1. A Common yellowthroat warbler in full song…
URBAN ECOLOGY INSTITUE 2009 Foundations of Urban Ecology Why do Birds Sing?
A Common yellowthroat warbler in full song…

2. Outline of Presentation
Why do birds sing?
Song learning
Noise pollution and bird song

3. Birds rely predominantly on acoustic and visual means of communication
Communication in Birds
Signal
Receiver
Vocal Plasticity
Communication loops
Interference occurs
Birds adjust to challenging environments (forest, shorebirds)
Evolution takes time
Birds rely predominantly on acoustic and visual means of communication

4. What is bird song?
complex, species-specific signal performed in mating and intra-sexual contexts
most commonly given by males to attract females and repel males.

5. Songs vs. Calls Songs Calls long (>2 s) repetitive loud spontaneous
from song perches
usually males
mostly passerine
Calls
short
bursts, not repetitive
loud or soft
stimulus specific
anywhere
male or female
all birds
Bird
Song
Call
American Robin, Turdus migratorius
Dark-eyed Junco, Junco hyemalis

6. Song Function Territorial defense
announce territory ownership for purposes of aggressive exclusion.
muting lowers success in deterrence
both sexes may sing
Mate Attraction
song is more common during breeding season, and prior to mating.
song stimulates female reproductive responses

7. Functions of Bird Song Mate attraction
Territory establishment and defense
Identification
Allow other birds to identify species, sex (if both birds sing) and/or individual identity
Motivation and fitness
Birds may provide information to conspecifics by way of variation in singing rates, song duration, amplitude, frequency, and/or song complexity

8. Other potential functions of Bird Song
Distraction of potential predators
Coordination of activities
Stimulate females
Attract females for extra-pair copulations
Mate guarding

9. Why do females sing? Territory defense Pair-bonding Mate guarding
Reproductive synchronization
Females often sing when:
High levels of female-female competition for resources or mates
Where ecology or mating system result in period male absence for territory
Common in birds which defend year-round territories and in polygamous species
The superb fairy-wren (Malurus cyaneus) of eastern Australia uses songs to defend territories against both males and females
From Langmore, 2000

10. Female Choice and the Evolution of Bird Song
Reid et al (2004) found
first year male song sparrow, Melospiza melodia, with larger song repertoires had higher mating success than those with smaller song repertoires
Females laid eggs earlier when mated with males with larger song repertories
Song repertoire size in song sparrows

11. Vocal performance and Female Choice: song as an honest indicator of male quality
Male swamp sparrows perform complex trills are forced with a trade-off between trill rate and frequency bandwidth
Ballentine (2004) identified songs which were performed with a higher degree of proficiency
Found female swamp sparrows (Melospiza georgiana) displayed significantly more to high-performance songs than low-performance song

12. Song Learning
Bird songs and other vocalizations can be inherited, learned, or invented.
For most songbirds, some aspect of their song is learned
In the Brown-headed cowbird (Molothrus ater), a nest parasite, young will develop a normal song even when raised in acoustic isolation.

13. Evidence that song is learned
William Thorpe (1954, 1961) : experiment on song development.
Tape recorded and spectrum-analyzed song
Reared birds in acoustic isolation (recorded “isolate” song which develops). (Isolate songs were very simple; lack the complexity of normal song).
Introduced ‘tutor songs’ and observed copying (learning from acoustic model).
Discovered that tutoring late in development does not reverse effects of isolation.
Thus, birds learn their songs by listening, usually to their fathers; and song learning takes place during an early ‘critical period’.

14. Stages of Song Learning for birds with fixed repertories
Critical Learning Period
Silent period
Subsong period
Song crystallization
White-crowned sparrow (Zonotrichia leucophrys) undergoes these 4 stages

15. 1. Critical Learning Period
Information stored for later use
Usually less than a year in duration
Often extends into 1st breeding season
White-crowned sparrow nestlings
Stages of development in White-crowned Sparrows
hatch
critical period

16. 2. Silent period
Song components that have been memorized during learning period are stored in brain
Up to 8 months
Stages of development in White-crowned Sparrows
hatch
no song
critical period

17. 3. Subsong period Canyon wren Catherpes mexicanus
Period of practice without communication
Begins with low volume, unstructured notes
Over time, sounds become more like species specific song
Subsong
Adult song
Stages of development in White-crowned Sparrows
hatch
150 days
no song
critical period
subsong

18. 4. Song crystallization
Plastic song becomes increasingly less “plastic”
By the end, the final “adult” version of the song is sung.
Stages of development in White-crowned Sparrows
hatch
150 days
200 days
no song
critical period
subsong
full adult song

19. Song learning
Sensory (or memorization) phase = a young bird must hear tutor song, critical period
Sensorimotor phase = attempt to match vocal output to the song memorized previously
Stages of development in White-crowned Sparrows
hatch
150 days
200 days
no song
critical period
full adult song
Sensory phase
Sensorimotor phase

20. Song learning is more complex
Song learning in the White-crowned sparrow has a distincts stages
In the some birds, such as the Zebra Finch (Taeniopygia guttata), these stages overlap

21. Song learning in the Zebra Finch
Critical
Period
ends
Singing
begins
Song
Crystallization
hatch
Days after hatching
Sensory phase
Sensorimotor phase

22. Diversity of Song Learning (1)
1. When the song is learned
Varies from brief sensitive period during first few months (e.g., white-crowned sparrow) to throughout its lifetime (e.g, willow warbler)
2. How many songs a bird learns
Approximately 70% of male songbirds sing more than one song type
Varies from a few (<5, e.g., chaffinch) to large (>100, e.g., common nightingale)
3. Copying Fidelity
Birds do not always copy tutor songs precisely
Varies from imitation to improvisation to invention

23. Diversity of Song Learning (2)
4. Role of early song experience
Isolation rearing does not always lead to development of abnormal song
5. Degree of canalization
An environmentally canalized song is one in which a bird copies tutor material only if it fits tightly constrained species-specific parameters (e.g., white-crowned sparrow)
Varies in highly environmentally canalized song to ability to copy most sounds heard (e.g., mockingbirds)
6. Social factors
Little known
Song learning may could depend on which bird is singing and how it since in addition to the amount and timing as song exposure
From Beecher and Brenowitz, 2005

24. Tutoring in white-crowned sparrows
Rose et al (2004) asked whether a representation of the full song is required for assembling the “normal” adult song.
Suggest the correct phrase order could be deduced only if information about the temporal order of adjacent phrases is represented separately in the tutor model, but not when birds are tutored with phrase types presented in temporal isolation
Therefore birds should be able to develop full songs if tutored with pairs of phrases that are normally adjacent but not when tutored with phrases presented in isolation

25. Tutoring Regimes
Group 1: Tutored with pairs of phrases normally adjacent
Group 2: Tutored with reverse-ordered phrases
Group 3: Tutored with pairs singly
Figure 1 Sound spectrograms of songs of two white-crowned sparrows and tutor models. a–c, Songs consist of four to five segments, referred to as 'phrases', denoted as A, B, C, D and E. Phrases generally are composed of repeated notes or syllables. Tutoring regimens consisted of single phrases (not shown) or pairs of phrases from the songs shown in a. Paired phrases were either in the normal (b) (for example, AB) or reversed (c) order; phrases in these pairs were always from the same song. Only the phrase pairs taken from the song of bird 2 are shown. wc 1 and wc 2, indicate the songs of birds 1 and 2, respectively

26. Results provide evidence for a minimal requirement of sequence information in song learning
Group 2: Tutored with reverse-ordered phrases  assembled phrases into songs with reversed phrase order
Group 3: Tutored with pairs singly failed to produce full normal songs
Group 1: Tutored with pairs of phrases normally adjacent  assembled phrases into full songs

27. Acoustic communication in urban environments

28. Acoustic Communication in Birds
Signal
Receiver
Noise can be defined as any environmental condition that interferes with signal transmission and detection
Vocal Plasticity
Communication loops
Interference occurs
Birds adjust to challenging environments (forest, shorebirds)
Evolution takes time

29. Birds have adapted communicate to different acoustic environments
Field Sparrow
Breeding Habitat: Successional-scrub
Calls of forest birds typically contain pure tones of relativel low frequency
This acts to reduce signal degradation in an environment tin which tress and abundant veg could case reverberation and scattering of higher frequency signals.
Black-capped Chickadee
Breeding Habitat: Woodland

30. Some birds can alter the characteristics of their song (Behavioral Plasticity)
For example, Black-capped Chickadees can alter the pitch of their songs.

31. Bioacoustics of Chickadee (Poecile atricapillus) song contests reveal hierarchies between competing males
Subordinate males alter the frequency of their territorial calls in response to playback songs of dominant males from nearby territories. Subordinate males sing at a higher frequencies.
Daniel Mennill & colleagues, Auburn University

32. The Urban Noise Issue
Rapid anthropogenic habitat modification generates new patterns of noise
Rapid change may not allow time for natural selection to occur
“Effective communication in these highly altered environments will be maintained only if signalers modify their call structure or if receivers are able to adjust their perceptual apparatuses in response to anthropogenic changes” – Rabin & Greene, 2002
Natural selection see rabin 138
==behavioral & physiological plasticity

33. Sources of Noise Pollution (contributions to the city soundscape)
Transportation systems account for main source of urban noise pollution
Road traffic
Aircraft
Railways (above & below ground)
Other noise sources
industry/factories
alarms & sirens
building equipment
(e.g., ventilation, air conditioners)
neighbor noise
(e.g., lawnmowers, vacuums, music & TV, domestic animals, social celebrations)

34. Types of Noise Pollution
Continuous noise: machinery that operates without interruption in the same mode
Intermittent noise: noise level increases and decreases rapidly like a passing vehicle
Impulsive noise: brief and abrupt from impacts or explosions

35. Urban noise tends to be found at lower frequencies

36. Noise Contour Map: Logan airport

37. Song Sparrow at West Roxbury High School being masked by school bus

38. Potential Behavioral Adaptations
Simply don’t live in environments with high levels of anthropogenic noise

39. Birds & Roads
motorway (100m)
Control
(950m)
Area  A [ha]
 24.5
  23.45
Total number of bird pairs T
202.5
244.5
Species richness S [number of species] 22 26
Total bird abund­ance T/A [pairs/ha]
   8.27
  10.43
Average bird abundance T/(A*S) [pairs/ha]
    0.376
    0.401
Simpson's reciprocal diversity index; D = 1/   P2 (where P =  proportion of pairs/species contributed to total)
  10.94
  13.25
Simpson's equitability E = D/S
    0.50
    0.51
Rheindt (2003) found lower species richness and abundance near a motorway than compared to a control transect.
Southern Grmany

40. Potential Behavioral Adaptations
Simply don’t live in urban environments
Vary song temporally or spatially
Vary song temporally or spatially
Alter pitch of song to sing above the urban noise.

41. More on Birds & Roads
Rheindt (2003) also showed birds with lower dominant frequencies tended to show a more marked decrease in abundance towards the motorway, whereas birds with higher frequencies tended to maintain or increase their level of abundance.

42. Parus major 37-52 million breeding pairs throughout Europe.
Breeds and winters in woods, parks, orchards, hedgerows and gardens

43. Slabbekoorn, H. , and M. Peet. 2003
Slabbekoorn, H., and M. Peet Birds sing at a higher pitch in urban noise. Nature 424(July 17):267.
The data the team have analyzed come from recordings of 32 males in various parts of Leiden. The researchers also took a series of recordings and background-sound measurements in each location before, during, and after rush hour.
The average minimum frequency of the males' songs, ranging from 2.82 to 3.77 kilohertz, was lower in quieter neighborhoods than in noisier ones. Urban noise, mostly from engines in cars, trucks, boats, and modern conveniences such as leaf blowers, encroached on birds' lower frequencies in the loud neighborhoods.

44. Potential Behavioral Adaptations
Simply don’t live in urban environments
Vary song temporally or spatially
Alter pitch of song to sing above the urban noise.
Sing louder

45. Environmental noise and song amplitude
Brumm (2004) found male nightingales (Luscina megarynchos) sang at higher sound levels in noisy territories compared to males situated in quieter territories.

46. Environmental noise and song amplitude
Brumm (2004) also found individual nightingales adjusted their song in response to traffic noise.

47. Potential Behavioral Adaptations
Simply don’t live in urban environments
Vary song temporally or spatially
Alter pitch of song to sing above the urban noise.
Sing louder

48. Song Sparrow at West Roxbury High School being masked by school bus