How does a a Honeyguide "guide"?

Isack and ReyerNative honeygatherers summon a honeyguide to their camp by using a specific whistle, which can be heard from the distance of over one kilometer.  The whistle, known in the language of the Boran tribe as "Fuulido", is produced by blowing air into clasped fists, modified snail shells, or hollowed out doum palm nuts. This noise doubles the encounter rate with the honeyguides, and when one hears it, it flies to the campsite and signals its presence by flying near to the people and moving around the trees, while emitting a certain "tirr-tirr-tirr-tirr" call. Then it begins a directional flight, during which the white outer tail feathers are displayed, periodically perching and calling again. If a person comes between 5 and 15 meters of the bird, it takes off while continuing to call. Some tribesman whistle and bang sticks to announce their position and keep the bird's attention. They claim that the bird has a specific guiding pattern that tells them about the direction of, distance to, and instance of their arrival at the hive. (Image from Isack and Reyer).

Research done investigating the Boran's claims (Isack and Reyer, 1989) have found them to be mostly true. When the guiding routes were plotted, a clear directional preference towards the nest was found. Once the researchers knew the location of a hive, they could elicit repeated guidings to it by not destroying it and returning to the initial starting point. Each time, the honeyguide would lead them more or less along the same route. If they went to different compass points birds would lead them using different, but still direct routes, as shown in Isack and Reyer's Fig. 2. If there happened to be two hives in the area, 88% of the time the honeyguide would lead them to the nearest one. This proved that the earlier claims that the honeyguides simply lead people around until they find a colony are for the most part untrue, and that the honeyguides have prior knowledge of the location of each hive.

The Boran claimed that there were three features of the honeyguide's behavior that change the closer they get to the colony. They are the amount of time they disappear after the first encounter, the distance between the perches where it waits for its followers to catch up, and the height of the perch. When they recorded these variables, they discovered that all of the claims w
ere true. These are shown in Fig. 3 from Isack and Reyer's article. The closer they came to the nest, the shorter amount of time the bird spent out of their sight. They guessed this was because the honeyguide probably kept flying back to the nest to confirm its position.  The distance between stops where the bird perched to wait also became shorter, and the perches got lower and lower.

                                   (Image source unknown)

When the humans
arrive at the hive site, the honeyguide sits near it and gives a specific "indication" call.  It has a softer tone than the guiding call, and the bird does not respond as much to the whistles and calls from humans.  It calls a few times and then falls silent. It may circle around the nest, but when the honeygatherers approach, it goes to a perch nearby, and the flight path reveals the colony's location. If the gatherer does not find the nest, the honeyguide may give up and leave, or start to guide them to another colony.  After the humans are finished plundering the nest, they leave behind some pieces of the comb for the honeyguide.

The Boran also claim that if the honeyguide is flying lower than the treetops, it will guide to a colony close to the ground, and when the nest is very far away, they will decieve their followers by stopping at shorter intervals. These claims have not been investigated by biologists yet.

(Image source unknown)