Killer Instinct

After deposited as eggs in the nests of other bird species, greater honeyguide hatchlings attack the nestlings of their hosts.

Eight-day-old chick with fully formed bill hooks

Claire Spottiswoode

The chicks of the greater honeyguide (Indicator indicator) are probably the avian world’s most lethal young killers. Despite being blind and looking as helpless as any other newborn chicks, they can cause carnage. In a new study, a duo of evolutionary ecologists provide astonishing footage of the chicks’ brutal deeds, which had been witnessed only once sixty years ago and never in the wild in host nests.

The greater honeyguides lead human honey gatherers to bees’ nests (hence their name). Like cowbirds and many cuckoos, they dispense with child care, laying their eggs in the nesting sites of other bird species, which become unwitting foster parents. Claire N. Spottiswoode and Jeroen Koorevaar of the University of Cambridge, England, and the University of Cape Town, South Africa, studied the behavior of the honeyguides’ chicks in southern Zambia using infrared cameras, which they installed in the subterranean burrows of several host species, including the little bee-eater Merops pusillus.

The footage showed in detail how the honeyguide hatchlings dispatch their hosts’ nestlings. Using their sharp bill hooks, the chicks repeatedly grasped and shook any host nestmates they sensed. That caused heavy bruising and hemorrhaging underneath the skin of the little bee-eater chicks, which survived eight hours at the most. The researchers also learned that a honeyguide mother stacks the deck in her offsprings’ favor by puncturing any host eggs she finds in a nest she invades. She also incubates her own eggs internally for an additional day prior to laying, which in com­bination with rapid honeyguide embryo development, assures that her offspring hatches ahead of host eggs. (Biology Letters)

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