Honeyguide

Honeyguides (family Indicatoridae) are a family birds in the order Piciformes. They are also known as indicator birds, or honey birds, although the latter term is also used more narrowly to refer to species of the genus Prodotiscus. They have an Old World tropical distribution, with the greatest number of species in Africa and two in Asia. These birds are best known for their interaction with humans. Honeyguides are noted and named for one or two species that will deliberately lead humans (but, contrary to popular claims, most likely not honey badgers ) directly to bee colonies, so that they can feast on the grubs and beeswax that are left behind.

Taxonomy
The Indicatoridae were noted for their barbet-like structure and brood-parasitic behavior and morphologically considered unique among the non-passerines in having nine primaries. The phylogenetic relationship between the honeyguides and the eight other families that make up the order Piciformes is shown in the cladogram below. The number of species in each family is taken from the list maintained by Frank Gill, Pamela C. Rasmussen and David Donsker on behalf of the International Ornithological Committee (IOC).

Description


Most honeyguides are dull-colored, though some have bright yellow coloring in the plumage. All have light outer tail feathers, which are white in all the African species. The smallest species by body mass appears to be the green-backed honeyguide, at an average of 10.2 g, and by length appears to be the Cassin's honeyguide, at an average of 10 cm, while the largest species by weight is the lyre-tailed honeyguide, at 54.2 g, and by length, is the greater honeyguide, at 19.5 cm.

They are among the few birds that feed regularly on wax&mdash;beeswax in most species, and presumably the waxy secretions of scale insects in the genus Prodotiscus and to a lesser extent in Melignomon and the smaller species of Indicator. They also feed on waxworms which are the larvae of the waxmoth Galleria mellonella, on bee colonies, and on flying and crawling insects, spiders, and occasional fruits. Many species join mixed-species feeding flocks.

Guiding
Honeyguides are named for a remarkable habit seen in one or two species: guiding humans to bee colonies. Once the hive is open and the honey is taken, the bird feeds on larvae and wax. This behavior has been studied in the greater honeyguide; some authorities (following Friedmann, 1955) state that it also occurs in the scaly-throated honeyguide, while others disagree. Wild honeyguides understand various types of human calls that attract them to engage in the foraging mutualism. In northern Tanzania, honeyguides partner with Hadza hunter-gatherers, and the bird assistance has been shown to increase honey-hunters' rates of finding bee colonies by 560%, and led men to significantly higher yielding nests than those found without honeyguides. Contrary to most depictions of the human-honeyguide relationship, the Hadza did not actively repay honeyguides, but instead, hid, buried, and burned honeycomb, with the intent of keeping the bird hungry and thus more likely to guide again. Some experts believe that honeyguide co-evolution with humans goes back to the stone-tool making human ancestor Homo erectus, about 1.9million years ago. Despite popular belief, no evidence indicates that honeyguides guide the honey badger; though videos about this exist, there have been accusations that they were staged.

Although most members of the family are not known to recruit "followers" in their quest for wax, they are also referred to as "honeyguides" by linguistic extrapolation.

Breeding
The breeding behavior of eight species in Indicator and Prodotiscus is known. They are all brood parasites that lay one egg in a nest of another species, laying eggs in series of about five during a period of 5–7 days. Most favor hole-nesting species, often the related barbets and woodpeckers, but Prodotiscus parasitizes cup-nesters such as white-eyes and warblers. Honeyguide nestlings have been known to physically eject their hosts' chicks from the nests and they have needle-sharp hooks on their beaks with which they puncture the hosts' eggs or kill the nestlings.

African honeyguide birds are known to lay their eggs in underground nests of other bee-eating bird species. The honeyguide chicks kill the hatchlings of the host using their needle-sharp beaks just after hatching, much as cuckoo hatchlings do. The honeyguide mother ensures her chick hatches first by internally incubating the egg for an extra day before laying it, so that it has a head start in development compared to the hosts' offspring.