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

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Ill. Survey sandbars. reservoir shorelines. sand and Eravel Dits
and other suitable habitats to determine breedinE
distribution.
Currently, the distribution of the interior least tern on
most of the Missouri River system is well-known and
monitored, although reservoir shorelines in the Dakotas and
Montana should be further surveyed for accurate population
estimates especially during drought years when reservoir
levels are low. Additional survey work is needed on ,the
Loup River in Nebraska and elsewhere in the Platte River
system. The Arkansas River system needs further survey work
in Arkansas, Kansas, Oklahoma and Texas. The length of the
Red River requires a thorough survey as does the Rio Grande
River system and rivers in central Texas. Additional survey
work is needed on the Lower Mississippi River to determine
distribution when the river rises and floods nesting
colonies. The Missouri Department of Conservation has a
study in progress to address this need. The status of
potential sites should be monitored and updated at least
once every five years.
112. DeveloD a method for standardization of census techniaues
and' timin~.
The exposure of sandbars in the spring follows the reduction
of river flows. The breeding cycle may commence at
different times throughout the interior least tern's range.
Differences in breeding chronology from south to north must
be determined. Because of the length of time involved in
surveying long stretches of rivers, surveys should be
correlated with reported river levels and the exposure of
sandbars. Surveys should account for renesting birds and
later nesting by younger adults (Massey and Atwood 1981,
Smith and Renken 1990).
113. Census known and Dotential breedinE sites.
Once sites are identified as containing breeding pairs,
annual censuses of breeding and non-breeding adults should
be carried out at essential breeding habitat <Appendix 4)
for several years. If the birds are established for several
years, censusing should continue at least once every year.
114. Monitor reDroductive success.
Census data provide an indication of an area's population
size, but estimates of reproductive success are also
necessary. More adults may be present in nesting areas than
actually breed. Frequent nest destruction further lowers
productivity of a site, rendering simple counts of breeding
pairs less meaningful than censuses of adults and fledged
chicks. Reproductive success or recruitment (measured in
terms of number of chicks fledged per pair) should be
monitored annually at essential sites and at least every
three years, on a rotating basis, at other sites. Causes of
reproductive failure should be identified whenever possible.
Because of possible early fledgling departure from colonies,
multiple counts of fledglings should be made for

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