Slate-crowned Antpitta Grallaricula nana has a widespread Andean distribution, with up to eight subspecies recognised (Krabbe & Schulenberg 2003, Donegan 2008). It ranges from the coastal mountains of Venezuela, west and south along the three Andean ranges in Colombia, and in the eastern Andes of Ecuador to northernmost Peru, with an isolated population in the tepuis of south-east Venezuela and adjacent Guyana (Greeney 2018). The taxonomy of G. nana is not fully resolved, as indicated by ongoing discussion as to the validity of G. nana cumanensis (with G. n. pariae) and G. n. kukenamensis as separate species (Donegan 2008, Remsen et al. 2017, Greeney 2018).

Between southern Colombia and northern Peru, G. nana has been recorded to date only on the Amazonian slopes of the eastern Andes (Krabbe et al. 2017). These populations have been assigned to G. n. occidentalis by some authorities (Donegan 2008, Krabbe et al. 2017, Greeney 2018) but to the nominate subspecies by Krabbe & Schulenberg (2003) who synonymised G. n. occidentalis with it (see also Ridgely & Greenfield 2001).

During field work on 3–7 February 2017 at El Corte (00°49′13.28″N, 78°05′40.63″W; 2,500–2,620 m elevation), Carchi province, north-west Ecuador, we discovered G. nana in natural secondary forests on very steep slopes adjacent to small streams. We located five territories in very dense and tangled understorey, with patchy bamboo and a broken canopy. Despite intensive efforts, we were unable to mist-net or photograph adults, but we recorded the vocalisations of two different individuals (Fig. 1; archived on xeno-canto.org; XC404700, 404702, 404706, 404707).

The geographically closest population to north-west Carchi is in the eastern Andes of Ecuador, which corresponds to G. n. occidentalis (fide Donegan 2008, Krabbe et al. 2017, Greeney 2018). The nudo de Pasto of southern Colombia—where the three Andean ranges of Colombia merge into a single plateau—reaches c.4,000 m at high passes, and isolates the eastern and western slopes of the Andes. However, several taxa (i.e. Golden-faced Tyrannulet Zimmerius chrysops, Sulphur-bellied Tyrannulet Mecocerculus minor, Rufoustailed Tyrant Knipolegus poecilurus, Bicoloured Antvireo Dysithamnus occidentalis) that occur on the eastern Andean slopes of southern Colombia and northern Ecuador ‘spill over’ the Andes into north-west Ecuador, north of the dry Mira Valley (Krabbe et al. 1998, Krabbe 2008), in some cases ranging into south-west Colombia as well. This pattern is probably shared by G. nana given the lack of records from the western Andes of Imbabura and ornithologically well-known Pichincha province, south of the Mira Valley. To date, there is a single, undocumented record of G. nana from the West Andes of southern Colombia, at Laguna de Cumbal (00°57′02.5″N, 77°49′05.7″W), dpto. Nariño, just 30 km north of the El Corte region, in 2015 (J. Zuleta;  https://ebird.org/view/checklist/S25166185). This record, however, requires confirmation as the locality appears unsuitable by elevation and habitat for G. nana. Other localities on the Pacific slope of the West Andes of Colombia are further north—beyond the Patía Valley, from dpto. Cauca northwards (Donegan 2008, Greeney 2018).

Figure 1.

Sonogram of four phrases of song (A); sonogram and oscillogram of a single phrase (B) of Slate-crowned Antpitta Grallaricula nana, El Corte, Carchi province, north-west Ecuador, February 2017. Recorded by JFF using a Zoom H4N Pro (Zoom North America, NY) with built-in microphone; sonogram and oscillograms prepared by PM using Raven Pro (Cornell Lab of Ornithology, Ithaca, NY).

Donegan (2010) suggested that the population in the West Andes of north-central Colombia and the headwaters of the Magdalena Valley, where the West and Central Andes meet, might represent an unnamed subspecies, due to its vocal characters. Curiously, Donegan (2008) included two localities from eastern dpto. Nariño, close to the Ecuadorian border on the east-facing slope of the Andes (Llorente and La Victoria; Paynter 1997), as being occupied by this putative subspecies. Our recordings suggest that the vocalisations of G. nana in north-west Carchi are similar to those of widespread G. n. occidentalis. Number of notes, song duration and pace are within or close to the range of variation in this subspecies (Donegan 2008), suggesting a closer relationship with cis-Andean populations of G. n. occidentalis and not to the West Andes population in northern and central Colombia (Donegan 2008). It remains to be determined if G. n. occidentalis ranges north to the Patía Valley onto the Pacific slopes of dpto. Cauca and northwards, and whether it meets the population in West Andes of Colombia (fide Donegan 2008).

We tentatively assign the population in north-west Carchi to G. n. occidentalis, but suggest the need for additional exploration of the area—including adjacent dpto. Nariño of southern Colombia—to obtain further audio-recordings and to collect specimens, considering the apparent geographic isolation from both G. n. occidentalis and the West Andes ‘vocal type’ of Donegan (2008, 2010). A better understanding of the distribution of G. nana subspecies in south-west Colombia will also aid in understanding the geographic variation in song postulated by Donegan (2008).