WSP01978

• File Number: 8460.500
• Description: Platte River Recovery Plan
• Basin: South Platte
• Date: 9/1/1990
• Author: USFWS
• Title: Interior Population of the Least Tern - Recovery Plan
• Water Supply Pro - Doc Type: Publication

Reasons For Current Status

Habitat alteration and destrrction: Channelization, irrigation, and
the construction of reservoir~ and pools have contributed to the
elimination of much of the tern' ~ sandbar nesting habitat in the Missouri, .
Arkansas, and Red River systemsl (Funk and Robinson 1974, HaUber et a1
1979, Sandheinrich and Atchisdn 1986). Ducey (1985), for examp'le,
describes the changes in the channel characteristics of the Missouri River
since the early 1900s under the Missouri River Bank Stabilization and
Navigation Project. The wide and braided character of the Missouri River
was engineered into a single n~rrow navigation channel. Most sandbars
virtually disappeared between S~oux City, Iowa and Saint Louis, Missouri
(Sandheinrich and Atchison 1986,i Smith and Stucky 1988).

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Where sandbars still occur along the Nebraska-South Dakota boundary
(Missouri River), approximately ~ ,156 ha of sandbar habitat have been lost
between 1956 and 1975 (Schmulbach et a1. 1981). Sandbars along the
Nebraska-Iowa Missouri River boundary have been virtually eliminated with
the exception of 890 ha inventQried along the 80-km Missouri National'
Recreation Area (Schmulbach et al. 1981).

Current regulation of Missouti River dam discharges pose additional
problems for interior least tern$ nesting in remaining habitats (Nebraska
Game and Parks Commission 1985c, Schwalbach et a1. 1988). Before
regulation of river flows, summ~r flow patterns were more predictable.
Peak flows occurred in March from local runoff and then again in May and
June when mountain snowmelt occurs. Flows then declined during the rest
of the summer allowing interior least terns to nest as water levels
dropped and sandbars became ~vailable (Stiles 1939, Hardy 1957).
Currently, the main stem system is supposed to be regulated for
hydropower, navigation, water ~uality and supply, flood evacuation,
irrigation, fish and wildlife: conservation, and public recreation.
However, system releases are d~signed to provide equitable service to
power and navigation demands, ex~ept when they conflict with flood control
functions of the system.

The demands are unpredictable and flows can fluctuate greatly, Flow
regimes differ greatly from histpric regimes. High flow periodB may now
extend into the normal nesting period, thereby reducing the quality of
existing nest sites and forcing ~nterior least terns to initiate nests in
poor quality locations. Extrem~ fluctuations can flood existing nests,
inundate potential nesting area~, or dewater feeding areas. Interior
least terns along the Arkansas Riyer in Oklahoma and Arkansas contend with
dam discharge problems similar to those on the Missouri River.

Along the Lower Mississippi' River, and elsewhere, natural river
discharge may exert considerable influence on reproductive success. A wet
spring may delay river fall and ~abitat may not be available until later.
Rises in the river during the sJ'ring and summer may inundate nests and
wash away chicks (Rumancik 1986, '989, Smith and Renken 1990). Renesting,
however, does occur and may be a adaptation to river fluctuationB. Dike
, .

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