The sound of sparrows can be music to our ears. But researchers say their birdsong is actually an aggressive form of swapping insults.

The species' soothing sounds actually have a lot in common with the profanity-strewn bragging of rappers, with male sparrows using them to prove how macho they are - and the tougher the area, the more they do so.

The birds usually have a large repertoire of songs, and just like their human equivalents, most of the boasting and trading of insults is all about impressing the girls.

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© Glenn CopusDon't push me, 'cos I'm close to the edge: London House Sparrows in a Fulham garden. Their song mirrors the battle rapping of up and coming hip hop stars
It seems sparrows are doing something similar according to the research conducted by a number of Canadian universities for the journal Behavioural Ecology and Sociobiology.

It mirrors the kind of 'battle rap' contests made famous by, among others, Eminem in his film 8 Mile.

Up-and-coming hip-hop stars hone their skills in one-on-one contests where they trade insults in rhyme against a music background until one of the two is deemed the winner.

The study by the Canadian researchers found that when they were advertising for a mate they performed a smaller selection.

And rather than simply tweeting sweetly, researchers say their performances become louder and more aggressive in an attempt to outdo their rivals.

Lead researcher Janet Lapierre, from the University of Western Ontario, said song-sharing - which involves males singing only their 'greatest hits' - is 'an aggressive behaviour akin to flinging insults back and forth'.

Sparrows living in more competitive environments are more likely to perform aggressively, the journal Behavioural Ecology and Sociobiology reports.

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© Universal StudiosBattle: Eminem stars in Eight Mile, the story of of a young white rapper who channels his rage into hit songs, giving him a shot at stardom
Ms Lapierre added: 'It is also a behaviour most often displayed by belligerent older males.'

Sparrows living in more competitive environments are more likely to perform the more aggressive, but smaller selection of birdsong.

This was like trying harder to prove themselves in a tough neighbourhood, said the researchers.

Those living in less competitive environments are more likely to sing their own songs rather than compete with other males by singing the same songs as them, the study added.