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Chestnut-backed Antbird Poliocrania exsul

  • Order: Passeriformes
  • Family: Thamnophilidae
  • Polytypic: 5 subspecies
  • Authors: Woltmann, Stefan, Ryan S. Terrill, Matthew J. Miller and Matthew L. Brady
Sections

Breeding

All published reproductive information pertains to subspecies exsul and occidentalis; no differences described between these two.

Nest

Figure 10. Nearly complete nest of Chestnut-backed Antbird (nominate exsul) in southern Nicaragua, with a 15 cm ruler for scale, 15 April 2004. Images by SW.Generally an untidy open cup made of dead leaves, rootlets, dead ferns and moss with the following approximate dimensions: 10 - 13 cm outside diameter; 6 - 7 cm inside cup diameter; 5 - 7 cm deep (inside cup; Skutch 1969, Wetmore 1972, Willis and Oniki 1972, SW unpub. data). The nest is typically lined to some degree with rhizomorphs ("horse-hair fungus"), and often has bits of green moss woven into the outer parts (Skutch 1969, Willis and Oniki 1972, SW pers. obs.; Figure 10).

Nest typically < 50 cm off the ground, but apparently rarely (if ever) on the ground itself (Skutch 1969, Wetmore 1972, Willis and Oniki 1972, Sieving 1992); Willis and Oniki mention a nest "in ferns on a rock in a gully." Placed on or in vegetation, live or dead, typically in or on the edge of dense vegetation (Skutch 1969, Wetmore 1972, Willis and Oniki 1972, Sieving 1992), but occasionally in surprisingly open situations for the species (SW pers. obs.).

Eggs

Typical measurements 22 - 24 mm by 16 – 18 mm (Skutch 1969, Wetmore 1972, Willis and Oniki 1972). Base color whitish, blotched (most heavily on large end) "purplish-chestnut" or "deep, rich purplish of rufous brown" (Wetmore 1972; Figure 11).

Figure 11. Chestnut-backed Antbird (nominate exsul) nest with eggs in Heredía, Costa Rica, 06 Mar 07. Image by SW.

Clutch size

Typically 2, not infrequently 1 (Skutch 1969, Wetmore 1972, Willis and Oniki 1972).

Incubation

Incubation 16 days – adults start incubating the night after the first egg is layed (W. D. Robinson, pers. com.). Males and females both develop full brood patches and incubate (Skutch 1969, Willis and Oniki 1972). Females are always on the nest at dusk, through the night, and at dawn (Skutch 1969, Willis and Oniki 1972). Diurnal incubation more or less equally divided among parents; bouts by both sexes averaged ca. 115 minutes, and eggs typically left uncovered for only a few minutes, although sometimes up to 39 minutes (Skutch 1969, Willis and Oniki 1972). Both Skutch (1969) and Willis and Oniki (1972) describe daily incubation patterns in some detail. Incubation effort (time) by adults increases over time (Rompré and Robinson 2008).

Parental care

The following taken from Skutch (1969) and Willis and Oniki (1972): Freshly hatched young "naked and blind; the viscera are visible through the blackish-pink skin" (Willis and Oniki). Weight at hatching 2.4 – 3.8 g. Eyes begin to open ca. day 3 after hatching. Both sexes brood and feed the nestlings. Nestling excreta removed by parents, occasionally swallowed by them. Nestling period typically 11 days (W. D. Robinson, pers. com.; Figure 12).
Figure 12. Chestnut-backed Antbird nestlings in Heredía, Costa Rica, 23 Mar 07. The nestlings are 7-9 days old (Willis and Oniki 1972, W.D. Robinson, pers. com.). This nest, like most Chestnut-backed Antbird nests, failed. The first nestling disappeared two days after this photo was taken, and the second disappeared within the next two days. Image by SW.

Cooperative breeding

Nothing published or suspected.

Brood parasitism

Nothing published.

Recommended Citation

Woltmann, Stefan, Ryan S. Terrill, Matthew J. Miller and Matthew L. Brady. 2010. Chestnut-backed Antbird (Poliocrania exsul), version 1.0. In Neotropical Birds Online (T. S. Schulenberg, editor). Cornell Lab of Ornithology, Ithaca, New York, USA. https://doi.org/10.2173/nb.chbant1.01