The black-billed capercaillie, eastern capercaillie, spotted capercaillie, or stone capercaillie, is a large grouse species closely related to the more widespread western capercaillie. It is a sedentary species which breeds in the larchtaiga forests of eastern Siberia as well as parts of northern Mongolia and China. In the far west of its distribution, the black-billed capercaillie has been known to hybridize with the western capercaillie.
Description
The length of a male black-billed capercaillie averages about 89-97 cm and weigh at 7-10 lbs, with femalesmeasuring around 69-75 cm and weighing 3-5 lbs. Their wingspan stretches approximately 29 to 46 inches long. Compared to the western capercaillie, it is slightly smaller in size with a slimmer body profile and longer neck, has a black beak instead of being horn-colored, and a longer, more spatulatetail. The eastern capercaillie has a somewhat glossy bluish-black head & neck down to a metallic turquoise breast. Distinct white markings at the tips of its upper tail and wing coverts coin this grouse the nickname 'spotted capercaillie'. The appearance of the female is similar to that of its western counterpart, except that its plumage is grayer with heavily-scaled underparts, lacks a solid rufous chest unlike the wood grouse, and has more noticeable white spots on her wings.
Behavior
When they display during the spring, males will fan out their tails, puff their chest feathers out, lower their wings, and angle their heads upward with an open beak to defend their space from other males and win over the mating rights of females. A group of hens will carefully squat with drooping wings while the lekking male is present to signal that they're ready for breeding. Their call consists of a series of loud repeating clicks ascending in tempo. Other performances involve flutter flights in which they will jump off the ground and rapidly beat their wings, generating a thundering flurry that resonates through the dense stands of conifers.
Subspecies
The University of Nebraska conducted a study on the morphological and regional differences of 3 identified subspecies, with leg feathers becoming thicker further north of this species's range:
