RESPONSE OF BLACK TERNS (CHLIDONIAS-NIGER) TO GLYPHOSATE-INDUCED HABITAT ALTERATIONS ON WETLANDS

The Black Tern (Chlidonias niger) is considered an endangered species in some states and is a category two species for listing as a federall y threatened or endangered species. In the northern Great Plains, catt ails (Typha spp.) have over-grown many wetlands, contributing to the d ecline in numbers of Black Terns. We aerially wetlands with glyphosate herbicide to assess the influence of habitat changes on Black Terns. In 1990 and 1991, two separate experiments were initiated in northeast ern North Dakota whereby wetlands were randomly assigned one of three spray coverages with glyphosate. In one experiment, Black Terns used t reated wetlands more than untreated wetlands (P < 0.1). In the other e xperiment, densities of Black Terns were similar between untreated and treated wetlands (P > 0.1). A stepwise multiple regression indicated a significant positive relationship between the number of Black Terns and hectares of water and dead emergent vegetation in the wetland ( r( 2) = 0.51). Black Terns use of a wetland may be positively influenced by floating mats of dead cattails, live emergent vegetation, and open water.