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…

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

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

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.

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

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

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

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

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

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

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

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.

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’.

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

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

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

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

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

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

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

Song learning in the Zebra Finch Critical Period ends Singing begins Song Crystallization hatch 0 30 60 90 120 Days after hatching Sensory phase Sensorimotor phase

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

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

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

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

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

Acoustic communication in urban environments

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

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

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

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

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

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)

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

Urban noise tends to be found at lower frequencies http://www.davidcoateconsulting.com/95berkelystreet.html

Noise Contour Map: Logan airport http://www.massport.com/logan/img_c_contour.html

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

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

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

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.

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.

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

Slabbekoorn, H. , and M. Peet. 2003 Slabbekoorn, H., and M. Peet. 2003. 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. http://acp.eugraph.com/news/news03/slabb.html

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

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.

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

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

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