Darwin’s finches sing out-of-tune call after parasites deform beaks

Concern over mating as malformed beaks and nostrils lead to ‘subpar songs’ - study

Ian Sample Science editor

Wed 12 Jun 2019 00.01 BSTLast modified on Wed 12 Jun 2019 00.36 BST

Tree finches made famous by Charles Darwin’s visit to the Galápagos islands in the 19th century have gone out of tune because of parasitic infections that damage the birds’ beaks and nostrils.

Researchers found that male finches that picked up the fly parasite had malformed beaks and enlarged nostrils that led to “subpar songs”, making it harder for the birds to find mates and reproduce.

The infection is caused by the Philornis downsi fly, which is thought to have been introduced to the islands by accident in the 1960s. The fly’s larvae infest birds’ nests and feed on the blood and tissues of their young.

Surveys on the Galápagos islands show that the larvae are now rife and kill more than half of all nestling finches. Those that survive can have badly damaged nasal cavities and nostrils, and their beaks can be deformed to the point that they no longer close properly.

In new research, Sonia Kleindorfer at Flinders University in Adelaide and colleagues examined the impact of the parasitic infections on what are commonly known as Darwin’s finches. Observations, measurements and sound recordings of the birds revealed that those with deformed nostrils had more “vocal deviation” when they sang to attract mates and produced lower notes than unaffected birds. The result was off-putting to females, and out-of-tune males struggled to find mates.

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