The Birds & Bee-eaters: Murderous African Birds Attack
Nestmates
Blindly yet brutally stabbing underground, the invader kills
his foster siblings. Although it sounds like the premise for a horror film,
this is the reality for African honeyguide chicks and their host families. A
study published in the September 2011 Biology
Letters, Dr. Claire N. Spottiswoode and Jeroen Koorevaar observed within
the underground nest honeyguide chicks killing host chicks (their would-be
foster siblings) with specialized hooked bills for the first time.
This murderous behavior is part of brood parasitism- the
parents lay eggs in the nest of other birds and do not deal with the
responsibility of childrearing. Unlike babies left on doorsteps, however, these
youngsters will hatch early and actively take out their nest mates for primacy
with their foster parents. Many species of cuckoo are brood parasites; their
preferred method of siblicide is pushing the other eggs or chicks out of the
nest. It certainly puts a spin on those hourly popouts by a cuckoo clock.
Honeyguides are drab African birds that are roughly the size
of a pigeon. Honeyguide interactions with humans are generally positive – they
are well known for guiding humans to beehives, eating the grubs left behind
when the people take the combs. Their parasitic nature is known; however the
only prior description of killing behavior is from 1952, when a chick bit a
host chick while being held.
Spottiswoode and Koorevaar placed infrared cameras at the
end of common bee-eater bird tunnels. The bee-eater is the most common host for
the honeyguides, and they typically nest in underground burrows. Honeyguides
visited most of the bee-eater nests that were observed and laid eggs in occupied
ones. The parents actually punctured host eggs with their beaks to improve
their offspring’s chance of survival. Luckily for the bee-eaters, sometimes
they would miss some eggs, or the bee-eaters would lay additional eggs later.
The honeyguide chicks hatch days before the bee-eaters and
are very aggressive- the authors noted that chicks immediately tried to bite
them with considerable strength when handled. In the videos, the honeyguide
chicks attacked the host chicks and held on, blindly stabbing by opening and
closing their jaws and shaking the host chick. Although it does not cause open
bloodshed, the biting produces bruising and hemorraghing under the skin. Host
chick deaths varied from nine minutes to seven hours after initial attacks. In
most nests, the corpses stayed and decomposed- a grisly background while the
imposter grows and develops.
Without a doubt, this systemically brutal system works for
honeyguides. But does such a well-developed system come at a cost? Spottiswoode
speculates that accelerated growth and exertion may have a huge energy cost for
honeyguides, though more research needs to be done to determine this.
Honeyguides are like the fairies of folklore: they leave changlings in nests,
equipped with built-in knives and the initial strength to wield them and cause
mischief.
Spottiswoode, C. & Koorevaar, J. A stab in the dark: chick
killing by brood parasitic honeyguides. Biological Letters. http://dx.doi.org/10.1098/rsbl.2011.0739
