Maps of Recoveries for Mallards and Blue-winged Teal Banded in the Central Flyway in 1996-2001
Blue-winged teal recoveries are included from bandings across the region including eastern Montana, eastern Wyoming, South Dakota and North Dakota. Mallard band sites are defined as occurring in the east (eastern South Dakota and eastern North Dakota) or west (eastern Montana, eastern Wyoming, western South Dakota and western North Dakota) based on analysis of the recovery distribution.
See below for an explanation of how the definition of Eastern and Western mallards was derived.
According to Jim Dubovsky who works for the U.S. Fish and Wildlife Service in Denver, the following procedure was used to describe Eastern and Western mallards. The full citation of referenced material is available in the Reference pages.
Geographic distribution of recovery locations of female mallards were compared among banding degree blocks using the multi-response permutation procedure (MRPP) (Biodini et al. 1988, Zimmerman et al. 1985). All recoveries of female mallards banded from 1990-2002 were used in analyses. The MRPP algorithm requires a minimum sample size of 12 observations (recoveries) per banding degree block. Thus, some degree blocks where banding occurred during the Central Flyway Preseason Duck Banding Program could not be included in analyses, because fewer than 12 recoveries were available.
MRPP test statistics from all possible pair-wise comparisons of banding degree blocks were assembled into a dissimilarity matrix and entered into a clustering program (CLUSTAR) (Romesburg 1990). The program produces a dendrogram, which can be used to make hierarchical clusters of degree blocks by identifying joining points of branches of the dendrogram. Several abrupt 'breaks' in the dendrogram can be used to infer the relative degree of similarity of recovery distributions among the groups of degree blocks.