As dawn breaks on a misty Welsh morning, the earliest birds to break into song are likely to include European robins, followed by blackbirds and song thrushes and then a plethora of other species as sunlight crowns the horizon. The last to join the chorus, such as chaffinches and blue tits, may not chime in until 100 minutes after the first crooners began.
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This pattern is repeated worldwide, and ornithologists have often pondered what determines when a particular species begins its morning singing. Now, scientists say that they’ve found the explanation: The larger a bird’s eyes, the earlier it starts to sing.