Status and behavior of the Black-necked Crane (Grus nigricollis) in the Altun Mountain Reserve, Xinjiang

Introduction

The Black-necked Crane (Grus nigricollis) is one of the most important protected animals in China as well as in the world and the only crane species living entirely on high plateaux. The Black-necked Crane is found at elevations of 2950–4900 m in the breeding season and between 1900 and 3950 m in the winter (Bishop, 1996). In China it is mainly distributed on the Qinghai-Tibetan and Yunnan-Guizhou plateaux (Li, 1997; Ma et al., 2000; Ma, 2011). A small part of their breeding range also extends into India, Bhutan and Nepal (Li et al., 2005; Li and Li, 2005).

The Black-necked Crane is evaluated as vulnerable (VU) according to the endangered categories of the IUCN, because it has a single small population that is declining due to the loss and degradation of wetlands, as well as changing agricultural practices in both its breeding and wintering grounds (BirdLife International, 2009). According to research of its migration patterns, Black-necked cranes are divided into a western, a central and an eastern population (Li and Bishop, 1999). Those that breed in Xinjiang at the northern edge of the Tibetan Plateau belong to the western population, the least studied of the three populations.

Since the 1970s, the Black-necked Crane has been studied primarily in Yunnan, Guizhou, Sichuan, Qinghai, Gansu and Tibet (Ran et al., 1999; Li and Yang, 2003; Kong et al., 2008; Tsamchue et al., 2008). Black-necked cranes have rarely been studied in Xinjiang and the few earlier studies are incomplete and likely inaccurate (Gao, 1987; Zhang and Zhang, 1991; Tian, 1999).

The Altun Mountain Nature Reserve is the most important breeding ground for Black-necked Cranes in Xinjiang (Ma et al., 2011). This remote reserve is one of the best-preserved plateau ecosystems in the world and one of the breeding areas for the Black-necked Crane in Xinjiang. In this study, we review the status of the cranes. We used direct observations to study their behavior, assessed the threats to the cranes and attempted to obtain more information essential for conservation of the species.

Study area

The Altun Mountain National Nature Reserve at 45000 km² is one of the largest plateau reserves. It is located in Ruoqiang County, Xinjiang Uyghur Autonomous Region, China (36°00′–37°49′N, 87°10′–91°18′E) and extends to the northwestern edge of the Tibetan Plateau, north of Tibet and west of Qinghai (Fig. 1). This reserve is characterized by its high location with an average elevation of 4500 m; the highest point is Muztagh Mountain (6973 m) and the lowest area is Ayakkum Lake (3876 m). The climate of the area is dry and cold. Precipitation is rare and sparse and frequently falls as snow or sleet, even in the summer (Achuff and Petocz, 1988). However, the landscape is mostly flat and plants are abundant around lakes and rivers. There are three large lakes in the reserve, together accounting for approximately 1220 km² of surface area, i.e., Ayakkum Lake, Aqikekule Lake and Whale Lake. There are also many other small lakes and rivers. Plants are short and small, many of them belonging to alpine cushion vegetations, such as Ceratoides compacta, Poa arjinsansis, Puccinellia arjinshanensis, Carex kunlunshansis, C. atrofusca, C. orbicularis, C. microglochin, Myriophyllum spicatum and others. It is a good breeding area for the Black-necked Crane.

Methods

From September to November of 2011, we used a sample spot survey and direct counts in the Altun Reserve as well as around the reserve to determine the distribution and number of cranes. Cranes live mainly in wetlands near lakes and rivers, hence wetlands near the water were our main observation spots.

From 20 September to 6 November, we used continuous recording and scan sampling at 10 min intervals (Altmann, 1974) to document Black-necked Crane behavior at the Yixiekepati wetland (37°18′N, 90°20′E). We observed cranes from 06:00 to 18:00 for a total of 216 hours and documented 21120 behavioral events with telescopes (Carl Zeiss, Diascope 85, 20–60; Minox BV 10 × 42 BR). The types of behavior of the Black-necked Crane was divided into eight categories: foraging (searching and handling food, drinking), preening (preening with beak or claw, shaking and washing), vigilance (stretching the head upwards, looking around while standing or working), walking, flying, resting (sleeping while lying or standing), chirping and other types of behavior (excretion, antagonism, dancing). We also counted some other water birds.

We interviewed local herders, miners and reserve staff to confirm crane habitats and assessed potential habitats within the reserve. The interviews also touched on information about the current status of cranes, including the impact of domestic livestock, illegal poaching and predators. Such information is critical for devising suitable methods for crane protection.

Results

Distribution

Through observation and analysis, a total of 220–260 Black-necked Cranes were found in Altun Nature Reserve and surrounding areas (Fig. 1, Table 1). Of these, 180–200 individual birds live in the reserve, primarily around Ayakkum, Aqikekule and Whale lakes. Dozens of crane families, totaling more than 130 cranes, were found beside the Yixiekepati River. About ten cranes lived in small lakes within the Kumkol Desert, the highest desert of the world (Fig. 1). Although we most often found Black-necked cranes in wetlands around rivers and lakes, we repeatedly found that the cranes were active far away from the water in alpine meadows and even at edges of the desert. About 42–60 cranes were scattered around the reserve in a variety of places such as Tiemulike Village, Wuzunxiaoer, Yusup Aleksei and Qarqan river basins, Yaziquan, Ada Beach and Tula Ranch (Fig. 1, Table 1).

Figure  1.  Location of Altun Nature Reserve and distribution points of Black-necked cranes in the reserve and adjacent areas

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Table  1.  Distribution and number of Black-necked cranes in Altun Nature Reserve and surrounding areas

Location	Number of birds
Qimantag Village	180–200
Tiemulike Village	8–10
Wuzunxiaoer	4–6
Kazakbeyti	4–6
Yusup Aleksei	4–6
Qarqan River Basin	4–6
Yaziquan	4–6
Tula Ranch	6–10
Urukzo River Basin	4–6
Ada Beach	2–4
Total	220–260

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Group sizes

A total of 158 cranes belonging to 68 families were observed at the Yixiekepati wetland in the autumn. Family group sizes were from one to four birds (Fig. 2). Cranes were rarely alone; our records show only four occasions where we found a single bird, accounting for 5.9% of the families (n = 68). Forty-one families consisted of pairs of cranes, accounting for 60.3% of the 68 families, i.e., the largest proportion. The second largest configuration is families with three members, of which we observed 20 families, accounting for 29.4% of the total number of families. The remaing three families belonged to four member households and accounted for 4.4% of all families. During our study period, 26 juveniles were observed in the Black-necked Crane population, representing 16.5% of all 158 cranes.

Figure  2.  Relative number of Black-necked Cranes by family size in autumn

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Changes in flock size

We observed changes in flock size of the Black-necked Crane at the Yixiekepati wetland from September to November 2011 (Fig. 3). Before October families moved around; in rare cases, some families walked together and gathered for a short time. The cranes started to gather into one large flock in October. At the start, only about 10 cranes came together, but by mid-October 40–60 cranes had gathered together. The number of the cranes in the flock continued to rise in the following days, but on 19 October, most cranes in this flock left because of grazing sheep. The cranes did not return until the sheep left two days later. The flock size increased to more than 60 birds by late October, with the highest number of 126 individual birds on 29 October 2011.

Figure  3.  Population changes of Black-necked Cranes at Yixiekepati wetland in autumn of 2011

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Black-necked cranes started migration on 29 October 2011 and nearly 79% of the birds flew away the following three days. There were less than 30 cranes left by November 2011. We found only three individual birds (one family) on 4–5 November and no cranes remained on 6 November 2011.

Time budgets and diurnal behavior rhythms

During the migration season, the predominant type of behavior of Black-necked cranes was foraging, accounting for 58.9% of their time budgets. The second most prevalent type of behavior was preening, about 13.2% of the time budgets. Meanwhile, vigilance (9.5%) and walking (8.2%) also made up important parts of their daylight activities. The other four types of behavior, flying, resting, chirping and others were rare at 3.5%, 3.4%, 2.7% and 0.6% of time budgets respectively.

Some behavior types of cranes showed rhythms during the daytime (Fig. 4). Foraging increased during the day with cranes foraging least often (24.5%) in the early morning (06:00–07:00) and most often (75.1%–81.5%) in the evening (16:00–18:00). Conversely, vigilance showed a decreasing trend peaking early in the morning and gradually decreasing during the day. Neither preening nor walking behavior showed a clear daily rhythm, but both showed a slight decline at nightfall. The peak time of flying occurred during the hours from 06:00–07:00 and 14:00–16:00 when cranes flew between foraging and resting places. The same situation also occurred in their resting behavior. The peak time of resting appeared before flying into foraging places in the morning and after flying into resting places in the evening. The peak time of chirping occurred from 06:00–07:00 after the cranes had flown to their feeding places. Other special types of behavior, such as fluttering wings, leg stretching, jumping and antagonism were rare and did not have daily rhythms.

Figure  4.  Diurnal behavior rhythms of Black-necked cranes in autumn of 2011 at Yixiekepati wetland

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Discussion

The Black-necked Crane is one of the most important, rare and protected birds both in China and abroad. They are monotypic species and are without subspecies differentiation (Wang et al., 2006). According to migration research, the population of this crane in China is divided into three populations, i.e., a western, a central and an eastern population (Li and Bishop, 1999). The cranes living in Xinjiang belong to the western and least-studied of the three populations. A few earlier studies are incomplete and contain some mistakes (Gao, 1987; Zhang and Zhang, 1991; Tian, 1999). For example, according to the data collected by the State Forestry Administration, there are about 1200 Black-necked cranes in Xinjiang, based on a total distribution area of 367998 km² with a density of 0.1884 individual birds per 100 km² (National Forestry Bureau, 2009). The distribution area estimated is too large, however, accounting for 23% of the total Xinjiang area and the data source is unknown (Ma et al., 2011). Based on our surveys and analysis, we estimated the population size of the Black-necked Crane to be about 180–200 in the Altun Mountain Nature Reserve and more than 260 birds in Xinjiang. Most are found in the Kunlun and Karakorum mountains.

The amount of time a bird allocates to different activities may approximately reflect its energy budget (Weathers et al., 1984; Ricklefs, 1996). The time budget is adaptive and information about it is useful for evaluating the relationships of species to their environments (Lu and Zheng, 2009). In autumn, the cranes need to store extra energy in preparation for migration. As a result, they spent most of their daily activity time in foraging (> 58%). Affected by physiological activities and environmental factors for cranes, the rhythm of various types of behavior varied during the day and the time spent feeding increased during the day. When flying into a feeding spot each morning, the cranes spent relatively much more time being vigilant. As time went on, they became familiar with the surrounding environment and their level of vigilance decreased; consequently, foraging could increase. In addition, crane group size may have been a factor because time used for foraging may increase due to reduced scanning for predators when animals live in groups (Beauchamp, 1998). Flying behavior had peaks in the morning and evening when cranes flew between foraging and resting places, but the cranes also flew during the daytime to practice for migration.

Natural selection favors those animals that can organize their activities to a proper schedule in response to local environments (Cuthill and Houston, 1997). By the end of October, snowy weather had increased and lakes were becoming frozen at Altun. Also by the end of October the cranes were in larger and larger groups and the aggregation of cranes began to migrate to the south. Some reports say that the western populations of the Black-necked Cranes may migrate to Tibet or Bhutan (Wu et al., 1993; Yan, 2006), but this has not been confirmed for the Xinjiang cranes. We observed that the cranes flew in a southeast direction, but future satellite tracking of cranes is necessary to clarify routes and stopovers to enhance Black-necked Crane conservation.

From October to March, wintering populations of Black-necked Cranes live in the south of Tibet (Cang et al., 1994). However, from November to March some flocks overwinter in Yunnan (Gao et al., 2007). Cranes reaching Xinjiang in early April and living there to November are adapted to the migration time of the Yunnan population. Maybe Black-necked Cranes at Altun Mountain belong to one of the populations of Yunnan, migrating every year between Yunnan and Xinjiang.

According to our field work and preliminary interviews, we found that because of environmental changes, livestock husbandry, mining and increasing eco-tourism activities, the population of Black-necked cranes has been faced with some threats recently. Increasing livestock husbandry, mining and eco-tourism activities potentially threaten the Black-necked Crane with poaching and egg collection. In response to these threats, the protection and management work of the reserve administration needs to be strengthened and herders, miners, tourists and reserve staff all need to be educated about the protected status of cranes. At the same time, a long-term monitoring program should be established to strengthen the conservation and management of Black-necked Cranes in the reserve. The number of juveniles that we observed (16.5%), out of a total of 158, can be used as a baseline to monitor future fecundity and population trends.

Acknowledgements

This research was supported by the National Natural Science Foundation of China (No. 31272291, 30970340), the Hong Kong Bird Watching Society China Conservation Fund and the Management Bureau of Altun Mountain Natural Reserve. We sincerely thank Weidong Li, Xiang Zhang, Huibin Zhang, Donghua Xu, Ming Liu, Huan Li, Ying Chen, Mardan Turghan, Tuson Sawut, Zhaosong Liu, Aishanjiang and Feng Gao and others.