Ornithol Sci 17: 187 – 194 (2018) ORIGINAL ARTICLE Wintering behavior of a Siberian Crane Grus leucogeranus in Niigata, Japan, with special regard to food, foraging and vocal habits Akira CHIBA#,* 1-13-11 Terao-Higashi, Niigata 950–2054, Japan ORNITHOLOGICAL Abstract An immature Siberian Crane Grus leucogeranus straggled to Niigata, Japan, in late autumn 2016 and remained over winter in an area of rice fields. In this SCIENCE paper the bird’s diet and foraging behavior during winter 2016/2017 are described. © The Ornithological Society During daytime, the crane foraged alone, mostly on post-harvest rice fields where of Japan 2018 it fed almost exclusively on Water Chestnut Eleocharis kuroguwai tubers. Other foods, such as rice grains, earthworms, grasshoppers and fishes, though eaten, were negligible in the bird’s diet. The density of water chestnut tubers in the foraging area was estimated to be 3.1±3.0/m2 and the biomass 2.0±2.1 g/m2. The crane’s foraging behavior generally included removing any superficial covering material, digging into and removing the soil, exploring the food in the beak and then consuming it with or without rinsing it in groundwater. During foraging, the frequency of food intake varied from 4.8±2.0/10 min to 41.3±9.5/10 min. These results indicate the great significance of water chestnuts in the diet of the Siberian Crane in winter, although further study is necessary for generalization. Key words Diet, Foraging, Grus leucogeranus, Rice field, Water chestnuts The Siberian Crane Grus leucogeranus is regarded al. 2017). Such information has contributed to our as a critically endangered species by the International understanding of the current situation of the species Union for Conservation of Nature, with a global pop- in the wild, and has promoted further investigation ulation of 3,500 to 4,000 individuals (Bird Life Inter- and conservation. national 2016). In China (its main wintering range) it Currently, the Siberian Crane is an accidental visi- is listed as a category I nationally protected species tor to Japan, where it has strayed as far north as (Li et al. 2012). The natural history of this species has Hokkaido and as far south as Okinawa, although been documented in various handbooks and reviews it was a common winter visitor in Kyushu before (Cramp & Simmons 1980; Flint & Kistchinski 1981; the mid 19th century (Takashima 1953; Brazil 1991, Johnsgard 1983; del Hoyo et al. 1996), which cover 2009; The Ornithological Society of Japan 2012). It a wide range of topics including the species’ distribu- typically occurs on agricultural and reclaimed land, tion, population status, feeding and breeding biology. marshes and mudflats in Japan. Although previous Recent studies, conducted from the perspective of sight records of the Siberian Crane in Japan have conservation biology have added important informa- been collected, behavioral and ecological information tion about food and foraging ecology at migration is very scarce (Moriguchi 1977; Fujii & Fujimura stopover sites and on the wintering ground, particu- 2006; Satoh et al. 2015). When a Siberian Crane was larly at Poyang Lake in China (the most important found in a suburb of Niigata, Japan and reported in wintering ground for the species) (Sun & Huang a local newspaper (Niigata-nippou) on 11 November 2010; Jia et al. 2013; Kong et al. 2013; Burnham et 2016, it provided an opportunity to study the bird’s wintering behavior in habitat far removed from the species’ main flyway (Prentice et al. 2006). Field (Received 18 August 2017; Accepted 14 February 2018) # Corresponding author, E-mail: [email protected] observations were conducted, focusing mainly on * Present address: 1-13-11 Terao-Higashi, Niigata 950-2054, Japan food and foraging behavior, with the aim of extend- 187 A. CHIBA ing our knowledge of the Siberian Crane in Japan. standing up alert, preening, or moving. This unit was In this paper, major findings on these subjects, and evaluated based on 180 instances obtained during a miscellaneous notes on external traits and voice, are total of 2.8 hr from 22 December to 20 January 2017. reported. In order to elucidate the bird’s potential dietary items, 10 quadrats (each 1 m×1 m) were set ran- domly in one of the foraging fields in early March MATERIALS AND METHODS and food items were searched for and collected from 1) Study sites the quadrats by digging down to a depth of approxi- This study was conducted in two rice farming areas mately 15 cm with a hand rake and a pair of tweezers. in Niigata City, on the coast of the Sea of Japan: The quadrat samples were then rinsed in freshwater Shiotawara (37°49′N, 139°00′E, 1 m above sea level) and kept in plastic bottles for further examination, and Sakai (37°49′N, 139°59′E, 1 m a.s.l.). After the when items were counted, identified and measured. fall rice harvest (about 1.5 months from early Sep- In addition, fallen feathers were collected from the tember to mid-October), the rice fields become dry foraging grounds and macroscopically examined. or partly dry, and are utilized as foraging grounds by wintering Tundra Swans Cygnus columbianus. Some RESULTS rice fields adjacent to residential areas are deliber- ately flooded (one is about 2 ha and another about 1.5 1) External traits ha in area and both, up to 10 cm in depth) to serve The focal bird was identified as an immature as the roost for the swans, which the Siberian Crane Siberian Crane in its second winter, based on external also used as the communal roost. Other species, such plumage. At a glance, the bird had generally white as Grey Heron Ardea cinerea, Great Egret A. alba, plumage, but retained some juvenile characteristics Carrion Crow Corvus corone and Black Kite Milvus such as its feathered forehead and buff or cinnamon migrans are commonly observed in the vicinity. feathers in the wing, tail and uppertail-coverts (Fig. 1). When it stretched its wings, buff feathers were 2) Field observations and sampling methods visible in the alular quill coverts, median primary Field observations were carried out mainly in the coverts, leading edge, outer greater coverts, outer afternoon over 21 days for periods of 0.7–2.3 hr/day secondaries and tertials (Fig. 1A, 1B). The bird occa- during the period from mid November 2016 to early sionally preened at its roost and foraging sites, and March 2017. Observations were made from a vehicle, fallen contour feathers were collected there in early using binoculars (8×) and a telescope (20×). A digi- March. tal camera (EOS 7D, Canon, Tokyo), with a 400 mm lens, was used to record still and video images, which 2) Daily behaviour patterns and foraging were analyzed in combination with field notes. A lin- After its arrival in the farming area of Niigata City ear PCM recorder (LS-7, Olympus, Tokyo) was used in November 2016, the crane continuously inhab- to record audio data, and digital files were converted ited the same area until its departure in early March to sonograms using Raven Lite Ver. 1.0 software 2017. During the winter, it followed a regular pattern (Bioacoustic Research Program, Cornell Laboratory of daily behavior. It left the roost at around sun- of Ornithology). rise; flew directly about 0.4–2.2 km to its foraging The frequencies of food intake, excretion, stretch- grounds, where it spent most of the daytime foraging, ing and preening during foraging were recorded for then returned to the roost before sunset (Fig. 2). In a total of 14.2 hours over 10 days from 1 December midwinter, however, this regular pattern was inter- 2016 to 23 February 2017. Food intake was expressed rupted for three consecutive days when snow fell and as the number of items consumed per 10 minutes, covered the ground completely to a depth of about based on a total of 680 min of observations when the 20–30 cm. During this period, the bird remained at bird was actively foraging. The frequency of other the roost throughout the day, apparently in a dormant behaviors (excretion, stretching and preening) was state. Usually, the crane foraged alone throughout the expressed as the number of corresponding behavioral day on post-harvest rice fields, where it fed almost events/hr during the observation time. In addition, exclusively on water chestnut Eleocharis kuroguwai “unit foraging time” was defined as the time spent tubers (Fig. 3, Table 1). The dead stems of water foraging continuously, between other behaviors, e.g., chestnut remaining on the ground surface were some- 188 Feeding and vocal habits of Siberian Crane Fig. 1. External features of the immature Siberian Crane, which wintered in Niigata City in 2016/2017. A, from behind when landing; B, Dorsal surface of the primaries; C, Ventral surface of the remiges; D, Reddish beak and feathered forehead; E, Reddish foot and leg. Fig. 2. Map indicating the study area (black dot in inset) and aerial photograph showing roosts (R1 and R2) and foraging sites (F1 and F2) of the Siberian Crane. White dots in circle F1 indicate active foraging sites. times visible and the tubers found underground were The foraging behavior of the bird included vari- connected with the main plant body by the root (Fig. ous movements, which included removing superficial 4A1, A2). The parenchyma of the tuber was filled covering materials (straw on the ground), digging with starch reserves (Fig. 4A2). Other foods were into and removing the soil, exploring food with the rarely consumed, e.g., rice grains (5 times), earth- beak and consuming food items with or without rins- worms (twice), grasshoppers (once) and fishes (once) ing them in groundwater (Fig.