Great spotted woodpeckers communicate with "talking drums", new research suggests.
Patterns of drum rolls from their pecking beaks may be used to identify individual birds and broadcast information about fitness, scientists believe.
Researchers in Poland recorded the sounds of 41 woodpeckers drumming against dead tree trunks and branches, including 26 males and nine females.
The drum rolls were studied by comparing the interval length between strokes as well as the number of "hits" within a roll.
Computer analysis showed that 86% of of the rolls were specific to individual birds. However, drum patterns could not be used to distinguish males and females.
Signature drum rolls may help the woodpeckers keep track of one another or their mates, said the team led by Dr Michal Budka, from Adam Mickiewicz University.
Both male and female woodpeckers use drumming to attract mates and ward off rivals.
The researchers wrote in the journal Public Library of Science ONE: "The results of our study suggest that the specific temporal pattern of drumming may be important in the discrimination of nearest neighbours or mates within a pair. However, experimental studies are needed to confirm this hypothesis."
Rate or duration of drumming may also signal fitness quality, the scientists speculated. This was because strong back and neck muscles were needed to produce fast, long-lasting drum rolls.
In Europe, many woodpecker species are rare and live in small, isolated populations, the researchers pointed out.
Some of the birds defended large territories and drummed from locations hundreds of metres apart, making accurate estimations of population size difficult.
Identification of individual drum patterns could improve census accuracy and aid the conservation of rare woodpecker species, said the scientists.