(1) Breeding population abundance
maps were derived from visibility-corrected segment-level count data collected
by USFWS air crews during the
Waterfowl Breeding Population and Habitat Survey.
(2) A spatial prediction procedure known as kriging was used to generate the
maps. An exponential function was used to model the semi-variance.
(3) For each species, all maps are plotted on a common scale to facilitate
visualization of changing distribution and abundance.
(4) These maps depict population abundance within the area covered by the
Waterfowl Breeding Population and Habitat Survey. Several species occupy
breeding habitats not presently covered by this survey. The graphic on this
page depicts the regions covered.
(5) There is an entry in the species list called "natural and man-made ponds."
Selecting this entry, the user will be able to view changes in the number and
distribution of wet basins in the prairie-pothole region of the U.S. northern
plains and the prairie provinces of Canada. These data are also collected as
part of the annual Waterfowl Breeding Population and Habitat Survey.
(6) For each species, an animated *.gif file is available for display that
portrays, as a movie, changes in abundance and distribution within the surveyed
area since 1960. This animated file is identified in the map database by a 'Y'
in the MOVIE field.
(7) Map legends accompany the abundance maps for individual years, however, no
legend is portrayed with the animated file.