Stream Habitat Comparisons in the Salt Plains National Wildlife Refuge, Oklahoma; Implications for Nesting Least Terns (Sterna antillarum)

Oklahoma's Salt Plains National Wildlife Refuge supports a nesting population of endangered interior least terns (Sterna antillarum), which are piscivorous and depend on the aquatic habitats of the Salt Plains National Wildlife Refuge. Eight creek sites at the Salt Plains National Wildlife Refuge were surveyed for water quality and habitat parameters, and comparisons were made between creek sites proximal to the Great Salt Plains reservoir (downstream sites) and sites at least one kilometer away from the reservoir (upstream sites). Statistical analyses did not show significant differences in dissolved oxygen, temperature, turbidity, stream width, stream depth, substrate size, and run/riffle/pool ratios. However, tests showed consistently higher conductivity readings at downstream sites as compared to upstream sites; this finding is significant in light of other studies which indicate that downstream sites harbor substantially higher numbers of Menidia beryllina, the inland silverside, than do upstream sites; M. beryllina is an euryhaline marine species, and its correlation with sites with high water conductivity suggests that the Salt Plains National Wildlife Refuge provides an excellent habitat for this population. Moreover, the surface-schooling behavior, small size, and slender form of M. beryllina, suggest that it is an important food source for least terns. Therefore, monitoring and conserving the habitat of M. beryllina may be critical to the conservation of the least tern