl within the survey unit. The survey is conducted annually beginning in early January. Beginning in 2001, the U.S. Fish and Wildlife Service has made available a data entry program that enables states to enter, error check, and upload data to a centrally maintained database. The Atlantic and Mississippi Flyways are presently using this program and it is anticipated that the Central Flyway and Pacific Flyway will begin using this program for data entry in the near future.

DATABASES
A count database for this survey is available online through the FWS/USGS Migratory Bird Data Center. This database contains raw count data for survey zones, segments, and sub-segments for each state. Data are available since 2001 for the Atlantic Flyway and since 2002 for the Mississippi Flyway. Data are not yet available online for the Central or Pacific Flyway, although efforts to incorporate data for these Flyways are ongoing. Historical data (prior to 2001) are presently not available online. Significant challenges exist to compiling these data at the survey zone, segment, or sub-segment level. Future efforts to compile historical data at the survey-unit level will require close cooperation between states and the U.S. Fish and Wildlife Service in order to document changes in survey units that have occurred over time. Presently, state total counts are available on a species-specific basis by contacting the appropriate FWS Flyway Representative.

DOWNLOADABLE FIELD DEFINITIONS

LIMITATIONS
The Mid-winter Survey has been criticized for its lack of a statistical sampling design, differences in field methods among states, changes in survey personnel and variability in personnel experience, variation in survey effort, and changes in surveyed areas within states. Eggeman and Johnson (1989) summarized many of the limitations with the Atlantic Flyway Mid-winter Waterfowl Survey. Because of these limitations, caution must be exercised in attempting the estimate and draw inferences about population trends using data from this survey. Any such attempts should be made in close consultation with state and Federal agency personnel that have knowledge of specific limitations of these data for individual states and species.

LITERATURE CITED
Eggeman, D. R. and F. A. Johnson. 1989. Variation in effort and methodology for the midwinter waterfowl inventory in the Atlantic Flyway. Wildlife Society Bulletin 17:227-233.

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