The biological basis of bird song production.

1. The biological basis of bird song production. • Bird song facts: • There are about 4000 species of song birds each of which usually produce 1 to many bird songs. • In all studied cases adult song has been shaped by learning. • In most cases it is the male of the species that produces song, • Females typically produce little or no sound/song. • Males within any single species tend to sing highly similar sets of songs. • There can be dialectic variations in different geographic regions for a given song. • In some cases, dialectic variations of a song within a region will change over time (i.e. across generations).

2. Three most common species used in the study of song production and learning White Crowned Sparrow Zebra Finch Canary • Function of bird song: • Attract mates • Advertise health • Genetic quality • Sync courtship behaviors • Maintenance of pair bond • Establish/defend territory • Flock control • Predator alarm • In flight flock movement • Parent offspring communication Chaffinch: A historically significant species

3. The syrinx: The song machine • Located at the point where the trachea branches into the two primary bronchi. • Sound is generated when: • Air from air sacs is forced through the bronchi & syrinx • Air vibrates as it passes through the narrow passageways between the external labia & the tympanic membrane. • Because there are 2 separate passageways and membranes, some birds are able to generate multiple sounds & harmonics at the same time:

4. Studying the song

5. Note (element) Syllable phrase Parts of a bird song

6. Song learning: Modern experimental studies of song learning in birds began in the 1950's in laboratory of W.H. Thorpe.  Birds that were hand-reared from an early age without hearing the normal adult song of its species, a simplified "isolate" song is produced. Isolate songs are highly variable within a species but tend to be related in some rudimentary way with a normal song.

7. A song developed by a male white-crowned sparrow that was tutored early in the first 2 months of life. Here is the tape-recorded song he was tutored with.  • Song learning facts: • Juveniles need adult “tutoring” to produce normal song. • There is variability across individual songs: this may be the basis of dialect formation. • Juveniles prefer/learn songs of their species better than they learn other species songs.

8. Experiment1: within vs between species tutoring Gene environment interactions: Within species preferences for song learning • Given a choice there is an innate preference for ones own species song • True even at the subspecies level. • If “wrong song” is paired with visual cues learning wrong song is enhanced Baptistia and Petrinovich

9. Within species preferences for song learning Experiment 2: between species ONLY tutor Conclusion: White Crowns will learn a song; if their own species is not present they will learn what is available Baptistia and Petrinovich

10. Stages of song development (learning) • Normal song development proceeds through a series of stages:  • Sensory: Young male memorize songs of one or more adult birds.  • Sensitive phase a developmental window where babies listen and learn (species specific but ~10-50 days post hatch).  • Sensory motor: Vocal production begins during or soon after the sensitive phasewhen the male begins subsong.  • Subsong has been compared to babbling in human infants.  • Birds that do not learn to sing do not produce subsong.   Example: subsong “babbling” performed by a 240 day old white-crowned sparrow.

11. Stages of song development: Sensory motor (cont.) • Subsong gives way to plastic song: organized imitation songs • The first evidence of imitations of tutor songs appears in the male's singing.   • Plastic song, imitations are often incomplete.  • Developed songs tend to be "hybrid" songs composed of parts of two or more different tutor songs.   • Overproducing: singing more imitations than eventually appear the final crystallized song.  • Crystallized songs can change over time. • Stages are • Species specific • Dependent on reproductive cycle • Some are plastic and dependent on environmental circumstances.

12. Stages of song development Example: Plastic songs by a 260 day old WC sparrow containing three different songs. The three tutors that the male memorized during the sensitive phase are shown above, and are connected by arrows to the young male's imitations. 

13. Stages of song development • Crystallized song: The emergence of the adult song occurs through the process of selective attrition of syllables from overproduced plastic song repertoire • Mediated by hearing the song of the tutor and auditory feedback.  • Cochlear ablation studies demonstrate that auditory feedback of ones own song is critical Example: The first song is the tutor, the second is the juveniles rendition of the matching song type.   This male has stopped singing his imitations of Tutors 2 & 3, (above) and will retain his crystallized imitation of Tutor 1.  **Selective attrition may lead to vocal dialects, in which neighboring males sing very similar songs that differ from the songs at other locations.

14. Dialectic differences in WC sparrow • Factors: • Environment • Error and learning “culture” • Genetic drift with natural selection