Measuring between 85-97 cm, the darter possesses a long, slender neck and a straight, pointed bill. The adult plumage is predominantly black on top, with silvery streaks along the wing coverts and tertials. The crown and neck are brown, shading into black toward the back. A distinct pale line runs over the eye and throat, giving the bird a striped look. One of its most striking features is the white iris surrounded by a yellow ring, which becomes brighter during the breeding season. Males often feature black speckles on the throat, while females typically have shorter bills and a wide buff band on the neck.