Laserfiche WebLink
. <br />23 <br />, <br />roads, utility lines and other development makes the perimeter of <br />grassl.and marginal habitat although the.vegetation appears <br />suitable (Currier et al. 1985). In smaller tracts of grassland, <br />a larger amount of the habitat is lost to the disturbance buffer <br />than in Iarger tracts. The impact of these habitat changes on <br />the endangered species and their habitats is described elsewhere <br />in this report. <br />Tn summary, the Platte River has undergone the following major <br />changes since pre-settlement times (from Currier et al. 1985): <br />(1) 65 to 79% reduction <br />reach of'the Platte <br />in encroachment of <br />(2) 58 to 87% reduction <br />River channel as a <br />encroachment; <br />in channel width in the Big Bend <br />River and a corresponding increase <br />the channel by wooded vegetation; <br />in the areal extent of the Platte <br />result of woody vegetation <br />(3) 73% loss of the grassland complex within 3.5 miles of <br />the Platte River; <br />(4) Extensive irrigation, ditching, and drainage of lands <br />adjacent to the Platte River channel. <br />C. Current influences in and adiacent to the Platte <br />River. <br />l. Least Tern and PiDincr Plover <br />Water Fluctuations - During 1975-1988, flows that caused nests <br />to,be inundated were observed on the Platte River during 7 of the <br />10 years that least tern and piping plover nesting surveys were <br />conducted (1975, 1979, 1981-88). Inundation after nest <br />establishment accounted for 74% of the eggs lost at sandbar <br />nesting colonies in 1986 (Table 9). Drowning of chicks and nest <br />destruction were observed or suspected at 7 qf the 9 sandbar <br />sites used for nesting.(NGPC 1986). Based on survey efforts in <br />the Grand Tsland to Lexington reach in 1979, Faanes (1983) <br />reported that all known least tern and pip.ing plover nests in the <br />river channel were inundated by rising water. Flow data recorded <br />at the Grand Island gage indicate that mean daily flow increased <br />from 1810 cfs on 20 June 1979 to 3,000 cfs on 21 June 1979, the <br />date when all nests in the central Platte River reach were <br />inundated (Faanes 1983). Flows on 21 May 1979 when the first <br />nests were observed was 911 cfs at Grand Zsland (Faanes 1983). <br />Nesting by least terns and piping plovers during 1988 was <br />initiated on sandpits in the Big Bend reach during late May when.