Dismal Years for Least Tern and Piping Plover Along the Middle Niobrara River

Portion of a sandbar used by Least Terns and Piping Plovers on the Niobrara National Scenic River. All images courtesy of the National Park Service office, Valentine.

By James Ed. Ducey. This article contains biological opinions of the author.

The number of Least Tern and Piping Plover present this season along the scenic river stretch of the Niobrara River was the lowest number recorded in the past twenty years.

Only four tern and six plover were noted during June and July surveys, according to a report from the National Park Service office in Valentine.

Heavy rains and subsequent higher water flows along the river may have washed away any nesting attempts. Weather related events also decimated river colonies last season.

The endangered Least Tern and threatened Piping Plover occupy variable sized, shifting sandbars each breeding season to scrape a small depression of a nest , then lay eggs and raise some young as they have for centuries.

The Niobrara valley is a challenging environment. Weather and rampaging water in a valley of different overall widths can result in flood flows that will wash away any nests, eggs or young on the sandbars elevated just inches above the river's usually languid surface. High water from heavy rains inundate the channel. Flood flows also shift river sediments that can modify and create suitable sandy bars habitat, with but a bit of vegetative growth.

Roaming predators and unconfined livestock from adjacent pastures can be a negative influence on colony sites for terns and the little brown plovers.

The species' recorded history for the Niobrara River extends back more than 100 years. Both species are first known from bird field notes from the Niobrara during the 1902 breeding season. Along the river south of Springview (now on Highway 183) were four Piping Plover, two of which were collected by scientists. A nest was found on June 21st; said nest with three known eggs then empty on June 25th. These plover "were noted commonly throughout the trip," down the river, said the bird journal of by professor Myron H. Swenk, along on an expedition from the University of Nebraska-Lincoln.

"The Least Tern was not observed until on August 4, when a few miles west of Badger we met with a flock of eight or nine flying about over the shallows. One male specimen was secured. From this point on to Niobrara it was very common, being noted every day, and every large bar was certain to have several of the little fellows hovering about, uttering their harsh, squeaky notes as they plunged into the shallows or chased each other about in the air. On one occasion one was seen flying straight towards a large bar with food in its mouth. Although lack of time prevented any stopping to search for nests, I have little doubt but that it breeds commonly on the large bars in that locality," the narrative said.

The active Badger postoffice was once near Big Sandy Creek, at the river in northwest Holt county.

Bird Surveys

Aerial views provided the results for the first surveys - starting in 1977 - and counting from Mariaville to Spencer Dam, and further east along the river course. These were continued by the Nebraska Game and Parks Commission for many years. Since 2002, numerous riverine surveys have been conducted by biological technicians of the National Park Service, along the Niobrara National Scenic River. These are the detail surveys now conducted.

Results of surveys for Least Tern and Piping Plover on Niobrara National Scenic River segments. Information courtesy of the Nebraska Game and Parks Commission, and National Park Service.
Date - Survey Segment	Least Tern	Piping Plover
1982, July 14 - Highway 183 to Meadville	25 adults	8 adults
1983 - Highway 183 to Meadville	7 adults on 13 July; 4 on 19 July; and 2 on 26 July	2 adults on 13 July; 5 on 19 July
1984, 22 June - Mariaville to Highway 183	10 adults	6 adults
1985 - Mariaville to Highway 183	16 adults and six nests on 4 June; 3 adults on 23 July	10 adults and 5 nests on 4 June; 20 adults on 23 July
1987, 9 June - Mariaville to Highway 183	10 adults and 3 nests	8 adults and 2 nests
1996 - 5 June - Highway 183 to Meadville - 18 and 20 June - Mariaville to Hwy 183	- 2 adults - 3 nests on 18 June and 2 adults on 20th	- 4 adults - 2 nests with eggs on 18 June and 1 adult
2001, 5 June - Highway 183 to Meadville - Mariaville to Highway 183	- 2 adults - 13 adults at four sites	- 4 adults - 6 adults at two sites and a nest with eggs
2002 - Highway 183 to Highway 7 - Highway 7 to Carns Bridge - Carns Bridge to Highway 137	- 6 adults and 3 nests - 4 adults - 4 adults	- 6 adults and 2 nests - 5 adults and 1 nest - 2 adults and 1 nest
2006 - 13-25 June - Highway 183 Bridge to Highway 7 Bridge - 12 June to 7 July - Carns Bridge to Highway 137	- colony 1 with 16 nests; colony 2 with 5 nests - 11 nests	- colony 1 with 9 nests; colony 2 with 4 nests - 6 nests
2007 - Highway 183 to Highway 7 - 22 June: - 27 June: - 6 July:	- 4 adults and nest with eggs - 2 adults - 2 adults	- 6 adults and nest with eggs - 6 adults and two additional nests, 3 fledged chicks - 6 plovers, 3 chicks
* Numbers given represent the highest seasonal count.

The count numbers for 2007 are exceptionally less, being the least number seen in any of the years with available survey results. There is no exact reason for this loss, according to Park Service staff.

Extensive rainfall from several early storms during the breeding season may have influenced the nesting by these species.

On May 5th a slow moving system dumped some rain, giving Valentine a record rainfall exceeding 1.25 inches. Tornadoes were reported, with hail prevalent. Ainsworth reported 4.3 inches in town and 5.83 inches elsewhere that washed out county roads.

Showers and thunderstorms brought a rainfall of 3.44 inches to Ainsworth on May 30th. Valentine had 1.73 inches.

On June 12th, another intense weather system moved through the Niobrara valley. Rainfall measured 1.97 inches at Valentine. O'Neill had 1.92 inches. Atkinson had a report for 1.62 inches. A flash flood watch was issued for the 13th, as showers continued. Weather reports indicated wide-spread 1-2" rainfall reports throughout the drainage of the Niobrara.

Another extensive storm accompanied by large hail hit the region on June 21st.

The magnitude of precipitation from these storms likely flooded the channel of the Niobrara River, with an influx from some tributaries adding to the flows. These weather events may have had an impact on the bird nests on the riverine sandbars inundated by higher water flows.

Least Tern nest along the Niobrara River.

Piping Plover nest along the Niobrara River.

The primary nest initiation dates for the Least Tern in 2006 were during June to early July, according to the Park Service survey report. For Piping Plover the period extends from latter May to early July.

Flooding may have been a recurring event during the breeding season, resulting in the low population when an initial survey was done in latter June.

Summary of number of birds surveyed along the scenic river section of the middle Niobrara River.
Year	Least Tern	Piping Plover	Notes
1982	25	8	aerial survey
1983	7	5	aerial survey
1984	10	6	aerial survey
1985	16	20
1987	10	8	aerial survey
1996	5	4
2001	15	10
2002	14	13	An adult and a juvenile Least Tern were at Cornell Dam in late July
2006	32, 22	18, 8	Highway 183 Bridge to Highway 7 Bridge, and Carns Bridge to Highway 137
2007	4	6	Three plover chicks fledged; defensive adult terns but no actual nesting success noted

Several large sandbars which appeared suitable for use by terns or plovers, did not have either, according to the season's summary report. At a colony location near Carns, "4-wheeler tracks criss-crossed the sandbar" that seemed promising for tern or plover use, the survey report said. There were 25 Killdeer present. Elsewhere, including between the Carns Bridge and Highway 137, a large number of Killdeer were present, raising the question if this species was out-competing the tern or smaller plover.

In 2006 on another obviously suited sandbar, the species showed the largest numbers recorded for these species within the scenic river section. Habitat had to be expansive enough for the many sites used for nesting. The counts indicate the extent of birds that can occur when there is exceptional, suitable habitat. Fewer Least Tern could be expected where there is a lesser extent of suitable sandbars habitat.

Piping Plover would be influenced by the river factors that create suitable habitat.

During the 2006 season, a smaller colony on the segment Highway 183 Bridge to Highway 7 Bridge was affected by two influences. The "sandbar experienced several weather events and cattle damages that led to multiple re-nest attempts by both species," according to the survey report. There was a large colony along the Carns Bridge to Highway 137 stretch, with 11 tern nests and 6 plover nests. "A large rain event wiped this colony off the river in early July."

Notable are the 1982 numbers for a colony on the river a few kilometers east of Meadville. Activities at this lively breeding place were gathered during avifauna studies in 1983 for the Niobrara Valley Preserve, after it was established. The colony had several plover nests and more than 15 chicks noted on July 22nd. There were nests with 3 eggs, chicks and a flying fledgling for the Least Tern on July 24th. The sandbar here was apparently very suitable habitat.

Survey results indicate there are usually fewer tern and plover during recent breeding seasons. There are enough exceptions to these lesser counts for larger numbers. There are no apparent trends or obvious population level represented. The numbers seem to highly variable to determine an average. The numbers do suggest a regular population of more than 15 Least Tern could be expected from the Highway 183 Bridge to east of Meadville. There could a similar number of Piping Plover. Habitat has more limitations in this region than further down the river, and is possibly the greatest limiting factor along the river.

Other facets which may have a role in the occurrence of these two species along the Niobrara, may include the extent of habitat along the Missouri National Recreation River influencing the bird's use of the running water tributary. Do fewer birds occur on the Niobrara when habitat is more prevalent on the wide variety of Missouri river sandbars?

Extensive and detailed Least Tern and Piping Plover surveys are conducted on the MNRR each season by Corps of Engineer staff.

Niobrara Tern and Plover Populations

The Niobrara River population of Least Tern and Piping Plover is highly variable, based on a summary of some survey results from aerial counts, and recent ground-based investigations.

Populations for the Niobrara River. Given is a summary of values recorded for multiple segments, sometimes with multiple entries referring to a colony locale. These estimates are based on several accounts added together to furnish an approximate total for the river. Detail survey information is courtesy of the Nebraska Game and Parks Commission and National Park Service.
Survey Information	Least Tern	Piping Plover
1977, 30 June - Mariaville to Spencer Dam	7	4
1978, 27-29 June - mouth to Mariaville	40	44
1979, 17 and 26 July - mouth to Highway 183, and westward from Meadville	45	No count data
1980, 13-14 July - mouth to Highway 183	82	No count data
1981, 5-7 July - Pischelville to Highway 183	87	92
1982, 1-2 and 13-14 July - mouth to Meadville	80	19 in partial count
1983, 20-22 June - mouth to Highway 183; mid-July, Highway 183 to Meadville	106	59
1984: 19-22 June - mouth to Highway 183	142	38 in partial count
1985 30 May - mouth to Mariaville 4-6 June - mouth to Highway 183 23-25 July - mouth to Highway 183	- 79 - 183 - 110	- NA - 114 - 60
1987 9-11 June - mouth to Highway 183 6-19 June - mouth to Mariaville 13-15 July - mouth to Highway 183	- 115, with more than 50 nests - 109 - 68	- 98, with more than 55 nests - 85 - 91 with nests and chicks
1988 14-16 June - mouth to Mariaville 19-20 July - mouth to Mariaville	- 181, more than 80 nests - 124, with 47 chicks noted	- 83, with more than 35 nests - 54, with 22 chicks noted
2001, 5-8 June - mouth to Meadville	148, with about 40 nests	88, with about 25 nests
2007 - 22 June - Highway 183 to Highway 7 - Lower Niobrara River	- 4 - 33	6 - 19

Counts doing using consistent survey methods in recent years has improved the means for devising the river's population of these two species. Populations can readily exceed 125 Least Tern and 75 Piping Plover, with greater numbers when suitable habitat conditions are more prevalent.

Niobrara River locales.