That Bird Blog – Bird Care and History for Pet Birds

Research conducted at New York’s Cold Spring Harbor Laboratory (Nature: May, 2009) has, for the first time, illustrated the complex interplay of genetics, learning and social situation in the acquisition of birdsong.

Learning What Song to Sing

As is true for all birds studied, zebra finches (Taeniopygia guttata) raised in isolation from others of their kind fail to develop the song typically sung by the species.

It was therefore long believed that birds learned species-specific notes by listening to the calls of adults.  In fact, zebra finches that are raised by society finch foster parents sing the song of the society finch, not their own, once mature.

The Surprising Influence of Genes

In the Cold Spring Harbor experiment, finches raised in isolation developed odd songs that were not typical of their species, and this song was mimicked by their chicks.  However, after 4-5 generations, the typical (natural, wild-type) zebra finch song began to emerge, despite the fact that the birds had never heard this song.

The shocked scientists concluded that the song is stored within the genome, but that several generations must pass before it emerges spontaneously.  Under normal circumstances (i.e. where the chicks are raised with exposure to the adult song), learning interacts with genetics to assure that the song is acquired right away.

Future Research Objectives

Ornithologists are interested in discovering if the same process is at work in other species as well…perhaps even the complex and beautiful song of the nightingale is encoded in each male chick.

This research also is expected to have important implications in the study of human language development, and will hopefully lead to new advances in speech therapy.

Further Reading

The zebra finch is one of our most important laboratory animals, and the story of its entry into the pet trade has some surprising twists and turns.  Please see my article The Unknown Side of the Zebra Finch for further information.

A review of this species’ vital role as a laboratory subject is posted at

http://genome.wustl.edu/genome.cgi?GENOME=Taeniopygia%20guttata

NightingGale image referenced from Wikipedia and originally posted by Orchi.

The chipper little zebra finch, ever popular in the lab and home, has once again shed some light on topics important to those who study both birds and people.

Hearing and Correcting the Song

Researchers at Switzerland’s Zurich University have shown that certain cells in zebra finch brains become active when the bird makes a mistake in its song, or when a disruption is introduced into a recording of another’s song.  This offers the first proof that birds listen to their own songs, and compare what they hear to an “ideal” song that is stored somewhere in the brain.

Implications for People

Human language skills are thought to develop in a similar manner, but the functioning of the neurons involved is largely unknown.  The recent discoveries concerning finches may point the way towards a better understanding of speech development in people.

Song and Speech Timing

In related experiments, it was discovered that a specific area of the brain, the High Vocal Center, controls the timing of zebra finch singing.  Cooling this area of the brain slowed the song’s tempo, but did not affect the sequence of the notes (one is tempted to wonder why the birds kept singing while their brains were being chilled!).

Birdsong and human speech both require a complex series of timing adjustments if they are to be understood by others of their species.  The Zurich researchers are hopeful that their work will have implications for those studying human speech impediments.

The zebra finch is one of the world’s most important laboratory animals, and studies of it have led to a staggering array of important discoveries.  An interesting summary of its many contributions is posted at:

http://genome.wustl.edu/genome.cgi?GENOME=Taeniopygia%20guttata

Zebra Finches in the Wild
We are so accustomed to seeing zebra finches in cages that it is easy to overlook their existence as vital members of a natural environment. However, free-living zebra finches are perhaps the most abundant birds in the interior of their native Australia. With the exception of coastal Victoria and New South Wales, they inhabit the entire continent. In fact, their range is expanding due to the provision of water (they must drink daily) on livestock farms. A subspecies of the zebra finch (which was actually the first member of the species to be brought into captivity), the Lesser Sunda zebra finch, occupies nearby Timor and the Lesser Sunda Islands.

Classification
Despite their common name, zebra finches are not true finches but rather are classified as waxbills, in the family Estrildidae. Nearly 150 species of waxbills range throughout Africa, Asia and Australia. A number of the zebra finch’s relatives, including the gouldian finch, the cordon blue and the white-backed munia, are also popular in the pet trade. The nearly 200 species of true finches (family Fringillidae) are absent from Australia.

Habitat and Adaptations
Zebra finches favor open woodlands, grasslands and farms, but can also be found in Australia’s harsh, arid interior scrublands. They feed mainly upon seeds, especially those of various grasses, and take insects as well. Populations living in salt marshes have evolved the ability to drink salt water – excreting excess sodium via the kidneys. They are fairly sensitive to temperature and cannot generate enough heat for egg incubation if temperatures fall below 53 F.

Breeding
Like many of its relatives, the zebra finch forages in large flocks. Within the flock, however, monogamous pairs form. The pair bond appears, in most cases, to be life-long. Breeding is sporadic throughout the year and may not occur at all during droughts. As an adaptation to the harsh environment, this species has evolved the ability to breed quickly at the onset of rains during nearly any time of the year.

Zebra finches nest as discrete pairs, but communally – that is, with many pairs occupying the same tree. The female chooses the nest site and constructs the nest with dried grasses and other materials brought by the male. The 4-5 eggs are incubated by both parents and hatch in 13-16 days. The young, fed by the male and female, fledge in 20-21 days. In years with favorable rainfall and food supplies, 3 or more broods may be raised. The zebra finch’s ability to take advantage of good conditions can be a handicap in captivity – in response to the abundance of food and water, females may lay so often that their health suffers (this problem can be ameliorated somewhat by removing all nesting material).

A View from Taiwan
As mentioned earlier, zebra finches are popular pets, both here and abroad. A Taiwanese friend has informed me that they are much more “house pet” than “cage bird” in her country, and are commonly allowed to roam about. Her pet zebra finch would perch on a chair while the family ate dinner – begging for food but not actually approaching the table, and would sleep in her shirt pocket in the evening.

Further information on the parallels between zebra finch song the acquisition of speech in people is available at:
http://www.zebrafinch.org/

The Role of the Brain
Although birds are linked in our minds, to song, only a very small percentage of the world’s 10,000+ species – those classified within the suborder Oscines – actually sing (and the voices of some of these, such as the crow, stretch the definition of “song”!). Baby zebra finches, much like human babies, babble on with an infinite variety of noises – practicing until they eventually learn the adult song. Once learned, the song is never varied.

Research completed last month (May, 2008) at MIT has revealed that two distinct brain pathways are involved – one for learning the song, the other for producing (singing) what has been learned. Damage to the learning pathway of a young finch prevents it from ever producing the adult song, but the same damage during adulthood has no effect on the bird’s singing abilities.

Bird Song and Human Speech
The MIT researchers have drawn some parallels to human learning abilities that bear further investigation. In zebra finches, the youngster’s vocal explorations cease once the adult song has been acquired, as the song never changes. However, the learning pathway is retained, possibly as a back-up system – damage to the song-producing pathway of an adult causes the bird to revert to sounds produced during the learning phase. We humans rely greatly on learning abilities, or pathways, throughout our lives, yet certain aspects of speaking, such as our ability to learn a language without an accent, must occur during childhood. So perhaps we also utilize, at least to some extent, two separate brain pathways when learning and producing sound.

Instinct and Mimicry
In all birds there seems to be an instinctive “song framework” that is filled in by learning and mimicry – male birds raised in isolation develop only incomplete songs that are not recognized by others of their species. The specifics of how the various popular pet birds learn their songs vary from species to species. Baby zebra finches pay attention only to the song of the male that actually feeds them. For example, zebra finches incubated (in captivity) by Bengalese finches grow up to sing the song of their foster parents – this despite the fact that the nestlings could hear other zebra finches singing nearby! How they know which song to choose among the many they hear is not yet understood.

The pet birds most valued for their singing abilities, such as canaries and shama thrushes, copy a wide variety of songs, not only those typical of their species. Indeed, owners of these birds can improve their pets’ vocal repertoires by exposing them to “tutor birds” of the same or different species. A favorite story among canary fanciers is that of a canary which learned to whistle the melody to “God Save the King” by listening to a trained bullfinch do the same in an adjoining room……if the bullfinch hesitated too long while singing, the canary would jump in and finish the melody at exactly the right point!