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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How songbirds teach themselves songs

Date: April 4, 2017

Source: University of Pennsylvania

Music can be a powerful form of expression. It's especially important for songbirds such as zebra finches, which learn the songs of their fathers in order to court mates.

Until now, scientists have typically thought of the bird's vocal development in terms of how one circuit in the brain learns a song. But a new study by researchers at the University of Pennsylvania investigated how zebra finches learn songs from a different perspective. Instead of looking at how the bird's brain learns a song, they studied how one part of its brain, which they dubbed the "tutor," teaches another part of its brain, the "student."

The researchers found that in order to teach effectively, the tutor must adapt its teaching style to how the student best learns. The study, titled "Rules and mechanisms for efficient two-stage learning in neural circuits," appeared today in the journal eLife.

The research was led by Vijay Balasubramanian, a physics professor in Penn's School of Arts & Sciences, and Tiberiu Tesileanu, a visiting scholar whose main appointment is at the City University of New York Graduate Center. Bence Ölveczky, a professor of organismic and evolutionary biology at Harvard University, also contributed to the study.

One can think of the bird's learning process as a musician learning a piece on the violin: After practicing the song over and over again until it sounds right, playing it becomes second nature to the violinist.

In the case of zebra finches, the bird hears the song, remembers it, sings it back and continues to adjust it over a period of about a month until it sounds right. As the bird sings, it learns to control its syrinx, the animal's vocal organ, and its respiratory muscles.

"They start out babbling, and then eventually this congeals into trills and phrases and sounds like a song," Balasubramanian said.

The key to this learning is that synapses in the brain strengthen or weaken based on one's experiences of the world. Much of the focus in the field has been on learning rules, how these synapses change strength. An example of this is the Hebb rule, which says that two neurons firing coincidentally at the same time will strengthen their synapse.

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Good fathers sing simple songs

June 14, 2016

The female Chinese Hume Warbler is attracted to males who sing simple songs, as opposed to the more common preference among birds of choosing males who sing the most complex songs. This preference for males with inconspicuous songs may be related to nesting behavior and driven by the threat of predation, according to research published in the open access journal Avian Research.

This subspecies of the Hume Warbler Phylloscopus humei mandellii (P.h.mandellii) is found in central China, is socially monogamous and both parents feed and raise the offspring together. As it is a ground-nesting species, it is particularly vulnerable to predation and the females seem to judge potential male partners based on subtle characteristics that are advantageous to minimize predation risk such as nesting behavior.

Researchers analyzed a total of 139 recordings of male bird song. Dr. Yue-Hua Sun from Institute of Zoology, Chinese Academy of Sciences, Beijing, China said: "Females that chose large males whose songs are shorter with a faster increase in volume, tended to lay their eggs earlier and produce more surviving young. The earlier-hatched nestlings grew up faster, probably benefitting from higher feeding rates or better food. This suggests that female preference for larger males, e.g. individuals with the longest wing and tail lengths, may be driven by greater ability of such males to provide for their young. Another possibility is that these individuals may occupy better territories with better food resources and/or better nest sites."

Dr. Yue-Hua Sun adds: "Most of the Phylloscopus warblers are accomplished singers with complex songs and large repertoires. However, the Hume warbler sings extremely simple songs, of which it only has two, a doubled whistle note and a long low buzz; P.h.mandellii only sings the buzz song type. The males' short song could also be better for territorial defense, allowing the males to hear their competitors' responses."

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Pair bonding reinforced in the brain: Zebra finches use their specialized song system for simple communication

Date:

October 28, 2014

Source:

Max-Planck-Gesellschaft

Summary:

In addition to their song, songbirds also have an extensive repertoire of calls. While the species-specific song must be learned as a young bird, most calls are, as in the case of all other birds, innate. Researchers have now discovered that in zebra finches the song control system in the brain is also active during simple communication calls. This relationship between unlearned calls and an area of the brain responsible for learned vocalizations is important for understanding the evolution of song learning in songbirds.

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Maybe birds can have it all: Dazzling colors and pretty songs

Date:

June 18, 2014

Source:

Cornell University

Summary:

A study of one of the world’s largest and most colorful bird families has dispelled a long-held notion, first proposed by Charles Darwin, that animals are limited in their options to evolve showiness. "Animals have limited resources, and they have to spend those in order to develop showy plumage or precision singing that help them attract mates and defend territories," said the paper's lead author. "So it seems to make sense that you can't have both. But our study took a more detailed look and suggests that actually, some species can."

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