Figure 1. The photo shows a male individual. In general, these birds are not shy, and one can quite easily approach them (or they may approach you), sometimes to a distance of 2-3 meters. They normally stay in the shade, though, and rarely sit still for very long; this can be a challenge for the photographer.
To top of pageSystematics of T. pelzelni
Thamnophilus pelzelni was formerly considered a subspecies of T. punctatus. Cory and Hellmayr 1924 recognized the following 9 subspecies of T. punctatus:Gorgonae,
atrinucha,
subcinereus,
punctatus,
interpositus,
leucogaster,
sticturus,
pelzelni,
ambiguus.
Thamnophilus punctatus pelzelni, the "Eastern Spotted-Tailed Ant Shrike", is the subspecies of the "Interior of Brasil (central table land), from ... Matto Grosso ... and northern São Paulo ... to ... Ceará, Piauhy and Maranhão" (Cory and Hellmayr 1924, p. 96/97). It is not clear whether the whole of Ceará is included in the range, since the coastal areas are not normally considered "interior", and other parts are not "central table land". Cory and Hellmayr described no other T. punctatus subspecies which would occur in Ceará.
Ridgely and Tudor 1994, following a suggestion by E.O. Willis 1982 (Pap. Avuls. Zool. 35(17):177-182), divided the T. punctatus complex into 2 species, each with subspecies: The Eastern Slaty Antshrike, T. punctatus, east of the Andes, comprises T. punctatus pelzelni, and also subspecies ambiguus, sticturus, punctatus, leucogaster (and others?). The Western Slaty Antshrike, T. atrinucha, in the north-west of the continent, includes subspecies gorgonae and atrinucha.
Isler et al. 1997 then proposed to subdivide the T. punctatus complex into several more species. Among others, subspecies T. punctatus pelzelni would become species T. pelzelni. The range would include most or all of Ceará, also the coastal areas (see Fig. 19 in Isler et al. 1997 and distribution map in Zimmer and Isler 2003). T. punctatus ambiguus, whose range extends from Rio de Janeiro to the northeastern states Bahia and Sergipe, and which is parapatric with pelzelni in some areas, would become T. ambiguus. The revised T. punctatus would now only include subspecies interpositus and punctatus, which occur north of the Amazon River, and east of the Andes.
The findings and conclusions of Isler et al. 1997 were also published, in shortened form, by Zimmer and Isler 2003, in the Handbook of the Birds of the World, Vol. 8; see plate 45 and corresponding species accounts.
The Brazilian Comission for Ornithological Registers (CBRO) recognized T. pelzelni, T. ambiguus, etc., as full species (CBRO). So has the South American Classification Committee of the AOU, and also Clements 2007.
My study sites are located in the interior of Ceará, which lies in the geographical range proposed for T. pelzelni. However, when I compared the local birds (photos) with the figures and description of T. pelzelni in Isler et al. 1997 and Zimmer and Isler 2003 (plate 45), I noted some discrepancies.
Female: According to Isler et al. 1997, the upper back of the female T. pelzelni is brown to reddish-brown. See fig. 12 (p) of their publication, p. 368. Zimmer and Isler 2003, in HBW 8 (Pl. 45, no. 38) describe the color of the back as cinnamon-rufous.
However, the back of the females which I observed, was olive-gray or olive-brown (photo). The local females look actually more similar to the female T. ambiguus, as described in Zimmer and Isler 2003: "Female has crown warm tawny-brown, back olive-grey with clay-coloured tinge, a few blackish feather tips centrally, ...tail dark brown."(p. 559; underlining in text by me). See also Fig. 6 in Isler et al. 1997.
Male: According to fig. 6 in Isler et al. 1997, the defining characteristic of the male pelzelni is an extensively whitish belly, as opposed to ambiguus, which has much less or no white on belly. This is also the criterium that Naumburg 1937 used to differentiate between the two forms.
Unfortunately, there is no series of museum skins of our local birds available, and I have to rely on field observations and some photos. I saw the underparts of many local Slaty-Antshrikes during the last 18 months or so, in Reserva Ecológica Mãe-da-Lua. There are birds with a medium- or light-gray breast, a withish belly and even whiter crissum and undertail-coverts; there are other birds with medium- or dark-gray underparts and little or no white. Between these two extremes, there are intermediate cases. In other words, some birds look more like pelzelni, and others more like ambiguus, or like an intergrade between the two. There is considerable interindividual variability.
For example, I looked for the best match between this photo of a local male, and the figures of the males in plate 45 in Zimmer and Isler 2003. I did choose T. ambiguus (fig. 39) as the most similar species, not T. pelzelni (fig. 38), precisely because T. ambiguus has less white on the belly.
My preliminary conclusion is that neither the local males, nor the local females, can unequivocally be classified as T. pelzelni sensu Isler et al. 1997. But I realize that field observations and photos alone are not sufficient evidence. A series of museum skins would be very helpful.The local Slaty-Antshrikes could be an intermediate form between pelzelni and ambiguus. The possibility of an intermediate form has already been seen by Zimmer 1933, who wrote: "In western Bahia, pelzelni and ... ambiguus intergrade and there are various specimens at hand which are not clearly assignable to either form together with others which, as a series, show a range of interindividual variation covering both extremes." (p. 12). However, Naumburg 1937, investigating the same series of birds, came to the opposite conclusion (p. 190).
It is interesting in this context that Isler et al. 1997 looked for, but did not find, statistically significant differences in vocalizations between T. pelzelni and T. ambiguus. See Lacerda et al. 2007 for a mitochondrial DNA study that supports (but does not clearly prove) the species distinctiveness of ambiguus and pelzelni.
Isler et al. 1997 were aware that their description of T. pelzelni might not be final. They wrote: "...Further data collection and a fine-grained analysis of distribution and plumage coloration are needed to understand geographical variation in T. pelzelni (p. 380)."
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