Platte River Whooping Crane Maintenance Trust, Inc.

Aerial photo of the Platte River in Central Nebraska

EACH SPRING, more than 500,000 sandhill cranes gather in the Platte River valley during their northward migration. Sandhill cranes have been making this migration annually for thousands of years, and fossil beds in several parts of Nebraska contain the remains of prehistoric cranes from 10,000 years ago.

The Platte is a "staging" area, where the cranes stop to rest and replenish their energy reserves before continuing on to their nesting grounds in Canada, Alaska, and Siberia. It is the only major staging area on the sandhill cranes’ northward migration—approximately 80% of all the sandhill cranes come to the Platte every spring—and the concentrations of cranes here are the greatest of anywhere in the world. The majority are lesser sandhill cranes (Grus canadensis canadensis), although some greater sandhill cranes (G. c. tabida) and Canadian sandhill cranes (G. c. rowani) also migrate along the central flyway. Though the subspecies differ in height, they intermingle while along the Platte and are difficult to distinguish visually.

Sandhill cranes migrate in individual family groups, but here at the Platte, the birds are social and gregarious, and numerous families gather into large groups while feeding and resting. A single meadow may contain as many as 100,000 birds. The cranes begin arriving at the Platte by mid-February and spend 4-6 weeks here each spring. The number of cranes peaks during the last half of March, though some birds remain on the Platte until the middle of April.

While on the Platte, the cranes spend their days in the fields and meadows near the river, feeding on waste corn in crop fields and a variety of earthworms, snails, insects, and plant tubers in wet meadows and grasslands. The cranes build up their body fat reserves, increasing their weight by 15-20% during the month here. They obtain the vast majority of their energy from corn (96%), but corn is not a complete diet. The sandhills also need specific mineral nutrients and proteins for successful egg laying and reproduction, and animal prey—primarily snails, earthworms, and insects—provides those essential nutrients. Animal prey is a minor portion of the cranes’ total caloric intake (4%), but it is critical that the birds get these nutrients for successful reproduction, so they spend almost half of their time searching for this part of their diet in the grasslands, wetlands, and alfalfa fields along the Platte.

Late in the afternoon, the sandhill cranes gather next to the Platte. As dusk approaches, they fly AERIAL VIEW OF SANDHILL CRANES ROOSTING ON THE PLATTE RIVER. THE CRANES GATHER ON SLIGHTLY SUBMERGED SANDBARS. to the river, and they sleep there, roosting where shallow water covers the sandbars in the middle of the channel. The wide, open, braided channels of the Platte provide ideal roost sites for the large concentrations of sandhill cranes—at the height of the migration, 50,000-100,000 cranes will pack into the most heavily used reaches in concentrations as high as 10,000 birds per half mile of river. The noise from so many birds calling to each other is deafening, and some people liken it to being in a crowded football stadium. The cranes quiet somewhat as they go to sleep and, at sunrise, they awaken and disperse again to nearby feeding areas.

The Platte River provides the combination of habitat components, in close proximity to each other, that the sandhill cranes need: crop fields with an abundant supply of food, wetlands and grasslands that provide critical nutrients, and secure roosting sites. The cranes are censused annually while they are here, and the mid-continent population has been stable or increasing recently. Recruitment into the population is approximately balanced by mortality due to hunting and other causes. Sandhill cranes are hunted in all the states and provinces along their migration route, except Nebraska.

Sandhill Cranes in Field

Ground Surveys

This graph summarizes information gathered during the 2008 spring migration of sandhill cranes in the Central Platte River Valley, Nebraska.

Trust staff, with the help of Trust graduate students from UNL and UNK, and a volunteer from Nebraska Game and Parks, continued ground survey efforts this year. Ground surveys were conducted along roads on the north and south sides of the river throughout the central Platte valley from Chapman to the Overton Bridge. Surveys commenced the week of March 6, 2008 , and were carried out weekly through the second week in April, the duration of the spring sandhill crane migration. Each of the five survey routes was between 60- 70 km and all were conducted on the same day of the week, and at the same time of day. Surveys began at 8:00 a.m. (9:00 a.m. after the daylight savings time change) and most were completed by 1:00 p.m. (although one survey route required additional time during the peak week). All birds within 0.8 km of the road were recorded. Flock size was noted, as was the type of habitat in which the cranes were observed. Additionally, a behavior scan was again incorporated to gain understanding of how each habitat type was being used over time.

Figure 1. Number of sandhill cranes observed along the Platte River from road surveys during the spring 2008 migration, by survey week. Information from years 2004-2007 is included for comparison. Although surveys were not necessarily conducted on the same day, they were conducted the same week during spring migration.

Aerial Surveys

A graduate student from UNK conducted the aerial surveys once weekly throughout the spring crane migration to determine location and size of crane flocks roosting along the Platte River. Surveys commenced the second week of March and continued through the end of migration in mid-April, covering the central Platte valley from Chapman to Elm Creek, Nebraska. Aerial surveys were initiated about a half-hour before sunrise, with time of departure changing weekly as the survey period progressed. Each survey flight was approximately 1 to 1.5 hours long.

This year, cranes were first heard roosting at the Trust during the week of February 11. However, surveys started during first week of March (identified as “Survey Week 2” , because Survey Week 1 is usually the last week of February). The greatest number observed on road surveys occurred in the third week of March, which was the same week as in the previous year and in 2004 (Figure 1).

Figure 2. Number of sandhill cranes observed roosting in the Platte River during aerial surveys between 10 March 2008 and 14 April 2008 . Information from 2005-2007 is included for comparison. Surveys were conducted on the same day of the week when weather conditions permitted it, otherwise the survey was conducted the same week during spring migration.

PHOTOS CREDIT INGRID BARCELO AND RICH READING


				EACH SPRING, more than 500,000 sandhill cranes gather in the Platte River valley during their northward migration. Sandhill cranes have been making this migration annually for thousands of years, and fossil beds in several parts of Nebraska contain the remains of prehistoric cranes from 10,000 years ago. The Platte is a "staging" area, where the cranes stop to rest and replenish their energy reserves before continuing on to their nesting grounds in Canada, Alaska, and Siberia. It is the only major staging area on the sandhill cranes’ northward migration—approximately 80% of all the sandhill cranes come to the Platte every spring—and the concentrations of cranes here are the greatest of anywhere in the world. The majority are lesser sandhill cranes (Grus canadensis canadensis), although some greater sandhill cranes (G. c. tabida) and Canadian sandhill cranes (G. c. rowani) also migrate along the central flyway. Though the subspecies differ in height, they intermingle while along the Platte and are difficult to distinguish visually. Sandhill cranes migrate in individual family groups, but here at the Platte, the birds are social and gregarious, and numerous families gather into large groups while feeding and resting. A single meadow may contain as many as 100,000 birds. The cranes begin arriving at the Platte by mid-February and spend 4-6 weeks here each spring. The number of cranes peaks during the last half of March, though some birds remain on the Platte until the middle of April. While on the Platte, the cranes spend their days in the fields and meadows near the river, feeding on waste corn in crop fields and a variety of earthworms, snails, insects, and plant tubers in wet meadows and grasslands. The cranes build up their body fat reserves, increasing their weight by 15-20% during the month here. They obtain the vast majority of their energy from corn (96%), but corn is not a complete diet. The sandhills also need specific mineral nutrients and proteins for successful egg laying and reproduction, and animal prey—primarily snails, earthworms, and insects—provides those essential nutrients. Animal prey is a minor portion of the cranes’ total caloric intake (4%), but it is critical that the birds get these nutrients for successful reproduction, so they spend almost half of their time searching for this part of their diet in the grasslands, wetlands, and alfalfa fields along the Platte. Late in the afternoon, the sandhill cranes gather next to the Platte. As dusk approaches, they fly to the river, and they sleep there, roosting where shallow water covers the sandbars in the middle of the channel. The wide, open, braided channels of the Platte provide ideal roost sites for the large concentrations of sandhill cranes—at the height of the migration, 50,000-100,000 cranes will pack into the most heavily used reaches in concentrations as high as 10,000 birds per half mile of river. The noise from so many birds calling to each other is deafening, and some people liken it to being in a crowded football stadium. The cranes quiet somewhat as they go to sleep and, at sunrise, they awaken and disperse again to nearby feeding areas. The Platte River provides the combination of habitat components, in close proximity to each other, that the sandhill cranes need: crop fields with an abundant supply of food, wetlands and grasslands that provide critical nutrients, and secure roosting sites. The cranes are censused annually while they are here, and the mid-continent population has been stable or increasing recently. Recruitment into the population is approximately balanced by mortality due to hunting and other causes. Sandhill cranes are hunted in all the states and provinces along their migration route, except Nebraska. Ground Surveys This graph summarizes information gathered during the 2008 spring migration of sandhill cranes in the Central Platte River Valley, Nebraska. Trust staff, with the help of Trust graduate students from UNL and UNK, and a volunteer from Nebraska Game and Parks, continued ground survey efforts this year. Ground surveys were conducted along roads on the north and south sides of the river throughout the central Platte valley from Chapman to the Overton Bridge. Surveys commenced the week of March 6, 2008 , and were carried out weekly through the second week in April, the duration of the spring sandhill crane migration. Each of the five survey routes was between 60- 70 km and all were conducted on the same day of the week, and at the same time of day. Surveys began at 8:00 a.m. (9:00 a.m. after the daylight savings time change) and most were completed by 1:00 p.m. (although one survey route required additional time during the peak week). All birds within 0.8 km of the road were recorded. Flock size was noted, as was the type of habitat in which the cranes were observed. Additionally, a behavior scan was again incorporated to gain understanding of how each habitat type was being used over time. Figure 1. Number of sandhill cranes observed along the Platte River from road surveys during the spring 2008 migration, by survey week. Information from years 2004-2007 is included for comparison. Although surveys were not necessarily conducted on the same day, they were conducted the same week during spring migration. Aerial Surveys A graduate student from UNK conducted the aerial surveys once weekly throughout the spring crane migration to determine location and size of crane flocks roosting along the Platte River. Surveys commenced the second week of March and continued through the end of migration in mid-April, covering the central Platte valley from Chapman to Elm Creek, Nebraska. Aerial surveys were initiated about a half-hour before sunrise, with time of departure changing weekly as the survey period progressed. Each survey flight was approximately 1 to 1.5 hours long. This year, cranes were first heard roosting at the Trust during the week of February 11. However, surveys started during first week of March (identified as “Survey Week 2” , because Survey Week 1 is usually the last week of February). The greatest number observed on road surveys occurred in the third week of March, which was the same week as in the previous year and in 2004 (Figure 1). Figure 2. Number of sandhill cranes observed roosting in the Platte River during aerial surveys between 10 March 2008 and 14 April 2008 . Information from 2005-2007 is included for comparison. Surveys were conducted on the same day of the week when weather conditions permitted it, otherwise the survey was conducted the same week during spring migration. PHOTOS CREDIT INGRID BARCELO AND RICH READING
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