Yellow-throated Euphonia

The yellow-throated euphonia is a small, short-billed, short-tailed arboreal passerine with pointed wings. An adult is 10–12 cm long with the tail contributing 3.3 to 3.6 cm. The wingspan is 5.8 to 6.1 cm and weight about 11.6 – 17.8 g. The adult male of the nominate species has a small bright yellow patch on its forehead that extends back to about the middle of the eyes. The rest of the head, upperparts including upper-wing coverts, and the upper-tail coverts are a glossy blue-black. The flight feathers are black with steel blue edgings and the entire underparts are yellow. The underwing coverts are white and the under-tail coverts are a dark dull grey. The inner webs of the outer 2–3 feather pairs are mostly white forming a large, white, oval-shaped area on the wing undersurfaces. The beak tip is black, becoming blue-gray beneath nostrils and on mandible. The irises are brown and the legs and feet are dusky dark gray. The adult female has an olive-green faintly glossy metallic coloration on top of her head, side of head, and upperparts. The throat, center of breast and lower underparts are whitish to greyish-white and sides of breast, sides, and flanks are bright yellowish olive-green. Under tail-coverts are pale olive-yellowish and the beak is similar to the adult male. …

The yellow-throated euphonia has a northern range limit in eastern Mexico of southern Tamaulipas, eastern San Luis Potosí, northeastern Puebla (east of Huauchinango), and northern Veracruz south to Tuxpan and Tlapacoyan. Its range extends south into Belize, Honduras, El Salvador, eastern Nicaragua, Costa Rica, and western Panama. E. h. gnatho is found in northeastern Nicaragua, Costa Rica (absent in southwest and Caribbean lowlands), and extreme Western Panama. It is found mainly in dry to humid regions along forest borders, second growth, shady plantations, and medium-height thick growing woods along river gorges and streams. Occurs from lowlands to 2100 m in Mexico and primarily in plateau and hill country in El Salvador and Costa Rica. Presumed to reside in foothills between 900 m and 1200 m elevation in western Panama. Resident over most of range with some local seasonal movement in response to food availability. In Mexico it is considered likely only a non-breeding visitor from October to May on the Pacific slope of Isthmus of Tehuantepec in Oaxaca. Found to be present in El Salvador only during the spring and summer months, so possible that it is migratory.

The yellow-throated euphonia feeds almost exclusively on fruits and berries, particularly feeding on mistletoe berries and locally feeds heavily on figs and ripe bananas. They are known as "mistletoe birds" in the islands of the Lesser Antilles and insects contribute considerably less to their diet than fruits. When they do hunt for insects, they look through leaves and small branches of trees as well as combing over seed heads of palms. They have also been observed catching insects and feeding them to their fledglings. Mistletoe berries have a moderately tough skin containing a seed and in feeding the euphonias break the outer skin with their bills and swallow the single seed surrounded by an adhesive pulp. The seeds pass through the intestinal canal wholly undigested and nutritive matter is readily assimilated without preliminary grinding. This subsistence on a particularly specialized food that does not require mechanical comminution to digest has resulted in the loss of the gizzard and the specialization of the digestive tract into a simple membranous sac connecting the esophagus and duodenum, which is arranged to permit the rapid and unobstructed passage of food through the entire length of the canal.

Yellow-throated euphonia breeding is reported in May and August in Mexico, June in Belize, March–May in Guatemala and April–June in Costa Rica. …