Baer's pochard

Baer's pochard
Male (wintering)
Female (breeding)
Conservation status
Critically Endangered  (IUCN 3.1)[1]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Anseriformes
Family:	Anatidae
Genus:	Aythya
Species:	A. baeri
Binomial name
Aythya baeri (Radde, 1863)
Resident   Breeding season   Passage   Non-breeding season
Synonyms[2]
List Anas leucophthalmos Kittlitz, 1829 Anas (Fuligula) baeri Radde, 1863 Aythya ferina Swinhoe, 1871 Fulix baeri Swinhoe, 1871 Fulix cristata G. R. Gray, 1871 Fuligula nyroca David, 1871 Fuligula baeri Dybowski, 1874 Fulix nyroca David and Oustalet, 1877 Nyroca ferruginea Blakiston and Pryer, 1882 Fuligula baueri Tristram, 1889 Nyroca baeri Salvadori, 1895

Baer's pochard (Aythya baeri) is a

It has a distinctive black head and neck with green gloss not present elsewhere in Aythya. While in poor light, it is likely to look completely black. It is very similar and closely related to the ferruginous duck, and they were previously considered to be a single species; Baer's pochard is differentiated by its white flanks when floating on the water, as well as its larger size and longer, more rounded head.

Its breeding season varies by latitude and environment. The nest, built from sedges, reeds and other plants, is placed among emergent vegetation, usually in shallow water or on small islands or ridges. Its clutch size ranges from 5 to 14. Males usually take on sentry duty, and females take on the responsibility of incubating.

Baer's pochard was once a common species in its range, but is now very rare. The number of mature individuals may be less than 1,000, and its population is still declining. Hunting and habitat loss are considered to be the main reasons. This species has been classified as

Breeding male has a black head and neck with green gloss, white or paler yellow eyes, blackish-brown back, dark chestnut breast, white or light chestnut flanks and a short and low tail. The green gloss on its head is unique among Aythya. While it is likely to look completely black in poor light. Female has a dark brown head and neck that blend into the chestnut-brown breast and flanks. Eclipse and first-winter male resembles female, but retain the white eyes, while female has brown eyes. Both male and female have wide white speculum feathers, white vent-side, dark-grey bill, black nail and dark-grey tarsometatarsus.^[13][8]

It is similar to its close relative, the ferruginous duck (A. nyroca), both have white vent-side and iris in males, black nail, and wide white speculum feathers. Although Baer's pochard is bigger, has a longer head, body and bill. Unlike the ferruginous duck's tall and triangular head, Baer's pochard has a more rounded head and a flatter forehead. ^[14] The white part on the belly extends to its flanks in Baer's pochard, which is visible when floating on the water, while the ferruginous duck has a smaller white part on its belly.^[12] The female Baer's pochard has a distinctly bright chestnut spot at the lore, which is absent in ferruginous duck.^[14]

Baer's pochard is usually a quieter duck, but during its courtship display, both sexes give harsh graaaak. Females may give kura kura kura and males may give kuro kuro at other times.^[13]

Distribution

Baer's pochard traditionally bred in the Amur and Ussuri basins in Northeast China and the southeastern Russian Far East. In recent years, it has also colonised North China and Central China. It winters in most areas south of the Yellow River in China, Taiwan, Japan, Bangladesh, India, North Korea, Laos, Myanmar, Nepal, Thailand and Vietnam, and occasionally appears in Bhutan, South Korea, Philippines or Pakistan as a rare vagrant.^[1] It leaves its wintering grounds by mid-March and returns to them by mid-October or early November.^[12]

The species has become extremely rare in its traditional breeding areas, and since 2010, there have been no confirmed breeding reports in all sites north of Beijing. However, the numbers recorded during the breeding season are smaller than those recorded in winter, so there may still be unknown breeding sites.^[15] For example, there are some doubtful breeding reports in the Chinese part of Lake Khanka, the Russian part of Lake Khasan, and the Muraviovka Park [ru]. Since 2012, new breeding sites have been discovered in several provinces of China, including Hebei, Hubei^[16] and Jiangxi;^[17] the latter two cities are far from traditional breeding sites in the Amur and Ussuri basins.^[1] In these new breeding areas, warmer climate conditions provide a longer breeding season (about twice as long as in the Amur and Ussuri basins) which allows birds to lay a replacement clutch if their first clutch fails.^[18] Baer's pochard is no longer migratory in central and eastern China.^[19]

The wintering grounds have also contracted significantly in recent years. Since at least the winter of 2010-2011, Baer's pochard no longer winters in any site outside mainland China, except as a vagrant. In its wintering grounds in mainland China, the population has also declined severely, by more than 99%.^{[note 2][1][20]}

Behaviour and ecology

Baer's pochard is a shy species, that inhabit open, slow-flowing lakes, swamps and ponds. It breeds around lakes with rich aquatic vegetation, nesting in dense grass, flooded tussock meadows, or flooded shrubby meadows. In winter, it forms large flocks on large and open freshwater lakes and reservoirs with other

Baer's pochard appears to have a monogamous mating system, at least within a breeding season.[18] In traditional breeding grounds in northeastern China, Baer's pochard gathers in gaps in the ice before it completely thawed. After the ice season, it gathers on the large, open lakes. They breed from mid-to-late May.^[12] While in Fuhe Wetland in Wuhan, Hubei, Baer's pochard gathers in large groups on the open lakes before breeding season. It is divided into small groups in mid-April, in which they will courting and mating.^[18][23] During courtship, the male swims around the female, repeatedly nods his head up and down. When other males approach, it swims toward them quickly to drive them away, but there is no violent fight between them. The female also nods her head in response. When the male approaches, the female straightens her neck and lowers her head to the water. He then climbs onto her body and bites her nape feathers to mate. After the mating, the male and female leave the flock for nesting.^[23]

Baer's pochard's nest is circular cylindrical, located among emergent vegetation, usually in shallow water or on small islands or ridges. The nest is made of sedges, reeds and other plants collected from the immediate vicinity, lined with a layer of down. Its clutch ranged from 5 to 14, with an average of 9.7.^[18] Males usually take on sentry duty at about 10 meters from the nest during hatching.^[23] Females leave the nest to forage 2–3 times a day, usually during 6:00-20:00, and lasted for 27–240 min. They cover the eggs with nest materials during forging, and place them onto their back when coming back. If water levels are elevated by heavy rainfall or human activity, females increase the height of the nest to avoid flooding. During the hottest days, females often stand on the nest and shelter eggs from the strong sunlight, whilst allowing circulation of air around them. Females also take water into their plumage and use it to cool the eggs. The incubation lasted for 23-26 days.^[18]

Studies have shown that the nest survival rate

• 
  Breeding pair in Wuhan, Hubei, China
• 
  Breeding male
• 
  Eggs^[18]
• 
  Hatching female^[18]
• 
  Female and ducklings^[18]

Biological interaction

Incomplete inter- and intra-specific

Baer's pochard has hybridized with lesser scaup, common pochard, ferruginous duck, New Zealand scaup, chestnut teal and wood duck in captivity.^[25] Ferruginous duck was observed displaying to Baer's pochards several times in China and South Korea. Some individuals showed mixed characteristics of common, ferruginous and Baer's pochards,^{[note 4]} so they may be currently hybridising in the wild. The Baer's pochard has declined sharply in recent years, but the ferruginous and common pochard has expanded their breeding grounds, and even to the core areas of Baer's pochard's, which makes the hypothesis possible.^[26]

The research on its gut microbiota showed that the richest microorganism phyla of Baer's pochard are Bacillota, Pseudomonadota and Bacteroidota, which were consistent with those of the domestic goose, duck and chicken. The gut microbiota in diarrheic Baer's pochard is low in diversity, and the species were also significantly different from healthy individuals. Most species in reduced numbers are thought to be intestinal beneficial bacteria.^[27]

Threats and protection

Baer's pochard was once a common species in its range, but is now very rare.

A study published in 2022 showed that most breeding sites (81.8%) and suitable habitats (94%) are not located in protected areas, and overlap with large cities. Current protected areas may be less effective for the conservation under predicted global climate change, closely coordinated cross-border cooperation would be critical for Baer's pochard.[19]

Explanatory footnotes

References

External links

Wikimedia Commons has media related to Aythya baeri.

Wikispecies has information related to Aythya baeri.

• Baer's pochard (Aythya baeri) at ARKive
• "Aythya baeri". Avibase.
• "Baer's pochard media".
  Internet Bird Collection
  .
• Baer's pochard photo gallery at VIREO (Drexel University)
• Interactive range map of Aythya baeri at IUCN Red List maps
• Audio recordings of Baer's pochard on Xeno-canto.