‘Maltreatment’ by older birds makes chicks abusers later in life

Scientists have found that chicks abused by older birds are more likely to grow up to become abusers themselves.

Researchers studying a colony of Nazca boobies, a colonial seabird, found the birds perpetuate a “cycle of violence”.

Juvenile birds that are maltreated by older, non-relatives grow up to become more violent towards other chicks.

It is the first evidence from a wild animal that, as in humans, “child abuse” can be socially transmitted down the generations.

The birds nest within dense colonies, and this proximity to each other encourages bouts of violence to break out.

While parent birds are away feeding at sea, non-breeding adults seek out unguarded nests and attempt to interact with the chicks within.

These can be positive interactions, but frequently they are abusive; the visiting adults try to perform sexual acts on the chicks or act aggressively toward them.

“The maltreatment of nestlings by adults is really obvious,” the BBC quoted Dr. David Anderson, from Wake Forest University, North Carolina, US, as saying.

“Essentially all nestlings experience some maltreatment,” Anderson added.

To better understand the causes, the researchers studied the interactions between a breeding colony on Espanola Island, Galapagos, over three breeding seasons.

The scientists found a strong correlation between the frequency that Nazca booby chicks were attacked by non-breeding adults, and the frequency that they themselves attacked chicks when they reached adulthood.

The high repeatability of the behaviour revealed it to be a consistent characteristic of each bird”s personality, the researchers wrote in the journal.

The team believes the nestlings” experience “conditions” them for life, and may even affect other aspects of the birds” personalities.

The scientists think they can rule out a genetic cause for the abusive behaviour, especially because the abuse is perpetrated between adult boobies and unrelated victims.

“The link we found indicates that nestling experience, and not genetics, influences adult behaviour,” said Dr Anderson.

The study has been detailed in the journal The Auk.