The Chestnut-breasted Partridge (Arborophila mandellii) is a species of partridge

Partridge

Partridges are birds in the pheasant family, Phasianidae. They are a non-migratory Old World group.These are medium-sized birds, intermediate between the larger pheasants and the smaller quails. Partridges are native to Europe, Asia, Africa, and the Middle East...

 endemic to the eastern Himalayas

Himalayas

The Himalaya Range or Himalaya Mountains Sanskrit: Devanagari: हिमालय, literally "abode of snow"), usually called the Himalayas or Himalaya for short, is a mountain range in Asia, separating the Indian subcontinent from the Tibetan Plateau...

 north of the Brahmaputra, and is known from Bhutan

Bhutan

Bhutan , officially the Kingdom of Bhutan, is a landlocked state in South Asia, located at the eastern end of the Himalayas and bordered to the south, east and west by the Republic of India and to the north by the People's Republic of China...

, West Bengal

West Bengal

West Bengal is a state in the eastern region of India and is the nation's fourth-most populous. It is also the seventh-most populous sub-national entity in the world, with over 91 million inhabitants. A major agricultural producer, West Bengal is the sixth-largest contributor to India's GDP...

 (Darjeeling only), Sikkim

Sikkim

Sikkim is a landlocked Indian state nestled in the Himalayan mountains...

 and Arunachal Pradesh

Arunachal Pradesh

Arunachal Pradesh is a state of India, located in the far northeast. It borders the states of Assam and Nagaland to the south, and shares international borders with Burma in the east, Bhutan in the west, and the People's Republic of China in the north. The majority of the territory is claimed by...

, north-east India

India

India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

, Nepal

Nepal

Nepal , officially the Federal Democratic Republic of Nepal, is a landlocked sovereign state located in South Asia. It is located in the Himalayas and bordered to the north by the People's Republic of China, and to the south, east, and west by the Republic of India...

 Himalaya and south-east Tibet

Tibet

Tibet is a plateau region in Asia, north-east of the Himalayas. It is the traditional homeland of the Tibetan people as well as some other ethnic groups such as Monpas, Qiang, and Lhobas, and is now also inhabited by considerable numbers of Han and Hui people...

.

It is a distinctive partridge with chestnut breast-band and grey belly. It is distinguished from the similar Rufous-throated Partridge

Rufous-throated Partridge

The Rufous-throated Partridge is a species of bird in the Phasianidae family.It is found in Bangladesh, Bhutan, China, India, Laos, Myanmar, Nepal, Thailand, and Vietnam. Its natural habitats are subtropical or tropical moist lowland forests and subtropical or tropical moist montane...

 A. rufogularis by more rufescent crown and head-sides, white gorget and entirely chestnut upper breast.

This bird has been classified as Vulnerable, with an estimated population of less than 10,000. It is threatened by forest degradation, which is fragmenting the population, and by hunting.
It is known from at least three protected areas, including Singalila National Park

Singalila National Park

Singalila National Park is a national park of India located on the Singalila Ridge at an altitude of more than 7000 feet above sea level, in the Darjeeling district of West Bengal. It is well known for the trekking route to Sandakphu that runs through it....

(West Bengal).