The immense variety in chicken appearance, from feathered legs to different comb shapes and plumage colors, often leads to questions about their classification. Despite this diversity, all domestic chickens belong to a single species.
The Domestic Chicken: One Species, Many Breeds
The common domestic chicken, despite its diverse appearances, is scientifically classified as a single subspecies: Gallus gallus domesticus. This means all the various types of chickens seen today, such as the egg-laying Leghorns, the large Plymouth Rocks, or the fluffy Silkies, belong to one biological species. These distinct groups are not separate species but are instead recognized as breeds. A breed refers to a specific group of animals that humans have selectively bred over generations for particular characteristics. These traits can include specific physical features, feather patterns, egg color and production rates, or suitability for meat production.
The process of selective breeding has allowed humans to develop hundreds of different chicken breeds, each with its own set of desired attributes. For instance, some breeds are known for laying a high number of eggs, while others are prized for their meat quality. This extensive breeding has resulted in the wide array of forms within the single domestic chicken subspecies.
The Wild Relatives: Junglefowl Species
The domestic chicken traces its primary ancestry back to the Red Junglefowl (Gallus gallus), a wild bird native to Southeast Asia. This species is found across much of South and Southeast Asia, inhabiting tropical forests and scrublands. While the Red Junglefowl is the main progenitor, genetic contributions from other wild junglefowl species have also been identified in the domestic chicken’s lineage.
Within the Gallus genus, there are three other recognized wild species, each with its own distinct characteristics and geographical range. The Grey Junglefowl (Gallus sonneratii) is endemic to the Indian subcontinent, primarily found in peninsular India. Its plumage features yellow-tipped hackle feathers.
The Green Junglefowl (Gallus varius) is native to Indonesia, specifically found on islands like Java, Bali, and Lombok, often inhabiting coastal areas and low-lying forests. The Sri Lankan Junglefowl (Gallus lafayettii) is endemic to Sri Lanka, where it is also the national bird. These wild junglefowl species are distinct from the domestic chicken but provide insight into its evolutionary history.