Chinese Merganser

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Common Name: Chinese or Scaly-sided Merganser
Scientific Name: Mergus squamatus

Size: 20.4-22.8 inches (52-58 cm); Wingspan: 26-29 inches (83-85 cm)

Habitat: Asia; south-east Russia, North Korea and Heilongjiang, Jilin and Inner Mongolia in north-east China. Some birds winter in south-east Russia and North Korea, but most winter in central and southern China (the majority of wintering flocks found on rivers and other water bodies in the Yangtze River catchment, with small numbers in Japan, South Korea, Taiwan (China), Myanmar and Thailand.

It breeds below c.900 m in mountainous areas, along rivers with tall riverine forest, mainly within the temperate conifer-broadleaf forest zone. It is largely confined to primary forests, with an abundance of potential nest-holes. During a study on the Russian breeding grounds, river size, mountain slope, human population, estimated forest cover and water clarity all failed to explain the observed distribution, but the species showed a marked preference for the middle reaches of rivers.

It prefers freshwater habitats in winter, only c.10% are known to winter on coastal waters. On passage and in winter, it feeds along large rivers. Flocks of up to 20 individuals have been noted on passage or in winter. In Russia, they molt on a range of water bodies within the breeding range and north and east of breeding range, including rivers, estuaries and the sea.

Status: Endangered. Global population: >2,500 individuals. This species has a very small population which is suspected to be undergoing a continuing and rapid decline as a result of habitat loss, illegal hunting and disturbance.

In the 1960s and 1970s, its decline in Russia coincided with economic development of the taiga. Primary forests in the valleys of all large rivers were greatly altered, but large-scale deforestation in river valleys is now prohibited; however, the new Russian Forest Codex (2007) requires a water protection zone (no deforestation) of only 100 m for large rivers (50 m on each side), and 50 m (25 m each side) for rivers shorter that 100 km, which is likely to significantly reduce suitable breeding habitat for this species, which nests up to 150 m from rivers. Logging of river sources and adjacent slopes has led to reduced spring water levels and changes in fish abundance; since logging began on the Avvakumovka River in 2004, spring water levels and merganser populations have undergone continuous declines. Other major threats within the breeding range include illegal hunting, drowning in fishing nets (a major cause of mortality at Russian breeding sites in 2003-2007, disturbance from motor boats during the breeding season, river pollution and natural predators. Increased hunting of waterfowl for sport together with poor regulation of the spring hunting season (which is intended to coincide with passage migration and avoid targeting locally breeding birds) is a significant and increasing threat; large numbers were reportedly shot in the Kievka River basin, southern Primorye, in spring 2008.

Threats in its breeding range in China include dam construction, deforestation, illegal hunting, human disturbance and the use of poisons and/or explosives for fishing. Fine-meshed nets were a significant threat to the post-breeding congregations at Song Jiang He in Jilin Province, China, but illegal fishing at the site has been reduced and only large-meshed nets are used in legal fish-farming. The site remains threatened by industrial pollution.

The proposed Korean Grand Canal project, which aimed to canalize 3,134 km of the Korean peninsula's rivers and radically alter the Han and Nakdong rivers (which currently support an estimated 30-50 birds in winter), was suspended in June 2008 and an alternative scheme, the Four Rivers Project, was proposed in December of that year, with an environmental impact assessment and launch of construction in 2009. In South Korea, the species is impacted by increased river turbidity due to construction and dredging, bridge-building activities, river-bank strengthening and road-widening schemes. Some of these activities are associated with the Four Rivers Project on several stretches of river used regularly or irregularly by the species. Other significant aspects of habitat modification will include the deepening of rivers and the removal of boulders and islands, which are used for roosting. Many stretches of river are expected to be rendered unusable for the species owing to habitat degradation and disturbance.

The species has low genetic diversity. High levels of heavy metals, especially As and Hg, were reported in females and their eggs after wintering in the Yangtze catchment. Poor egg hatchability recorded within Sikhote-Alin population could be a result of pollution on the wintering grounds.

Diet: Aquatic arthropods and small or young fish. Stonefly (Plecoptera) and giant caddisfly larvae (Phryganeidae) may constitute the bulk of its diet when available. Beetles and crustaceans are eaten less regularly, though the latter may be more important in autumn. As aquatic insect larvae hatch in the course of the summer, fish become more prominent in the diet. Favorite fish species include the Dojo Loach (Misgurnus anguillicaudatus) and the lenok (Brachymystax lenok). More rarely eaten are such species as the lamprey (Eudontomyzon morii), the sculpin (Mesocottus haitej, or the Arctic Grayling (Thymallus arcticus). Food is caught by diving and is typically swallowed while still underwater.

Nesting: It has a thin red bill and a scaled dark pattern on the flanks and rump. Both sexes have a crest of wispy elongated feathers, reaching almost to the shoulders in adult males and being fairly short in females and immatures. The legs are orange-red. The adult male has a black head and neck, white breast and under parts, and blackish mantle and wings, except for the white inner wings. The scaling is also black, while the tail is medium grey. The female has a buffish head and greyish neck.

Cool Facts: They are shy birds and startle easily. They spend most of the daylight time foraging, except around noon when they take some time to rest, preen and socialize at the river banks, where they also sleep.

Primary forests are protected at some breeding localities in China and at the most important breeding site in North Korea. Small proportions of its breeding and non-breeding populations occur inside protected areas, notably Sikhote-Alin' State Biosphere Reserve, Lazovskiy State Reserve and Botchinskiy State Reserve (Russia), and Changbai Shan Nature Reserve (China). An artificial nest program in Russia, involving the provision of at least 180 nest boxes, has shown positive results, increasing habitat capacity along rivers with logged flood-plains. The program involves the continued maintenance of artificial nests, liaison with hunters and fishers and collaboration with local communities, including information and education activities and the construction of a research and visitor center. This has already resulted in a change in fishing practices by local people. It has also facilitated the capture of females for tagging with geolocators, allowing the identification of staging and wintering sites.

Found in Songbird Remix Waterfowl Volume II: Diving and Sea Ducks

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