The White-plumed Antbird can’t survive without army ants. They find them the first thing in the morning and follow them all day.
By Rex Graham
If they can’t find a swarm at the previous day’s bivouac site, they quickly fly around, listening for the vocalizations of other birds that also follow ant swarms.
Very little is known about how antbirds actually feed. Legendary naturalist Alexander Skutch reported that chickens eat army ants, but they have little nutritional value. The chickens may actually have been eating wasp larvae carried by the ants. Tinamous sometimes peck at army ants. The stomachs of Rufous-vented Ground-cuckoos have contained many army ants, but the birds may have eaten large prey covered by ants. The common assumption is that antbirds and other ant-following birds eat spiders and other arthropods and similar prey fleeing ant columns, but that may tell only part of the story.
Specialized beetles in army ant colonies are often shaped like ants and accepted by them. These beetles eat mites that attack the ants, and also ingest the dead bodies of ants, thereby preventing the growth of mold. They or their larvae may also eat ants or their grubs. If these beetles are seen outside the nest by birds, they may become bird food.
Army ants also routinely “quarantine” foreigners in their nests, but some invaders give off drug-like substances that placate the ants. The foreigners are then treated as guests, which then eat their hosts. However, discriminating birds may be able to spot the foreigners, researchers Edwin Willis and Yoshika Oniki reported in a review article in the journal Annual Reviews in Ecological Systems.
“Individual birds low in the pecking order sometimes steal bits of booty from homeward-bound army ants or pick up insets near ant trails and bivouacs,” Willis and Oniki wrote. Parasitic flies also follow army ants, seeking to steal booty or commensal hangers-onjust as antbirds may be doing. “They could thus eliminate any poorly mimetic commensals other than ones that stay inside the ant nest,” they wrote. “Being like an army ant keeps one from being bird food.”
Deforestation in central Amazonia has clouded the prospects of many wildlife species, but the White-plumed Antbird seems to adapt to the resulting mosaic of forest fragments, pasture and second-growth forest. Newly cleared forests are nearly devoid of birds, but many, especialy White-plumed Antbirds, return after about 7 years when vegetation re-emerges.
Tree regrowth after cutting is often dominated by Cecropia species. Ant-following and typical forest birds forage in these recovering forests. However, if primary forests are cut and burned, regrowth vegetation is dominated by Vismia species, and these areas are used by a different group of birds – omnivorous and non-forest insect-eating birds. “White-plumed Antbirds dominated captures in both types of second growth,” researchers with Institute National de Pesquisas da AmazBnia in Brazil and Southeastern Louisiana University said in the journal The Condor. Other studies have reported similar results.
Found in lowland forests north of the Amazon River, this antbird has a unique assortment of white facial fathers – upright, shaggy feathers above its bill and a white beard below. Females and males look very similar, but behave very differently during the breeding season.
White-plumed Antbird Mating
At first, everything seems normal. A female mate with a male and she lays a clutch of eggs in his nest. However, she quickly leaves him with full responsibility to raise the young. She then routinely finds another male and repeats the cycle.
The mating behavior, called sequential polyandry, also is seen with a few other birds. Females of those species may use it as a type of reproductive insurance: if one male turns out to be infertile of unlucky, she hasn’t made the mistake of, well, putting all her eggs in one basket.
Another healthier or luckier male may help her make up for lost time and missed opportunities to produce the next generation of birds.
For example, all her eggs in one nest could be eaten by predators. Another nest might escapes detection, or face different perils. “Unfortunately, quantitative information on the breeding biology of this species is lacking,” wrote Italian scientists who studied the White-plumed Antbird and published their findings in Journal of Avian Biology.