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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.

Data notes: In many years, a few survey units within a flyway may not be surveyed because of problems with weather, aircraft, crews, etc. However, these problems do not affect the use of the data at the flyway scale. Occasionally, there are major disruptions to the survey of which users of the data should be aware. Inconsistencies that occurred during the period covered by this database are listed below.

Atlantic Flyway

• 2001 - Estimates for portions of Florida were based on previous 3-year average.
• 2003 - Florida data are incomplete. Data from the USFWS Redhead Survey areas are unavailable.
• 2004 - No survey conducted in Florida. Estimates for Florida based on 2000-2002 average.
• 2005 to present - No survey conducted in Florida. Totals for mottled ducks, whistling ducks, blue-winged teal, redheads, scaup, ring-necked ducks, and to a lesser extent, wigeon and shovelers are especially suspect.
• 2007
  • No survey conducted in Vermont
  • Connecticut conducted a ground-based survey of black duck and brant concentration areas only.
  • New York survey data are from Long Island only. Counts for black ducks and brant are probably reasonable, but counts for other species are likely too small, especially mallards, canvasbacks, Canada geese, and mute swans.
• 2008 - No survey conducted in South Carolina
• 2009 - No survey conducted in Florida. New York survey data is from Long Island only.

POINT OF CONTACT
Jon Klimstra
Wildlife Biologist, Atlantic Flyway
US Fish and Wildlife Service
11510 American Holly Drive, Room 212
Laurel, MD 20708-4038, USA
voice mail: (301) 497-5852
fax:  (301) 497-5885
Jon_Klimstra@fws.gov

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.

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. Data are not yet available online for the Mississippi, 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

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