306. (American Ornithologists' Union check-list #) Heath Hen: Tympanuchus cupido (Linn.) These birds bear a close resemblance to the prairie hen, the principal difference being in the neck tufts, which are pointed instead of rounded. Length--18.00. Breeding Range--Martha's Vineyard. Nest on the ground; eggs brownish drab or buff. Size--1.73 x 1.29. The Heath Hen is almost extinct, being restricted to the island of Martha's Vineyard, where they are "in imminent danger of total extinction."