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Version 1.0

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Scaled Ground-Cuckoo Neomorphus squamiger

Janice M. Hughes
Version: 1.0 — Published June 29, 2018


Geographic Variation


Described as Neomorphus squamiger Todd 1925; type locality from Colonia do Mojuy, Santarém, Pará, Brazil.

Griscom and Greenway (1941) described a second subspecies, iungens, from the west bank of the lower Rio Tapajós, with nominate squamiger occurring on the east bank of the Tapajós. Characters attributed to iungens are: feathers of forecrown and crown buffy brown tipped dull bluish and with bluish centers; slightly more bronzy green mantle; greener and less coppery red secondaries; auriculars much deeper cinnamon buff; chin and throat uniform rich buff instead of whitish or grayish; dark subterminal area on breast feathers less extensive; and a more distinct breast band. This description apparently is based on a single specimen. However, with a slightly larger sample of specimens (a total of four, two from each bank of the Tapajós), Gyldenstolpe (1945) concluded that these purported distinguishing characters were due to age differences and individual variation.

Firme et al. (2014) subsequently examined plumage characters in 17 known museum specimens of Scaled Ground-Cuckoo. They determined (a) forecrown coloration exhibits significant individual variation unassociated with geography; (b) mantle color can be highly variable, but some specimens from opposite banks of the Rio Tapajós are virtually identical; and (c) there are no consistent differences in the color of auriculars, chin and throat, subterminal portions of breast feathers and breast band between specimens collected on opposite banks of the Rio Tapajós. Thus, Firme et al. (2014) also concluded that the supposed diagnostic characters of iungens reflect merely individual variation, and that iungens Griscom and Greenway 1941 must be treated as a junior synonym of squamiger Todd, 1925.

Related Species

Recently, many authors have considered Scaled Ground-Cuckoo to be a subspecies of Rufous-vented Ground Cuckoo (N. geoffroyi) (Pinto 1964, Haffer 1977, Payne 1997, 2005, BirdLife International 2018b). For example, Haffer (1977) suggested that Rufous-vented Ground-Cuckoo comprised two distinct subspecies groups that could be distinguished based on crown and breast color. His geoffroyi assemblage included a clinal group of four subspecies (N. g. geoffroyi, N. g. amazonicus, N. g. australis, and N. g. squamiger) in southern Amazonia, for which squamiger represented the population that occupies the south side of the Amazon on both the east and west banks of the lower Rio Tapajós. Haffer (1977) added that more specimens — particularly from the upper Tapajós drainage, and from the Xingu and lower Madeira Rivers — would be required to confirm his belief.

In addition, Payne (1997, 2005) considered squamiger to be a subspecies of N. geoffroyi due to the presence of intergradation in plumage characters across the geographic range of these purported subspecies in Amazonia. Payne (2005) also suggested that the genetic distance (based on the mitochondrial genes 12S and ND2) between one specimen each of N. g. salvini from Panama and N. squamiger (Sorenson and Payne 2005) was much less than that between either of these taxa and other ground-cuckoos, indicating that squamiger was best classified as only a subspecies of N. geoffroyi.

However, others have maintained that Scaled Ground-Cuckoo should be considered a species separate from Rufous-vented Ground-Cuckoo. For example, Sick (1997) wrote that squamiger occurred without intergradation adjacent to geoffroyi along the Amazon near Rio Tapajós. Raposo et al. (2009) suggested that the two forms could be separated conclusively by aspects of their plumage.

A comprehensive discussion of both sides of this controversy can be found in Firme et al. (2014). For example, they note that conclusions in Payne (2005) regarding squamiger may be questioned because genetic distances derived in that study for N. squamiger and N. geoffroyi are actually greater than those observed between other cuckoos considered by Payne to be valid species.

In addition, Firme et al. (2014) provide substantial support for the species status of N. squamiger. Their examination of diagnostic characters in 17 specimens of N. squamiger across its distribution — including a more-recently collected specimen from the east bank of the Rio Xingu (Graves and Zusi 1990; see Distribution) — demonstrated no significant variability between them, and no evidence of intergradation with the Rio Xingu specimen and nearest population of N. geoffroyi. They also examined 83 specimens of both squamiger (n = 17) and geoffroyi (n = 66) and their type specimens and concluded that the purported diagnostic plumage characters across the geographic range are relatively uniform. Thus, Firme at al (2014) concluded that Scaled Ground-Cuckoo should be recognized as a distinct species.

Recommended Citation

Hughes, J. M. (2018). Scaled Ground-Cuckoo (Neomorphus squamiger), version 1.0. In Neotropical Birds Online (T. S. Schulenberg, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/nb.scgcuc1.01