Angry birds

The African greater honeyguide lay their eggs in the nest of other birds, and expect the foster parents to look after their offspring. The chicks – still blind and naked – kill their foster siblings in order to eliminate competition for parental care.

The young chicks are equipped with a needle-sharp hook at the tip of their beaks which they use to repeatedly grasp, bite and shake chicks of their host family until they die, reveals a shocking new video from researchers at the University of Cambridge.

“While the apparent violence with which young honeyguides attacked their newly hatched foster siblings was quite shocking at first sight, it shows the power of evolution to shape amazing adaptations in parasites,” said Claire Spottiswoode, lead author of the paper published in Biology Letters.

Although this behaviour has been inferred – honeyguides are usually found with the maimed bodies of their foster siblings, this is the first time scientists have observed this type of behaviour under natural conditions. Host nests are often underground and scientists used infrared cameras to see exactly what the honeyguides were doing under the cloak of darkness.

“The killing behaviour is actually a culmination of a sequence of specialised adaptations that ensure that the young honeyguide has sole access to the food the host parents bring to the nest,” said Spottiswoode.

The honeyguide mother incubates the egg for an extra day before laying to ensure her chick hatches first, puncturing host eggs as she goes said Spottiswoode. Her chick – which is about three-times the weight of the host chick by the time it hatches – has a head start in development compared to the host.

Unaware of what has happened, the foster parent takes care of the honeyguide for about a month, before it leaves the underground burrow. By the time it leaves, there’s no sign of the specialised hook which has grown out, or the honeyguide’s siblicidal beginnings.

A stab in the dark: chick killing by brood parasitic honeyguides