High Plains Swan Population Continues to Thrive

The number of Trumpeter Swans in the high plains flock continues to thrive.

Results of the 2010 autumn survey indicated a population of 524 swans, which is a "record-high count," but only one more bird than in 2009.

"There was an increase in the number of breeding pairs and birds in groups," according to the survey report. "The number of non-breeding pairs decreased by 16, but the number of broods and average brood size remained relatively unchanged."

The total population has shown a steady increase in the past few years, according to survey results:

1995: 214

2000: 321

2005: 358

2006: 427

2007: 398

2008: 429

2009: 523

2010: 524

Notably, the population has more than doubled in 15 years.

There were 174 cygnets noted during the 2010 survey, which compares to 171 in 2009. The total number of broods was 65 in 2010, and 63 in 2009.

The survey report indicates there were 65 pairs with cygnets in 2010 (60 in 2009) and 56 pairs without cygnets this past season (72 in 2009).

"The increase in total birds could be credited not only to the number of reproductively active pairs, but also wetland habitat quality," the survey report says.

The aerial survey was done from August 30 to September 1, and on September 8. The area surveyed has been similar in the past few years, and does not extend beyond the eastern boundary of Cherry county.

Survey results are available in a report by Shilo Comeau, of the Fish and Wildlife Service, out of Martin, SD, and Mark Vrtiska, of the Nebraska Game and Parks Commission.

Considering the Survey Report

The 2010 report of the autumn survey of Trumpeter Swans, is a slight variation on the 2009 report.

The introduction is the same text. The only items changed in the methods section were the dates for the survey, and temperatures.

The results section conformed to the changes as a result of the survey.

Figure 1 - a map of the region - is the same. Figure 2 was slightly modified by including an additional year of results.

The boiler-plate presentation of the results continues with Table 1 and Figure 3. There were no substantive changes in the Habitat Conditions section.

Once again on Page 5, was an aerial photograph of a sandhill's wetland, showing the mosaic of habitat, with three swans and a Great Blue Heron within the view.

The caption for the 2009 report said: "Picture taken from the airplane during the survey, ..." The same picture with the exact same caption were used in the 2010 report.

Obviously this is misleading since the exact same picture could not have been taken two years in a row. A slight change in the caption text could have indicated that the picture was from a previous year's survey, but this was not done.

Another item mentioned in the survey reports for 2010 and 2009, is "Habitat availability in the Sandhills is currently being modeled using data collected from previous surveys, and this should give managers an idea if there is enough habitat available for this flock to persist at the current objectives."

Since the exact same text has been issued for two years, will this same statement be given next year? There is no information available to indicate what is involved with this habitat modeling effort.

The value of this report is its presentation of the number of swans, but the report could be so much more than another rendition of what has already been presented. Conditions for Trumpeter Swans of the High Plains Flock change every year, and this years report did not indicate anything new in this regard.

Habitat Management

Nothing was said in the survey report for 2009 and 2010 regarding the potential for habitat management to provide additional habitat for breeding swans and their young.

One point of consideration is the potential for restoring a Grant County lakebed to its former condition.

The Sandhills Task Force has an application on file to the Nebraska Environmental Trust to recreate historic hydrological conditions at Egan Lake. The landowners are supportive.

If the site, which is not currently a lake, is no longer pumped to remove water, but which could have a greater extent and variety of wetland habitats, might provide an additional nesting site for a pair of swans, as well as other wetland birds.

There may be other similar opportunities for lake restoration within the sandhills, which is the core habitat of the High Plains Flock. There is no known evaluation which has focused on the potential to increase habitat among the hills' dunes.

Habitat restoration could be a key element to ensure a healthy population of the Trumpeter Swan, as well as other birdlife of the region's lakes and marshes.

Analysis of Waterfowl Populations Released by FWS

A summary of waterfowl surveys in northern America shows dramatic fluctuations in populations this season, and during the historic period since 1955.

"The preliminary estimate of total ducks from the 2008 Waterfowl Breeding Population and Habitat Survey was just over 37 million, which is a nine percent decline from last year's estimate, but still 11 percent greater than the 1955-2007 average. In the U.S. and Canadian prairies, population estimates of many species declined; while populations increased in the boreal forest to the north, likely reflecting in part those birds that overflew the prairies because of drier habitat conditions there." Fish and Wildlife Service press release.

There are 50 survey transects within the traditional regions - whichh samples "two million square miles" and is the "largest and most comprehensive survey of its kind in the world" - around the following places:

Alaska - Yukon Territory -Old Crow Flats ¶ C. & N. Alberta - N.E. British Columbia - NWT ¶ N. Saskatchewan - N. Manitoba -W. Ontario ¶ S. Alberta ¶ S. Saskatchewan ¶ S. Manitoba ¶ Montana & western Dakotas ¶ Eastern Dakotas

There was also an eastern breeding area that continued to the Atlantic Coast of Canada and the United States.

"Figure 1: Strata and transects of the of the Waterfowl Breeding Population and Habitat Survey
(Yellow = traditional survey area, green = eastern survey area)."

The preliminary report "does not include estimates from surveys conducted by State or Provincial agencies." The extensive wetlands of the Nebraska Sandhills are not considered as a survey area.

Populations were graphically compared for each year since 1955, for these species:

Mallard ¶ Gadwall ¶ American Wigeon ¶ Green-winged Teal ¶ Blue-winged Teal ¶ Northern Shoveler ¶ Northern Pintail ¶ Redhead ¶ Canvasback ¶ Scaup (greater and lesser combined)

The latter portion of the report includes graphs of the trends from 1955 to 2008. Each chart includes a demarcation for the population goal desired according to the North American Waterfowl Management Plan.

There is a constant flux in numbers, with teal showing steady increases in numbers for the past couple of season. While the number of Redheads was up, Canvasback showed a dramatic decline, from above 800,000 to near 500,000 for the survey area considered.

Summary charts for the eastern breeding area are also included, from the period since 1990. This includes summary details with mergansers, the Ring-necked Duck, goldeneyes (common and Barrow's), Bufflehead, and the Black, White-winged and Surf Scoters.

"Trends in Duck Breeding Populations, 1955-2008" was issued in early July.

Breeding Survey Shows Slight Decline in High Plains Swan Population

James Ed. Ducey

The population of Trumpeter Swans in the High Plains flock of Nebraska and South Dakota had a successful breeding season in 2007 as shown by the annual early autumn survey results recently released by the U.S. Fish and Wildlife Service.

The 398 adults and young noted was 7% less than the number of these majestic waterfowl counted in 2006, according to the report. An aerial survey was conducted during September 4-6, 2007 by the F.W.S. and Nebraska Game and Parks Commission.

The lesser number of swans was "attributed to a decrease in nonbreeding pairs and single white birds," according to the survey report. "The majority (68%) of the pairs observed had no cygnets, and the number of white birds in groups continues to increase. This may be because many of the white birds counted have not reached breeding age or are just maturing. In 2004 a record number of cygnets were counted, and these birds are now three years old and are likely reproductively mature but may not be breeding because of limited nesting habitat. Also, many of the highest quality wetlands are occupied by pairs that nest at these locations year after year. Due to the drought conditions, such high quality breeding habitat for newly formed pairs may have been limited."

The total number of swans counted is the second highest breeding population in the region, based on results of surveys dating back to 1993, with the highest count 427 birds in 2006.

Thirty-three broods were noted during the survey, with an average of 2.33 cygnets for each adult pair.

Survey biologists noted that the number of breeding pairs was consistent, with an increase of ten, in the number of young cygnets. The number of young raised during a years' season varies from season to season, based on count results since 1993.

The distinct mix of lakes and wetlands in the Sand Hills region is especially essential habitat for this flock.

"The sandhills provide high quality wetlands with dependable water and forage, in an area that is relatively free from human disturbance," said Shilo Comeau, a FWS biologist at Lacreek NWR, who helped count the birds and prepare the report. "The majority of the nesting pairs for this flock are located in the this region and the population really began to grow once they expanded into the sandhills. If the swans had not 'discovered' the sandhills I don't believe the population would be at the level it is today."

The vast majority of the nesting area of this flock is in Cherry County within 75 miles of the refuge," Comeau said. Clubhouse, Winslow, and South Cody lakes are notable breeding locales within the sandhills. Breeding swans can usually be readily seen from a very accessible vantage point at Avocet WMA, just east of Hyannis, Nebraska.

Trumpeter Swan populations are closely monitored throughout their range in western North America.

"It is important to monitor this species to see if we are achieving the population goal set for this flock, and to monitor the overall health of the flock and its habitat," said Comeau.

Waterfowl biologists hope for an increased number of Trumpeter Swans in the interior region of the birds' range. A growth of 4.5% annually has occurred in the High Plains population since 1990, according to report details.

"Five hundred total birds is what we believe the population should be around given habitat availability and to maintain a self sustaining flock within the Interior population, Comeau said.

A survey of wintering swans is also conducted by the two agencies, during January. Results should be available by latter summer.

Trumpeter Swan Society

Sandhill Cranes Subject of Ongoing Research Investigations

By James Ed. Ducey.

Flocks of the gray Sandhill Cranes and a myriad of waterfowl visiting the central Platte River this season continued to be the focus of bird research.

The Platte River Whooping Crane Trust conducted annual surveys of the wild birds. Ground counts about assigned routes documented the cranes and waterfowl weekly from early March to mid-April. Flights in a fixed-wing airplane were also done from Chapman to Overton, several times during this period.

Although cranes were present at the end of January, the first wave of cranes arrived around the second week of February” said Dr. Daniel Kim, avian ecologist at the Trust. “The real influx did not occur until early March when the cranes arrived en masse.”

Kim has experienced crane migration for four years, describing the shear number of cranes as overwhelming, noting that “when in a blind with 40,000 cranes just outside, their calls are at least half the experience!”

Peak numbers on the river for Spring 2007 were estimated at 300,000, not including cranes already off roost, which, depending on the morning, may be as many as 40% of all birds.

“From a wildlife perspective, this is one of the greatest migratory events on earth,” Kim said. “The resources, corn and the river, draw 500,000+ cranes that winter from New Mexico to Louisiana. Some birds add an addition 1000 miles to their migratory route just to use the Platte.”

“In general cranes settle the eastern part of the valley first, with roosts filling in to the west. Cranes leave roosts in the same order, that is they leave the eastern part of the big bend first. The cranes display a combination of hard wiring and migratory flexibility that influences when they migrate.”

The amount of water in the river influences the roosts used by the cranes. “Years with an abundance of water appear to distribute cranes throughout the river while low water levels seem to restrict cranes to a few favored roosts,” Kim said.

River management appears to have profound effects on crane use of riverine roosts. Due to low flows, the river must now be maintained, or it would be choked with vegetation such as cottonwood saplings and willow thickets, and the channel would be obstructed with perennial vegetation bank to bank, reducing the river's ability to absorb flood waters. Both channel clearing and tree removal appear to encourage roosting cranes.

Large roosts are associated with channel maintenance, while unmanaged reaches of the river receive very little crane use.

In general, cranes off the river use corn fields to a greater degree than all other land types (foraging), but the largest groups use wet meadows for loafing and social interactions.

“Poor weather during the end of March and beginning of April held many cranes through April 12. Two very fine days led to a mass exodus by the 16th.”

During their visit, local weather has a huge influence on when migratory peak occurs, typically between the second and fourth week of March, Kim said. Some years cranes trickle in and trickle out.

Aerial and road surveys conducted by the Trust are considered an index of crane abundance. Surveys have been conducted since 1998. The aerial surveys have not occurred during high flows, so the impacts of a full river have not been documented, Kim added.

Survey results indicate that the Central Flyway population is steadily growing at about 3-6% annually, according to surveys documenting crane population increases by the U.S. Fish and Wildlife Service, Kim said. Crane trust surveys are not used to calculate population numbers, but provide important information needed to help manage cranes.

During their seasonal staging, Sandhill Cranes interact very little with the large numbers of geese present, according to the research.

“There is very little direct interaction,” Kim said. Both species may co-occur on the same field, but very few antagonistic behaviors are observed. Geese prefer to roost on ponds and lakes, while cranes appear to prefer running water. Also, when there is water in the western rain water basins, geese congregate in the basins, when the basins are dry, geese spill over into the Platte valley.”

Investigations into other aspects of Sandhill Crane biology are underway along the central Platte. Current research topics are:

1) Questions of competition for food (corn) between cranes and geese. While not direct, geese generally arrive 2 weeks prior to cranes, Kim said. “Some scientists believe geese may deplete waste corn, forcing cranes to either forage further from the river, or leave the valley in poorer condition.”

2) Landscape level questions are being addressed by a Ph.D. student at UNL, but meaningful conclusions are still at least two years off.

The U.S. Fish and Wildlife Service undertakes seasonal counts of the Whooping Crane along the central Platte valley. Dr. Kim said the number of documented whooping cranes seen in the Platte valley was a highlight of the past season.

There are concerns for migratory birds in the central Platte valley.

Kim mentioned the interaction between crane watchers and the birds: “(1). People try to get too close to cranes, whether on the road, or by visiting the river. If people want an up close experience with the cranes, they should use one the guided tours available through either Crane Meadows or Rowe Sanctuary. (2) People here to visit cranes are visitors, and simple etiquette needs to be observed … Respect private lands, and if you pull off the road to see cranes, make sure that both farm equipment as well as cars can pass.”

As regional climates may change, Kim said “the impact for cranes may be due to increased variations in both temperature and precipitation. The lack of predictable conditions, especially precipitation, may constrict a large number of cranes into ever decreasing spaces in the river. The greatest potential impact to cranes will Sandhill Cranes likely track favorable conditions (water availability) during the winter. Prolonged drought in the southwest and northern Mexico could have severe impacts to winter crane populations.”

River management is conducted by a partnership including U.S. Fish and Wildlife Service, Nebraska Game and Parks Commission, The Nature Conservancy, National Audubon Society, The Platte River Whooping Crane Trust, Prairie Plains Resource Institute, and dozens of private land owners, Kim said. Most of the funding is secured through grants, some private, others federal. The Nebraska Environmental Trust has been a major source of funds for river management.