Location and Habitat Size of Sandhill Lakes Used by Swans

Scattered among the vast grassland expanse of the Nebraska Sandhills are numerous lakes and marshes that are breeding habitat for an interesting diversity of nesting waterbirds, including the Trumpeter Swan, the largest of the North American waterfowl.

Before the turn of the century this swan was reported as a breeding bird on Watt's Lake, southwest of Valentine in Cherry Co. (Bates 1900), and was considered to have probably once bred at many lakes throughout the Sandhills region (Bruner 1904).

Trumpeter Swans as nesting birds were eventually extirpated from the lakes and marshes, due to indiscriminate shooting and disturbance, as the Sandhills were settled. Reintroduction efforts undertaken during the 1960's were required to return breeding Swans to Nebraska. Birds released at Lacreek National Wildlife Refuge in South Dakota eventually became established and a portion of this growing population entered the state to once again nest (Monnie 1966).

Since that time the population status of the Trumpeter Swan, as well as other breeding ducks and geese, has been evaluated during an annual waterfowl survey carried out to compare yearly trends (pers. comm., Rolf Kraft, U.S. Fish and Wildlife Service, and John Sweet, Nebraska Game and Parks Commission). During these aerial surveys the lakes where Swans are observed and possibly breeding are recorded.

In order to assess the characteristics of the different lakes where Swans were present during the breeding season, an analysis of satellite imagery was undertaken to evaluate the relative amount of water and marsh habitat.

The habitat maps used to figure the amount of open water or marsh are available at the Remote Sensing Analysis Laboratory of the University of Nebraska at Omaha. This laboratory has prepared an inventory of the location and size of wetlands for the Omaha District of the U.S. Army Corps of Engineers. The survey used picture elements from the scanner system of the Landsat Satellite to classify four wetland types: open water, marsh, subirrigated meadows, and riparian wetland. Any area inundated by surface or groundwater frequently enough to support vegetation adapted to survive in water-saturated soil was identified and mapped on a mylar overlay the size of the relevant U.S. Geologic Survey 7.5 minute quadrangle map (Turner et. al. 1980).

These overlays were used to measure the amount of open water or marsh at the Sandhills lakes where Trumpeter Swans had been observed. A measuring device connected to a Numonics Electronic Digitizer/Planimeter was traced around the elements designated by the survey. The area of open water or marsh could be determined in this fashion and the size in acres was then easily converted to hectares.

Alkalinity data was included because of the impact it has on the vegetation of the marsh plant community. This information is from a conibrehensive study of the lakes in the region (McCarraher 1977).

Results

The 23 lakes utilized by Trumpeter Swans occurred primarily in Cherry, Sheridan, and Garden counties (Figure 1, Table 1). They ranged in size from 12 hectare (ha) West Cottonwood Lake up to 253 ha Alkali Lake. Nineteen of the 23 were from 23 to 103 ha in size. West Cottonwood was exceptionally small. The average size was 72 ha. Omitting the lowest and the 3 highest overall size values (those over 103 ha) gave an average size of 56 ha.

Figure 1. Locations in the sandhills region where Trumpeter Swans have been observed during the breeding season.

All of the lakes, except for Hoover, had greater than 56% open water. The range was from the low value of 32% at Hoover Lake to 89% at the two Alkali Lakes in Cherry Co. The average amount of open water was 76% for all 23 lakes.

Open water habitat in the Sandhills has been classified as a submersed aquatic zone. This zone, which is one of three possible wetland zones, is characterized as open water containing floating and submerged aquatic vegetation. Representative species include common duckweed (Lemna minor), star duckweed (Lemna triscula), sago pondweed (Potamogeton pectinatus) and common bladderwort (Urticularia vulgaria) (Gilbert et. al. 1980). Yellow water lily is an additional floating aquatic plant that is present.

Marsh was much less extensive than open water at the lakes, with only about one-fourth the amount of the total surface area. The values ranged from 11% to 68%, with an average of 24%. The marsh area has two plant zones. Dominant plants of the inner marsh zone are hardstem bulrush (Scirpus acutus), duckweed (Lemna spp.), and arrowhead (Sagittaria spp.). Also found in this zone are common cattail (Typha latifolia), river bulrush (Scirpus fluviatilis) and giant burreed (Sparganium eurycarpum). The outer marsh zone has a highly variable plant composition of hydric grasses and sedges and an interspersion of mesic and zeric species from the marsh and neighboring upland plant community (Gilbert et. al. 1980).

Of the 21 lakes for which alkalinity is known, 12 (57%) are slightly alkaline, 1 (5%) is moderately alkaline, and 8 (38%) are of medium alkalinity.

Table 1. Habitat characteristics of sandhill lakes where Trumpeter Swans have been observed during the breeding season.
Map Site. No.	County	Habitat Size (Hectares)					Water Chemistry
	Lake Name and Location	Marsh	%	Open Water	%	Total	Alkalinity 1
	Garden
1.	Gimlet (T21N R44W)	12	38	20	62	32	slight
1.	Black Steer (T21N R43W)	14	17	68	83	82	slight
1.	Miller (T22N R43W)	12	32	25	68	37	moderate
	Sheridan
2.	Spade Ranch (T27N R41W)	17	20	70	80	87	medium
3.	Dolly Warden (T28N R42W)	9	35	17	65	26	medium
3.	Round (T28N R42W)	7	20	28	80	35	medium
4.	Frye (T35N R41W)	11	22	40	78	51	slight
4.	Hoover (T35N R41W)	36	68	17	32	53	slight
	Cherry
5.	Alkali (T34N R40W)	20	11	157	89	177	medium
5.	South Twin (T33N R39W)	15	36	27	64	42	medium
5.	Spall (T35N R39W)	13	39	20	61	33	slight
6.	Cody (T35N R33W)	37	23	125	77	162	slight
7.	Wolf (T29N R35W)	8	22	28	78	36	slight
7.	Home Valley (T29N R37W)	13	13	84	87	97	no report
7.	West Cottonwood (T28N R38W)	3	25	9	75	12	medium
8.	Rat (T29N R39W)	12	28	31	72	43	slight
8.	Fawn (T28N R39W)	6	26	17	74	23	slight
8.	Turpin (T28N R39W)	16	30	38	70	54	slight
9.	Alkali (T26N R39W)	28	11	225	89	253	medium
9.	School Section (T26N R40W)	38	37	65	63	103	slight
9.	Castle (T25N R39W)	25	25	76	75	101	slight
10.	Twenty-one (T29N R27W)	32	43	42	57	74	slight
	Brown
11.	Amer. Game Assoc. (T27N R24W)	10	19	42	81	52	no report
	Total	394	24	1271	76	1665
1. Data from McCarraher, 1977

The higher values for the amount of open water would seem to indicate that this lake characteristic may have more of an influence on use by Trumpeter Swans than the extend of marsh vegetation. Also, Swans were recorded more often on lakes that had only slight alkalinity.

Acknowledgements

I would like to thank John Sweet and Rolf Kraft for providing the lake names and locations.

Literature Cited

Bates, J.M. 1900. Additional notes and observations on the birds of northern Nebraska. Proceedings of the Nebraska Ornithologists' Union 1: 15-18.

Bruner, L., R.H. Wolcott, and M.H. Swenk. 1904. A preliminary review of the birds of Nebraska. Klopp and Barlett Co., Omaha, Nebraska. 116 pp.

Gilbert, M.C., M.W. Freel, and A.J. Bieber. 1980. Remote sensing and field evaluation of wetlands in the sandhills of Nebraska. U.S. Army Corps of Engineers, Omaha, Nebraska.

McCarraher, D.B. 1977. Nebraska's sandhills lakes. Nebraska Game and Parks Commission, Lincoln, Nebraska. 67 pp.

Monnie, J.B. 1966. Reintroduction of the trumpeter swan to its former prairie range. Journal of Wildlife Management 30: 691-696.

Turner, J.K., D.C. Rundquist, A. Bieber, and L.C. Hamilton. 1980. Wetlands inventory of the Omaha District. Final Report, U.S. Army Corps of Engineers. Omaha, Nebraska. 110 pp.

March 1984. Location and habitat size of lakes in the Nebraska sandhills utilized by trumpeter swans. Nebraska Bird Review 52(1): 19-22.

Vehicular Pursuit of Fishowls in Eastern Russia

In relentless pursuit, a hearty rig filled with chasers moved steadily across the wild and mysterious lands of eastern Russia. The men within were searching for data, the grail of research findings.

The blue Kamaz was driven rough deep snows and to frozen rivers. The crew within included gear, fare and endless thoughts of some pairs of Blakiston’s Fish Owl (Bubo blakistoni).

Reports from the wilderness were recently issued that revealed the drama and times after these owls which feed in fish from rivers such as the Tunsha or Amgu Rivers, in the Primorsky Krai district, or Primorye, a federal subject of Russia.

It is a tale of owl research and high-tech trackers that denoted the neighborhood used by a breeding pair of the birds under study, under the direction of Jonathan C. Slaght, with field research just completed, and reported in three updates available at a Fish Owl's home on the web.

Traveling among the places in wintry March, a trusty vehicle, brand name Kamaz - new this season to owl research crew - made every destination and returned safely to base. It was the place for the researchers to dwell while making to owl territories and tempting the owls with an easy catch. Again and again.

The trackers were recovered, and the birds are back flying free, after providing newly discovered details on range and habitat for the mighty-big owls.

These are some images of the great Kamaz, courtesy of Jonathan C. Slaght from his recent research, and used with his permission.

Kamaz, taken in the middle of February 2010, on the bank of the Amgu River, on the outskirts of the village Amgu.

Kamaz, taken in late March 2010, on the 23rd, probably on the bank of the Tunsha River, about 20 kilometers north of Ternei, Russia.

Slaght is now writing reports, dealing with the relics of business from the research trips. Next comes analysis of the myriad of gathered data, he said in an email. He hopes to achieve his PhD. by the end of 2010.

"The Wild Russia series that aired on Discovery and Animal Planet channels in the United States (and National Geographic channels elsewhere) is shipping 11 May 2010. The Primorye episode features footage of several of our fish owl study animals, including Avdei and Manya of Saiyon Territory, and Genri and Yanna of Mineralnaya Territory." - J.C. Slaght, www.fishowls.com

Climate Change and Birds Audubon Presentation

Retired meteorologist John Pollock gave a presentation on climate change and how it may affect birds at the April 8th monthly meeting of the Audubon Society of Omaha.

The talk - Climate Change: It's Not for the Birds - was based on his recent investigations into climate change, and the hour-long presentation gave detailed information depicting how climate change is known to be occurring.

His presentation was well presented and vividly conveyed how science is being used to understand dramatic changes to the global climate. Slides included many graphs and figures, essential to showing the climatic situation.

Especially useful examples included these specifics:

• Changes in global temperatures since the early 1800s.
• Changes in the concentration of Carbon Dioxide in the atmosphere: the atmospheric level was about 315 ppm in 1958, 385 ppm in 2007 and based on projections may exceed 500 ppm before A.D. 2100. The levels of this gas, have a huge impact on weather and temperature, according to solid scientific studies.
• Climatic change depicted by research on conditions thousands of years in the past, including studies of ice cores and tree rings.
• How biome shifts will change as climatic conditions differ; this would include shifts in elevation for plants or animals, changes to the conditions of islands due to differences in sea levels, how refugia for species can be altered, and the dramatic influence of global scale differences caused by changes in ice sheets or glacial conditions.

The influence of volcanic eruptions was also a topic of discussion.

Based on the research their is the possibility "twenty-first century CO2 levels resemble the early Miocene period," of about 3.2 million years ago, Pollock mused during the discussion among the more than 35 people attending.

Illustrated during the presentation were results from long-term studies indicating dramatic fluctuations in climatic conditions.

As climates change - with variable temperatures and precipitation - vegetation adapts and will significantly respond to the growing conditions, which can alter the range suitable for animal species dependent on particular vegetation for their survive.

Most of the details he presented to the members of the local conservation group were about the climate, but Pollack finished up with some details pertinent to birds.

Shifts in the ranges of birds can occur for several reasons, Pollock indicated, including changes in the distribution of vegetation, habits of birds which may pioneer into new areas and change the known range of a species, new behavioral strategies, to cite some examples.

Negative influences of a warming climate apparent to Pollock were: vanishing islands, inundated deltas of rivers at the sea coast, influences of invasive species, impacts from large regions of human disturbance, shrinking or vanishing biomes.

"Changes are probably on the way," Pollack said. "We don't know when drastic climate changes will take place," but they can be expected.

Pollock urged some conservation strategies to help lessen the impacts to birds because of differences in habitat as the climate changes. He also did not expect to see efforts made to address this issue, and pondered if a climatic disaster was necessary to change the political climate enough for people to become concerned with the issue to make the changes necessary to reduce the human impact on the environment.

Pollack plans to continue his efforts to educate people about climate change. He retired early in 2009, after working for the National Weather Service since 1978 and now gives particular attention to researching climate change. Before he started his career, John Pollack received a B.S. and M.S. degree in meteorology.

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The 2010 State of the Birds report was recently released, with its entire content a discussion of climatic influences on wild birds. The report "shows that climate changes will have an increasingly disruptive effect on bird species in all habitats, with oceanic and Hawaiian birds in greatest peril."

"Climate Science Centers will help support a network of new Landscape Conservation Cooperatives that will engage federal agencies, tribal, state, and local governmental and non-governmental partners, and the public in crafting practical, landscape-level strategies for managing climate change impacts on land, natural, and cultural resources within the eight regions."

The 32 report includes key findings and was a cooperative project by numerous agencies and NGO's involved with bird conservation.

Analysis of Trumpeter Swan Habitat Underway for Greater Yellowstone Region

Research is currently underway in the Yellowstone National Park region to understand habitats features of breeding habitat available for the majestic Trumpeter Swan, the largest swan in the world.

Laura Cockrell - a Master's program student at the Department of Biological Sciences of Eastern Kentucky University - is evaluating the "Historical Nest Site Use by Trumpeter Swans in the Greater Yellowstone Ecosystem."

The study revolves around the use of LANDSAT imagery in an "attempt to find ideal Trumpeter Swan nesting habitat based on the spectral reflectance" shown by the aerial images of habitat conditions, Cockrell said. This analysis includes a comparison of recent and historic images to "determine if the satellite images can be used to detect changes in the habitat over time. We are trying to see if the LANDSAT images can determine habitat features that have changed over time, which would cause the swans to abandon previously used nesting sites."

Laura Cockrell, with Grizzly Lake (one of our territories sampled) in the background. Images courtesy of Laura Cockrell.

Laura Cockrell, in an orange safety-vest worn when sampling in the eye of the public; in this case, along the roadway where Pelican Creek meets Yellowstone Lake.

"I plan to discern differences between historically used ponds and currently used ponds, and to identify local and landscape-level features that may have changed over the years and influenced the nesting preference and success of breeding Trumpeter Swans," Cockrell said in her research proposal. Information derived from the satellite imagery will be further evaluated, based on on-site evaluations conducted during the field studies phase of her research, that will include measuring vegetation, food availability, distance from the nesting pond to nearby ponds, water quality and an evaluation of the extent of lead present at nesting sites.

"The Yellowstone nesting population of Trumpeter Swans has decreased a great deal in the last few years, to the point that only three pairs of Trumpeter Swans occurred in the park" in 2009, with only one pair attempting to nest, she explained in an email.

"Although it has been long thought that the population that is nesting within the park is a sink population, which relies on populations in higher quality habitat outside of the park as the source population, there is still an interest - primarily fueled by bird watchers - in why the Yellowstone Park nesting population has declined."

Weather is a prominent, potential factor.

"Currently the Palmer Drought Severity Index shows that the Greater Yellowstone Region has been in an extended drought, which is likely a factor in the decline. Nesting populations outside the park have also recently seen reductions in nesting attempts as well as cygnets produced."

During July this year, Cockrell, and Matt Manuel, the research assistant, traveled to Yellowstone to sample habitat characteristics of sites historically used by Trumpeter Swans. Line transects were used to evaluate aquatic vegetation in 16 former swan territories, she said. The next onsite visit will be during late August and early September, 2010, when 20 territories can hopefully be sampled.

"I am using the UTM coordinates of line transects to determine the reflectance characteristics of the LANDSAT images and evaluate whether the LANDSAT reflectance is capable of determining" the suitability of the habitat for swans.

By mapping nesting locations and characteristics of "used" versus "potential" habitat, her research can be used to identify potential nesting sites. This information is expected to be a "valuable tool" for achieving objectives for management of the Trumpeter Swan in the Greater Yellowstone ecosystem.

An example of LANDSAT imagery showing Trumpeter Swan habitat. This is an image of the "undisclosed location" where the swans attempted to nest during the summer of 2009.

If the research works as planned, "it will allow the park an easy method to track the quality of nesting locations," she said. "As the park does not actively manage for wildlife, but instead attempts to have a 'hands-off' approach to allow nature to take its own course, no management efforts are in place to improve or create nesting sites within the park. If conditions continue to change in an unfavorable manner, it is possible that resident swans could leave the park entirely, however this tool could help park biologists to monitor locations for potential future nesting swans. We certainly hope that natural conditions will change in time that the swans will again be successful within the park, however we cannot predict how the conditions will change.

"If this tool does work, managers of areas outside the park (e.g. Red Rocks Lake NWR) can use it to locate suitable nesting habitat, as well as locating suitable habitat outside of managed areas that could potentially be preserved. As the park population is thought to be a 'sink' population, with the breeding population outside the park as the 'source'. If these sites can be located and managed appropriately, there will be a greater number of swans looking for potential breeding sites in the future, and hopefully moving back into the park as conditions improve.

"As the Greater Yellowstone Ecosystem is linked as a whole, it will be beneficial to evaluate these locations and protect them from development or degradation. The trumpeter swan was brought to the brink of extinction, and the Greater Yellowstone population has been critical in bringing the entire trumpeter swan population back to stable levels. Through management efforts within the GYE, we are now seeing relocation and breeding efforts in the US and Canada trying to restore populations in historical areas, including much of the mid-west. If we can fine-tune this tool to locate these ideal sites, it could potentially assist agencies who are attempting to find suitable relocation sites for their population restoration efforts.

Her biological research with the Trumpeter Swans is a continuation of Cockrell’s interest in studying waterfowl, which started with a college course.

"I became interested after working in my undergrad at California State University, Chico (my hometown college) where I took a natural History course on waterfowl from Jay Boggiatto, Cockrell explained. Under Professor Boggiatto, "I worked on a wintering ecology project with American and Eurasian Wigeon, as well as working for the California Department of Fish and Game, monitoring for waterfowl die-offs during the winter and Wood Duck monitoring during the spring and summer. I also worked for the California Waterfowl Association banding ducks in the Sacramento Valley."

The swan project was started by her adviser, Dr. Robert Frederick, whom did work similar to this during a sabbatical in 2006, working with Rick Sojda from the United States Geological Survey. "My graduate work is a continuation of the work that he began which originated by trying to find appropriate wintering locations for trumpeter swans in the Greater Yellowstone Ecosystem."

A trumpeter swan research sign posted in the Targee National Forest, just south of Yellowstone Park.

An "undisclosed" location where trumpeter swans attempted nesting this year. The birds are visible in the distant background.

The trip to evaluate swan habitat at Yellowstone Park last summer, was her visit, Cockrell said. "It was an amazing experience, especially working for over three weeks. The majority of park visitors never travel through the back country, whereas the majority of our work took us through back country hiking trails. We sampled across virtually every area of the park this year, and I look forward to traveling back to the park next year and seeing an entirely different season of the park, as well as new sampling locations. Traveling through areas such as the Lamar and Hayden Valleys were incredible with the amount of wildlife present. We were forced to re-think our travel plans more than once because of wildlife (such as a bison 'surprise' or grizzly kill along a hiking trail)."

"We went into this project not expecting to encounter any of the swans, however we were excited to see a total of five trumpeter swans during our trip; one pair that attempted nesting and failed, one pair that did not attempt to nest, and a solitary swan who has lost its mate and has not yet re-mated (we did not locate the third pair during our trip this year). It was rather bitter-sweet to see the swans - they are beautiful birds but it was sad to see them knowing that no cygnets were produced. The solitary swan prevented us from sampling the territory since drought conditions have shrunk the pond it was on to a size where we could not sample without disturbing the swan, which would have violated park policy. In all of our swan sightings, we were very careful to minimize any potential disturbance that would cause the swans to abandon their chosen territory.

"It was definitely an incredible journey!"

A $10,000 grant from the Yellowstone Foundation was provided for this research to fund a stipend, and to pay for lodging and travel and field equipment, and for which Cockrell is very appreciative.

Staff at Yellowstone National Park were also very helpful: "Thanks to Dr. Doug Smith of YNP for his help coordinating my field research and funding, and to Christie Hendrix from YNP permit office, Lisa Baril, Leslie Henry, and Josh Irving (all of YNP) for their assistance with field work. A big thanks to Matt Manuel, who was my field assistant during the entire trip, and to Dr. Frederick - my adviser at EKU." Additional financial support is being provided by Eastern Kentucky University.

A final report for this project is expected in October 2010.

Cockrell hopes to continue working with waterfowl following the completion of her thesis research and coursework at EKU.