Euler's flycatcher (''Lathrotriccus euleri'') is a small

passerine A passerine () is any bird of the order Passeriformes (; from Latin 'sparrow' and '-shaped') which includes more than half of all bird species. Sometimes known as perching birds, passerines generally have an anisodactyl arrangement of their ...

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

in the family

Tyrannidae The tyrant flycatchers (Tyrannidae) comprise a Family (biology), family of passerine birds which is found virtually throughout North America, North and South America. It is the world's largest family of birds, with more than 400 species, and is ...

, the tyrant flycatchers. It is found on

Trinidad Trinidad is the larger, more populous island of the Republic of Trinidad and Tobago, the country. The island lies off the northeastern coast of Venezuela and sits on the continental shelf of South America. It is the southernmost island in ...

and in every mainland

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

n country except

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

.Remsen, J. V., Jr., J. I. Areta, E. Bonaccorso, S. Claramunt, G. Del-Rio, A. Jaramillo, D. F. Lane, M. B. Robbins, F. G. Stiles, and K. J. Zimmer. Version 30 January 2025. Species Lists of Birds for South American Countries and Territories. https://www.museum.lsu.edu/~Remsen/SACCCountryLists.htm retrieved 31 January 2025 It formerly was found on

Grenada Grenada is an island country of the West Indies in the eastern Caribbean Sea. The southernmost of the Windward Islands, Grenada is directly south of Saint Vincent and the Grenadines and about north of Trinidad and Tobago, Trinidad and the So ...

Taxonomy and systematics

Euler's flycatcher has these five subspecies: *''L. e. flaviventris'' ( Lawrence, 1887) *''L. e. lawrencei'' ( Allen, JA, 1889) *''L. e. bolivianus'' (Allen, JA, 1889) *''L. e. argentinus'' ( Cabanis, 1868) *''L. e. euleri'' (Cabanis, 1868) Euler's flycatcher has a complicated taxonomic history. What are now the subspecies ''L. e. euleri'' and ''L. e. argentinus'' were originally described in the same 1868 publication as ''Empidochanes euleri'' and ''Empidochanes argentinus'' respectively. Subspecies ''L. e. flaviventris'' was originally described as ''Blaccicus flaviventris''. Subspecies ''L. e. lawrencei'' was originally described as ''Ochthaeca flaviventris'' but later renamed ''Empidonax lawrencei''. In the early 1900s genus ''Empidochanes'' was merged into '' Empidonax''. Some early twentieth century authors treated the northern subspecies ''L. e. flaviventris'', ''L. e. lawrencei'', and ''L. e. bolivianus'' as the separate species "Lawrence's flycatcher" but by mid-century all five taxa were generally regarded as subspecies of ''L. euleri''.Remsen, J. V., Jr., J. I. Areta, E. Bonaccorso, S. Claramunt, G. Del-Rio, A. Jaramillo, D. F. Lane, M. B. Robbins, F. G. Stiles, and K. J. Zimmer. Version 30 January 2025. A classification of the bird species of South America. American Ornithological Society. https://www.museum.lsu.edu/~Remsen/SACCBaseline.htm retrieved 31 January 2025Farnsworth, A. and D. J. Lebbin (2020). Euler's Flycatcher (''Lathrotriccus euleri''), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.eulfly1.01 retrieved March 28, 2025 The

Clements taxonomy ''The Clements Checklist of Birds of the World'' is a book by Jim Clements which presents a list of the bird species of the world. The most recent printed version is the sixth edition (2007), but has been updated yearly, the last version in 202 ...

subdivides the species into the "Lawrence's" and "Euler's" groups in recognition that the earlier treatment as two species might be valid.Clements, J. F., P.C. Rasmussen, T. S. Schulenberg, M. J. Iliff, T. A. Fredericks, J. A. Gerbracht, D. Lepage, A. Spencer, S. M. Billerman, B. L. Sullivan, M. Smith, and C. L. Wood. 2024. The eBird/Clements checklist of birds of the world: v2024. Downloaded from https://www.birds.cornell.edu/clementschecklist/download/ retrieved October 23, 2024 Many authors retained Euler's flycatcher in ''Empidonax'' through most of the twentieth century. By the very early twenty-first century it was generally agreed to properly belong to ''Lathrotriccus'' which had been erected in 1986. During the several reclassifications some subspecies received new

specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

s to comply with the

principle of priority Priority is a principle in Taxonomy (biology), biological taxonomy by which a valid scientific name is established based on the oldest available name. It is a decisive rule in Botanical nomenclature, botanical and zoological nomenclature to recogn ...

. Euler's flycatcher is named for the Swiss

ornithologist Ornithology, from Ancient Greek ὄρνις (''órnis''), meaning "bird", and -logy from λόγος (''lógos''), meaning "study", is a branch of zoology dedicated to the study of birds. Several aspects of ornithology differ from related discip ...

Carl Euler. It shares genus ''Lathrotriccus'' with the gray-breasted flycatcher (''L. griseipectus'').

Description

Euler's flycatcher is long and weighs . The sexes have the same plumage. Adults of the

nominate subspecies In biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics ( morphology), but that can successfully interbreed. ...

''L. e. euleri'' have a warm olive-brown crown, nape, and cheeks. They have a whitish

eye-ring The eye-ring of a bird is a ring of tiny feathers that surrounds the orbital ring, a ring of bare skin immediately surrounding a bird's eye. The eye-ring is often decorative, and its colour may contrast with adjoining plumage. The ring of feather ...

and a faint pale stripe above the lores. Their upperparts are mostly olive-brown with a brown rump. Their wings are dusky with pale buff ends on the

coverts A covert feather or tectrix on a bird is one of a set of feathers, called coverts (or ''tectrices''), which cover other feathers. The coverts help to smooth airflow over the wings and tail. Ear coverts The ear coverts are small feathers behind t ...

that show as two wing bars. Their secondaries and tertials have pale buffy-brown edges. Their tail is dusky. Their throat is grayish white, their breast is washed with brownish olive, and their belly is pale yellow to white. The other subspecies of Euler's flycatcher differ from the nominate and each other thus: *''L. e. flaviventris'': similar to nominate *''L. e. lawrencei'': more olive upperparts than nominate, with whitish throat, drabber gray breast, and white belly *''L. e. bolivianus'': more olive upperparts than nominate but less so than ''lawrencei'' with pale olive-gray breast and a slightly less yellow belly than nominate *''L. e. argentinus'': drabber gray breast than nominate with whitish throat and white belly All subspecies have a dark iris, a black

maxilla In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxil ...

, a dull pinkish or orangish pink

mandible In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

, and blackish brown legs and feet.

Distribution and habitat

The subspecies of Euler's flycatcher are found thus: *''L. e. flaviventris'': Grenada (possibly extinct) *''L. e. lawrencei'': Colombia's Eastern Andes, Andes and Coastal Ranges of western and northern Venezuela, Trinidad, and locally in

the Guianas The Guianas, also spelled Guyanas or Guayanas, are a geographical region in north-eastern South America. Strictly, the term refers to the three Guianas: Guyana, Suriname, and French Guiana, formerly British, Dutch, and French Guiana respectiv ...

*''L. e. bolivianus'': Amazonas and Bolívar states in southern and eastern Venezuela south through eastern Ecuador and eastern Peru into northwestern Bolivia and east into much of Amazonian Brazil *''L. e. argentinus'': central and eastern Bolivia, northern and northeastern Argentina, and Paraguay; in migration eastern Peru and eastern Brazil *''L. e. euleri'': southeastern Brazil, northeastern Argentina, and Uruguay; in migration Peru, Bolivia, and Brazil Euler's flycatcher inhabits moist to humid

primary Primary or primaries may refer to: Arts, entertainment, and media Music Groups and labels * Primary (band), from Australia * Primary (musician), hip hop musician and record producer from South Korea * Primary Music, Israeli record label Work ...

and secondary forest and woodlands in the tropical and lower subtropical zones. It favors the lower levels and edges of its habitat. In elevation it ranges from sea level to in Brazil. In Venezuela it is found below north of the

Orinoco River The Orinoco () is one of the longest rivers in South America at . Its drainage basin, sometimes known as the Orinoquia, covers approximately 1 million km2, with 65% of it in Venezuela and 35% in Colombia. It is the List of rivers by discharge, f ...

and below south of it. It reaches in Colombia, in Ecuador, and in Peru.

Behavior

Movement

Most populations of Euler's flycatcher are year-round residents. Subspecies ''L. e. argentinus'' and the more southerly individuals of ''L. e. euleri'' move north for the austral winter into Peru and Brazil and perhaps as far as Venezuela. The species' migration timing, routes, and extent are barely known.

Feeding

Euler's flycatcher feeds on

arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

s. It typically forages singly or in pairs and rarely to occasionally joins mixed-species feeding flocks. It perches upright in low vegetation, usually somewhat hidden, and captures prey in mid-air with sallies from the perch ( "hawking"). It returns to the same perch or another one about equally.

Breeding

The breeding season of Euler's flycatcher varies geographically, spanning May to July on Trinidad, September to November in Brazil, and October to as late as January in Argentina. Its nest is an open cup made from plant fibers and lined with soft black fibers, built in a branch fork or perched on the edge of a hole in a trunk. It typically is placed within about of the ground but may be higher. The clutch is two or three eggs. They are white, marked with reddish brown mostly at the larger end, and in a study in Argentina weighed about and measured roughly . In that study only the female incubated, for 16 to 18 days, and fledging occurred about 15 days after hatch. Both parents provisioned the nestlings. In the study area

predation Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

was found to be moderate to light.

Vocalization

In Brazil Euler's flycatcher sings a "varied series of 2-5 notes, 1st one normally stressed and slightly longer than slightly descending notes; thereafter ''Tjeew-tjuh'' or ''Tjeew-terduh''". In Venezuela its song is described as "an abrupt, almost explosive ''FEEU! pe'pe 'pe'p'p'', 1st note loudest, last notes run together, buzzy and downscale". In Peru it is described as "a repeated, 2-note, buzzy, descending ''DZEER-hur'' (''hur'' sometimes lacking) interspersed with sneezing ''DZEER-wee'chew'' phrases". There its call is "a buzzy, descending series of 2-7, usually 4, notes ''DZEE-dzee-dzee-dzer'' or ''DZEEW-dzew-dzew-dzeer''".

Status

The

IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...

has assessed Euler's flycatcher as being of Last Concern. It has an extremely large range; its population size is not known and is believed to be decreasing. No immediate threats have been identified. However, subspecies ''L. e. flaviventris'' has not been recorded since 1950 and is possibly extinct. It is considered "uncommon to locally fairly common" in Venezuela, "rather uncommon and possibly seasonal" in Colombia, "scarce and local" in Ecuador, and "uncommon but widespread" in Peru. The species is found in many protected areas across its range.