Nazca boobies (Sula granti) are beautiful birds, but with a very dark side.
A female lays two eggs days apart, the second as insurance against the death of the first. But if both eggs hatch, chick A will expel chick B from the nest to face certain death.
It gets worse. In a typical Nazca booby colony in the Galapagos, there is an excess of non-breeding adult males. Many of these unemployed males will seek out and abuse unguarded Nazca nestlings, jabbing at them with their bills, plucking out their down or even biting and shaking. Occasionally, these advances are sexual too, the aggressor climbing onto the chick’s back and squashing it beneath its feet as it attempts to mate.
The nestlings may end up injured and die. But if they don’t it appears that they may be traumatised by these brutal formative events. Those boobies that were targeted as chicks appear to be more likely to commit similar offenses as adults.
In an extraordinary paper published in Auk in 2011, ornithologists referred to a “cycle of violence” in Nazca booby society, a phrase usually reserved for discussions of child abuse in humans. “The results,” they wrote, “provide the first evidence from a nonhuman of socially transmitted maltreatment directed toward unrelated young in the wild.”
Nasty.
Müller, M.S. et al. (2011) Maltreated nestlings exhibit correlated maltreatment as adults: evidence of a “cycle of violence” in Nazca boobies (Sula granti). The Auk 128: 615-619
