DISTRIBUTION
Distribution of the Least Tern
in interior North America
John G. Sidle, John J. Dinan,
Mark P. Dryer, John P.
Rumancik,
Jr., and John W.
Smith
HE
INTERIOR
POPULAT
OF
THE
LeastTern(Sternaanti!!arurn)was
recently added to the federal list of
endangered
andthreatened
wildlife
(United StatesFish and Wildlife Service
1985a). Although the American Ornithologists Union (1983) continues to
recognize three Least Tern subspecies
in North America, debate continueson
the validity of thesesubspeciesand the
extent of genetic and ecologicalinteractions among the coastal Least Tern
(S. a. anti!!arurn),California Least Tern
(S.
a.brownt)
and
the
interior
Least
Tern
(S. a. athalassos)(A.O.U. 1957). Massey
(1976) reported no consistentmorphological,behavioral, or vocal differences
between
thecoastal
Least
Tern
andthe
California Least Tern. Electrophoretic
analysisindicate little genetic differentiation amongLeast Ternsproducedon
?
\
Exposedsandbarson the centralPlatte River.
Much openriverchannelhabitat has disappearedalongthe centralPlatte. Photos/John
Sidle.
Volume 42, Number 2
195
Adult tern on nest.Photo/NebraskaGame Commission.
the Texas coast and Texas Panhandle
rivers (McCament and Thompson
1987). Coastal Least Terns have been
known to populate interior breeding
sites.Boyd and Thompson (1985) captured an incubatingLeast Tern at Quivira National Wildlife Refuge, Kansas,
that had originally been banded as a
chick on the Texas coast.
Because of the taxonomic
uncer-
tainty of LeastTern subspecies
in North
America, the United States Fish and
Wildlife Servicedid not specifythe interior subspeciesin the listing. The
United States Fish and Wildlife
Service
designatedas endangeredthe population of Least Terns (hereafter referred
to asthe Interior LeastTern) occurring
in the interior
of the United
States.
Taxonomic and population questions aside, the status of the Interior
Least Tern concerns various federal and
stateagencies.As a result of the listing
of the Interior Least Tern, census and
Least Ternchicksand egg.Photo/JohnSidle.
field researchcontinue. The data presented here have been compiled from
our surveys and from published and
unpublished sources for the period
(U.S.F.&W.S. 1987; Hill 1985). In
the Upper Missouri River Basin they
are very often breeding associatesof
1985-1987, and record recent data on
numbers and distribution.
the threatenedPiping Plover (Charadrius melodus), whose status and conservation are also a major concern
(U.S.F.&W.S. 1985b, 1988). Nesting by
Interior LeastTerns beginsin the spring
Methods
and earlysummer.Boatand aircraftare
the principal means of transportation
for locatingand censusingthe birds.
Along 192kilometersof the Missouri
River in North Dakota, Dryer and
Dryer (1985) arrived at all suitable
nestingsitesby motorboatand searched
on foot. Interior Least Terns actively
sandbars have been exposed. Attempts
defend their nestingcolonies,and this
aids in locating nest sites and adult
sandbars in rivers, but some nest on
to census Interior
terns. Least Terns and their nests are
sandpits and gravel pits along rivers
during surveysof rivers when suitable
censusedfirstin late June and early July
and
habitat conditions exist in the spring
in North Dakota and a return visit is
after
Most
196
on
Interior
the
Least Terns
shores
of
nest on
some
lakes
water
levels have receded
Least Ierns
and
occur
American Birds, Summer 1988
made from mid-July to late July to record the fate of nests and to locate new
nests. The Nebraska Game and Parks
Commission(1985a) usedan airboat to
censusthe ternsalong the Niobrara and
Platte rivers, Nebraska.
Fixed-wing aircraft, operatingat altitudes from
six meters to 61 meters
by the Urnted StatesFish and Wlldhfe
Service (1985a; Table 1). Additional
and more complete surveysthan those
that were conducted prior to endangered statusare likely explanationsfor
association with P•plng Plovers The
producUv•tyand dlstnbut•onof Interior
the current estimates of Interior
levels (Schwalbach et al. 1986, 1988,
Schwalbach 1988). The amount of
sandbar habitat and often reproductive
successdepend upon the dischargeof
Least
Terns. The surveyby Downing (1980),
for example, did not include North Da-
aboveground, have been usedto locate
kota, South Dakota, or Texas and was
tern colonies and to census adult terns.
basedupon a brief flightoverjust a portion of the Interior Least Tern's range.
The differencesamong the years 1985
to 1987 probably are also due to improvedcensustechniquesand coverage.
This is particularly true on the Mississippi River.
The breeding range of the Interior
Along the Platte, Loup, Middle Loup
and Niobrara rivers in Nebraska, and
the Cimarron
River
in Kansas and
Oklahoma, aerial surveysof tern coloroesare followedby groundchecks,and
in someyearscoloniesare visitedevery
three to sevendays to evaluatereproductlvesuccess(Boyd 1986, 1987; Nebraska Game
and Parks Commission
Least Tern is restricted to a few loca-
tions (Fig. 1) and representsremnants
1985a, 1986a; Schwalbach et al. 1986,
of a wider distribution that existedprior
1988). Evans (1984) used fixed-wing
atrcraftto locatesuitablenestinghabitat
to the impoundmentand channelingof
the Mississippi River drainage in this
century (Hardy 1957). Destruction,
on the Ohio River and scanned sand-
bars from a boat, landing only at sites
where terns were observed. To deter-
lometer
reation River (Schmulbachet al. 1981;
U.S.F.&W.S. 1986). In Missouri, the
Missouri River between Kansas City
beheved to be the most efficient and ac-
curate survey for Interior Least Terns
on the Lower MississippiRiver.
Results and Discussion
Census data indicate
that there are
currently more adult Interior Least
Terns than the 1250 reported by
Downing (1980) for the mid- 1970sand
more than the 1400 to 1800 reported
Volume 42, Number 2
dams. For ex-
ample, Dryer and Dryer (1985) est•mated that on June 10, 1983, an average
daily dischargeof 492 cubic metersper
second had exposed approximately
2000 hectaresof sandbarhabitat along
192 kilometers
of the Missouri
River
below Garrison Dam, North Dakota.
On August 11, 1983, an averagedaily
dischargeof 742 cubic meters per second had exposedabout 970 hectaresof
sandbars. Untimely discharges from
Garrison Dam have inundated
Least Tern colonies.
Interior
braska Game
The U.S. Army Corps of Engineers
(Rumancik 1986;M. Smith 1986)twice
surveyed1100 kilometersof the Lower
M•sslssippiRiver by fixed-wingaircraft,
once by small boat during which observerslanded on sandbars,and once
by a larger vesselfrom which observers
than any aerial survey.This surveywas
water from mainstem
to water
channels have eliminated
River.
and recorded 40% more Least Terns
of sandbar habitats
Substantial lossesof eggsor young,
or even entire colonies,due to flooding
have been documented every year on
the Missouri River since 1980 (Ne-
River Valley. Channelization along
Nebraska's Missouri River boundary
hasvirtually eliminated sandbars,with
the exceptionof 890 hectaresof exposed
sandbarsinventoried along the 80 ki-
The smallboat surveyfollowedan aerial
surveywithin three to four days.It was
conductedwhen chickswere hatching
relation
modification, and curtailment of the
birds' habitat and range continue
(U.S.F.&W.S. 1985a).
On the Missouri River, dams and
mine habitat use by terns, J.W. Smith
(1985, 1986) usedfixed-wingaircraft to
Inventory potential nestinghabitat on
the Missouri and Mississippirivers in
and adjacentto the State of Missouri,
followedby ground checksby boat of
sintable nesting habitat during the
breeding season. Sweet (1985) and
Smith and Shepherd(1985) usedhelicopters to censusInterior Least Terns
at two islandsin the MississippiRiver
and alonga longstretchof the Arkansas
censused terns but did not disembark.
Least Terns on these short stretches of
the Missouri River is influencedby the
most sand-
bars. Lake Sakakawea,behind Garrison
Dam, North Dakota, and Lake Oahe,
Oahe Dam, South Dakota, have inundated hundreds of miles of the Missouri
Missouri
River National
Rec-
and St. Louis still contains at least 15
and Parks Commission
1985b). Recommendations have been
made to modify dischargesat Garrison
Dam (U.S.F.&W.S. unpubl. memo
1983) and Gavins Point Dam in South
Dakota (Nebraska Game and Parks
Commission1985b). The United States
Army Corps of Engineersis currently
consulting,under Section7 of the EndangeredSpeciesAct, with the United
States Fish and Wildlife
Service on the
effects of the operation of mainstem
dams on the Interior
Least Tern and
Piping Plover.
Most of the Missouri River's tribu-
sandbars that have potential as Least
taries do not support Interior Least
Tern nestinghabitat, but they do not
presently nest anywhere along that
stretchof the river (J.W. Smith 1985).
Eleven of thesesandbarsare ownedby
the Missouri Department of Conservation, providing long-rangepotential
for Least Tern restorationin that part
of the state;however,presentflooding
regimesin the MissouriRiver may preclude nestingin the region.The habitat
dynamics of Missouri River sandbars
have not been fully evaluated.
Terns. The Yellowstone River in North
Dakota is one of the northernmost
nestingareas,althoughthereis very httie suitable habitat on this river. Least
Terns occupy a short segmentof the
CheyenneRiver in South Dakota, but
are absent on other tributaries in South
Dakota becauseof inadequate nesting
habitat (Schwalbach1988). The Niobrara River in Nebraskais largelyfreeflowingwith little regulationand retains
a natural systemof sandbarssimilar to
In North Dakota, South Dakota, and
what must have existedin the past (Du-
Nebraska, free-flowingstretchesof the
MissouriRiver containingsandbarsoc-
cey 1985). Interior LeastTerns neston
cur below most of the mainstem dams
rata River and reproductive successlS
high (Nebraska Game and Parks Commission 1985a).
However, the Platte River Valley
in Nebraska has undergone signifi-
(Dryer and Dryer 1985; Schwalbachet
al. 1986, 1988; Schwalbach1988). Interior LeastTernsoccuralmostentirely
on these short stretchesand usually in
the lower 190 kilometers of the Niob-
197
Figure 1. Breedingdistributionof Least Ternsin interiorNorth America. Numbersreferto the locationslisted in Table 1.
198
American B•rds,Summer 1988
Table 1.
Census data on the population of the Interior Least Tern, 1985-1987.
Approximate
Location
Numberof adult
lengthof river
Least Terns
stretch(km) where
nestingleastterns
intermittentlyoccur
1985
1986
1987
SouFee
Missis•ppiRiver Sy•em
1 Below Garrison Dam, Missouri
River, North Dakota
114
169
175
192
26
2 CheyenneRiver, SouthDakota
--*
31
54
3 Lake Oahe, Missouri River,
--
16
21
206
292
(Dryer and Dryer 1985; M. Dryer unpubl. rep
1986, 1987)
(Schwalbachet al. 1986, 1988; Schwalbach
1988)
4
South Dakota
Below Fort Randall and Gav-
ins Point Dam, Missouri
River, South Dakota to
Ponca, NE
5 Niobrara River, Nebraska
6 Platte River, Nebraska
7 MississippiRiver, Cape Girardeau, Missouri to Vicksburg,
Mississippi
8 ArkansasRiver, Arkansas
(above Little Rock)
9 ArkansasRiver, Oklahoma
10 Quivira National Wildlife Refuge, Kansas(Rattlesnake
Creek of ArkansasRiver)
11 Greht Salt PlainsNational
Wildlife Refuge, Oklahoma
(Salt Fork of the Arkansas
River)
12 Cimarron River, Kansasand
202
-140
(Schwalbachet al. 1986, 1988; Schwalbach
1988)
(Schwalbachet al. 1986, 1988; Schwalbach
1988; Nebraska Game and Parks Commission (1986b)
174
256
-438
1264
2244
143
706**
2488
190
502
1100
(NebraskaGame and ParksCommission 1985a)
(NebraskaGame and ParksCommission 1986a,
J. Dinan pers. comm.)
(Rumancik 1985, 1986;J.W. Smith 1985, 1986,
19,87;
M. Smith1986;W. Kingpers.comm)
50
80
130
256
-48
70
48
150
54
119
--
(Smith and Shepherd 1985; K. Smith 1986;
Smith et al. 1987)
(Hoffman 1986; L. Hill pers. comm.)
(Boyd 1986, 1987)
140
110
--
(Boyd 1986, 1987)
82
150
132
121
(Boyd 1986, 1987)
45
52
60
--
(Boyd 1986, 1987)
127
182
--
253
44
50
--
241
(McCament and Thompson 1985, 1987; U.S.F
& W.S. unpubl. data)
(McCament and Thompson 1985, 1987)
Oklahoma
13 Optima Reservoir, Oklahoma
(Beaver River)
14 Canadian River, Oklahoma
and Texas
15 Prairie Dog Town Fork of the
Red River, Texas
Rio Grande River System
16 Falcon Reservoir,Rio Grande
17
River
Lake Casa Bianca
--
150
--
--
(McCament and Thompson 1985, 1987)
--
5
--
--
18 AmistadReservoir, Rio
---
9
--
--
(McCament and Thompson 1985, 1987)
(McCament and Thompson 1985, 1987)
Grande River
19 Bitter Lake National Wildlife
--
6
--
--
(S. Hoffman; U.S.F. & W.S. unpubl. data)
Refuge, New Mexico (Pecos
River)
Total***
2406
4046
4515
3140
* (--) signifiesno census
conducted
in thatyear.
** tncludes104 InteriorLeastTernscensused
in 1987on theLoupRiver,a tributaryof thePlatteRiver (H.B. Gravesunpubl.rep.).
*** The total doesnot include22 and 20 Interior Least Ternscertsused
in 1986 and 1987, respectively,
on the Yellowstone
River,North Dakota (Kreil and Dryer 1987;M
Dryer unpubl.data),'28 InteriorLeastTernsat ashlagoons
of a powerplantnearCouncilBlu•, Iowa in 1986(Wilson1986);4 InteriorLeastTernson theFort Peck
Reservoirwithinthe CharlesM. RussellNational WildlifeRefuge,Montana,in 1987 (MontanaPipingPloverCommittee1988);and 2, 4 and 4 InteriorLeast Terns
censused
in 1985, 1986,and 1987, respectively,
at a publicservice
powerplant'scoolinglake nearEastMount Carmel,Indiana,alongthe WabashRiver (Johnson
1987,
Mtlls 1987).
Volume42, Number 2
199
cant vegetatlonal and morphological
changesdue to water w•thdrawalssince
settlemen for irrigation and power
(U.S.F.&W.S. 1981; Sidle et al. [in
prep];Williams 1978). The resultshave
been a significam reduction in the
amount of Least Tern nestinghabitat
along the central Platte River (North
Platte to Columbus)througha narrowing of the river channeland a tremendous increase in riparian vegetation
and adjacent to the State of Missouri.
To provide protection for the Least
Tern, the Missouri Department of
Conservation has designated certain
state-ownedMississippiRiver islandsas
inviolate refugesduring the breeding
LeastTerns nestprimarily in the vm•n•ty of reservoirs (McCament and
Thompson 1985, 1987). Nestingoccurs
on shell beaches along the reservoirs
(Neck and Riskind 1981). Further surveyson the Rio Grande may revealad-
season.These islands, consideredto be
ditional Least Terns.
wide river channel. Currem use of cen-
criticaltern habitatby the state,are annually postedwith large, conspicuous
signsdescribingthe reasonfor posting,
the time frame for refugestatus(May
15-August 31 unlessthe signsare removedearlierby stateofficials),and the
penaltiesthat could apply in casesof
trespass.Public information programs
tral Platte River channels by Least
have ameliorated
Terns indicates that areas with unob-
bance problem (J.W. Smith 1987).
Conservationprogramsare ongoingfor
(Currieret al. 1985;Ducey 1985).The
present riverinc environment contrasts
sharplywith the historictreelessness
and
structedvisibility are usedproportionatelyhigherthanthe availabilityof such
areas(David C. Carlsonpers. comm.).
Interior Least Terns often nest at sand
and gravel pits adjacem to the Platte
River. However,reproductivesuccess
is
low due to human disturbanceand predation (Nebraska Game and Parks
Commission 1986a; G.R. Lingle unpubl. data). Most sandbar nestingby
LeastTerns usingthe Platte River now
occurs on the lower Platte River (east
of Columbus) (Nebraska Game and
Parks Commission 1986a), where the
unobstructedchanneliswiderand large,
barren sandbarsare more plentiful than
on the central Platte River. The United
States Fish and Wildlife Service is cur-
rently collaboratingwith severalpublic
agenciesand private organizationsregarding studiesto determine instream
flow regimessuitable for Least Terns
and other threatenedand endangered
species.
On the Mississippi River, Interior
LeastTernsoccuralmostemirelyin the
lower valley south of Cairo, Illinois.
Nestingoccurson mid-channelislands
Interior
the human
Least Terns in North
reached to permanently protect the
sandbar environment
of the terns.
Dakota
of the Lower Mis-
sissippiRiver, includingthe Ohio River.
Throughoutwatersheds
of the Arkansas
and Red rivers, reservoirs and other
river managementschemeshave had a
similar impact on the distribution of
Interior
termittentlyalongonly a few segments
of rivers.Breedinghabitatscontinueto
be disrupted, and agreementsamong
numerous agencies will have to be
distur-
(Kreil 1987) and Nebraska.
Currently,United StatesArmy Corps
of Engineersdredgepermitsrequirethe
permittee to contact the Corps 30 days
prior to dredgingto obtain updatedinformation concerningthe location of
InteriorLeastTern colonieswhichmay
be affectedby the dredging activities
(RichardKaiserpets.comm.).If surveys
reveal Least Tern breeding activity
within one-half mile of the proposed
dredginglocation, dredgingmust not
proceeduntil the impacts of the dredging havebeenreviewedby the Corpsof
Engineers.
Interior LeastTerns no longeroccur
on most tributaries
Recent surveysconfirm that the Interior Least Tern continues to occur in-
Least Terns as occurs on the
Missouri,Mississippi,and Platte riven.
The upper Arkansasand Red river watershedssupport Interior Least Terns.
LITERATURE
AMERICAN
UNION.
CITED
ORNITHOLOGISTS'
1957. Check-list
of
North
American birds. Fifth edition. Baltimore,
__.
Amer. Ornithol. Union.
1983. Check-list of North
Amencan
birds. Sixth edition. Lawrence, Kansas,
Amer. Ornithol.
Union.
BOYD, R. L. 1986. Habitat management
and population ecology studiesof the
least tern in Kansas. Kansas Fish and
Game Commission, Unpubl. Rep.
__.
1987. Habitat managementand population ecologystudiesof the leasttern
in Kansasand Oklahoma. KansasDept.
of Wildl. and Parks, Unpubl. rep.
and B.C.
THOMPSON.
1985. Ew-
denceof reproductivemixingof leasttern
populations.J. Field Ornithol. 56:405-
or on sandban within dike fields. Sur-
For example, on the Arkansas River,
veysby the United StatesArmy Corps
of Engineers(Rumancik 1985, 1986,
1987; M. Smith 1986) and Missouri
Department of Conservation (J.W.
Smith 1986, 1987) indicate that about
terns nestingin Oklahoma occur only
below dams suchas the KeystoneDam
(Hoffman 1986). In Kansas, Schulenberg and Ptacek (1984) reported that
reproductive successis low and much
River Whooping Crane Critical Habitat
one-half of all Interior Least Terns oc-
of the breedinghabitat is threatened,
althoughthe populationof ternson the
braska.
cur along 1100 kilometersof the Lower
MississippiRiver. As on the Missouri
River, thereare untimely risesin water
levels which inundate
nests. Human
disturbance is infrequent, but casual
disturbance during the broodrearing
period has been implicated in chick
mortality at MississippiRiver terneries.
J.W. Smith (1986) cited human disturbance as an importam factor limiting
the breeding successof Least Terns in
200
Cimarron
River is believed to be stable
(Boyd 1986, 1987). The constructionof
Lake Meredith on the Canadian River
in Texashas greatlyreducedthe magnitude of both high flows and average annual flows and suitable nesting
sandbar habitat
has been eliminated
along stretchesof the Canadian River
(U.S.F.&W.S. unpubl.data).
On the Rio Grande River, Interior
406.
CURRIER, P. J., G. R. LINGLE and J G.
VanDERWALKER. 1985. Migratory
bird habitat on the Platte and North
Platte Rivers in Nebraska. The Platte
Maintenance Trust, Grand Island, Ne-
DOWNING, R. L. 1980. Surveyof interior
leasttern nestingpopulations.Am. Btrds
34:209-211.
DRYER, M.P. and P. J. DRYER. 1985
Investigations into the population,
breeding sites, habitat chamcteristms,
threatsand productivityof the leasttern
in North Dakota. U.S. Fish and Wildhfe
Service,Bismarck, North Dakota.
DUCEY, J. E. 1985. The historic breechng
distribution of the least tern in Nebraska
Nebraska Bird Rev. 53(2):26-36.
AmericanB•rds,Summer1988
EVANS, S A 1984ßSurveyof interior least
tern nestingcolonieson the Mississippi
and lower Ohio Rivers in Kentucky.
Mississippi
Valley. Publ.Mus. Michigan
Mississippi1986ßUßSßArmy Corps of
Engineers,Memphis District Unpubl
Rep.
ß1987.Populationsurveyof the interior
leasttern on the MississippiRiver from
Cape Girardeau, Missouri, to Greenville,
Mississippi1986ßU.S. Army Corps of
State Univ., Biol. Ser. 1:1-60.
Engineers,Memphis DistrictßUnpubl.
KentuckyDept. of Fish and Wildl. Res.
Unpubl. Rep.
HARDY,
J. W. 1957. The least tern in the
HILL, L. A. 1985. Breedingecologyof interior least terns, snowy plovers, and
American avocets at Salt Plains National
Wildlife Refuge, Oklahoma. Oklahoma
State University,Stillwater.
HOFFMAN, J. C. 1986. The distribution of
Rep.
SCHMULBACH, J. C., J. J. SCHUCKMAN, and E. A. NELSONß 1981.
Aquatic habitat of the Missouri River
from Gavins Point Dam to Ponca State
Park,Nebraska.U.S. Army Corpsof Engineers,Omaha. Unpubl. Rep.
the interior least tern in northeastern
Oklahoma during the 1986 nestingseason. Unpubl. Rep.
JOHNSON, R. 1987. Least tern surveyof
the Wabash River, 1987 and evaluation
SCHULENBERG,
SCHWALBACH, M. 1988. Conservationof
of availablehabitat.Endangeredspecies
projectrep. E-I-I. Indiana Dept. of Nat.
leastternsand piping ploversalongthe
Missouri River and its major western
Res.
tributaries in South Dakota. South Da-
KREIL,
R. 1987. Least tern conservation
program. North Dakota Game and Fish
Department ProjectSE-I.
__ and M.P. DRYER. 1987. Nesting of
kota StateUniversity, Brookings.
--,
MASSEY, B. W. 1976. Vocal differencesbetweenAmericanleastternsand European
little tern. Auk 93:760-773.
__.
1985. Interior least tern distribution and
taxonomy.TexasParksand Wildlife Department.PerformanceRep. FederalAid
project no. W-103-R-15.
and
.1987. Interior least tern dis-
NEBRASKA
GAME AND PARKS COMMISSION.
1985a. Niobrara River inte-
rior leasttern and piping plover nesting
survey.Unpubl. Rep.
__.
1985b. Missouri River least tern and
piping plover habitatmanagementproposalpresentedto the U.S. Army Corps
of Engineers.Unpubl. Rep.
__.
lations on the Missouri River for 1983-
1986. Unpubl. Rep.
MILLS, C. E. 1987. Indiana's first least tern
nestingrecord.Indiana AudubonQuart.
65:42-44.
NECK, R. W. and D. H. RISKIND.
1981.
Direct and indirect human impact on
leasttern nestingsuccessat Falcon reservoir, Zapata County, Texas. Bull.
Texas Ornith. Soc. 14(1 & 2):27-28.
RUMANCIK, J.P., Jr. 1985.Surveyof the
interiorleasttern on theMississippiRiver
from Cape Girardeau, Missouri to
Greenville,Mississippi.
U.S. Army Corps
of Engineers,
MemphisDistrict.Unpubl.
Rep.
--.
1986.Populationsurveyof the interior
leasttern on the MississippiRiver from
Cape Girardeau,Missourito Greenville,
Volume 42, Number 2
1988. Status,distribution,and production of interior leastternsand piping
plovers along the mainstem Missouri
River in SouthDakota, 1986-1987.Rep.
no. 88-01 to the U.SßArmy Corps of Engineers,MissouriRiver Division,Omaha,
U.S. FISH
AND
WILDLIFE
SERVICE
1981ßThe Platte River ecology study
Specialresearchreport.Northern Prairie
Wildl. Res. Ctr., Jamestown,North Dakota.
__.
1985a.Interior populationof the least
tern determinedto be endangered.Federal Register50:21784-21792.
__.
1985b.Determination of endangered
and threatened status for the piping
plover. Federal Register 50:5072050734.
__.
1986. Location of habitat important
to federally listed bird specieson the
Missouri
National
Recreation
River
Pierre, South Dakotaß
__.
1987. Leasttern in: Endangeredspeciesinformation system(computerdata
base)ßU.S. Department of the Interior,
Fish and Wildlife Service, Division of
EndangeredSpeciesand Habitat Conservation,Washington, D.C.
ß 1988. Great Lakes and northern Great
Plainspipingploverrecoveryplan.U.S.F
& W.S., Twin Cities, MN.
WILLIAMS, G. P. 1978. The case of the
shrinking channels--the North Platte
and Platte Rivers in Nebraska. UßS. Geol
Surv. Circ. 781.
WILSON, B. L. 1986ß Special birds of
CouncilBluffs-- 1986. Unpubl Rep.
Nebraska.
SIDLE, J. G., G. MILLER, and P. J. CUR-
RIER. (In prep)ßChanginghabitatsin the
PlatteRiver Valley, Nebraskaß
SMITH, J. W. 1985. Improving the status
of endangeredspeciesin Missouri:Interior least tern habitat and nest survey.
Performancereport,EndangeredSpecies
ProjectNo. SE-01-12, Missouri Dept. of
Conservation, Columbiaß
__.
1986a. Platte River interior least tern
and piping plover nestingsurvey.Unpubl. Rep.
__.
1986b.Preliminarysummaryof least
tern and piping plover breeding popu-
and K. HIGGINSß
Nebraskaß
McCAMENT, D. and B.C. THOMPSON.
tnbution andtaxonomy.TexasParksand
Wildlife Department.PerformanceRep.
Federal Aid project No. W-103-R-16.
G. VANDEL
1986. Status,distribution, and production of the interior leasttern and piping
plover along the mainstem Missouri
River in South Dakota, 1986. Rep. no.
86-10 to the U.S. Army Corpsof Engineers,Missouri River Division, Omaha,
the interior least tern on the Yellowstone
River in North Dakota. Prairie Nat. 19:
135-136.
__
J. H. and M. B. PTA-
CEK. 1984. Status of the interior least
tern in Kansas. Am. Birds 38:975-981.
Louisiana UßSßArmy Corps of Engineers,VicksburgDistrict Unpubl Rep.
SWEET, M. J. 1985. Leasttern population
survey,1984.Illinois Deptßof Cons.Unpubl. Rep.
1986ß1986 surveyof the interior least
tern on the MississippiRiver (Cape Girardeau, Missouri to Island no. 20, Tennessee).
MissouriDeptßof ConsßUnpubl.
Rep.
__.
1987. Improving the statusof endangered speciesin Missouri: least tern investigations.Performance rep., endangeredspeciesprojectno. SE-01-12.MissouriDept. Cons.
SMITH, K. L. 1986. Results of the 1986
surveyof the ArkansasRiver for interior
leastterns. ArkansasNational Heritage
Commissionß
Unpubl. Rep.
__
and W. M. SHEPHERDß
1985. A sur-
vey of the interior least tern on the Arkansas and White
Rivers in Arkansas.
ArkansasNatural Heritage Commissionß
Unpubl. Rep.
__,
S. BARKLEY and C. GATES. 1987.
A surveyof interiorleastternson the Arkansas River in Arkansas. Arkansas Nat-
ural HeritageCommission.Unpubl Rep.
SMITH, M. 1986.Field surveyof the interior
leasttern (Sterna antillarum athalassos)
on the MississippiRiver and Red River,
--U.S.
Fish and Wildlife Service,
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and Parks Commission, P.O. Box
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(Dryer); U.S. Army Corpsof
Engineers,B-202 CliffordDarts
Federal Bldg.,Memphis, TN 381031894 (Rumancik); Missouri
Departmentof Conservation,
Fish and
Wildlife ResearchCenter, 1110
CollegeAve., Columbia,MO 65201
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