The effects of glyphosate herbicide-induced changes in wetland emergen
t vegetation (largely cattails, Typha spp.) on densities of ducks (Ana
tinae) were assessed in northeastern North Dakota. In 1990 and 1991, 1
7 cattail-dominated wetlands were randomly assigned to 0% (reference w
etlands), 50%, 70%, or 90% areal spray coverages with glyphosate herbi
cide. Densities of green-winged teal (Anas crecca), blue-winged teal (
Anas discors), gadwalls (Anas strepera), and ruddy ducks (Oxyura jamai
censis) were similar among treatments during both post-treatment years
(P greater than or equal to 0.1). One year post-treatment, mallard (A
nas platyrhynchos) and northern pintail (Anas acuta) abundances did no
t differ among treatments (P greater than or equal to 0.1), whereas tw
o years post-treatment their abundances were greater in the sprayed we
tlands than in the reference wetlands (P less than or equal to 0.1). D
ensities of northern shovelers (Anas clypeata) and redheads (Ayrhya am
ericana) differed among treatments in both post-treatment years, with
the 50% sprayed wetlands harboring more ducks than did the other three
treatments. Percent coverage and hectares of open water were positive
ly correlated with numbers of diving ducks (Aythyini and Oxyurini) (P
less than or equal to 0.1). Dabbling duck (Anatini and Cairinini) numb
ers correlated positively with hectares of open water and dead vegetat
ion, whereas their numbers were negatively correlated with percent cov
erage of live vegetation (P less than or equal to 0.1). Results of thi
s study suggest that numbers of ducks were positively influenced by cr
eating a mosaic of open water, live vegetation, and dead vegetation wi
th glyphosate herbicide.