Wintering Ground Surveys
The mid-winter survey provides population indices for most species of ducks and geese on wintering areas throughout the United States. It has been conducted annually since 1935. Unlike the Waterfowl Breeding Population and Habitat Survey conducted in May, the mid-winter survey is not based on a statistical sampling plan and some wintering habitats are not covered, so results are best used for relative abundance and distribution on wintering habitats for most species. However, it does provide the best population data available for some species, including tundra swans and brant. For these species, there is special consideration taken during the mid-winter survey to ensure that their winter range is well covered and that standardized survey protocols are followed. Mid-winter surveys are conducted within each of the four flyways. Because of some differences in survey methodology, the results are not combined into a single, national report. Instead, results are reported through the four Flyway Councils. Even with its limitations, the mid-winter survey has provided valuable data over the years to plan and evaluate habitat conservation activities and to evaluate the effects of proposed development on migrating and wintering areas. Because of its long history, it may prove valuable in understanding better the effect of changing winter weather patterns on waterfowl distribution and abundance during the non-breeding period.
The U.S. Fish and Wildlife Service provides access to all data from the mid-winter surveys*. (*Note after clicking the link you will need to select "Access Population Data", then scroll down to click the Mid-Winter Waterfowl Survey link, then review and accept the disclaimer to proceed.)
Mexican Waterfowl Survey
The Mexican waterfowl survey is a winter aerial survey conducted cooperatively by biologists from Canada, Mexico, and the United States. Parts of the survey are conducted annually, but the entire survey is now carried out at three-year intervals. The Mexican waterfowl survey is not part of the mid-winter survey; however, it augments the winter surveys conducted in the United States by providing additional coverage of waterfowl species that winter extensively in Mexico. For example, species such as mallard are well covered by the mid-winter survey, but a large proportion of some species such as blue-winged teal, northern pintail and redhead winter far into Mexico.