Xiphorhynchus eytoni (P.L. Sclater, 1854 )

Raposo, Marcos A., Kirwan, Guy M., Fonseca, Odirlei, Selvatti, Alexandre Pedro, Höfling, Elizabeth & Stopiglia, Renata, 2025, Towards a more coherent taxonomy for the woodcreepers Xiphorhynchus guttatus and X. guttatoides (Aves: Passeriformes: Dendrocolaptidae), Zootaxa 5683 (4), pp. 492-512 : 504

Xiphorhynchus eytoni (P.L. Sclater, 1854)

Dendrocolaptes eytoni P.L. Sclater, 1854: 69

Xiphorhynchus eytoni gracilirostris Pinto & Camargo, 1957: 60

Type material: Two syntypes of Dendrocolaptes eytoni P.L. Sclater, 1854 , are held at Natural History Museum, Tring, collected by Alfred Russel Wallace: NHMUK 1889.5.20.477, along the Capim River, at “Vizinhanças do Pará”, Pará, Brazil, in June 1849; and NHMUK 1889.5.14.584, along the lower Rio Amazonas, Pará, in May 1849 ( Warren & Harrison 1971; M.A. R. and R.S. pers. obs.).

Diagnosis: Xiphorhynchus eytoni differs from all other forms within the X. guttatus group by its pattern of white rather than buff streaks on the underparts, particularly the throat. The spots on the head, nape, mantle, and underparts, as well as the supercilium, are also white, often noticeably so, or are somewhat stained rusty, but separable from all other taxa when these characters are considered in conjunction with bill colour (see Table 4) and morphometrics. The breast spots have variable chestnut borders, which can be very dark ( 223 in Smithe 1975) in some but, rarely, the species can possess breast feathering similar to X. guttatus in that the borders are brown (121). Compared to those populations of X. guttatoides in Goiás and Mato Grosso, Brazil (previously named X. g. dorbignyanus ( Pucheran & Lafresnaye, 1850)) , X. eytoni has a black bill (slightly paler on the maxilla), and abundant buff upperparts spotting, heavily washed white, with dark brown borders, whereas X. guttatoides has a paler bill (horn-coloured to dusky) and much-reduced upperparts spotting. Xiphorhynchus eytoni also tends towards a “blackcapped” appearance on account of the dark margins to the crown feathers contrasting with the pale supercilium and upperparts spotting, which character is less conspicuous in most other forms in the group. The westernmost member of the species group, X. vicinalis Todd, 1948 , has a less slender bill, and more rusty plumage. Xiphorhynchus eytoni has pure whitish markings on the underparts, whereas the former is nearer to the colouration found in the parapatric population of X. guttatoides (in Amazonas and Acre).

Variation: A specimen taken by Helmut Sick (MN 53803) at an ornithologically poorly known locality on the upper Rio Cururu, Pará, Brazil has slightly larger, even whiter, and different-shaped spotting on both surfaces than all of the other specimens examined. Fresh material taken on the banks of the same river during the present study are rather different, having plumage otherwise typical of X. eytoni . As we have only a single specimen from the Cururu River, we prefer to await the collection of additional individuals from the area before proposing an explanatory hypothesis for the case. It is worth noting, however, that this is a region of particular zoogeographic interest, as it harbours at least one remarkable endemic species, Lepidothrix vilasboasi ( Sick, 1959) . Furthermore, we draw attention to the fact that populations of X. eytoni from Ceará were described as Xiphorhynchus eytoni gracilirostris Pinto & Camargo, 1957 . Although none of the characters proposed by these authors are diagnostic of taxon separation, increasing the representation of these populations in scientific collections is desirable so that the hypotheses underpinning additional taxa can be more thoroughly evaluated.

Morphometrics: Males of X. eytoni have mean values larger than females, especially in culmen length. Xiphorhynchus eytoni has significantly the longest culmen of all species in the group, except X. vicinalis . Wing and tail lengths are also significantly larger than X. guttatoides and X. polystictus (see Tables 2 and 3).

Range: Endemic to Brazil, where it occurs in the humid forests of Ceará and Piauí as well as in the Xingu and Belém areas of endemism, through the Xingu-Tapajós interfluvium, including Ilha de Marajó (see Figs. 3‒4 ) .

Figures

FIGURE 3. Map depicting the distribution of plumage analyses: black circles, morphotype 1, green area, Atlantic Forest area of endemism (AE); white triangles, morphotype 2, purple area, Guiana AE; black diamonds, morphotype 3, red and grey areas, Napo-Inambari AE and Cerrado Biome, respectively; and grey squares, morphotype 4, yellow and blue AEs, Xingu-Belém and Rondônia-Tapajós, respectively, and grey and light green areas, Cerrado and Caatinga Biomes, respectively.

FIGURE 4. Map depicting results of taxognosis analyses and the taxonomic proposal: black circles, Xiphorhynchus guttatus; white triangles, X. polystictus; black diamonds, X. guttatoides; white stars, X. vicinalis; and grey squares, X. eytoni.