A hidden pattern in birdsong that mirrors a core rule of human language has been revealed.

The study was led researchers at The University of Manchester and Chester Zoo scientists.

It found that birds appear to follow Zipf's Law of Abbreviation (ZLA) – the idea that more frequently used sounds tend to be shorter.

This rule, found in all human languages, helps make communication more efficient.

The findings provide a new foundation for researchers exploring whether birds, like humans, shape their vocal signals according to the 'principle of least effort'.

"Studying ZLA in birdsong is far more complex than in human language", said co-author Dr Rebecca Lewis, conservation scientist at Chester Zoo.

"Our research has taught that it's important to look across a wide range of species when looking for language patterns and we hope ZLAvian will make it easier for other researchers to explore these patterns in more birds but also other animals in the future."

Lead author Dr Tucker Gilman, senior lecturer at The University of Manchester said: "In human language, if we say something a lot, we tend to shorten it – like saying 'TV' instead of 'television'.

"It turns out that the same pattern exists in birdsong.

"This is the first time we've been able to detect a consistent pattern of ZLA across multiple bird species. There's still a lot more work to be done but this is an exciting development."

Although previous studies hinted that animal communication might follow ZLA, it has been difficult to find clear evidence of ZLA in birdsong.

That's partly because most birds have much smaller repertoires compared to humans. While humans use thousands of words, birds may only produce a few dozen distinct sounds.

To tackle this, the researchers developed new method for studying ZLA in birdsong.

It focuses on how often individual birds use certain note types and how long those notes last, allowing them to examine communication at an individual rather than population level.

Using ZLAvian, an open-source computational tool, the team analysed more than 600 songs from 11 bird populations - spanning seven different species.

The team says that further studies are needed across a broader set of bird species to confirm their findings.