The Least Flycatcher, known scientifically as Empidonax minimus, is a diminutive avian insectivore and the smallest member of the Empidonax genus found in eastern North America. This bird is characterized by its dull olive-gray upperparts and a notably brighter whitish underbelly compared to its congeners. It sports two distinctive white wing bars and has white eye rings that add to its identification. The beak of the Least Flycatcher is short, with a yellowish lower mandible. Adult birds typically measure between 12 to 14 cm in height, possess a wingspan ranging from 19 to 22 cm, and weigh around 10.3 grams. Juveniles resemble adults but have slightly darker wing bars tinged with tawny or olive hues.
To distinguish the Least Flycatcher from other similar species, one should pay close attention to its vocalizations and preferred habitats. Its wings are marked with two white bars, and it has white rings around its eyes. The bird's call, a piercing "che-bec" with the second syllable louder than the first, is a reliable identifier, especially when heard in its favored environments.
The Least Flycatcher frequents aspen groves, orchards, open woods, and shade trees. It breeds in deciduous or mixed forests, sometimes in coniferous stands, often near clearings or edges. In winter, it migrates to Central America, where it can be found in forest edges and secondary growth.
This species breeds in the Eastern Rockies of Canada, Central-North, and Northeastern United States. Come winter, it migrates to Central America, from Mexico to Panama, and can also be found in villages, city parks, and along rural roads within its range.
The Least Flycatcher is known for its territorial nature, with both males and females aggressively defending their breeding grounds. Males sing to establish and maintain territories, while females are more subdued but will defend the nest with vigor when necessary.
The bird's call is a distinctive, emphatic "che-bec," with the second syllable louder. Males sing this call repeatedly, especially in the morning, to defend their territory. Females use a "chweep" note for communication with their mate and offspring, and when defending the nest.
Breeding pairs of Least Flycatchers select sites based on the proximity of neighbors rather than habitat quality. The female weaves a tidy cup-shaped nest using grass, bark, spider webs, and other materials. She lays three to five creamy-white eggs, which she incubates for 13 to 16 days. Both parents feed the nestlings, which fledge at 12 to 17 days old.
The Least Flycatcher is often confused with other Empidonax species due to similar markings. However, its distinctive call and habitat preferences aid in its identification.
The diet of the Least Flycatcher consists mainly of insects, including wasps, ants, beetles, caterpillars, and spiders. It forages by watching from a perch and catching insects mid-flight or from vegetation, often hovering to attack prey.
The Least Flycatcher is currently listed as Least Concern by the IUCN, indicating that it is not at immediate risk of population decline or habitat loss at a global scale.