The Groove-billed Ani is about 34 centimetres (13 in) long, and weighs 70–90 grams (2.5–3.2 oz). It is completely black, with a very long tail almost as long as its body. It has a huge bill with horizontal grooves along the length of the upper mandible. It is very similar to the Smooth-billed Ani, some of which have bills as small as the Groove-billed and with grooves on the basal half. The two species are best distinguished by voice and range. In flight, the ani alternates between quick, choppy flaps and short glides.
Tropical dry forest in NW Costa Rica 5 weeks into the rainy season.