Gm. Linz et al., RESPONSE OF AMERICAN COOTS AND SORAS TO HERBICIDE-INDUCED VEGETATION CHANGES IN WETLANDS, Journal of field ornithology, 68(3), 1997, pp. 450-457
The effects of herbicide-induced changes in wetland vegetation (largel
y cattails, Typha spp.) on densities of American Coots (Fulica america
na) and Soras (Porzana carolina) were assessed in northeastern North D
akota. In 1990 and 1991, 17 cattail-dominated wetlands were randomly a
ssigned to 0% (reference wetlands), 50%, 70%, or 90% spray coverages w
ith glyphosate-based herbicide. American Coot densities were lower in
the reference wetlands than in the glyphosate-treated wetlands during
one (P = 0.09) and two years post-treatment (P = 0.04). Numbers of Ame
rican Coots were positively correlated with coverages of water and dea
d vegetation, but were negatively correlated with coverage of live veg
etation (Ps < 0.1). One year post-treatment, reference wetlands harbor
ed more Soras than did the treated wetlands (P = 0.08) but Sora number
s were similar among treatments two years post-treatment. Sora numbers
were positively correlated with coverage of live vegetation (P < 0.1)
. Our results suggest that managers should strive to create a mosiac o
f open water, live emergent vegetation, and floating mars of dead vege
tation to maximize wetland use by American Coot and Sora populations.