This is because higher pitched and louder tunes are easier to hear in a city which is packed with buildings which ‘bounce’ back the sound.

Researcher Emily Mockford from Aberystwyth University said: "Our cities are blocked with reflective surfaces, open spaces and narrow channels which you just don’t get in woodland.

"Because sounds bounce and travel in different ways, birds have to use songs that can cope with this. The higher notes mean the echoes disappear faster and the next note is clearer."

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