Yellow-thighed Brushfinch

The yellow-thighed brushfinch is about 18 cm (7.1 in) long and weighs 27 to 35 g (0.95 to 1.2 oz). The sexes have the same plumage. Adults have puffy lemon yellow feathers on their tibiae that give the species its English name. They have a black crown. The rest of their head and their upperparts are sooty slate and their wings and tail are almost black. Their chin and throat are blackish and their underparts are dull slate. They have a dark rusty brown iris, a black bill, and black to gray legs and feet. Juveniles are generally duller overall than adults and do not have the yellow tibial feathers.

The yellow-thighed brushfinch is found in Costa Rica's Cordillera de Tilarán, Cordillera Central, and Cordillera de Talamanca. In the last its range continues into western Panama's Chiriquí Province. It primarily inhabits montane evergreen forest and secondary forest in the subtropical and temperate zones. It also is found in brushy pastures and clearings and in gardens. Sources differ on its elevational range. A twentieth century source places it between 1,500 and 3,400 m (4,900 and 11,200 ft). A 2007 field guide says from 1,400 m (4,600 ft) to treeline and a 2020 source says from 1,200 m (3,900 ft) to treeline.

The yellow-thighed brushfinch's diet has not been systematically studied, but it is known to feed on insects, spiders, seeds, fruits, and nectar. It forages in pairs and family groups, and often joins mixed-species feeding flocks. It forages mostly on the ground and in the forest understory but will feed as high as the canopy.