Euler's flycatcher

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.{{cite journal |last=Cabanis |first=Jean |title=Neue Arten der südamerikanischen Gattung Empidochanes, im Berliner Museum | date= 1853 | journal=Journal für Ornithologie |volume=XVI |number=93 |pages=195–196 |language=German | url=https://www.biodiversitylibrary.org/page/33009775 |access-date=March 28, 2025 }} Subspecies L. e. flaviventris was originally described as Blaccicus flaviventris.{{cite journal | editor-last=Lawrence |editor-first=George N. |last=Wells |first=John Grant |title=A catalogue of the birds of Grenada, West Indies, with observations thereon | date= 1886 | journal=Proceedings of the United States National Museum | publisher=Smithsonian Institution Press, [etc.] | volume=IX |pages=617–618 | url=https://www.biodiversitylibrary.org/page/7601349 |access-date=March 28, 2025}} The article's byline is given to John Grant Wells with Lawrence listed as editor. Wells collected the specimens and sent them to Lawrence for their formal description. The journal issue is for the year 1886 and was published in 1887. Subspecies L. e. lawrencei was originally described as Ochthaeca flaviventris but later renamed Empidonax lawrencei.{{cite journal |last=Allen |first=J. A. |date=1889 |title=Descriptions of New Species of South American Birds, with Remarks on various other little known Species |url=https://digitallibrary.amnh.org/items/7986edfb-79e9-440a-bc80-ef2c499d36fb |journal=Bulletin of the AMNH |volume=2 |pages=150–151 |access-date=March 28, 2025 }} 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 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 epithets to comply with the principle of priority.{{cite journal |journal=The Auk |title=Generic Status of Euler's Flycatcher:A Morphological and Biochemical Study |url=http://sora.unm.edu/sites/default/files/journals/auk/v103n02/p0341-p0350.pdf |volume=103 |issue=2 |pages=341–350 |last1=Lanyon |first1=Wesley E |last2=Lanyon |first2=Scott M|year=1986 |doi=10.1093/auk/103.2.341 |access-date=March 28, 2025 }}

Euler's flycatcher is named for the Swiss ornithologist Carl Euler.{{cite book|last=Beolens|first=Bo|title=Whose Birds? Men and Women Commemorated in the Common Names of Birds|year=2003|publisher=Christopher Helm|location=London|page=121|author2=Watkins, Michael}} It shares genus Lathrotriccus with the gray-breasted flycatcher (L. griseipectus).

Euler's flycatcher is {{convert|12.7|to|13.5|cm|in|sigfig=2|abbr=on}} long and weighs {{convert|9|to|13.8|g|oz|sigfig=2|abbr=on}}. The sexes have the same plumage. Adults of the nominate subspecies L. e. euleri have a warm olive-brown crown, nape, and cheeks. They have a whitish eye-ring 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 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.{{cite book | last =van Perlo | first = Ber| title =A Field Guide to the Birds of Brazil | publisher =Oxford University Press | date =2009 | location =New York | pages =312–313 | isbn =978-0-19-530155-7 }}{{cite book | last =de la Peña | first =Martín R. | last2=Rumboll |first2=Maurice| title =Birds of Southern South America and Antarctica | publisher =Princeton University Press | series =Princeton Illustrated Checklists | date =2001 | location =New Jersey | pages =Plate 74, map 74.2 | isbn =0691090351 }}

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{{cite book | last =Hilty | first =Steven L. | title =Birds of Venezuela | publisher =Princeton University Press | edition =second | date =2003 | location =Princeton NJ | pages =611 | language =English }}
• 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{{cite book | last =Ridgely | first =Robert S. | last2 =Greenfield | first2 =Paul J. | title =The Birds of Ecuador: Field Guide | publisher =Cornell University Press | volume = II| date =2001 | location =Ithaca | pages =505 | isbn =978-0-8014-8721-7 }}{{cite book | last =Schulenberg | first =T.S. | last2 =Stotz | first2 =D.F. | last3 =Lane | first3 =D.F. | last4 =O'Neill | first4 =J.P. | last5 =Parker | first5 =T.A. III | title =Birds of Peru | publisher =Princeton University Press | edition =revised and updated |series=Princeton Field Guides | date =2010 | location =Princeton, NJ | pages =446 |isbn = 978-0691130231 }}
• L. e. argentinus: drabber gray breast than nominate with whitish throat and white belly

All subspecies have a dark iris, a black maxilla, a dull pinkish or orangish pink mandible, and blackish brown legs and feet.

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{{cite book | last1 =McMullan | first1 =Miles | last2 =Donegan | first2 =Thomas M. | last3 =Quevedo | first3 =Alonso | title = Field Guide to the Birds of Colombia | publisher = Fundación ProAves| date =2010 | location =Bogotá | pages =159 |isbn =978-0-9827615-0-2 }}
• 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 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 {{convert|1500|m|ft|abbr=on}} in Brazil. In Venezuela it is found below {{convert|1600|m|ft|abbr=on}} north of the Orinoco River and below {{convert|1000|m|ft|abbr=on}} south of it. It reaches {{convert|800|m|ft|abbr=on}} in Colombia, {{convert|1300|m|ft|abbr=on}} in Ecuador, and {{convert|1600|m|ft|abbr=on}} in Peru.

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.

Euler's flycatcher feeds on arthropods. 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.{{cite journal |author1=Vagner de A. Gabriel |author2=Marco A. Pizo |year=2005 |title=Foraging behavior of tyrant flycatchers (Aves, Tyrannidae) in Brazil |journal=Revista Brasileira de Zoologia |volume=22 |issue=4 |pages=1072–1077 |doi=10.1590/S0101-81752005000400036 |url=http://www.scielo.br/pdf/rbzool/v22n4/a36v22n4.pdf|doi-access=free }}

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 {{convert|2|m|ft|0|abbr=on}} 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 {{convert|1.7|g|oz|abbr=on}} and measured roughly {{convert|18|x|13.5|mm|in|abbr=on}}. 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 was found to be moderate to light.{{cite journal |author=Sonya K. Auer |author2=Ronald D. Bassar |author3=Joseph J. |author4=Fontaine |author5=Thomas E. Martin |name-list-style=amp |year=2007 |title=Breeding biology of passerines in a subtropical montane forest in Northwestern Argentina |journal=The Condor |volume=109 |issue=2 |pages=321–333 |doi=10.1650/0010-5422(2007)109[321:BBOPIA]2.0.CO;2 |url=http://www.umt.edu/mcwru/files.pdf/Tom's%20PDF/Auer%20et%20al%20%202007%20Condor%20Argentina%20breeding%20biology.pdf |url-status=dead |archive-url=https://web.archive.org/web/20080408083929/http://www.umt.edu/mcwru/files.pdf/Tom%27s%20PDF/Auer%20et%20al%20%202007%20Condor%20Argentina%20breeding%20biology.pdf |archive-date=2008-04-08 }}

{{birdsong|url=https://xeno-canto.org/species/Lathrotriccus-euleri |species=Euler's flycatcher}}

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".

The IUCN 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.

{{Reflist}}

• ffrench, Richard; O'Neill, John Patton & Eckelberry, Don R. (1991): A guide to the birds of Trinidad and Tobago (2nd edition). Comstock Publishing, Ithaca, N.Y. {{ISBN|0-8014-9792-2}}
• Hilty, Steven L. (2003): Birds of Venezuela. Christopher Helm, London. {{ISBN|0-7136-6418-5}}

{{Taxonbar|from=Q532646}}

Euler's flycatcher

Category:Birds of the Amazon rainforest

Category:Birds of Brazil

Category:Birds of Colombia

Category:Birds of Venezuela

Category:Birds of Trinidad and Tobago

Category:Birds of Bolivia

Category:Birds of Paraguay

Category:Birds of Uruguay

Euler's flycatcher