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LIMITATIONS
The survey was designed primarily to estimate breeding population size of mallards, black ducks, wood ducks, and Canada geese. Breeding population estimates for other species encountered during this survey frequently have unacceptably large standard errors.

Estimates most appropriate at the survey-area (11-state) level. Appropriateness and precision decrease as the spatial scale becomes finer, from stratum-level to state-level to stratum-within-state-level estimates.

The survey protocol uses criteria derived in the mid-continent to determine the number of indicated pairs and total indicated birds from count data. The applicability of these criteria to eastern waterfowl populations have not been evaluated.

Correction factors have been suggested for population estimates derived from this survey (Heusmann and Sauer, 1997, 2000). These include a time-of-day correction, especially useful in wood duck and mallard estimates. A correction for aggregations at feeding sites is applicable for mallard estimates. Estimates presented here are uncorrected for time-of-day and feeding-site effects. Although estimates provided are useful in examining population trends or relative changes in populations, they should not be considered absolute measures of abundance, especially for mallards and wood ducks.

POINT OF CONTACT
Anthony Roberts
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
anthony_roberts@fws.gov

LITERATURE CITED
Heusmann, H. W. and J. R. Sauer. 1997. A survey for mallard pairs in the Atlantic Flyway. Journal of Wildlife Management 61:1191-1198.

Heusmann, H. W. and J. R. Sauer. 2000. The northeast states’ breeding waterfowl population survey. Wildlife Society Bulletin 28:355-364.

PURPOSE
Prior to 1989 no regional survey existed of waterfowl breeding populations in the northeast United States. In 1989, the Atlantic Flyway Technical Section initiated this breeding waterfowl survey in 11 northeast states ranging from New Hampshire to Virginia. The purpose of this survey was to collect breeding population abundance data that would support effective management of eastern waterfowl breeding populations. Prior to this survey (and Federal breeding waterfowl surveys initiated in 1990 in eastern Canada and Maine) eastern waterfowl populations were managed based on data collected for mid-continent populations. This survey was designed primarily to estimate population sizes of mallards (Anas platyrhynchos platyrhynchos), black ducks (Anas rubripes), wood ducks (Aix sponsa), and Canada geese (Branta canadensis), however all observed waterfowl are recorded.

PROCEDURES
During this survey, approximately 1,500 1-km2 plots are surveyed each spring by biologists from participating states. The survey plots are randomly allocated among nearly 20 physiographic strata. Prior to 1993 certain plots were checked annually, while others were reselected each year. In 1993, all plot locations were fixed and plots were surveyed every year. In addition to recording waterfowl observations on each plot, the time of day (twilight or daylight) that each plot is surveyed is recorded. Analyses of survey data indicate that the time of day that a plot is surveyed can significantly affect detection probability.  Since 1993, survey participants have been instructed to survey plots consistently during the twilight or daylight periods from year to year. Sample plots are surveyed in most cases from the ground by either automobile, boat, or on foot.

From 1993 until 2002, only total birds were counted for green-wing teal (Anas crecca), blue-wing teal (A. discors), gadwall (A. strepera), common mergansers (Mergus merganser), hooded mergansers (Lophodytes cucullatus), and mute swans (Cygnus olor). Beginning in 2003, more detailed data were collected for these species, as is done for mallards, black ducks, wood ducks, and Canada geese.

Also in 2003, the formula for calculating total indicated birds (TIB) for Canada geese was changed. Previously, TIBs for Canada geese were calculated as (2 × pairs) + singles + grouped birds. In order to have population estimates more comparable to those from other goose surveys and estimates for other species in this survey, the formula was changed to: TIB = 2 × (pairs + singles) + grouped birds. As raw data are not currently available to recalculate TIBs for Canada geese for the previous years, population estimates based on both formulae will be presented for at least 5 years to allow comparison. The Division of Migratory Bird Management, USFWS, is responsible for performing data analyses.

More detailed information about survey procedures or analyses of these data can be found in Heusmann and Sauer (1997, 2000).

DATABASES
Two databases for this survey can be accessed online through the FWS/USGS Migratory Bird Data Center. A count database is available that contains raw waterfowl counts at the sample plot-level. A second database of population estimates is available that contains species-specific, annual population estimates for physiographic strata and state units.

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