Ant followers are
bird
Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...
s that feed by following swarms of
army ants and take prey flushed by those ants.
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, regularly feeding away from the swarms as well.
Many species of tropical
ant
Ants are Eusociality, eusocial insects of the Family (biology), family Formicidae and, along with the related wasps and bees, belong to the Taxonomy (biology), order Hymenoptera. Ants evolved from Vespoidea, vespoid wasp ancestors in the Cre ...
s form large raiding swarms, but the swarms are often
nocturnal
Nocturnality is a ethology, behavior in some non-human animals characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnality, diurnal meaning the opposite.
Nocturnal creatur ...
or raid underground. While birds visit these swarms when they occur, the species most commonly attended by birds is the
Neotropical species ''
Eciton burchellii'',
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
The Afrotropical realm is one of the Earth's eight biogeographic realms. It includes Sub-Saharan Africa, the southern Arabian Peninsula, the island of Madagascar, and the islands of the western Indian Ocean. It was formerly known as the Ethiopi ...
birds do follow driver ants in the genus ''
Dorylus''.
In 1978, Willis and Oniki suggested that the relationship between the 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. This has resulted in a number of behaviours by the ants in order to reduce
kleptoparasitism, including hiding secured prey in leaf litter and caching 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 few as four stings from fire ants.
Ant Army Invasion! – Wild South America – BBC
YouTube (2009-02-27). Retrieved on 2013-02-23.
References
{{Reflist
Bird behavior
Biological pest control
Ants