About Catharus gracilirostris Salvin, 1865
The slaty-backed nightingale-thrush (also called the black-billed nightingale-thrush, scientific name Catharus gracilirostris Salvin, 1865) is approximately 15 cm (5.9 in) long and weighs about 20 g (0.71 oz). The sexes have identical plumage. Adults of the nominate subspecies have a slate-gray forecrown, an olive-brown crown, and a slate-gray face. Their upperparts, wings, and the upper side of their tail are olive-brown. Their throat is whitish, the center of their lower belly is light gray to whitish, and all other underparts are slate-gray, with an olivaceous band crossing the breast. They have a dark brown iris, a black bill, and dark gray legs and feet. Juveniles have more olive coloring in their upperparts than adults, with an olive-tinged sooty gray face and throat, darker underparts, and some spotting on the breast and upper belly. Subspecies C. g. accentor has more reddish-brown upperparts, a paler breast band, and blacker legs and feet than the nominate subspecies. C. g. bensoni also has more reddish-brown upperparts, along with a blackish brown forecrown, a dark reddish brown breast band, and blacker legs and feet. This species has the smallest range of any Catharus thrush, and its distribution is disjunct. The nominate subspecies is found in the Cordillera Central and Cordillera de Talamanca of Costa Rica. In the Cordillera Central, it lives on four volcanos separated by low passes, and a large valley separates these volcanos from the Cordillera de Talamanca. The other two subspecies are located in Chiriquí Province, western Panama: C. g. accentor is found in the western part of the region, and C. g. bensoni in the eastern part. The exact geographic boundaries between the three subspecies across eastern Costa Rica and western Panama have not been fully determined. The black-billed nightingale-thrush primarily lives in montane evergreen forest, elfin forest, and paramo in the upper subtropical and temperate zones. It also appears in pastures, gardens, and along roads when searching for food. Overall, sources record its elevation range from 1,800 m (5,900 ft) up to the timber line. In Costa Rica specifically, it ranges from 2,200 m (7,200 ft) to above the timberline.
