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UUU626 6 Prairie Naturalist 24(1): March 1992 ships at each of our sites was a task far beyond the resources of our study, and our water travel time estimates were as precise as possible with the available data. We accepted the error inherent in our methodology as the only practical means of deriving comparable elevation data at a large number of sites. To estimate the mean and maximum elevation of potentially suitable nesting habitat at a site, we derived a random sample from the transect data and then removed patently unsuitable points according to the following procedure. We computed the elevations of points between actual measured points at 0.3-m (1- ft) intervals by simple linear interpolation. We assigned interpolated points the vegetative characteristics of the nearest measured point, except where a meas- ured point was expressly identified as a boundary between two vegetative cover types on the transect. Where noted, boundary points defined the assignment of vegetative characteristics to interpolated points. We randomly selected 30 points per transect from the combined set of measured and interpolated points. From these 30 points, we selected those having the vegetative cover character- istics observed at nest locations, as measured during the nest site ground survey. We computed the mean and maximum elevations of the final set of points at each site. We tested the hypothesis that the means of these measurements at nest sites and systematic sample sites were equal using independent-sample t-tests. We measured the elevation of each nest relative to the water surface eleva- tion. We computed the nest's elevation above the adjusted datum and its eleva- tion above water at the time of nest initiation in the same manner that the tran- sect elevation data were adjusted to a common datum. We tested the hypothesis that the mean elevation of nests and the mean elevation of sites were equal us- ing paired-sample t-tests. The analysis of nest elevations involved estimating the discharge corresponding to each nest elevation; we determined the mini- mum, median, and maximum of these values for use as reference points in fur- ther analysis of hydrologic records. Analysis of Hydrologic Records From discharge records for Grand Island, North Bend, and Louisville, NE, gaging stations (U.S. Geological Survey Water Resources Data, 1959-1988) we computed mean annual hydrographs and the frequency of occurrence of dis- charges corresponding to nest elevations. RESULTS Location of Nesting Sites We located a total of 222 least tern nests at 30 sites and 82 piping plover nests at 30 sites on the Platte River during 1988. Terns nested exclusively at three sites and plovers at three. Most nesting occurred on the Lower Platte (Figs. 2 and 3a). We measured habitat characteristics at 177 tern nests at 26 sites and 60 pip- ing plover nests at 26 sites. Terns nested exclusively at two of these sites and plovers at two. We determined nest initiation dates for 155 of the 177 measured tern nests and for 46 of the 60 piping plover nests (Fig 3b). Tern nest initiation dates