- Order: Passeriformes
- Family: Thamnophilidae
- Polytypic 3 Subspecies
Ocellated Antbirds forage exclusively at army ant swarms (Willis 1973, Cody 2000, Chaves-Campos 2011). These ants perform daily raids, in which the colony spreads forward in a column from their bivouac site. As the ants move over the ground, they scare up arthropods from the leaf litter. Though the ants bring much of this prey back to the bivouac, some animals escape the swarming insects. A specialized guild of ant-following birds, including Ocellated Antbird, feeds on the arthropods flushed by the swarming army ants (Willis and Oniki 1978). Some, including Ocellated, are obligate army ant followers, and do not forage apart from ant swarms.
Various hypotheses exist for how these birds locate and track army ant swarms. Because these swarms are nomadic, antbirds must follow their location daily to keep tabs on them. Observers have noted that they check ant bivouacs daily, whereas more recent studies have suggested that they also take cues from conspecifics’ vocalizations and group knowledge to investigate new swarms (Willis 1973, Chaves-Campos 2011).
While foraging, Ocellated Antbirds generally perch on branches and stems within one meter of the ground. They move from perch to perch, looking for flushing arthropods. When a potential prey item flushes, they sally down to the ground to attack, then quickly fly back up to a perch to consume the prey (Willis 1973).
Ocellated Antbirds eat essentially anything of reasonable size flushed by the army ant swarm. Most prey items are under 25 mm in length, though they have been witnessed capturing small lizards and large cockroaches up to 55 mm long (Willis 1973).
Ocellated Antbirds are particularly adept at clinging to thin, vertical stems. Their feet and legs are strong, and their toes are capable of wrapping around thin perches. When moving between perches, birds generally hop and flutter, rarely moving more than 20 m at a time. Their flight appears slow, and birds occasionally glide during longer flights. Upon landing, birds spread their wings as they approach the perch. The tail is occasionally flicked while perched, and appears to drag in flight.
Antbirds foraging around an army ant swarm maintain a dominance hierarchy. Ocellated Antbirds preside over the smaller antbirds, frequently displacing them from preferred perches near the front of the ant swarm (Willis 1973, Willis and Oniki 1978, Touchton 2011). However, there is also a dominance hierarchy among conspecifics foraging at a swarm. Submissive behaviors include wing fluttering, gaping, and whining/chittering vocalizations. Displays of dominance include spreading wings and tail, ruffling feathers, and erect posture (Willis 1973).
Like most other ant-following birds, Ocellated Antbirds do not maintain exclusive foraging territories. Rather, each antbird pair visits multiple ant swarms per day, where they are co-attended by one or two other antbird pairs (Willis 1973, Chaves-Campos 2009). These feeding ranges may be up to 50 hectares in size. However, birds maintain a smaller territory for roosting and feeding; these areas are roughly 6 hectares (J. Chaves-Campos 2007, unpublished data).
Pairs are monogamous and mate for life. Males display via the loud song, but the main courtship activity is pair feeding, in which the male delivers prey items to the female. Females allow copulation after several repeated courtship feedings (Willis 1973).
Social and interspecific behavior
Often, many birds are present at feeding aggregations around army ant swarms. In addition to Ocellated Antbirds, there are frequently several other obligate and facultative army-ant-following species in attendance. These birds have occasionally been reported to move between ant swarms together, and may glean information from each other regarding the location of active ant swarms (Willis 1973, Chaves-Campos 2003, Chaves-Campos 2011). At the very least, Ocellated Antbirds travel together in pairs and family groups (Willis 1973); this may also help offer young birds protection from severe competition with unrelated adults.
Ocellated Antbirds exhibit three main responses to predators: freezing with keening calls, fleeing and tail flicking ("panicking") with chipping calls, and mobbing with chirring calls (Willis 1973). Freezing is generally exhibited in response to distant danger, whereas tail flicking in given in response to closer danger. Mobbing is generally reserved for large terrestrial animals, such as humans (Willis 1973).
The nest is a cup located on the ground between the buttresses of a tree. The cup consists of twigs, vine tendrils, and leaves attached to each other and the buttresses by fungal rhizomorphs. The eggs are whitish and heavily marked with red-brown spots and streaks. Clutch size is generally two, and the young are naked at hatching (nest descriptions from Buehler et al. 2004, Class 2009). Both parents share incubation and feeding duties (Willis 1973, Class 2009).
Fledgling birds stay low on tree buttresses or dense treefalls, where adults bring food to them from the ant swarm (Willis 1973). Birds begin foraging at ant swarms at roughly 3-4 weeks of age, and gain near complete foraging independence by 6 weeks of age (Willis 1973).
Populations and Demography
Young birds may stay near the adults in a clan-like society for up to 6 months (for females, the dispersing sex) or longer (for males, which often breed locally) (Willis 1973). There is no further information related to topics such as age at first breeding, life span and survivorship, or population regulation.
Batcheller, Hope. 2012. Ocellated Antbird (Phaenostictus mcleannani), Neotropical Birds Online (T. S. Schulenberg, Editor). Ithaca: Cornell Lab of Ornithology; retrieved from Neotropical Birds Online: http://neotropical.birds.cornell.edu/portal/species/overview?p_p_spp=694736