Tag Archives: zebra finch

Researchers peer into the brain of birds as they’re singing their best song

Birds, just like artists or athletes, train and finesse their songs. When it’s crunch time, they’d better be ready to bust out their best song — or they may end up not having anyone to mate with. In a new study, researchers have zoomed in on the brains of birds practicing and

Zebra finches. Image via Pixabay.

Zebra finches are common birds in Australia. They’re loud and boisterous singers, and they spend a lot of time working on perfecting their songs. Male zebra finches will often go about their days practicing their courtship melodies, producing variations and trialing different versions of the song. But when they spot an attractive female zebra finch, they stop screwing around.

Researchers have observed that when the game is on, they always sing a singular, perfected version of their song — no more variations or experiments. Essentially, they produce the best song they can.

Researchers wanted to figure out how they do this and what happens inside their brain once they do, and thanks to a novel approach that allows them to monitor up to a hundred bird neurons at a time, they did.

“To figure out how to move, it needs to first try out many different movements, to try out different ways of accomplishing a goal of moving their body,” said Jonna Singh Alvarado, who led this project for his Ph.D. dissertation at Duke. “They need to learn, ‘If I think this, how am I about to move? How will that move my body?’ and it needs to do that in many variations.”

Credits: Alvarado et al. / Nature.

To the human ear, these differences are subtle and hard to detect, explains Richard Mooney, Alvarado’s thesis advisor. But female zebra finches are very receptive to these subtleties. They dislike practice songs, but a precise game-time song makes them intrigued and attentive.

When the males practice the not-serious song, neurons in an area of the brain called the basal ganglia (which is also responsible for controlling major movements) allow variation in the song. Various neuron circuitries are used, corresponding to different songs. But when it’s go-time, these alternative pathways are shut down by a squirt of the neurotransmitter noradrenaline in the basal ganglia.

“You’ve established this kind of brain-to-movement dictionary, where you’ve explored all these different ways that you can give commands and they can move your body,” said Alvarado, who is now a post-doctoral researcher at Harvard University. “And then, you can exploit the mapping you’ve created. ‘I’ve explored, I have this dictionary, let me grab the right words from this dictionary and perform exactly what I know I can perform, given what I know the female wants to hear.’ “

To keep this ‘best’ song in good shape, a lot of practice is required. Much like a human athlete or artist, birds practice a lot — and also just like in humans, practicing variations helps build a “dictionary” of workable notes that can then be used. The birds explore their vocal range and different musical combinations until they zoom in on the one they want to use. To Mooney, a self-described Jimi Hendrix fan, the males’ practice songs are a bit like Hendrix’s music.

“It kind of goes everywhere, there’s the kernel of one song, but then it sort of morphs. It’s like free jazz or something. And, you know, I think he was just really, really good at exploring when he was alone.”

Of course, tracking the neurons responsible for this is not an easy task. It took a lot of work from a lot of people working in different fields, Mooney explains.

“One of the things that’s been really hard in other animals is to figure out what the link is between the variability you’re producing, and the variability you want to produce,” said John Pearson, an assistant professor of biostatistics and bioinformatics at Duke, who led the statistical analysis of the neurons. “This is the first time that people have gotten a real sizable population of these cells, and we can begin to try to link the variability in vocal performance to the variability in neural activity.”

In addition to understanding how birds do things, this type of study could also be useful from a human perspective. The basal ganglia are present in all vertebrates, and in humans, it’s linked to conditions such as Parkinson’s, Huntington’s disease, and Tourette’s syndrome, among others. Understanding

But the work is important because insight into the bird’s basal ganglia has direct relevance to human movement disorders, including Parkinson’s and Huntington’s diseases, Tourette’s syndrome, and others, Mooney said. Understanding how basal ganglia neurons function normally and what happens when they malfunction is paramount to understanding how these conditions take shape — and how they can be fixed.

Journal Reference: Alvarado et al, Neural dynamics underlying birdsong practice and performance, Nature (2021). DOI: 10.1038/s41586-021-04004-1

zebra finch

It’s not just the genes: zebra finches show love is essential too

Love is complicated enough, even without intense scrutiny from scientists. Do we fall in love with someone because we find our partner’s genetic makeup to be satisfying and thus improve the chance of having better offspring? Or is it a bit more mysterious than this – a lot more personal? For humans, the latter looks like the case, but we’re far from being alone. Zebra finches, which are also monogamous, choose their mates for idiosyncratic reasons as shown by researchers at the Max Planck Institute for Ornithology. The finches who chose their partners based on behavioral compatibility were less likely to shrug from their parental duties and had offspring which had the best chance of reaching adulthood. This elegant experiment proves that choosing a mate isn’t all about who has the brightest plumage or the biggest stomach – love has a huge part to play as well. The similarities to humans are uncanny.

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Male and female zebra finch. Source: efinch.com

 

Malika Ihle, the lead author of the study, collected 160 zebra finches from the wild and split them into four groups made of 20 males and 20 females each. Left free to roam, the birds soon bonded and chose their prospective mates. Already, the researchers could not spot a pattern.  A female could be interested in a certain male with a flashy plummage, but another was not – she might have been more interested in males who share the same drive for exploring, for instance. Then, the researchers played dominating parents and split the birds again into two groups. Half were allowed to stay with their chosen partners, while the other half was split again into different groups in which their partners  were arranged. Because the finches are monogamous, the researchers had to trick the birds that their partner was dead.

To ensure statistical relevancy, the researchers once again split the birds. Two-thirds of the zebra finch pairs from the first breeding season were broken up and these individuals were placed into an aviary where they again chose a new partner. One-third of the birds who had either chosen their partners or had it arranged were allowed to breed per usual.

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Illustration: Malika Ihle et al (2015)

During this whole time, the researchers studied an extensive library of recorded material (1,424 hours of video and 285 hours worth of direct observations). They found the females in arranged marriages had sex less often and their nests had nearly three times as many unfertilized eggs as the free-choice pairs. As for the males, these were much more likely to skip their parental duties and visited the nest less frequent. Strikingly, the final number of surviving chicks was 37 per cent higher for individuals in chosen pairs than those in non-chosen pairs, as reported in PLOS Biology.

“The percentage of eggs that contained a dead embryo was equal between chosen and assigned pairs. In contrast, the percentage of nestlings that died before reaching independence was twice as high if chicks were raised by assigned pairs”, said Dr Ihle.

“If a chick hatched in such a nest, it only had a 50% chance of surviving.”

To rule out direct genetic benefits, the researchers tricked the birds and swapped eggs from the arranged and self-paired nests. They found the rates of embryo mortality between both free-choice and assigned pairs did not differ, suggesting the birds did not choose their partners based on genetic benefits, nor was the striking difference in offspring survival based on genes. Chicks survived more often in self-made pairs because the parents cared more and were both involved in parenting. The missing ingredient – the glue that holds everything together – might be love.

That’s not to say that genetics don’t play a role – it’s evolutionary essential, after all. Females and males might choose their mates based on superior traits, but not always. All things being almost equal (a diseased male or female will have little luck with “love”), there’s a second important element: parental compatibility. What this means is that those individuals with the best genes and the flashiest behavior are not necessary the best mates for all individuals in the population. The more unique and idiosyncratic an individual is (in this case a zebra finch or human), the more important this ‘click’ becomes in forecasting a fruitful relationship that bears fit young.

The next step for Ihle and colleagues is identifying how exactly parent compatibility leads to better care. Ultimately, research like this might one day unravel the secrets of love. What evolutionary forces shaped it and how? Is there more to it than just producing better offspring?

“To me, love is a peculiar attraction toward a specific individual that is not necessarily shared by other choosing individuals,” Dr Ihle says. “It seems that the chosen pairs, those ‘love marriages,’ invested more into reproduction, were more committed, more faithful, and more motivated to raise their family.”