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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3-D scans reveal flexible skull patterns are key to island bird diversity

March 7, 2017 by Bruno Martin

A study of the super-diverse bird groups, which include Darwin's finches, has found that modular skull parts helped them adapt to different roles. 

Adaptive radiation is the rapid evolution of many diverse species from a single ancestor. Typically this occurs in the colonization of island habitats, as a group of birds diversifies to exploit different ecological niches – the lifestyles, or roles, available within an ecosystem.

Two classic examples of adaptive radiation are Darwin's finches - a group of species native to the Galapagos Islands which have different beak shapes depending on whether they feed on seeds, fruits or insects - and Hawaiian honeycreepers, some of which have long beaks adapted to feeding on the nectar of different flowers.

Darwin's finches were named after Charles Darwin, whose study of this group of birds played a central role in his research into evolution. 

Previously, scientists have analysed the shape of beaks to understand how birds diversify and adapt to these specialist ecological functions. However, because the beak is integrated with the rest of the skull, examining beak evolution alone does not provide a complete picture of how these island birds have achieved such remarkable diversity.

In a new study, published in Philosophical Transactions of the Royal Society B, researchers compared the 3-D structure of the entire skull in Darwin's finches, Hawaiian honeycreepers, and in their common ancestral group, from which the two diverse groups are descended.

The authors performed X-ray microcomputed tomography scans (very fine resolution CAT scans) of hundreds of cleared and dried bird skeletons and fossils of extinct species to compare the external and internal structure of their skull.

They found that skull shapes are much more diverse in Darwin's finches, and especially in Hawaiian honeycreepers, than in their ancestral group or in non-related groups of other bird species. This whole-skull variation was greater than the variation observed from looking at just their beaks. The finding suggests that variation of the entire skull plays an important role in the adaptive radiation of these birds.

Continued  https://phys.org/news/2017-03-d-scans-reveal-flexible-skull.html

Darwin's finches may face extinction

Date:December 18, 2015

Source:University of Utah

Mathematical simulations at the University of Utah show parasitic flies may spell extinction for Darwin's finches in the Galapagos Islands, but that pest-control efforts might save the birds that helped inspire the theory of evolution.

The new study "shows that the fly has the potential to drive populations of the most common species of Darwin's finch to extinction in several decades," says biology professor Dale Clayton, senior author of the study published online Dec. 18 in the Journal of Applied Ecology.

But the research "is not all doom and gloom," he adds. "Our mathematical model also shows that a modest reduction in the prevalence of the fly -- through human intervention and management -- would alleviate the extinction risk."

Several approaches may be needed, such as introducing fly-parasitizing wasps, removing chicks from nests for hand-rearing, raising sterile male flies to mate with females so they can't lay eggs in finch nests, and using insecticides, including placing pesticide-treated cotton balls where birds can collect them to self-fumigate their nests.

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A gene that shaped the evolution of Darwin's finches

Date:

February 11, 2015

Source:

Princeton University

Summary:

Researchers have identified a gene in Galápagos finches studied by English naturalist Charles Darwin that influences beak shape and that played a role in the birds' evolution from a common ancestor. The study illustrates the genetic foundation of evolution, including how genes can flow from one species to another, and how different versions of a gene within a species can contribute to the formation of new species.

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Is self-fumigation for the birds? Save threatened species by giving them treated cotton for nests

Date:

May 5, 2014

Source:

University of Utah

Summary:

When biologists set out cotton balls treated with a mild pesticide, wild finches in the Galapagos used the cotton to help build their nests, killing parasitic fly maggots to protect baby birds. The self-fumigation method may help endangered birds and even some mammals.

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