Ornithology - Bird sounds and their meaning

What are the physical properties of sound?

Frequency, amplitude, harmonics, and temporal structure

What is frequency?

Number of sound wave cycles per second (Hz)

perceived as pitch

What are harmonics?

Integer multiples of the fundamental frequency that determine timbre

What is the acoustical environment?

The physical habitat that affects sound transmission (vegetation, wind, humidity, terrain)

How does the acoustical environment influence bird sounds?

Vocalizations evolve to reduce degradation and maximize transmission

How is sound measured visually?

Spectrograms and oscillograms

What does a spectrogram display?

Frequency (y-axis), time (x-axis), and intensity (darkness)

What does an oscillogram display?

Amplitude of sound over time

What is the syrinx?

The bird vocal organ located at the base of the trachea

What structures are involved in bird sound production?

Syrinx, tympaniform membranes, intraclavicular air sac

What is unique about the bird syrinx?

It allows independent sound production from each side

What is a call?

Short, simple vocalizations used year-round with specific functions

What are the main call types?

Alarm, contact, warning, courtship, aggressive

What is a song?

Lengthy, complex, repeated vocal displays often performed by territorial males during the breeding season for mate attraction and territorial defense

What are the main functions of bird vocalizations?

Species recognition, individual recognition, social cohesion, mate attraction, territorial defense

How do Bank Swallows and Rough-winged Swallows use calls?

Adults and chicks have individually distinctive calls

How does parent recognition work in Bank and Rough-winged Swallows?

Each parent recognizes calls of its two chicks (converged)

How does chick recognition work in Bank and Rough-winged Swallows?

Each chick recognizes calls of its parents (not converged)

What happens in Thick-billed Murres, Common Murres, and Razorbills?

Single chick taken to sea by male parent with mutual recognition between male and chick

How does Atlantic Puffin chick care differ?

Chick isolated in burrow

no recognition by parent or chick

Which birds have complex songs?

Hermit Thrush and Northern Mockingbird

Which bird has a relatively simple song?

Henslow’s Sparrow

What is a song repertoire?

The number of different song variants sung by an individual

Which species sings a single song?

White-throated Sparrow

Which species has a moderate repertoire?

Western Meadowlark

Which species have large repertoires?

Mockingbird and Marsh Wren

How can bird vocal repertoires be acquired?

Inheritance (innate), learning, invention, or combinations

How do non-passerines typically acquire songs?

Songs and calls are mostly innate

How do interspecific brood parasites acquire songs?

Songs are innate (e.g., cuckoos and cowbirds)

How do passerines acquire songs and calls?

Calls often innate

songs learned with a bias toward conspecifics

What is Order Passeriformes?

Songbirds with extreme development of vocal learning

What type of learning do passerines exhibit?

Vocal imitative learning (culture)

When does song learning usually occur?

Mostly in the first year of life

What happens if a bird is isolated during the learning period?

It never acquires species-typical songs

Who conducted classic song isolation experiments?

Fernando Nottebohm (canaries)

What are the four phases of song learning?

Critical learning period, silent period, subsong (babbling), song crystallization

What is the anti-habituation hypothesis?

Song variation prevents listeners from losing interest

What is the different songs

different functions hypothesis?

What is the Beau Geste hypothesis?

Repertoires confuse rivals about how many individuals occupy an area (Great Tit)

What is the badge of status hypothesis?

Large repertoire signals experienced, high-quality male

What is the location confusion hypothesis?

Multiple song types prevent accurate localization by neighbors

What is the sexual selection hypothesis?

Females prefer males with larger, more elaborate repertoires

What is the functionless epiphenomenon hypothesis?

Song repertoires have no adaptive function and arise from big brains and learning ability

What are song dialects?

Geographic variation in learned songs

Which species is a classic example of song dialects?

White-crowned Sparrow

What is the null hypothesis for song dialects?

Unselected consequence of learning

What is the social signaling hypothesis for song dialects?

Birds imitate successful neighbors

What is the ecological hypothesis for song dialects?

Dialects signal genetic adaptation to local environments

Why are bird vocalizations unique among vertebrates?

They are the most complex acoustic signals

Why does learning promote song as culture?

Songs are passed down as learned local traditions

Which bird order shows extreme vocal imitative learning?

Order Passeriformes.