LIMITATIONS
All the surveys have the following problems:
- the birds occur in large groups clumped in
small parts of the available area
- their location changes depending on the time
of day and weather; usually on the wetlands in the morning but not in the
afternoon
- no birds are found in dry areas
Referring to #1, we do not know whether ducks just move to wetter
adjacent wetlands or their survival is hampered in drier years. Birds
occur in huge concentrations in tens of thousands to greater than a hundred
thousand. In these large groups, the pilot maneuvers the plane so the
observer can count most of the birds. The birds are thought to use
wetlands adjacent to the ones that are dry. Rivers are flown along and
counted in one pass. How far up a river/stream to survey is arbitrary.
The biologist stops when they think that the river is small enough that they
will not see any more ducks.
POINT OF CONTACT
Mark Otto
Biometrician, Branch of Population & Habitat Assessment
Division of Migratory Bird Management, USFWS
11510 American Holly Drive
Laurel, MD 20708-4002
voice mail: (301) 497-5872
fax: (301) 497-5871
Mark_Otto@fws.gov
LITERATURE CITED
Otto, M.C., and P.A. Frechtel. 2001. Temporal and Spatial Changes in
the Mexican Mid-Winter Inventory 1937-1998. U.S. Fish and Wildlife
Service, Laurel, Maryland. 8 pp.
Saunders, G. B., and D. C. Saunders. 1981. Waterfowl
and their wintering grounds in Mexico, 1937-64. U.S. Fish and Wildlife Service.
Resource Publication 138. 151 pp.
PURPOSE
The Mexican Mid-winter Waterfowl Survey provides wintering habitat conditions,
waterfowl habitat utilization, waterfowl distribution patterns, and general
population trends.
The data obtained from this survey is used to manage Mexican duck
populations and to study the effects of wetland drainage and development. This is not a statistical survey where the
location counts can be extrapolated to regions. This survey is incomplete
for goose species which occur inland from the coasts.
PROCEDURES
Since 1947 the survey has been run as three surveys: the Gulf Coast,
the Interior Highlands, and the Pacific Coast. Since 1985, the surveys
have been run every three years, 2006 being the last. Consistent waterfowl
counts by location for each wetland is obtained. It is conducted
cooperatively by the U.S. Fish and Wildlife Service and Mexican
officials. In the off years, a redhead survey is flown in Laguna
Madre on the Gulf Coast and a Brant goose survey on the upper (from Mexicali to Cuyutlan on the West Coast and from Bahia de Magdalena
to San Quintin in the Gulfo de California) part of the Pacific Coast.
DATABASES
The files within this database are in a relational format. For now, you
have the ability to download each data file separately. Below is a
description of the downloadable data files and what each contain.
allcount.dat - a table of only the consistently surveyed waterfowl species
with the zero and nonzero counts in all the areas sampled.
mexsp.dat - a defined list of how some of the species are combined into
generic categories within the allcount.dat file.
The following files describe and reference the regions, areas, species, and
years sampled in the survey:
allmexsp.dat - Reference list of all species codes and descriptions
region.dat - Reference list of all regions within the survey
area.dat - Reference list of areas in the different regions and their
descriptions
year.dat - Reference list of years surveyed
Next the structure of the more complicated tables are described.
Count.dat is the main table of the nonzero counts. It is supported by sample.dat that tells which areas were sampled in each year and whether they
were dry or not. Some areas in a few years have counts reported for a
combination of areas. What areas area combined are in comb.dat. The observers in
the survey are recorded in observers.dat by region and year, not by area. The
observer initials are tied to observer names in personnel.dat. The planes used
are in flight.dat, and the plane ids tied to the type of plane in plane.dat. A
consolidation of sample.dat used with the observer and plane tables is
regsmp.dat. It identifies the regions sampled by year. The center points of each
of the areas is in location.dat, and the rough boundaries are in boundary.dat.
DOWNLOADABLE FIELD DESCRIPTIONS
| Field Name |
Field Definition |
| All Count Table |
|
| year |
survey year |
| area |
numeric code
identifier - area in which species was sighted |
| alpha |
four letter
alphabetic code for a species |
| count |
total number of counts for waterfowl species |
| Species Table |
generic categories |
| mexsp |
waterfowl species defined within the
allcount.dat file |
| alpha |
four letter
alphabetic code for a species |
| Species Table |
all alpha codes & descriptions |
| alpha |
four letter
alphabetic code for a species |
| description |
description of species alpha code |
| Region Table |
|
| regcode |
alpha code for survey regions |
| region |
description of survey region |
| Area Table |
|
| area |
numeric code identifier - area in which species was
sighted |
| region |
alpha code for survey regions |
| name |
name of the area |
| description |
physical description of the area |
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