Originally issued: 1985. The Historic Breeding Distribution of the Least Tern in Nebraska. Nebraska Bird Review 53(1): 26-36.
There has been quite a lot of attention given in recent years to the status of the Least Tern (Sterna antillarum) in the United States. Most of the information published to date, however, has dealt with changes of the beach habitat and breeding occurrence of coastal populations, but the interior subspecies (S. a. athalassos) that nests on and along the rivers of the Great Plains has been affected by different circumstances. In Nebraska there are records available that document the breeding season occurrence of the Least Tern for over 125 years and show how changes in habitat have led to a decline in their range.
Although early observations were on an occasional basis and scattered throughout the state they nonetheless indicate sites where Terns were known to occur and help to determine their historic range. The period covered is from 1804 to 1975, when the first aerial count of Terns was made (Downing 1975, Downing 1980).
The breeding occurrence of the Least Tern is dependent on the availability of the open sand substrate on which they dig out scrapes for their eggs. Colonies in Nebraska have been recorded on river sandbars and sand beaches, with any vegetation present usually covering less than 5 to 10% of the area. Colony size varies, with nests spread about the suitable habitat. The Belted Piping Plover (Charadrius melodus circumcinctus) is often associated with the Terns.
The first historical observation of the Interior Least Tern in Nebraska was made in 1804 by the Lewis and Clark expedition. This party was traveling up the Missouri River to explore the Louisiana Territory that had just recently been purchased by the government. Another government sponsored expedition was undertaken by G.K. Warren in the middle 1850's to find a travel route to the Black Hills. During the reconnaissance and exploration in the Nebraska and Dakota Territories, three Least Tern specimens were collected, with a notation in the expedition narrative of their occurring on western rivers (Warren 1875). These were the first two known records of this bird in the present-day Nebraska. A river by river analysis of sightings made by university professors, resident birders, and others follows.
Missouri River
The historic Missouri River had a dynamic ever-changing character. The natural channel had islands, sandbars, wetlands, open water of various depths, and forested lands. High flood flows would cover the floodplain or cut a new path and leave oxbow lakes behind. The river water with its heavy sediment load would deposit sand and alluvium at one spot but wash it away from another site. This constant hydrologic cycle of erosion and deposition would continually create and destroy sandbars, which were an obvious feature of the channel and were used by breeding Terns and other wildlife.
The steamboats traveling up the Missouri ran aground on a regular basis while making their way up the river. Sandbars, shallow water, and snags were a navigation hazard that had to be continually dealt with. The Lewis and Clark journals had numerous entries that referred to sandbars. The boat would pass a sandbar, the party would camp on a sandbar, or an elk would be shot on a sandbar are just a few examples (Thwaites 1969).
An expedition along the Missouri in 1833 and 1834 also gives some indications of the common occurrence of sandbars. Prince Maximilian of Wied traveled along the present boundary of Nebraska in the first half of May, 1833, which was probably too early to see Terns, but made numerous references to sandbars. Notes in the journal include mentions of sandbanks far and wide, the boat running into a large sandbank, that sandbanks soon emerged, and numerous sandpipers on the sandbanks (Orr and Porter 1983).
Vegetative encroachment on the open sand was noted on several occasions when willow sandbanks were seen, when the sand or, the bank was covered with young cottonwoods or willows a foot high, and when sandbanks with low-lying willows were seen. Plants would grow on the sandbars but the spring rise or scouring flood flows would remove the vegetation or entirely destroy a sandbar but create one at another site. The open sandbar habitat needed by Terns was an obvious feature during both expeditions, but changes took place that were to further increase the amount of sandbars.
The Missouri River in the early 1800's had different characteristics above and below the confluence of the Platte River. North of the Platte the channel was more meandering, while to the south the channel was semi-braided, with several subchannels. Sometime after this period, during a later part of the century, there was a transformation in the channel above the Platte. The river became more semi-braided, with the change attributed to a long period of frequently occurring high flood flows (Hallberg et al. 1979).
By the late 1800's the river had similar characteristics along both stretches, due to the natural evolution of the channel. There were, however, some differences on the lower part of the Missouri River as it changed its form to compensate for the influx of water and sediment from the Platte. In 1879 there was about 136 acres of sandbar and island habitat per river mile above the confluence of the Platte, while to the south of this point there was a broader channel, with about 264 acres of sandbar and island per mile. By 1923 the channel was similar both above and below the Platte (Hallberg et al. 1979).
Detailed maps prepared in the 1890's provide additional documentation of the extensive distribution of sandbars in the Missouri River along the entire eastern boundary of Nebraska (Missouri River Commission 1892-95). Drawings made in the last three months of the year show a multitude of sandbars of various sizes, both in the channel and completely surrounded by water, and connected to the bank on the inside of river bends. Their size varied from very small to very large, with one sand area near Fort Calhoun over 5 miles long and in some places .5 mile wide. Another was 2 miles long and .5 mile wide. These sandbars were often cut through by small water subchannels. An example of sandbar habitat in the southeast part of the state is shown in figure 1.
Figure 1. Channel characteristics of the Missouri River near Rulo, Nebraska, around 1890 (modified from Missouri River Commission 1892-95).
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Breeding activity of Least Terns on the Missouri River was noted during the period of record for more than 170 years. The many records of breeding Terns along the Missouri River illustrate the availability of suitable habitat along this river.
Breeding occurrence records begin with the notes in the zoology portion of the journals of Lewis and Clark. They refer to the Least Tern as a frequently observed aquatic bird that finally was collected on 5 August 1804 in the vicinity of the current Washington County. Several downy young were captured and the Terns were more plentiful in this area than on the river below the Platte (Thwaites 1969).
Sixty-two years later, in 1866, young Least Terns were recorded in the Dixon County area (Bruner et al. 1904) and were still present and a summer breeding resident in the same general area in southeast Dakota Territory during the 1880's (Agersborg 1885). Records from around the turn of the century added the Omaha and Peru areas as breeding locations (Bruner 1896).
Observations in the Clay County area of South Dakota, especially during 1910-13, recorded nesting of the Tern on the Missouri near the mouth of the Vermilion River, with nests found on several occasions in small colonies, consisting of not more than 7 to 8 pair (Vischer 1915).
Cutoff, or Carter Lake as it is now called, was formed north of Omaha in 1877 when the channel of the Missouri River moved to the east. The first record of breeding at this site was in 1893 (Bruner et al. 1904). About thirty years later Least Terns were counted at the lake during waterbird censuses carried out in 1926, 1929, and 1930. Highest numbers were 20, 6, and 12 respectively, and the birds were noted several times during the summer, so were resident, although no information was given on nesting activity (Nebraska Ornithologists' Union Letter of Information 34: 4, 44: 3, and 52: 3).
The last recorded observations of breeding at Carter Lake were in 1940 and 1941 (Moser 1940, Moser and Haecker 1941). The nesting site used in these years was dredged sand fill with only a small amount of vegetation. The area with Tern nests originally had water on only two sides, but later became completely surrounded when a dike was built to act as an outlet for lake dredging operations. Breeding at the Cut-off Lake locality covers almost fifty years, with Terns probably present until vegetation became established on the open sand.
The first observations made in the Dakota County-Sioux City area were in the 1910's, and eventually the Tern was considered to be a fairly common summer resident, known to nest on sandbars of the river and on narrow dirt ledges in the almost vertical banks of the river (Stephens 1957). The second nesting site given does not conform with the usual behavior of Terns to nest on ground with a sand substrate.
There are several confirmed nesting records from 1929 through the 1930's near Sioux City. In 1929 several fledglings were noted on a large sandbar in the river while the adults foraged at a nearby lake (Youngworth 1930). Two years later birds were noted in many parts of northeast Iowa and southeast South Dakota, but the birds nested in particular at a sandbar near Sioux City. On 2 August 1931 no less than 150 Terns, including many immatures, were gathered for migration (Youngworth 1931). The next year conditions for nesting were not favorable, due to government work on the channel of the river, but the birds were expected to have moved upriver (Youngworth 1932).
Nesting Terns did remain in the area, since habitat must have still been available, and a colony of 14 nests was located near Sioux City, in Dakota County, Nebraska, and Woodbury County. Iowa, in both 1937 and 1938. Sandbars were used for nesting. As a result of these observations the Tern was considered to be a comomon summer nester (Stiles 1938, Stiles 1939).
Three locations along the Missouri on the Iowa side of the river provide additional information on nesting distribution along Nebraska's eastern boundary. In 1933, nesting was recorded in Pottawattamie County. (DuMont 1933). Two observations were made at lake locations in 1934. One site was at a marsh 11 miles east of the river, along the Little Sioux River in Monona County (Bennett 1934). On 25 June, 30 birds were observed and birds were still present on 25 July. On the same date, at a 400 acre lake and marsh 2 miles southwest of Anthon in Woodbury County, Least Terns were also observed, although no numbers were recorded (Bennett 1934).
Two other localities along the northern part of the Missouri River in Nebraska with nesting activity were north of Decatur in Thurston County, where the birds were also considered as being commonly found flying overhead along the river (Haecker 1937a) and near the town of Arizona in extreme southeast Burt County (Haecker 1937b).
But as the Missouri River valley was settled there were many drastic changes made in the river. The most profound alteration was the result of construction of the Missouri River Bank Stabilization and Navigation Project. This project was initiated when statutes authorized a 6-foot-deep channel as far as Kansas City, Missouri. A 200-foot-wide channel was added in 1925, with both features extended to Sioux City in 1927. In 1945 the design was modified to create a 9-foot-deep and not less than 300-foot-wide channel between Sioux City and the mouth of the river. A variety of engineering works, such as revetment of banks, closing of subchannels, and dike construction to narrow and deepen the main channel, meant a permanent change in riverine wildlife habitat.
Even though the laws were enacted years earlier, the first changes in the character of the Missouri did not begin along the Nebraska-Iowa boundary until 1923 (Hallberg et al. 1979). Project construction that would modify the natural uncontrolled river through major realignment of the channel began in earnest during the mid 1930's in the Nebraska region. Youngworth at this time noted that Least Terns that nested at Sioux City were disturbed not only by construction activity but were expected to move upstream to undisturbed areas. Habitat was still available at alternate sites but eventually, as the Corps of Engineers moved along the river, all available habitat was affected.
The braided character of the channel was engineered into a single navigation channel. An example of this change is at Indian Cave Bend in Richardson County, where pictures taken through the years document channelization (Figure 2). Not only was the river shortened but midriver sandbar and island habitat was lost (Table 1). The Missouri River became at least 58 miles shorter and sandbar habitat was lost entirely from Ponca State Park, Dixon County, Nebraska, downriver to Kansas City, Missouri, due to project implementation from 1923 through 1976. Further upriver, Gavins Point Dam was built in the 1950's to create Lewis and Clark Lake, which inundated additional river habitat.
Figure 2. A series of pictures showing the channelization of the Missouri River at Indian Cave Bend. The 1934 picture is the original, natural river; the other pictures show subsequent changes (photographs courtesy of the U.S. Army Corps of Engineers, Omaha).
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As a result, in the latter historic period Terns would have been limited to nesting in the only portion of the river with suitable sandbar habitat within the channel area and other offriver locations. The only two sites with any record of Tern use were the unchannelized Missouri River from Gavins Point Dam to Ponca State Park and at an upland, open sand area at DeSoto National Wildlife Refuge.
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Table 1. Changes in the channel characteristics of the Missouri River. |
|
Year |
River Miles - Rulo to Niobrara* |
Bar Area Present in Iowa, acres ** |
|
1879 |
-- |
24,547 |
|
1890 |
404 |
35,272 |
|
1923 |
-- |
31, 481 |
|
1941 |
371 |
-- |
|
1947 |
-- |
3,120 *** |
|
1960 |
346 |
-- |
|
1976 |
-- |
57 |
- * Based on U.S. Corps of Engineers information
- ** From Hallberg et al. 1979
- *** Active channel only, which omits cutoff areas
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Terns were observed at Gavins Point Dam from 1959 through the early 1970's. The impression, based on recorded observations, was that the birds were becoming scarce in the area, due largely to development of the nesting site, which measured 900 feet along the beach and 220 feet back from the water line, and was located .25 mile below the dam. The changes noted were that the beaches and sandbars once present were being replaced by swimming beaches, boat ramps, and park-like transformations, with an associated increase in the number of people (Hall 1975).
Numbers recorded at this site were:
- 1959 6 nests
- 1960 immature birds observed
- 1961 1 nest 10+ birds *
- 1962 1 bird
- 1969 1 nest, 4 adults
- 1972 2 birds *
- 1973 2 birds *
- 1974 2 birds *
- * highest count
Two additional records for this areas of the Missouri River were made in 1968. A colony with an estimated 35 birds with 5 nests was found southeast of Vermillion, South Dakota, and 4 nests with eggs were observed west of Elk Point, South Dakota (Harris 1968).
The main feature of DeSoto National Wildlife Refuge is an oxbow lake formed when the channel of the river was cut off. The nesting area used by the Terns was sand beaches along the waters edge and on the inside of the lake. Annual Refuge narrative reports provide the number of birds counted but the only reference to actual breeding activity would be a comment such as "Least Terns again used the large sandbar area for nesting" (Vischer 1980). Peak numbers observed were:
- 1960 40
- 1961 30
- 1963 50
- 1964 75
- 1965 40
- 1966 30 *
- 1967 40
- 1968 25
- 1969 20
- 1970 20
- 1972 15
- 1973 12
- 1974 3
- 1975 4
- * A nest with eggs was found on the beach at the north end of the lake (Cortelyou 1966).
Use of this area declined as vegetation developed on the sandy sites used for breeding, and the numbers reflect this decline. The last year that nesting was believed to occur was 1972.
Platte River
The Platte River was characterized as being a mile wide and an inch deep during the early settlement period in Nebraska. Lewis and Clark wrote that near where the river emptied into the Missouri it was 2 to 3 miles wide in many places, and contained a great number of small islands and sandbars (Thwaites 1969). The central Platte near Grand Island during the period of 1813-57 varied in width from .5 to 3 miles across. Additional documentary evidence provides measurements in the same area that list the width as greater than 1,100 yards prior to 1899, but showing a drastic decrease to about 550 yards in 1899, 330 yards in 1913, and 305 yards in 1919 (Williams 1978). Further west, the North Platte River in the fall of 1845 was merely a succession of sandbars among which the channel was divided into rivulets a few inches deep (Fremont 1845: 77).
Although historic observations beginning in 1804 along the Platte indicate the availability of suitable sandbar habitat within the channel, the first record of Tern occurrence on this river system wasn't until the 1920's.
At this time, Least Terns were found nesting in a colony on sandbars in the South Platte River near North Platte (Tout 1947). Observations made from 1926 through 1929 showed populations were:
- Year - Population - Nests
- 1926 - 34 * - 17
- 1927 nesting
- 1928 - 36 * - 18
- 1929 - 50 - 22
- * based on number of nests found
Terns were also present in 1930, but a terrific storm killed some adults and reduced the colony to about half its former size.
The next observation was in 1941 when birds were found nesting on sandbars in the river near Columbus (Shoemaker 1941). Ten and possibly more nests indicate the colony size was at minimum 20, but the difficulty of telling the difference between Tern and Piping Plover eggs makes the exact number uncertain.
Downriver, in 1943, a single nest, and then young, was found at Merritt's Beach swimming lake, northwest of Plattsmouth (Heineman 1943).
Two miles east of Brule, 6 pair of Terns were found nesting on a sandbar in the South Platte River in 1948 (Benckeser 1948). In 1949 nesting was recorded again on the South Platte River in the North Platte area (Audubon Field Notes 3: 244).
The longest field study of Least Terns on the Platte was carried out by Dr. Ray S. Wycoff, who studied activity south of Lexington for 17 years (Wycoff 1960). The nesting area was a low sandbar not over 75 feet wide and about 200 feet long. Observations made throughout the years include limited population data, dates of arrival and departure, behavioral notes, nesting dates, and how habitat changes forced the birds to move to a different breeding site. Some of the higher populations recorded were: 1949 35; 1950 20; 1953 24; and 1954 25. Vegetative encroachment on the sandbar decreased the suitability of the site, and the birds eventually moved to nearby sandpits to nest. And although observations for the long term study ended in 1959, nesting was observed again in this locality ten years later (Wycoff 1969).
As the Platte River valley was settled and developed, the character of the river changed dramatically. Changes in the flow regime led to narrowing of the water channel and an increase in vegetation, which included growth of woody plants on once open sandbars (Williams 1978, Fish and Wildlife Service 1981). Wycoff noted that following the building of dams along the Platte the river in the vicinity of the colony site became covered with sprouting cottonwoods, willows, and other vegetation (Wycoff 1960). Most of the trees on the floodplains in the central Platte valley developed due to a change in the river flow characteristics and became established after the closure of Kingsley Dam, that was built to create Lake McConaughy (Fish and Wildlife Service 1981).
This decrease in channel size and the plant development on open sandbars meant an extensive decline in the amount of suitable riverine habitats available for Terns along the western and central Platte. Fewer changes took place on the lower reaches of the river, where flow characteristics were less affected by water depletions and construction of dams.
One change that occurred as the river was developed was the extraction of sand for commercial use. The pumping of sand created open sandpit lakes and open sandpiles on the floodplain adjacent to the channel that were used by breeding Terns. Wycoff was the first to observe this shift in habitat use.
Middle Loup River
The only historic record documented were specimens collected during the Warren Expedition that were attributed to the Loup Fork (Coues in Hardy 1975: 11), which would be the Loup River. The exact location was not given in the expedition narrative. on the Middle Loup River, 3 miles south of St. Paul (Short 1966).
Niobrara River
The historic condition of the lower portion of the Niobrara River was described in the 1850's as having a width that exceeded that of the Missouri, with the water spread out over sandbars (Warren 1875).
The first recorded observation on the Niobrara River was in 1902, by an expedition from the University of Nebraska that floated the river from north of Long Pine, Brown County, to Niobrara, Knox County. The first observation of Terns was a flock of 8 to 9 observed near the historic settlement of Badger, in north-central Holt County. From this point on to the town of Niobrara, Terns were very common, being noted every day, and every large bar had birds present. They were said to breed commonly from Badger to Niobrara (Ducey 1983).
During the middle 1950's nesting was recorded 5 miles southeast of Spencer, Boyd County (Short 1966), with an additional notation that Terns were known to breed far out on the Niobrara River in the 1950's period (Youngworth in Hardy 1957: 10). Nesting no doubt took place on a yearly basis on the Niobrara River as suitable habitat was available and there were no major changes that would cause a loss in habitat. This river is still very similar to what it was in the past.
Off-River Sites
Three other historic records of Tern breeding activity were made that were not associated with the typical river system nesting sites used by this species. In 1896 and 1897, 5 nests with eggs were reportedly found on the shore of a nearly 600 acre wetland basin southwest of York (Tout 1902).
Another set of records from a wetland basin were made near Lincoln. In 1920 and 1922 Least Terns were observed at Capital Beach for several weeks during the summer. The dates in 1920 were 20 and 27 June and 4, 18, 25, and 28 July. In 1922 observation dates given were 28 May, 3 June, and 31 July (unpublished field notes of Ralph E. Dawson, Lincoln, located at the Nebraska Hall museum library, University of Nebraska at Lincoln). With birds being present over a period of weeks during the breeding season, this would indicate the Terns were resident and possibly nesting. Piping Plover, which use similar habitat, nested at this same locality in 1922, on sand and gravel spoil from a dredging operation (Pickwell 1925).
A final offriver location was found in 1955. A small colony with at least 6 birds, since 3 nests were found, was present at a small sandpit north of Aurora. Nesting was on a small area of sand, covering no more than a "half block" (Swanson 1956). These three records from two types of locations are unusual in that they are not similar to all the other observations of breeding activity that occurred in riverine habitat or associated lakes.
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Table 2. Summary of historic breeding season occurrence records of the Least Tern in Nebraska. |
|
Map No. |
Year |
Location |
|
Missouri River |
|
1 |
1804 |
Washington County and downstream |
|
2 |
1866 |
Dixon County |
|
3 |
1885 +- |
southeast Dakota Territory |
|
4 |
1893 |
Cut-off Lake (Carter Lake), Douglas County |
|
4 |
1896 +- |
Omaha, Douglas County |
|
5 |
1896 +- |
Peru, Nemaha County |
|
6 |
1915 +- |
south of Vermillion, Clay County, South Dakota |
|
7 |
1920 |
Dakota County |
|
4 |
1928-30 |
Carter Lake, Douglas County |
|
7 |
1929, 31, 32 |
near Sioux City, Woodbury County, Iowa |
|
8 |
1933 +- |
Pottawattamie County, Iowa |
|
9 |
1934 |
Monana County, Iowa |
|
10 |
1934 |
southwest of Anthon, Woodbury Co., Iowa |
|
11 |
1936 |
north of Decatur, Thurston County |
|
12 |
1937 |
near Arizona, southeast Burt County |
|
13 |
1960 +-, 1969 |
below Gavins Point Dam, Cedar County |
|
14 |
1966-72 |
DeSoto NWR, Washington County |
|
6 |
1968 |
southwest of Vermillion, Clay County, S.D. |
|
3 |
1968 |
west of Elk Point, Plymouth County, S.D. |
|
Platte River System |
|
15 |
1926-29, 30 |
common breeder in Lincoln County |
|
16 |
1941 |
near Columbus, Platte County |
|
17 |
1943 |
Northwest of Plattsmouth, Cass County |
|
18 |
1948 |
S. Platte River near Brule, Keith CountyCounty |
|
15 |
1949 |
S. Platte River near North Platte |
|
19 |
1948-59, 69 |
south of Lexington, Dawson County |
|
Loup River System |
|
--- |
1855 +- |
collected on Loup River, no locality given |
|
20 |
1955 |
south of St. Paul, Howard County |
|
Niobrara River |
|
21 |
1902 |
Holt and Knox counties area |
|
22 |
1955 |
southeast of Spencer, Holt County |
|
--- |
1955 |
breed well out on the river, no localities given |
|
Off-river Sites |
|
23 |
1896-97 |
near York, York County |
|
24 |
1920, 22 |
near Lincoln, Lancaster County |
|
25 |
1955 |
north of Aurora, Hamilton County |
|
+- general period instead of actual year |
Summary
The historic breeding range of the Least Tern included the entire stretch of the Missouri River along the state's eastern boundary, the Platte River (including portions of the North and South Platte rivers), the Middle Loup River, and about 75 miles along the lower portion of the Niobrara River (Table 2, Figure 3).
Major losses of nesting habitat were a result of channelization of the Missouri that destroyed all midriver sandbars below Ponca State Park, and changes in the flow regime that reduced channel size and increased riverine vegetative growth along the Platte. No major changes have occurred along the Loup and Niobrara rivers. Overall, there has been a marked decline in the availability of suitable habitat within the breeding range of the Least Tern In Nebraska, which would have caused an associated reduction in populations. Differences in distribution are especially apparent when the historic period of record from 1804 to 1975 is compared to modern survey efforts and records (Ducey 1981).
Literature Cited
Agersborg, G.S. 1885. The birds of southeast Dakota. Auk 2: 289.
Benckeseer, H. R. 1948. Notes from Brule. Nebraska Bird Review 16: 94-96.
Bennett, W.W. 1934. Miscellaneous unpublished Missouri River waterfowl refuge project reports. Prepared by the Iowa State Planning Board for the Iowa Fish and Game Commission.
Cortelyou, R.G. 1966. Cornell nest record card. Cornell Laboratory of Ornithology. Ithaca, New York.
Downing, R.L. 1975. Details of interior least tern survey. 10 pp. Unpublished manuscript.
Downing, R.L. 1980. Survey of interior least tern nesting populations. American Birds 34: 209-211.
Ducey, J.E. 1981. Interior least tern Sterna albifrons athalassos. U. S. Fish and Wildlife Service, Pierre, South Dakota. Unpublished report. 56 pp.
Ducey, J.E. 1983. Notes on the birds of the lower Niobrara valley in 1902 as recorded by Myron H. Swenk. Nebraska Bird Review 51(2): 37-44.
Dumont, P. 1933. A revised list of the birds of Iowa. University of Iowa Studies in Natural History 15: 1-71.
Fish and Wildlife Service. 1981. The Platte River ecology study. Fish and Wildlife Service Special Research Report, Jamestown, North Dakota. 187 pp.
Fremont, J.C. 1845. Report of an exploring expedition to the Rocky Mountains. Washington, D.C. 693 pp.
Haecker, F.W. 1937a. The eastern least tern breeding in Thurston county. Nebraska Bird Review 5: 9.
Haecker, F.W. 1937b. The eastern least tern breeding in Burt County. Nebraska Bird Review 5: 110.
Hall, W. 1975. Personal communication to the Fish and Wildlife Service. Pierre, South Dakota.
Hallberg, G.R., J.M. Harbough, and P.M. Wittinok. 1979. Changes in the channel area of the Missouri River in Iowa, 1879-1976. Iowa Geological Survey; Special Report Series Number 1, 32 pp.
Hardy, J.W. 1957. The least tern in the Mississippi valley. Michigan State University Biological Series 1(1). 60 pp.
Harris, B.K. 1968. Nesting records for the least tern and piping plover. South Dakota Bird Notes 20: 70-71.
Heineman, L.D. 1944. Nesting of the piping plover and least tern in Cass County. Nebraska Bird Review 12: 9-10.
Missouri River Commission. 1892-1895. Map of the Missouri River from its mouth to Three Forks, Montana. 83 pp. and 9 pp. index.
Moser, R.A. 1940. The piping plover and least tern nesting in Omaha. Nebraska Bird Review 8: 92-94.
Moser, R.A. and F. W. Haecker. 1941. The piping plover returns to its nesting site in Omaha. Nebraska Bird Review 9: 14-15.
Orr, W.J. and J. C. Porter. 1983. A journey through the Nebraska region in 1833 and 1834: from the journals of Prince Maximilian of Wied. Nebraska History 64(3): 325-453.
Pickwell, G. 1925. Some nesting habits of the belted piping plover. Auk 42:326-332.
Shoemaker, F.H. 1941. Notes on nesting least tern and piping plover. Unpublished field notes. 1 p.
Short, L.L., Jr. 1966. Notes on birds distribution in the central plains. Nebraska Bird Review 29: 2-22.
Stephens, T.C. 1957. The birds of Dakota County, Nebraska. Nebraska Ornithologists' Union Occasional Paper #3. 28 pp.
Stiles, B.F. 1938. Nesting of the least tern in Iowa. Wilson Bulletin 50: 61.
Stiles, B.F. 1939. The least tern in Iowa. Iowa Bird Life 14: 18-21.
Swanson, K.S. 1956. Least tern nests near Aurora. Nebraska Bird Review 24: 25.
Thwaites, R.G. 1969. Original journals of the Lewis and Clark expedition. Arno Press. New York. Vol. 1 and 6.
Tout, W. 1902. Ten years without a gun. Proceedings of the Nebraska Ornithologists' Union 3: 42-45
Tout, W. 1947. Lincoln County Birds. Privately published. 191 pp.
Vischer, S.S. 1915. Birds of Clay County, South Dakota. Wilson Bulletin 3: 321-335.
Visscher, L. 1980. Interior least tern, DeSoto NWR. Fish and Wildlife Service memorandum.
Warren, G.K. 1875. Preliminary report of explorations in Nebraska and Dakota in the years 1855-56-57. Government Printing Office, Washington, D. C. 125 pp.
Williams, G.P. 1978. The case of the shrinking channels - the North Platte and Platte Rivers in Nebraska. Geological Survey Circular 781. 48 pp.
Wycoff, R.S. 1960. The least tern. Nebraska Bird Review 38: 39-42.
Wycoff, R.S. 1969. Cornell nest record card. Cornell Laboratory of Ornithology. Ithaca, New York.
Youngworth, W. 1930. Breeding of the least tern in Iowa. Wilson Bulletin 42: 102-103.
Youngworth, W. 1931. The American egret and least tern in South Dakota. Wilson Bulletin 43: 309-310.
Youngworth, W. 1932. Field notes from Sioux City, Iowa. Auk 49:494.
