This local species is distributed in the Guianas, north-east and southern Venezuela, Amazonian Brazil, north-east Ecuador and east Peru. In Colombia it is known only from north-east Guainía, in the municipality of Inírida near the border with Venezuela (Hilty & Brown 1986, Hilty 2003, Fitzpatrick 2004b, Flórez & Kirwan 2017) (Fig. 1).

We present nine additional records in Colombia, all in the understorey of várzea forest. On 12 October 2014 one was observed for c.10 minutes moving low down (c. 1 m above ground) near the Guaviare River (02°35’N, 72°39’W, 200 m), at Playa Nueva, municipality of Puerto Concordia, dpto. Meta (WAR), with further observations in the same area on 16 January 2016 and 22 January 2016 (WAR, CA). On 22 December 2015, two were observed for c.10 minutes near Laguna María (02°33’N, 72°39’W, 180 m) at Buena Vista II, municipality of San José del Guaviare (WAR, CA). On 11 January 2016, an individual was observed for c.5 minutes near Kioscos Lagoon, Buena Vista II, vocalising in response to playback (WAR, CA, RC). On 31 January 2016, two were observed for c.15 minutes beside Caño Grande at Jordản Bajo, municipality of El Retorno, dpto. Guaviare (02°20’N, 72°37’W, 200 m), and the vocalisations of one were recorded (www.xeno-canto.org/367853) (WAR, CA). On 28 December 2016, one was observed at Damas de Nare, municipality of San José del Guaviare (02°45’N, 72°14’W, 185 m) (CA). On 14 January 2017, an individual vocalised several times near the Guaviare River, at Playa Alta, municipality of Puerto Concordia, dpto. Meta (02°37’N, 72°40’W, 180 m) (WAR, CA; Fig. 2). Finally on 22 July 2017, one was observed at Playa Güio (02°34’N, 72°42’W, 180 m), near a transitional lagoon, and responded to playback by approaching the source (WAR, SCH, ALS). It was accompanied by Greenbacked Trogon Trogon viridis, White-chinned Jacamar Galbula tombacea, Speckled Spinetail Cranioleuca guturata, Buff-throated Woodcreeper Xiphorhynchus gutatus and Dugand’s Antwren Herpsilochmus dugandi. These records extend its distribution 495 km west in Colombian Amazonia.

The species was differentiated from similar taxa in the region, such as Forest Elaenia M. gaimardii or Euler’s Flycatcher Lathrotriccus euleri, mainly using vocalisations and plumage, respectively. M. gaimardii produces a short, upward-inflected disyllabic pitchueeet, typically as isolated calls or separated by intervals of 30+ seconds (Fitzpatrick 2004a), while M. flavivertex makes a distinctive, loud jéw, jee‐jee‐jew or wééchéché‐e‐e‐e (Fitzpatrick 2004b; www.xeno-canto.org/367853, www.xeno-canto.org/365007). L. euleri vocalises similarly to M. flavivertex (www.xeno-canto.org/122356) but its plumage is quite different (see Farnsworth & Lebbin 2004).