Abstract
The black-necked crane (Grus nigricollis) is a species endemic to China. It is rare and estimates indicate a total of 900 birds exist. Ornithologists from many countries have always wanted to know more about this species. So, between June and August 1986, a group traveled to the Nongbaotan marshland to observe and study the reproductive habits and characteristics of the black-necked crane.
Geography
Nongbaotan is in Yushu County, Yushu Tibetan Prefecture, Quinghai Province, Peoples Republic of China. The lake is located two-thirds of a mile (1.08 km) from Exining. The area involved in the study is a vast expanse of low-lying land. Many springs and seven streams empty into one large wetland. The marsh is 15.5 miles (25 km) long, from one to two miles wide, and is completely surrounded by mountains. This area is a popular habitat for the black-necked crane. The entire wetland covers an area of 29 square miles (75 sq. km), but only 17 square miles (45 sq. km) of the wetland is actually suitable crane habitat. The habitable area is a grassy marshland interspersed with five ponds. Water depths range from eight inches to 98 inches (0. 2 to 2. 5 meters). Grassy mounds also prevail.
Nongbaotan is 13,780 feet (4,200 m) above sea level. The air is thin. This means that there may be breathing difficulties when walking in this area. There is an average of 2,300 hours of sunshine per year. Temperatures vary greatly, running about 13 to 15 °C at noon, dropping to 2 to 4 °C between 2:00 a.m. and dawn.
Rain was plentiful in 1986. As a direct result of this rain, an island used by the birds, 1600 feet long and 330 feet wide (110 m), was in evidence. This island was primarily used by bar-headed geese. In 1980, the area supported but a few dozen birds; while in 1986, 2,000 nests were counted. Nests of the common Merganser and white-headed ducks were also observed. There were 19 breeding pairs of black-necked cranes in the entire Nongbaotan region; eight pairs brooding in each district. One lone pair appeared to move about in an idle manner. A single crane, whose mate was shot by a hunter the previous year, moved about with no real purpose. There were many additional black-necked cranes in this area. These birds moved in flocks and the study party was unable to locate their mating area. Because of these difficulties, the study team decided to concentrate their work on the activities of a single pair of black-necked cranes.
On June 3rd, the study party started early in the morning. At 9:00 a. m., a pair of birds flew into the midst of a herd of cows, landing less than 650 feet (200 m) from the study group. After landing, the birds walked about slowly, foraging for food. Suddenly, one of the birds spread its wings and picked a stick up from the ground with its bill. The stick was tossed into the air. The bird flapped its wings, and ran around in a large circle. As it was running around in this circular pattern, it appeared to be in a "happy" mood. At almost the same time, the other bird lowered its head, bowed, spread its neck and beat its wings. All the while the bird was, in effect, rising and falling and presenting an elegant figure. When the study team attempted to take pictures of the birds, the birds "spotted" the people. The dance stopped and the birds immediately walked toward the hinterland of the marsh. As they walked away, they issued rhythmically and in unison, a unique cry. The male had a sonorous, monosyllable cry, sounding like "ga-ga-ga " The female bird, however, sounded a disyllabic, uneven cry, in a shrill voice, sounding a "ga-ge-ge-gagege!' As the birds sang in unison, they raised their bills and pointed them vertically toward the sky. All these sounds were quite different than those uttered by the red-crowned crane. Distinctive differences between the activities of the blacknecked crane and the red-crowned crane were noted. For example, while singing in unison, the black-necked crane will usually partially spread its wings, while the red-crowned will never spread its wings.
The study team followed the birds as they headed toward a nearby rivulet. The birds managed to keep an unchanging distance between themselves and the study party. When the study party walked faster, the male crane would utter some very short, quick sounds of fear. Finally the two cranes, one following the other, took to the sky.
As the birds flew, they stretched and straightened their long legs to the rear. Their heads and necks extended forward. They flapped their wings slowly. While in flight, they uttered a deep cry: "gage-gage.' The two birds then landed about 1,000 feet (300 m) from the study party. As the birds landed, they held their legs in a vertical position, flapping their wings repeatedly. When they touched the ground, they ran with long strides for a short distance. Eventually the birds stopped, craning....