Choco Vireo

The Choco Vireo (Vireo masteri) is a small, poorly known passerine in the family Vireonidae, with a highly restricted range in the western Andes foothills on the Pacific slope of Colombia and possibly adjacent Ecuador. It was described scientifically only in 1997, reflecting the challenges of survey work in the remote, wet, and botanically complex terrain of the Colombian Chocó. The Choco Vireo is a small greenish-yellow vireo with a distinctive facial pattern including a pale supercilium and dark eye-stripe. Like other vireos, it forages methodically through mid-canopy and sub-canopy foliage, gleaning caterpillars, beetles, and other invertebrates from leaves. Its song is a series of high, slurred phrases repeated with characteristic vireonid persistence. The species appears restricted to humid montane and foothill forest at elevations roughly between 800 and 1,800 metres — a zone severely impacted by the expansion of coca cultivation, illegal logging, and cattle ranching in the Colombian Pacific region. The IUCN classifies the Choco Vireo as Endangered given its extremely small and severely fragmented range and continued loss of suitable forest habitat. Very little is known about its population size, ecology, or breeding biology, making targeted survey and monitoring urgently needed.