The yellow-faced grassquit (Tiaris olivaceus) is a passerine bird in the tanager family Thraupidae and is the only member of the genus Tiaris. It is native to the Central America, South America, and the Caribbean. It is a small bird with a conical bill, sharper than that of the related seedeaters. It is 10–10.7 cm (3.9–4.2 in) long and weighs about 8–10 g (0.28–0.35 oz), depending on subspecies. The adult male has an olive-green back, and its face and breast are black apart from a bright yellow throat, supercilia, and lower eyelid spot. The rest of the underparts are greyish olive. The beak and eyes are dark, the legs are grey.
The Yellow-faced Grassquit occurs from Mexico to northwestern South America, and it is a common resident throughout the Greater Antilles and the Cayman Islands in the Caribbean (Raffaele and others 1998). In Puerto Rico, it is found throughout the main island but occurs mostly in the municipalities of Humacao and Fajardo at the eastern region (Biaggi 1997). It also occurs sporadically in El Yunque National Forest and near El Verde field station along grassy roadsides (Recher and Recher 1966). In addition, it has also been reported from Culebra (Bond 1961, Wetmore 1917) and Vieques islands (Bond 1961, Saliva 1994, Sorrié 1975, Wetmore 1916), in the latter being an uncommon resident (Gemmill 2015). The species usually inhabits open grassy areas from the lowlands into the high mountains (Raffaele and others 1998), as well as marshy areas, open brushy fields, and roadsides with tall grasses (Oberle 2018). The atlas fieldwork yielded a total of 532 records within 316 hexagons or 66 percent of the 479 total hexagons (see map). Of the 316 hexagons where this species was found, breeding met the atlas definition of confirmed in 10 percent (33) of the hexagons, probable in 40 percent (125), and possible in 50 percent (158) (see map). Yellow-faced Grassquit distribution. The map shows the highest breeding code by hexagon and overlaying the ecological life zones in Puerto Rico. Note: percentages may not total 100 due to rounding. 283Yellow-faced Grassquit/Gorrión Barba Amarilla
Previously published reports indicate that the Yellow-faced Grassquit breeds throughout the year (Raffaele and others 1998) but primarily during February, March, and April (Biaggi 1997). The nests are dome-shaped structures made mostly of fine grasses and are built just off the ground in grass clumps (Raffaele and others 1998). Atlas results show that this species breeding season extends throughout the year with the most breeding activity from March to June (see chart). The breeding activity peaks in May at the onset of the rainy season, and it mostly occurs in the subtropical moist forest life zone (see chart). Results show that this species breeds mostly within the subtropical moist forest life zone (62 percent of the hexagons) and less frequently at higher elevations within the subtropical wet forest life zones (20 percent of the hexagons) and in the subtropical dry forest life zone (17 percent of the hexagons) (see table and map).
The Yellow-faced Grassquit is currently listed as a species of least concern by the IUCN (BirdLife International 2018). Locally, this species is not listed in any of the threatened categories of PRDNER and USFWS. In Puerto Rico, it has a protected habitat in land of 12 percent or 928 km2 of the total area covered by the hexagons where evidence of breeding was found for this species (7557 km2).