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SECTIONFOUR least Tern I ,. I I 1 :1 iJ 1 J ~ I ~ Williams 1978). This vegetation encroachment has eliminated much of the sandbar habitat previously utilized by the least terns (Currier et al. 1985; Sidle et al. 1989; FWS 1981). The loss of open river channel has been greatest along the Platte River from the confluence of the North Platte and South Platte rivers downstream to Lexington (Sidle et al. 1989). Least terns no longer nest on this reach of the river except at a few artificial sites created by sand and gravel mining. Extensive vegetation encroachment has also occurred in the Central Platte Valley study area and only a few sites on the river are still used for nesting. Commercial sand and gravel mining operations near the river have created sandy spoil piles that may be used for nest sites. Least terns initiate nesting on spoil piles early in the breeding season when river flows are inundating sandbars. Eggs and chicks are vulnerable to predation and human disturbance from pit operations and adjacent housing projects. Eventually, nesting habitat is lost to vegetation encroachment and/or housing and recreational development (FWS 1988). Increased urbanization and use of beaches has brought an increase in the number of unleashed pets and unnaturally high densities of wild predators such as gulls, skunks, etc. Cattle trampling of nesting habitat may on occasion also affect nest success and chick survival (FWS 1988). Even though the species had been declining for many years, past regulatory mechanisms were unable or inadequate to provide the least tern with the protection necessary to prevent further decline. Federal recognition (federal endangered species) of the species status and the implementation of Recovery Plan for the interior population of the least tern has provided additional protection for the species. 4.3 BIOLOGY The least tern is a small, swallow-like bird that is 8 to 9 inches in length and has a wing span of about 20 inches and is the smallest (average weight of an adult is 1.5 to 2.0 ounces) member of the tern family (FWS 1990; Kirsch 1988). Sexes are alike, characterized by a black-capped crO'.'.T., white forehead, grayish back and clor~al wing surfaces, snowy white undersurfaces, legs. of various orange and yellow colors depending on the sex, and a black-tipped bill whose color also varies depending on the sex of the bird (FWS 1990). The long, black wing feathers and the short, deeply forked tail are conspicuous in flight (NGPC 1997). Least terns usually arrive on the breeding grounds in late April to mid-May and begin to establish feeding areas and nesting territories (NGPC 1997). Least terns nest in areas with similar habitat attributes throughout their North American breeding range. Beaches, sand and gravel spoil piles, sandbars, and peninsulas are the principal breeding habitats for least terns. Artificially created nesting sites, such as sand and gravel pits, dredge islands, reservoir shorelines, and power plant ash disposal areas are also used. Unconsolidated substrates such as small stones, gravel, sand, debris, and shells comprise the nesting substrate. A mixture of coarse sand, shells, and other fragments may offer preferred cryptic qualities, stability in wind, and water permeability. Least terns along the Platte River and the majority of the interior range do not have shell substrate available to them. Vegetative cover is usually less than 20 percent (less than 10 percent appears to be preferred) .at the time of nest initiation (FWS 1997). Least tern _SteiDer ~CI1f/e 4-2 68FOD97'286OOlr1.OOC 6I2f1999(9:S2AM)lURSG'NCFS/2 FeIIet2I"./~