Tag Archives: songbirds

Lost in translation: To the untrained zebra finch ear, jazzy courtship songs fall flat

(Physorg 10 July 2017)

Zebra finches brought up without their fathers don’t react to the singing of potential suitors in the same way that female birds usually do, hinting that the environment in which the birds are raised can have a determining effect on their behaviour.

The finding, published in the Proceedings of the Royal Society B by McGill researchers, highlights how learning and experience, including developmental auditory experience, can shape how the brain perceives vocal signals.

The research adds to a growing body of evidence underscoring how specific experiences are necessary to shape the developing brain, and how the absence of specific inputs can have long-lasting effects on perception, neural processing, and behaviour.

Songbirds use courtship signals such as song to identify individuals and select a mate.

Zebra finch males each produce a single song, but they perform a “better” version when courting a female. There is accumulating evidence that females choose mates based on how well their potential suitor performs this “improved version”, providing information about his quality, condition and fitness.

Given the importance of being able to judge the subtle difference in the male zebra finches’ song, scientists imagined this skill to be innate within female zebra finches. To test that idea,

Sarah Woolley, professor at McGill’s Department of biology, and graduate student Nancy Chen decided to investigate how developmental exposure to adult male song might affect behavioural responses to song in female zebra finches.

“Because females use song in selecting a mate, we expected that females might have an inherent bias to recognize and prefer high-performance songs”, professor Woolley says.

Surprisingly, they found that a bird’s capacity to distinguish courting versus non-courting singing greatly depends on its upbringing.

Female zebra finches brought up with both of their parents reacted in the “normal” way and preferred the courtship songs of potential suitors. Females reared without their father’s songs didn’t consistently prefer high-performance courtship songs.

In other words, female zebra finches need to hear dad’s singing to help her distinguish which suitor sings best.

“In the wild, females would rarely be raised without a father/tutor,” professor Woolley notes. “That said, it could mean that the environment that birds are raised in will influence song preferences. We already know that male birds can shift their songs to make them easier to hear in noisy, urban environments. Our data could mean that the ability of females to detect those songs may be affected by what they hear when they are young.”

Advertisements

Fuel loads acquired at a stopover site influence the pace of intercontinental migration in a boreal songbird

(Camila Gómez, Nicholas J. Bayly, D. Ryan Norris, Stuart A. Mackenzie, Kenneth V. Rosenberg, Philip D. Taylor, Keith A. Hobson & Carlos Daniel Cadena 13 June 2017)

 

Although migration is an adaptive behaviour in a wide range of animals1,2,3, it is also thought to impose significant costs on individuals4. Studies on various migratory birds5,6,7, mammals8 and fish9 provide evidence that mortality can be higher during migration than during stationary periods of the annual cycle. In addition, work on birds10, 11 and insects12 indicates that migrating individuals often undergo significant metabolic and behavioural adjustments to fulfil the high energetic demands of migration. Time spent and energy used during migration can also determine subsequent breeding success10, 12,13,14,15, emphasizing the high costs that individuals pay when migrating. Because migration is costly, migratory organisms are expected to maximize their fitness behaviourally via minimizing either the time spent, energy consumed, or the risks incurred during migratory journeys16, 17.

In terms of time, the highest cost of migration is generally thought to be experienced during stopovers rather than during periods of flight18, 19, and birds rely on the time spent at stopover sites to rest and refuel for the next leg of their journeys20. Optimal migration theory provides a framework to study stopover behaviour and its consequences by testing whether migrants are time- or energy-minimizers using data on fuelling rate, stopover duration, fuel loads and potential flight ranges17. Individuals attempting to minimize the overall time spent on migration are expected to maximize the amount of fuel they can acquire at each stopover in the shortest time possible. A key consequence of this strategy is that it maximizes the distance that can be flown between stopovers18, 21. Consequently, the fuel loads (amount of fat carried) of a time-minimizer should be tightly linked to local conditions at stopover sites as well as to the conditions expected ahead because these conditions influence fuelling rates18, 21. Furthermore, stopover durations in time-minimizers are expected to have been shaped by or to respond directly to experienced fuelling conditions17, 18. Larger departure fuel loads should allow for longer flights and a faster overall pace of migration because individuals acquiring sufficient fuel in the shortest time possible will need to make fewer stopovers and be able to take more direct routes to their destination, including being able to fly over physical barriers or large areas of unsuitable habitat such as deserts or oceans rather than circumventing these areas22.

Read more

Genetic differences across species guide vocal learning in juvenile songbirds

songbird

(Physorg 12 June 2017)

Juvenile birds discriminate and selectively learn their own species’ songs even when primarily exposed to the songs of other species, but the underlying mechanism has remained unknown. A new study, by researchers at Uppsala University, shows that song discrimination arises due to genetic differences between species, rather than early learning or other mechanisms. The results are published in Nature Ecology & Evolution.

Songbirds are our primary animal model for studying the behavioral and neural basis of vocal learning and memory formation in general. The tremendous variety in the songs of birds delights ornithologists and fascinates evolutionary biologists as a marker of species diversity. Explaining how species differences in song are maintained is a challenge because birds typically learn their songs by imprinting on songs heard when they were juveniles. What prevents juveniles from imprinting on the songs from a wide-variety of other species in their environment? When exposed to a mixture of different songs from their own and other species, juvenile songbirds discriminate and selectively learn songs typical of their own species, which suggests a remarkable fine-tuning of sound perception during the earliest stages of development. Despite the importance of these findings for our understanding of the vocal learning process, the mechanism underlying early song discrimination has remained unknown.

A new study by researchers from Uppsala University in Sweden resolves this mystery by first demonstrating that juvenile pied and collared flycatchers from the wild discriminate their own species’ songs before they’ve left the nest. Nestling flycatchers as young as 10 days old look at the sound source and produce more begging calls during experimental playbacks of their own species’ songs than to playbacks of the other species’ songs, demonstrating that song discrimination develops incredibly early in these two species. Next, the researchers swapped developing eggs from the nests of each species so that they were raised completely by parents from the other species. These nestlings also discriminated in favor of their own species’ songs, despite having no experience with their own species, demonstrating that song discrimination is not a result of early learning. Finally, to definitively show that genetic differences between species underlie discrimination, the researchers showed that hybrid nestlings formed as a result of matings between parents from each species discriminate in favor of the songs of one of the species, the pied flycatcher. Taken together, these results show that song discrimination has a genetic basis.

‘Song differences across species are vital for birds to choose appropriate mates and negotiate complex social interactions. A genetic basis for song discrimination in early life may help explain how song differences are maintained in a noisy, diverse world’, says David Wheatcroft, researcher at the Department of Ecology and Genetics at Uppsala University and co-author of the study.

The song learning process in birds and the language learning process share remarkable behavioral and neural parallels. One of the longest standing problems has been to determine how the brain encodes the vocal memories that underlie learning. The results of this study suggest that this process begins with a genetic blueprint expressed early in life.

How capuchino seedeaters have such big differences in plumage despite little genetic diversity

(Bob Yirka 29 May 2017)
A team of researchers from the U.S., Brazil and Argentina has found clues that help explain why southern capuchino seedeaters have such wide differences in plumage despite being so closely genetically matched. In their paper published on the open access site Science Advances, the group describes the genetic analysis they conducted on the South American birds and what they found by doing so.

Southern capuchino seedeaters are a type of song bird, one of a group with familiar finch-like bills. They live in different parts of South America and have evolved in a unique way—the males have widely different plumage coloring and large differences in their songs. Prior research has shown that despite the differences in plumage, the birds are all quite genetically close. This led the team to wonder how or why that might be possible. They devised a theory that suggested that strong selection in an important part of the genome could perhaps lead to such differences. To find out if they were right, they conducted a DNA analysis of 56 individual birds from five species representing different plumages and found their genetic makeup to be nearly identical.

The team then took a closer look at the part of the genome known to be involved in creating melanins, a group of natural pigments. They found that 99 percent of the genome differences between the species occurred in such regions. But because speciation in seedeaters came about quickly, that led the researchers to suggest that it was due to actions by females—by exhibiting certain preferences in plumage or songs, the researchers theorize, the females were causing the males to adapt quickly.

The researchers conclude that natural selection due to female behavior has driven faster-than-normal speciation in the birds, resulting in wildly divergent plumage and song types—similar, they note, to the way the bills of Darwin’s finches have changed to adapt to conditions in the Galapagos. They suggest their work offers new insight into the ways strong genetic processes acting on a few key genes can bring about fast evolutionary changes.

Land around powerlines could be boon to birds

(Michael Casey 21 May 2017)

Transmission lines may be eyesores for most people but for songbirds, the forest around them might just be critical habitat.

A team of researchers want to see if these birds are populating land cleared along the route of a powerline—as well as areas that have been recently logged—in New Hampshire and Maine.

In other parts of the country, the shrubby habitat of these younger forests have been found to offer much-needed protection for the birds from predators, as well as a steady diet of insects and fruit.

One of the researchers says these habitats are “incredibly important” for the songbirds in those parts of northern New England.

“Our goal is to get a better understanding for how these habitats function in our landscape,” said Matt Tarr, a wildlife specialist at the University of New Hampshire Cooperative Extension.

Tarr and his colleagues will catch the songbirds in mist nests starting later this month, band them and then track them over the next two years. They will be focused on 24 transmission line rights of way and 12 areas that been logged in southeastern New Hampshire and southern Maine.

Tarr said there are as many as 40 species of songbirds that nest in young forests and another group that nest in mature forests.

“However, there is growing evidence suggesting that after their birds finish their nesting and the young leave the nest, they leave mature forests and come into the young forest to complete their development.”

The nearly $250,000 study is being funded by the federal Natural Resources Conservation Service as well as the National Fish and Wildlife Foundation’s New England Forests and Rivers Fund. A contributor to the New England fund is the utility Eversource, which has proposed the Northern Pass energy transmission project that has sparked criticism from property owners, tourism officials and others.

Northern Pass entails building a 192-mile electricity transmission line from Pittsburg to Deerfield, New Hampshire, carrying enough Hydro-Quebec energy to southern New England markets to power about a 1.1 million homes.

Tarr said the study isn’t about finding an upside to transmission lines but rather trying to determine how birds use the forests that emerge after a project is built.

“It helps us understand how transmission lines function in providing that habitat on the landscape,” he said.

The information they get could be critical to policymakers as they work to create more young forests for birds as well as other species like cottontail rabbits in New England.

“Do they have positive effects or do they have negative effects?” he said. “We might find these rights of way aren’t used as we think they are for mature forest birds. That would be important for us to know.”

Researchers investigate how songbirds teach themselves songs

(Ali Sundermier; 4 April 2017)

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 Te?ileanu, 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.

Read more

Scientists Track, For the First Time, One of the Rarest Songbirds on Its Yearlong Migration

Kirtland's Warbler

(Wendy Mitman Clarke; March 6, 2017)

At .48 ounces, your average Kirtland’s warbler weighs about as much as a handful of tortilla chips (seven, stacked), or about the same as one baby carrot. And every year, this rare North American songbird travels nearly 4,000 miles round trip, across mountain ranges, the body of a continent, the Gulf Stream and open ocean. Most of this journey has been a mystery, until now.
Using light-level geolocators, Smithsonian scientists have for the first time tracked and mapped the migratory paths of Kirtland’s warblers for an entire year, following them from their breeding grounds in Michigan to their winter homes in the central Bahamas and back. The scientists hope the data will enable conservation managers to better understand how to manage habitat for the warblers, which were close to extinction in the 1970s and have made a significant comeback as an endangered species.

The research, published in the Journal of Avian Biology, also represents a breakthrough for studying other small species’ migrations, which are an elusive but pivotal element of their lives.

“However difficult it may be, it is critical that we understand the full annual cycle of birds, not just what is happening during breeding,” says Nathan Cooper, lead author of the study and postdoctoral fellow at the Smithsonian’s Migratory Bird Center, part of the Smithsonian Conservation Biology Institute. “There is a significant amount of mortality for songbirds that happens during migration, indicating that the conditions birds encounter while migrating might be major factors in a species’ overall success or failure.”

“We know so little about migration for so many species,” says Pete Marra, head of the Migratory Bird Center and co-author on the paper. “This is the rarest songbird in North America, one of the most endangered. The goal is to move toward tracking the same individuals throughout the year to understand where and why birds are dying, and we’re getting closer with this species.”

Kirtland’s warblers are easy to study in one respect; they only nest in dense, young jack pine forests predominately in specific regions in Michigan. But those forests depend upon frequent fires to propagate the jack pines’ seeds, and fire suppression in the mid-century, coupled with nest predation by the brown-headed cowbird, devastated the species. In 1966 the U.S. Fish and Wildlife Service declared the birds endangered; in 1974, researchers identified only 167 singing males.

By planting new young jack pine forest and implementing a cowbird removal program, conservation managers helped the warblers begin to recover their numbers. Today, their population is estimated at about 2,300 males. It’s a success story, but continued management is crucial.

Although scientists know a great deal about the birds on their breeding grounds in Michigan, they know less about their distribution in the Bahamas during the winter, and migration—which kills an estimated 44 percent of Kirtland’s populations—has remained an unknown.

“Given that they’re flying 2,000 miles in two weeks, it makes a lot of sense that there could be a lot of mortality during that period,” Cooper says. “But we don’t know if it’s driven by things that happen during migration, or if it is set up by events that happen during the wintering period.” For instance, a drought in the Bahamas can mean less food, so the birds might be malnourished before they even begin the strenuous, stressful flight of migration. “That’s why things like climate change [contributing to drought in the Bahamas] can affect migration and, in turn, the breeding period.”

The more widely used satellite and GPS tracking devices that work well on larger animals are too bulky and heavy for most birds, but in the 1990s, British researchers developed light-level indicating devices that were small enough to attach to wandering albatrosses. The concept of using light levels to determine location has been used by mariners for centuries. By determining precise sunrise, midday and sunset times, one can calculate a rough position, because the length of a day varies predictably depending upon one’s latitude and longitude.

New light-level geolocators are finally small enough for even diminutive songbirds to carry them, Cooper says.

“They measure the intensity of sunlight every two minutes and save it to the device. It gathers that data over the whole year. We can estimate sunrise and sunset time every day of the year, and from that you can get day length and solar noon,” Cooper says. That data enables researchers to roughly estimate and map the birds’ location.

Read more