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LIMITATIONS
The spatial sampling design and timing of the eastern survey are focused primarily on black ducks, a species that is important in the annual duck harvest in the eastern United States and Canada. The survey has known limitations for species which breed in significant densities well beyond the strata boundaries of the survey such as green-winged teal and many sea ducks. Likewise, the timing of the survey, while near optimal for black ducks, may be too early for some diving and sea ducks, and may result in counting birds prior to reaching their breeding grounds terminus area.

POINT OF CONTACT
Guthrie Zimmerman
Population & Habitat Assessment Branch
Division of Migratory Bird Management, USFWS
3020 State University Drive East
Modoc Hall, Suite 2007
Sacramento, CA 95819
voice mail: (916) 278-9421
Guthrie_Zimmerman@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.

Link, W. A. and J. R. Sauer. 2002. A hierarchical analysis of population change with application to cerulean warblers. Ecology 83: 2832-2840.

Smith, G.W. 1995. A critical review of the aerial and ground surveys of breeding waterfowl in North America. Biological Science Report 5, National Biological Service, Washington, D.C. 252pp.

U.S. Fish and Wildlife Service. 2014. Waterfowl population status, 2014. U.S. Department of the Interior, Washington, D.C. USA.

Zimmerman, G.S., Sauer, J.R., Link, W.A., Otto, M. 2012. Composite Analysis of Black Duck Breeding Population Surveys in Eastern North America. Journal of Wildlife Management. DOI: 10.1002/jwmg.351

PURPOSE
Two primary surveys are used to monitor waterfowl in eastern Canada, Maine and northern New York state. A plot-based survey conducted by the Canadian Wildlife Service was fully implemented in 1990 and covers 10 strata (51, 52, 63, 64, 66, 67, 68, 70, 71, and 72). The US Fish and Wildlife Service began implementing a transect-based survey in 1990 that covered strata 51 through 56. The area covered by US Fish and Wildlife Service surveys was expanded to include stratum 62 in 1995, strata 63 through 68 in 1996, and strata 69 and 70 in 1998. Further, surveys were conducted in stratum 57 in 1992, 1993, 2001, 2002, 2004 through 2009, and 2011; stratum 58 in 1993, and 2005 through 2009; and stratum 59 from 2006 through 2009. The primary purpose of the survey is to provide information on spring population size and trajectory for black ducks. Consequently, population estimates are reported at scales relevant to black duck biology. In addition to presenting strata-specific population estimates, we provide estimates for the plot survey area (i.e., the core breeding area for black ducks; strata 51, 52, 63, 64, 66, 67, 68, 70, 71, 72 combined), which has been surveyed consistently since 1990. These data are used extensively in the annual establishment of hunting regulations in the United States and Canada for some species and provide a time series important for researching bird-environment relationships critical to effective conservation planning for waterfowl. While population estimates for the total area are used for informing black duck harvest recommendations, mallard harvest management is based only US Fish and Wildlife Service data from strata 51 through 54 and 56 in combination with data collected by states in the North Eastern Plot Survey area (Heusmann and Sauer 1997). Note: We do not provide data for the CWS plot survey. Please contact Dr. Adam Smith from the CWS for information about obtaining those data (Adam.Smith@ec.gc.ca).

PROCEDURES
Procedures for the eastern portion of the Waterfowl Breeding Population and Habitat Survey are identical to the traditional area and are described in detail by Smith (1995). Within strata, ducks are counted by two-person aerial crews while flying fixed-wing aircraft along established transect lines approximately 50 m above ground level. Transects are 400m wide and divided into segments, each roughly 29 km in length. Aerial observers do not count lone hen ducks. For strata that include both CWS plot surveys and US Fish and Wildlife Service surveys, US Fish and Wildlife Service population estimates are corrected by CWS estimates to compute visibility correction factors (VCFs) for each species and stratum. VCFs for strata where only US Fish and Wildlife Service surveys have been conducted are calculated from helicopter surveys conducted along a sample of segments. Population estimates for strata (strata 71 and 72) or years that include only CWS plot surveys (e.g., stratum 68 estimates include only CWS helicopter surveys from 1990 through 1995) are not adjusted by a VCF. The high cost of helicopter operation currently prohibits extensive double sampling in boreal forest strata. The total number of birds in each stratum is estimated from a Bayesian hierarchical modeling approach (Link and Sauer 2002). Hierarchical estimates are integrated into a single population index in strata with both US Fish and Wildlife Service and Canadian Wildlife Service surveys (i.e., strata 51, 52, 63, 64, 66, 67, 68, and 70) and are based on single survey data in strata with no overlap between the two surveys (i.e., 53, 54, 55, 56, 57, 58, 59, 62, 65, and 69 have US Fish and Wildlife Service surveys only, whereas strata 71 and 72 have Canadian Wildlife Service surveys only). Note: (1) Because the eastern estimates are based on a hierarchical model, the entire time series is updated annually and past estimates will change slightly each year. (2) We only provide population size estimates for species for which the hierarchical models reached convergence. These species include black ducks, American green-winged teal, goldeneyes, mallards, mergansers, and ring-necked ducks. For the rarer species in this group (goldeneyes and mergansers) we used an overdispersed Poisson model to derive estimates.

DATABASE
The strata estimate database derived from the eastern portion of the Waterfowl Breeding Population and Habitat Survey is available online through this website. The strata estimates database includes species- and year-specific estimates and standard errors of absolute waterfowl abundance for individual survey strata. Users querying this database will need to specify the time interval, species, and geographic region of interest.

Notes:

The US Fish and Wildlife Service did not conduct surveys in the eastern area in 2013. Consequently, the 2013 estimates are based on the CWS data alone. Further, we do not have estimates for strata 53, 54, 56, 62, and 69 because there are no CWS plot surveys in those strata.

The eastern survey raw data are archived as they are recorded: from 1990-1999 as segment totals, and from 2000-current as geo-located observation-level data. The raw data are available by request. These files contain many records and it is recommended that data requests be as specific as possible, in terms of species, strata and years needed.

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