Ant followers are birds that feed by following swarms of army ants and take prey flushed by those ants. [1] The best-known ant-followers are 18 species of antbird in the family Thamnophilidae, but other families of birds may follow ants, including thrushes, chats, ant-tanagers, cuckoos, motmots, and woodcreepers.
Ant followers may be obligate, meaning that they derive most of their diet by following ant swarms, or non-obligate, meaning they derive only some of their diet from this behaviour. Some species may feed extensively at ant swarms yet may not be obligate ant followers, being able to and regularly feeding away from the swarms as well.
Many species of tropical ants form large raiding swarms, but the swarms are often nocturnal or raid underground. While birds visit these swarms when they occur, the species most commonly attended by birds is the Neotropical species Eciton burchellii , [1] which is both diurnal and surface-raiding.
It was once thought that attending birds were actually eating the ants, but numerous studies in various parts of E. burchellii's range has shown that the ants act as beaters, flushing insects, other arthropods and small vertebrates into the waiting flocks of "ant followers". Because E. burchellii is the only regular diurnal army ant specialised and regular ant-followers mostly occur in its Neotropical range, but Afrotropical birds do follow driver ants in the genus Dorylus . [2]
It was once suggested that the relationship between the obligate and regular ant-followers and the army ants, particularly Eciton burchellii, was mutualistic, with the ants benefiting by having the birds chase prey back down towards them. However experiments where ant followers were excluded have shown that the foraging success of the army ants was 30% lower when the birds were present, suggesting that the birds' relationship was in fact parasitic. [3] This has resulted in a number of behaviours by the ants in order to reduce kleptoparasitism, including hiding of secured prey in the leaf litter and caching of food on trails. It has been suggested that the depressive effect of this parasitism slows the development of E. burchellii swarms and in turn benefits other ant species which are preyed upon by army ants.
Despite the easier availability of prey, ant followers face an element of risk, as these small birds can be killed by as little as four stings from fire ants. [4]
Swarm behaviour, or swarming, is a collective behaviour exhibited by entities, particularly animals, of similar size which aggregate together, perhaps milling about the same spot or perhaps moving en masse or migrating in some direction. It is a highly interdisciplinary topic.
The antbirds are a large passerine bird family, Thamnophilidae, found across subtropical and tropical Central and South America, from Mexico to Argentina. There are more than 230 species, known variously as antshrikes, antwrens, antvireos, fire-eyes, bare-eyes and bushbirds. They are related to the antthrushes and antpittas, the tapaculos, the gnateaters and the ovenbirds. Despite some species' common names, this family is not closely related to the wrens, vireos or shrikes.
The woodcreepers (Dendrocolaptinae) comprise a subfamily of suboscine passerine birds endemic to the Neotropics. They have traditionally been considered a distinct family Dendrocolaptidae, but most authorities now place them as a subfamily of the ovenbirds (Furnariidae). They superficially resemble the Old World treecreepers, but they are unrelated and the similarities are due to convergent evolution. The subfamily contains 63 species in 16 genera.
A bivouac is an organic structure formed by migratory driver ant and army ant colonies, such as the species Eciton burchellii. A nest is constructed out of the living ant workers' own bodies to protect the queen and larvae, and is later deconstructed as the ants move on.
The name army ant (or legionary ant or marabunta) is applied to over 200 ant species in different lineages. Because of their aggressive predatory foraging groups, known as "raids", a huge number of ants forage simultaneously over a limited area.
The flame-colored tanager, formerly known as the stripe-backed tanager, is a medium-sized American songbird in the family Cardinalidae, the cardinals or cardinal grosbeaks. It is found from Mexico throughout Central America to northern Panama and occasionally in the United States; four subspecies are recognized. The flame-colored tanager is 18 to 19 cm long, the male having predominantly red-orange while the female is more yellowish orange.
A mixed-species feeding flock, also termed a mixed-species foraging flock, mixed hunting party or informally bird wave, is a flock of usually insectivorous birds of different species that join each other and move together while foraging. These are different from feeding aggregations, which are congregations of several species of bird at areas of high food availability.
Ant mimicry or myrmecomorphy is mimicry of ants by other organisms; it has evolved over 70 times. Ants are abundant all over the world, and potential predators that rely on vision to identify their prey, such as birds and wasps, normally avoid them, because they are either unpalatable or aggressive. Some arthropods mimic ants to escape predation, while some predators of ants, especially spiders, mimic them anatomically and behaviourally in aggressive mimicry. Ant mimicry has existed almost as long as ants themselves; the earliest ant mimics in the fossil record appear in the mid-Cretaceous alongside the earliest ants.
Eciton burchellii is a species of New World army ant in the genus Eciton. This species performs expansive, organized swarm raids that give it the informal name, Eciton army ant. This species displays a high degree of worker polymorphism. Sterile workers are of four discrete size-castes: minors, medias, porters (sub-majors), and soldiers (majors). Soldiers have much larger heads and specialized mandibles for defense. In lieu of underground excavated nests, colonies of E. burchellii form temporary living nests known as bivouacs, which are composed of hanging live worker bodies and which can be disassembled and relocated during colony emigrations. Eciton burchellii colonies cycle between stationary phases and nomadic phases when the colony emigrates nightly. These alternating phases of emigration frequency are governed by coinciding brood developmental stages. Group foraging efforts known as "raids" are maintained by the use of pheromones, can be 200 metres (660 ft) long, and employ up to 200,000 ants. Workers are also adept at making living structures out of their own bodies to improve efficiency of moving as a group across the forest floor while foraging or emigrating. Workers can fill "potholes" in the foraging trail with their own bodies, and can also form living bridges. Numerous antbirds prey on the Eciton burchellii by using their raids as a source of food. In terms of geographical distribution, this species is found in the Amazon jungle and Central America.
Eciton hamatum is a species of army ant in the subfamily Dorylinae; it is found from Mexico to central Brazil and Bolivia. The species differs from Eciton burchellii, in that it does not fan out into the underbrush when foraging. Rather, it forages in columns, often in trees and preying exclusively on the larvae of other social insects. Its prey are often broods of vespid wasps and ants of genera Dolichoderus and Camponotus, suggesting that E. hamatum is mainly an arboreal forager.
Eciton is a New World army ant genus that contains the most familiar species of army ants. The most predominant and well-known species is Eciton burchellii, which is also more commonly known as the army ant and is considered the type species.
The white-throated antbird is a species of bird in the family Thamnophilidae. It is found in Bolivia, Brazil and Peru. Its natural habitat is subtropical or tropical moist lowland forests.
The blue-lored antbird is a species of antbird in the family Thamnophilidae. It is found at low levels in humid Andean forests in western and northern Colombia, western Venezuela. It formerly included the Zeledon's antbird as a subspecies. The blue-lored antbird feeds on insects, and regularly follows swarms of army ants in order to catch prey flushed by the swarms, but it is not an obligate ant-follower like some species of antbirds. The blue-lored antbird is strongly sexually dichromatic: the male has an entirely black plumage, while the female has a rufous-brown plumage and a black mask. Both sexes have a blue patch of skin around the eyes.
The black-faced antbird is a species of bird, about 12–13 cm (5 inches) long, in the antbird family Thamnophilidae. It is endemic to a wide range across the Amazon basin. It feeds on insects and spiders and sometimes follows army ants to catch the insects disturbed by their march.
The ocellated antbird is a species of antbird in the family Thamnophilidae. It is monotypic within the genus Phaenostictus and is found in southern Central America and the northwestern part of South America. Its natural habitat is the understory of tropical moist lowland forest, foothill forest, and tall secondary growth woodlands.
The white-plumed antbird is a small species of insectivorous bird found in the understories of rainforests. It is smaller than most species of its family (Thamnophilidae), weighing 26 grams on average. The family Thamnophilidae is known commonly as the antbirds, as they use the presence of ants to locate food. This species is largely solitary except during the breeding season, and different individuals will follow individual ant swarms.
Myrmecophagy is a feeding behavior defined by the consumption of termites or ants, particularly as pertaining to those animal species whose diets are largely or exclusively composed of said insect types. Literally, myrmecophagy means "ant-eating" rather than "termite eating". The two habits often overlap, as both of these eusocial insect types often live in large, densely populated nests requiring similar adaptations in the animal species that exploit them.
Zeledon's antbird is a species of antbird in the family Thamnophilidae. It is found at low levels in humid forests from Nicaragua to Panama, and in the Chocó of western Colombia and western Ecuador. Zeledon's antbird feeds on insects, and regularly follows swarms of army ants in order to catch prey flushed by the swarms, but it is not an obligate ant-follower like some species of antbirds.
Edwin O'Neill Willis was an American ornithologist who studied the birds of Central and South America.
Neivamyrmex sumichrasti is a species of doryline army ant in the genus Neivamyrmex. It is found in Central America, from southern Mexico to Costa Rica.