Acorn woodpeckers are renowned food hoarders. Every fall they stash as many as thousands of acorns in holes drilled into dead tree stumps in preparation for winter. Guarding these “granary trees” against acorn theft is a fierce, familial affair. But all hell breaks loose when there are deaths in a family and newly vacant spots in prime habitat are up for grabs.

The news travels fast. Nearby woodpecker groups rush to the site and fight long, gory battles until one collective wins, according to a study published Monday in Current Biology. These wars also draw woodpecker audiences, the researchers reported, who leave their own territories unattended, demonstrating the immense investment and risks the birds are willing to take in pursuit of better breeding opportunities and intelligence gathering.

“I think these power struggles are major events in the birds’ social calendars,” said Sahas Barve, an avian biologist at the Smithsonian National Museum of Natural History and lead author of the study. “They’re definitely trying to get social information out of it.”

Acorn woodpecker societies are complex. Each family consists of up to seven adult males, often brothers, which breed with one to three females, often sisters but unrelated to the males. They live with nest helpers who are typically their offspring from previous years. Together they defend 15-acre territories, on average, encompassing one or more granaries in the oak forests along coastal Oregon down into Mexico.

Source: New York Times

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