#2 Communication

Why are bird vocalizations important to study?

They are a key feature of avian ecology and behavior

What are some theoretical or intrinsic reasons to study bird vocalizations?

• Explore nature vs. nurture in behavior

• Understand individuality

• Appreciate beauty and complexity

What are some applied (management/conservation) values of bird vocalization study?

• Similarities to human speech development

• Monitoring of secretive species

• Reveal species differences

  • songs can indicate geographically distinct or even separate species

What are some secretive species that you can study via vocalizations?

• Owls

• Rails

• Soras 

• Birds that don’t want to be seen but want to be heard by other birds-> hide from predators but still find a mate

What role can vocalizations play in speciation?

Songs can act as isolating mechanisms between species

How do avian brain centers relate to vocalizations?

They provide a model for studying human language learning and acquisition

What are the first 3 structures that can produce sound in birds?

• feathers

• feet

• air sacs

What are the last 3 structures that can produce sound in birds?

• syrinx**

• Internal & external tympaniform membranes

• Paired bronchial openings

Syrinx

The primary organ of sound production located where the trachea splits into bronchi

• Recall “flow-through” respiratory system

How is sound produced in the syrinx?

• Muscles contract, forcing air through bronchi and syrinx.

• Air molecules vibrate over tympaniform membranes.

• Vocal tract modifies the sound

How do birds modify pitch and tone?

By changing the tension and shape of the syrinx via muscles

What is the typical frequency range of bird vocalizations?

Most are under 12 kHz

How do thrushes create harmonies?

Each side of the syrinx produces a different pitch simultaneously

• humans hear it as one blended tone

Song

A complex, repeated series of notes, typically used for mating and territorial defense

Call

A simpler sound, used for communication such as alarm, contact, or coordination

What are the main functions of bird song?

• Territory defense

• Mate attraction

  • especially rich vocal repertoires

What can females learn from a male’s song?

• Species identity

• Geographic origin (dialect)

• Health and fitness

• Mate quality (song complexity and repertoire size)

Who sings?

• Primarily adult males in dimorphic species

• Both sexes in monomorphic or tropical species

What are the functions of female song?

• Territory defense

• Pair bonding

• Mate guarding

• Synchronizing during breeding

Who gives calls?

Birds of all ages and sexes

What are the main functions of calls?

• Alarm/anti-predator

• Courtship and parental care

• Locating others

• Aggression or agonistic behavior

How does the syrinx differ among bird groups?

• Primitive syrinx: owls, pigeons, swans

• Suboscines: flycatchers

• Oscines: songbirds

Which group of birds has the most advanced syrinx?

songbirds

• Oscines

What brain area controls song production and perception?

The HVc (High Vocal Center)

What differences exist between males and females?

• M: song production

• F: song discrimination

Which groups have similar neural systems?

• oscines

• parrots

• hummingbirds

Are bird songs learned or innate?

Most are learned; some are innate.

How do birds learn their song?

Through a sequence of learning stages, similar to human speech development

What are the 3 learning stages

• Sensory (Critical) Period

• Sensorimotor Period

• Crystallization

Sensory (Critical) Period

• Listen and memorize adult songs.

• Isolation leads to incomplete song learning

Sensorimotor Period

• Practice via “subsong” (baby talk).

• Compare sounds to memorized template

Crystallization

• Song becomes fixed and final.

• Usually the only song sung for life

Which avian groups show vocal learning?

• Passeriformes (songbirds)

• Psittaciformes (parrots)

• Caprimulgiformes (nightjars)

What are the three main patterns of vocal learning across taxa?

1. Brief learning period (closed-ended)

2. Extended learning as a young adult

3. Lifelong learning (open-ended)

What are the 2 types of song learners?

• closed-ended learner

• open-ended learner

Closed-ended learner

Learns one song, crystallizes, and sings it for life

Open-ended learner

Continues learning and adding new songs, sometimes mimicking other species

Is there a “Middle” between closed-ended learners and open-ended learners?

Yes

• Take a long time to do form their song

• Sometimes there is a delay

How can vocal learning influence speciation?

Different learned songs can isolate populations reproductively

What happened in the Grant & Grant finch study?

• A hybrid finch with a unique song formed a small, endogamous lineage

  • Ground Finch x Common Cactus Finch

• Followed for 7 generations and 31 years

What type of example did the Grant & Grant finch study show?

early-stage speciation driven by song difference

Song dialect

Regional variation in song within a species

• bird “accents”

Are song dialects genetic?

No, they result from learning and cultural transmission

What is easy to see in spp that are non-migratory?

song dialects

• Find which population of birds one comes from based on the dialect

Vocal repertoire

The number of different songs an individual can sing

Why do females prefer males with larger repertoires?

Indicates better learning ability, resource access, and fitness

Mimicry

Copying other birds’ or environmental sounds

Why might birds mimic sounds?

• Scare predators

• Practice or play

• Display fitness or complexity

• Manipulation

• Species recognition

  • parasitic birds

Which bird has the best/most versatile mimics?

Lyrebirds

• Menuridae

  • 2 species

• E. Australia

What are some other birds that can mimic?

• Jays, crows, ravens

• Northern Mockingbird, thrashers, starlings

EX: indigobird for species recognition

• Males mimic host species calls

• Females recognize and are attracted to these calls during mate choice

What are 2 bird spp that mimic for manipulation?

• Drongos

• Steller’s Jay

Why do Drongos use mimicry for manipulation?

• Mimic other species to maintain mixed flocks (“safety in numbers”)

  • Playback experiments show other species respond to mimicked calls

• May also mimic predators to scare competitors

Why do Steller’s Jay use mimicry for manipulation?

Mimics predators to scare others from nests or food sources

How does mimicry relate to sexual selection?

Males with larger, more complex repertoires (including mimicked sounds) signal high quality and age

What bird spp is an example for using mimicry for sexual selection?

Superb Lyrebird

• As males age, they mimic more accurately and expand their repertoires

What non-vocal traits are used in communication?

• Plumage color

• Specialized feathers

• Display flights

• Courtship dances

What is the function of these nonvocal communication displays?

Usually related to breeding and mate attraction