The Dull-mantled Antbirds is a perching bird species in the antbird family (Thamnophilidae). Its scientific name is presently Myrmeciza laemosticta, but as it does not seem to be closely related to the White-bellied Antbird (M. longipes) – the type species of the highly paraphyletic “wastebin genus” Myrmeciza – it is liable to be assigned to a different genus in the near future.
Description and systematics
The Dull-mantled Antbird is 13–14 cm long and weighs around 24 g. Overall, these birds look essentially blackish grey in the front half and dark reddish brown in the hind part, with a black wing patch with white spots right where the two main colors meet. But in the dusky forest understory, the birds may appear all-black, with only the white spotting standing out.
The plumage of the male is blackish grey on the head, neck, upper mantle, and on the underside up to the upper belly, and reddish brown on most of the remaining upperparts and underparts; remiges (= flight feathers – typically only visible in flight) and rectrices (the long flight feathers of the tail) are somewhat darker, with dark reddish brown edges. The throat is black, extending onto the breast as irregular black spotting.
The primary coverts are tipped cinnamon and the secondary and tertiary coverts are black with white tips on the upper wing; the underwing coverts are all grey. As in many antbirds, there is a white patch between the shoulders; it has some black specks around it.
The iris is red, the bill black, and the feet are lead-grey.
The female is similar but slightly lighter overall; its black throat color has many white spots and does not extend onto the breast. Its secondary coverts and sometimes the crown are tinged cinnamon.
Calls / Vocalizations
The loud song of the male consists of a rapid series of short but individually distinct notes, 8 per 1.8 seconds, the first three being slightly up slurred or flat, while the latter 5 are down slurred. Possibly, there is some geographic variation in the song, an indication that the two subspecies might indeed be valid: the songs of the southern population apparently transition smoothly between the two parts, while in northern birds, it seems that the first notes are all markedly up slurred, abruptly changing to the down slurred notes.
The female loudsong resembles that of the male initially, being just raspier; the second part however consists of 2-4 short notes that successively become deeper and more muted. In mated couples, the male often sings first, followed immediately by the female.
The Dull-mantled Antbird also gives very short (0.1 to 0.2 seconds) down slurred burr as well as an abrupt chip or chip-chip calls.
Systematics
There are two subspecies currently recognized, differing little in plumage. Though the variation in appearance might be clinal the different songs argue against the species being monotypic:
- “Myrmeciza” laemosticta laemosticta Salvin, 1865 – Caribbean slope of E Costa Rica to Panama (on both slopes).
Plumage darker.
- “Myrmeciza” laemosticta palliata Todd, 1917 – N Colombia and NW Venezuela, south to Department of Córdoba, east to Mérida and Zulia states. Includes bolivari and venezuelae.
Plumage paler.
Among the Thamnophilidae, the “Myrmeciza” assemblage belongs to the main clade – conceivably to be treated as a subfamily, but as of yet unnamed – which also contains the typical antwrens of genus Myrmotherula and its relatives. Traditionally, the “Myrmeciza” antbirds were treated as the namesake genus of the tribe Myrmecizini, but while there indeed seems to be a clade encompassing the bulk of the presumed tribe – including genera such as Myrmoborus and the fire-eyes (Pyriglena) –, the undetermined relationships of its type species Myrmeciza longipes make it unclear whether “Myrmecizini” is actually a valid taxon and even if this is so, whether it refers to the group traditionally named thus, for some other species of “Myrmeciza” are known not to belong there.
As mentioned above, the Dull-mantled Antbird probably does not belong to Myrmeciza proper, as it is rather unlikely to be a close relative of the White-bellied Antbird (M. longipes). It is part of a group of species whose heads are uniformly grey, typically dark or even blackish, in males and females, only the throat being black – sometimes spotted white –, pale, or (very rarely) brownish in some taxa. Without a doubt, its closest living relative is the Esmeraldas Antbird (“M.” nigricauda), a sister species occurring to the southwest of the Dull-mantled Antbird’s range. The Stub-tailed Antbird (“M.” berlepschi) is a hyper melanic species whose close relationship to the preceding two is still quite obvious; the Chestnut-backed Antbird (“M.” exsul) and Grey-headed Antbird (“M.” griseiceps) are somewhat more distantly related and uniquely apomorphic; still, they also have an almost completely grey head in both sexes, unlike all other “Myrmeciza”.
Ecology
Its natural habitat is tropical moist lowland forests, usually between 300-750 m ASL (Above mean sea level), but occasionally almost at sea level and sometimes up to 1,500 m ASL. It occurs in the understory and forest floor, and particularly frequents deep damp ravines in the foothills, in slopes next to streams, and in other areas that have a densely vegetated herbaceous understory.
The diet of the Dull-mantled Antbird is composed of insects and other arthropods; recorded prey items are spiders (Araneae), cockroaches (Blattaria), beetles (Coleoptera), crickets (Gryllidae), woodlice (Oniscidea) and indeterminate insect larvae. It feeds as an individual, as a pair, or in small family groups, moving close to the ground – usually not more than 10 cm above the forest floor –, every now and then jumping up to a low branch to take a look around and immediately descending again. Its prey is usually caught by gleaning, pecked up from between the leaf litter or, after a jump up or a short flutter, from vegetation. It rarely rummages through the leaf litter to search for prey; rather, it will observe its surroundings tensely, beating down its tail forcefully and slowly raising it up again, and then strike directly at something that has attracted its interest. Small prey is devoured immediately; larger animals are beaten vigorously on branches to make them easier to swallow. The species will occasionally follow army ants but it is not an obligate ant-follower like some other true antbirds or ground antbirds (Formicariidae); while it may join mixed-species feeding flocks on occasion, it usually prefers to forage on its own or with its family.
Little is known about its breeding behaviour. The only described nest, found in Colombia in March, was a simple flimsy cup placed low in a pepper plant (Piper sp.) growing on a steep gorge. The two eggs were white with cinnamon spots at the blunt end. Hardly anything is known about the breeding habits of its relatives either; two-egg clutches seem to be the norm however, and the available evidence points towards a prolonged breeding season starting early in the year and lasting perhaps to June in northern South America, and maybe starting in spring and lasting to September or so further north.
