About Margarornis rubiginosus Lawrence, 1865
The ruddy treerunner, scientifically named Margarornis rubiginosus Lawrence, 1865, measures 15 to 16 cm (5.9 to 6.3 in) in length and weighs 17 to 24 g (0.60 to 0.85 oz). Males and females have identical plumage. Adults of the nominate subspecies have a buffy whitish supercilium and eyering on an otherwise dull rufescent brown face. Their crown is dull reddish brown, and they have a narrow, paler reddish collar. Their upperparts and wing coverts are reddish chestnut. Their flight feathers are dark fuscous with rufescent edges. Their tail is a slightly paler reddish chestnut than the back; the ends of the tail feathers lack barbs, which creates a spiny appearance. Their throat is whitish with a buffy white lower edge. Their upper breast is dull rufescent brown marked with pale buff V-shaped markings, while the lower breast has darker buff spots. Their belly is almost unmarked dull rufescent brown, and their flanks and undertail coverts are a darker chestnut brown. Their iris is dark brown to brown, their maxilla is brown to black, their mandible is pinkish horn to pale pinkish white, and their legs and feet vary in color from grayish olive to dull pinkish to grayish brown. Juveniles have less distinct breast markings than adult individuals. The subspecies M. r. boultoni differs from the nominate by having a deeper buff supercilium, slightly darker upperparts, and deeper, richer cinnamon underparts with smaller and fewer markings. The ruddy treerunner is a highland bird with a disjunct distribution. The nominate subspecies occurs from the Cordillera de Guanacaste in northern Costa Rica south into Panama's Chiriquí Province. Subspecies M. r. boultoni is found in eastern Chiriquí and Veraguas Provinces, Panama. This species lives in the interior and edges of montane evergreen forest, at elevations between 1,200 and 3,000 m (3,900 and 9,800 ft).
