Tag Archives: song

How the White-Crowned Sparrow changes its tune to be heard through the urban din

Last October, I was invited by Laurel Serieys (a graduate student at UCLA)  to present a paper at The Wildlife Society’s 20th Annual Conference in a symposium on how urbanization can cause wildlife populations to diverge by altering behavioral, physiological, and genetic aspects of populations occurring in cities compared to non-urban areas. This is an emerging field of research as we are beginning to build a better understanding of how different cities are as habitats for many species, and the different ways by which they may adapt to city life – or not. This approach is part of the research strategy which should help explain some of the broader patterns we are observing in the distribution of biodiversity in the world’s cities.

I spoke about the effects of urban noise on bird song, based on the excellent Masters thesis project by my (now former) graduate student Jenny Phillips, who studied migratory White-Crowned Sparrows spending the winter in California’s Central Valley. Jenny has since gone on to a Ph.D. program at Tulane University, working in the lab of Elizabeth Derryberry, who was on her MS thesis committee (and with whom I intend to continue collaborating to extend this research).

Photo of White-Crowned Sparrow sitting in a fence

A white crowned sparrow framed in the demarcated landscapes of California’s Central Valley. Photo by Madhusudan Katti, 2008.

I just remembered that TWS was recording talks and sessions throughout the conference, and went looking to see if my talk was recorded. Indeed it was! So if you are interested in hearing about some of Jenny’s and my work on urban bird song, have a listen to my talk on this page, which shows you my slides coupled with my ghati-accented voice:

Singing in the urban din: the effects of anthropogenic noise on song structure in urban birds

Note: the audio had glitches when I tried listening through Safari, but worked fine on Google Chrome; YMMV.

Here’s my abstract for that talk:

Female birds often use male song as an indicator of mate quality; thus the study of song provides insights into reproductive success. Song structure is constrained by the acoustic environment with selection favoring songs that transmit best through available channels given ambient noise and atmospheric conditions. Ecology_specifically those components of the environment that influence sound transmission_thus influences the cultural evolution of songs. One relatively new selection pressure on many birds’ song, is anthropogenic noise, from car traffic as well as industrial machinery and other urban sources. Urban noise resonates at low frequencies and has been shown to influence song frequencies in sedentary populations of song sparrows, great tits, and blackbirds. Increase in ambient noise has also been shown to diminish discriminatory ability in female zebra finches. I first present a brief conceptual overview of the potential and documented effects of urban noise on bird song and behavior. I then share results from ongoing studies of the effects of noise on song in White-crowned Sparrow, Zonotrichia leucophrys gambelii, a long distance migrant wintering in urbanizing areas of central California. Songs and noise were recorded across the urban-rural noise gradient in Fresno-Clovis Metropolitan Area and compared for acoustic differences in frequency and duration. Modulated note components of the song, the buzz and trill, decreased in bandwidth with increasing noise. The duration of the buzz portion can also be predicted by noise and habitat type. This trend towards short, pure tones in noisy areas is likely an adaptation to be better heard through the roar of the city. Playback experiments also found increased latency to respond to territorial simulations under high ambient noise levels. This may contribute to a breakdown of territoriality in urban habitats. Anthropogenic noise is likely to be an important driver of population divergence due to urbanization.

To be a bird, oh to keep on singing, in a noisy urbanizing world

Among the many ways we are transforming the planet and its habitats for other species, one that is only now receiving some attention is that of sensory pollution. This is when we pollute the environment in such ways as to interfere with the sensory perception and communication systems of animals – i.e., dull their senses in potentially important ways. While much attention has been paid—and justly so, ever since Rachel Carson’s clarion call—to the wide variety of chemical pollutants we’ve introduced into habitats all over the world, we haven’t really paid much attention to the sensory effluvia that come in the wake of modern civilization. Two common ways we mess up the sensory systems of animals are by interfering with the visual and auditory channels of communication: e.g., increasing turbidity in water makes it difficult for fish to see and communicate with each other using visual signals (color patterns, changes to and movements thereof); increasing noise from our cacophonous machinery on land and in water makes it difficult for animals to talk to each other. We are a flashy, noisy, brash, uncouth, species indeed! No consideration for the sensibilities of our planet-mates…

But that may be changing. Sensory pollution is getting increasing attention from biologists in recent years, as exemplified by a symposium on the topic at Behavior 2011, the joint meeting of the Animal Behavior Society and the International Ethological Conference, being held at Indiana University this week. I wish I had been able to attend, especially for this symposium, because I’ve been thinking about and trying to study the effects of urban noise on bird song and behavior for some years now. Although I couldn’t travel to the meeting, I’m happy that my lab was well represented – see below!

After co-authoring the first comprehensive review of urban bioacoustics (i.e., the study of how animals use sound; in cities), then moving to Fresno with this job, actually measuring the effects in wild birds, and testing some of the theoretical ideas outlined in our review was one of my first priorities. Easier said than done, though – especially for a naive faculty member coming to grips with the nature of teaching and the student body at an institution like CSU-Fresno! Between my increasingly heavy and chaotic teaching load, and several unreliable graduate students, it became rather a stop-start project – more stop than start for several years. That all changed a year ago, however, when two eager new graduate students entered my lab, already interested in birdsong and very keen to tackle the subject of urban noise. Over the past year, Jenny Phillips and Pedro Garcia have been studying the effects of noise on the songs of two species (seen above) that occur in urban and rural areas around here: the White-crowned Sparrow, winter visitor to the valley from northern breeding grounds, and the House Finch, year round resident in these parts. An interesting opportunity to compare what noise pollution does to the songs and singing behavior of two rather different species: one migratory, the other sedentary, one singing to claim territory and warn competitors, the other warbling in the spring to attract mates!

Today, Jenny and Pedro presented the first results from their research as a poster at Behavior 2011. Having helped them analyze their data and design the poster over the past few days, I’ve been something of an anxious parent this week, wondering how they are doing out there on their own, even as I followed the #behav11 hashtag on twitter to see what I was missing! A short while ago, a tweet (of course) informed me that “…they did a gr8 job!!” Phew! Not that I expected anything less…

If you, like me, missed the whole meeting, allow me to share their poster here, starting with this abstract:

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EFFECTS OF URBAN NOISE ON SONG STRUCTURE IN A SEDENTARY AND A MIGRATORY BIRD SPECIES
Jenny Phillips, Pedro Garcia, Lauryn Moles & Madhusudan Katti 
California State University, Fresno, United States

Many animal species are dependent upon vocal communication to mate and defend territories. Selection will favor individuals that produce vocalizations that transmit best in their environments. The sensory drive concept suggests that environmental conditions, such as ambient sound, will influence the evolution of vocal behavior. Thus, background noise levels may have a profound effect on communication. We study how urban noise affects the cultural evolution of birdsong in two species: the migratory white-crowned sparrow (Zonotrichia leucophrys gambelii) and the sedentary house finch (Carpodacus mexicanus). These two species are ideal study organisms because they each have one song type, are territorial, and are easy to identify. We recorded songs and ambient noise concurrently across the Fresno-Clovis Metropolitan Area (FCMA) and in outlying rural areas for comparative analysis of acoustic properties, in particular the frequency and temporal structure of songs. Because song influences fitness via phenotypic and genotypic mate quality, understanding how song changes in an urban environment may allow us to predict species adaptability in a changing world.

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And here is the full poster – leave a comment if you have any thoughts on this ongoing study:

Phillips_et_al-ABS2011-Poster.pdf
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Why do some birds mimic strange noises in their songs?

That was the question asked of me a few days ago by Janaki Lenin, a conservationist and writer (and recent Facebook friend) researching for her column in The Hindu. Janaki is particularly curious about Racket-tailed Drongos which she has heard mimicking a variety of sounds including “cats fighting, truck horn etc. in the Andamans”.

The following video demonstrating a remarkable exhibition of mimicry by a Gray Catbird therefore seems apropos as I ponder this question:

http://s.ytimg.com/yt/swf/watch_as3-vfl174813.swf

A remarkable Gray Catbird mimics dozens of bird species (and a frog too!) in northern California. Listen as Greg Budney, audio curator at the Macaulay Library, dissects the recording and notes each snippet of mimicked song.

Mimicry, of course, is the very basis of avian song learning: in most songbirds, juvenile birds hear adults singing, and try to reproduce the songs they hear (i.e., mimic adult song) in order to develop their own individual songs and repertoires. From that basic root, mimicry has evolved to encompass a wide range of vocal behaviors, from copying conspecific calls/phrases/songs, through imitating sounds of other species, all the way to mimicry of random noises from the environment! So the question then becomes: why does the extreme mimicry of random noises evolve in some species?

The most likely explanation, if you ask me, is that this seemingly odd behavior has evolved (like so many other odd things males do throughout the animal kingdom!) through sexual selection. Female birds are often very picky, so male birds must compete to impress them by showing off in a variety of ways, visual and auditory. Courtship is more likely to be successful if a male can serenade a female with a variety of melodies, and research in many species has shown a male’s song repertoire size (i.e., number of distinct songs he can sing) to correlate strongly with his reproductive success. Competition in this case will push males to incorporate ever more diverse sounds into their repertoires, and sexual selection can run away with this, with some males ending up imitating all kinds of random noises! A facility with copying and reproducing such diverse sounds may also indicate a male’s superior quality to the female in several ways: a good mimic may have superior brain circuitry (at least in the song system in the forebrain), may be well traveled, and may be sufficiently well off to be able to devote idle time to the pursuit of the vocal arts! Or, some females may simply be too susceptible to elaborate vocal seduction!

An complex vocal repertoire is therefore the auditory analog of elaborate plumage seen in other species that rely on visual communication to catch the ladies’ eyes. A song sparrow’s large repertoire of songs may therefore be likened to a peacock’s tail-feather train, while the more eclectic selections sung by the above catbird, the Eurasian reed warblers, and likely the racket-tailed drongo, are more like the colorful furnishings of a bowerbird’s nest (look below the fold).

These are just my initial thoughts on the question, scratching the surface of the phenomenon; I will try to elaborate this post, with references, as time permits. For now, let me leave you with a couple more videos demonstrating the extraordinary vocal and visual displays of some otherwise drab looking birds:

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