This data layer contains waterbird density blocks extracted from the Minerals Management Service's Mid-Atlantic Waterbird Data Beta Version 1.0. This application is based on their Marine Mammal and Seabird Computer Database Analysis System (MMS-CDAS). The origin of the underlying data is a U.S. Fish & Wildlife Service aerial survey conducted between December, 2001 and March, 2003. The source data were collected on-transect (120m width, 60 m each side) for transects conducted in the mouth of Chesapeake Bay, in Delaware Bay, and in offshore waters from the beach outward. Aerial surveys of waterbirds were flown to at least 12 nautical miles (22.2 km) offshore from northern New Jersey to the Virginia / North Carolina border. All waterbird species in the USFWS database from winter surveys only were exported to density blocks. Information in the MMS application suggests the winter surveys only are valid for calculating densities because they were flown on specific transects. The spatial extent of the database (and thus of this data set) is from the Virginia/North Carolina border to the Hudson Canyon (including Delaware Bay and the lowest part of Chesapeake Bay).