Hello, birdbrain-ga!
Your question was quite challenging, to say the least! However, as a
wildlife biologist in Alaska during the 1970’s, I felt compelled to
take it on and see what research I could find to help you in your
quest. I have come up with some interesting articles that tackle your
main question…the possibility of recognizing different bird species in
the field by their vocalizations.
The ability to recognize bird species in the field by analyzing their
vocalizations is supported by the literature.
An article titled “Applications of Acoustic Bird Monitoring for the
Wind Power Industry,” by William R. Evans, Cornell Laboratory of
Ornithology, Ithaca, NY., highlights various methods of identifying
night-flying birds near wind turbines. The author states that about
“200 species of North American birds are known to give calls during
night migration, with ** roughly 150 of those being distinctive enough
to identify with certainty.”** The other species are “lumped into a
number of similar call complexes,” with the calls of species within
these groups not yet able to be distinguished with reliability.
The study utilized three methods of acoustic monitoring at recording
stations.
At one location, a pressure zone microphone was sheltered within
concrete housing, with the audio cable carried through PVC piping
where the signals were recorded on hi-fi video-cassette recorders.
“The tapes were analyzed each season for species composition…..both by
ear, and with the help of sound analysis software developed by the
Cornell Laboratory of Ornithology’s Bioacoustics Research Program.”
A second location was similar in recording methods, with the
difference being a series of microphones set up in plowed fields,
powered by 12-volt, deep-cycle batteries.
The third location utilized “eight, skyward-facing PZM microphones”
positioned in a field. The layout of the microphones in different
areas of the field potentially allowed the bird calls to be received
by all eight microphones. Bird calls were analyzed with the help of
software developed by the Cornell Bioacoustics Lab.
An interesting result of the recordings was the availability of the
sound technology to not only pick up bird collisions near the wind
turbines, but “alarm calls” as well.
A discussion of radar monitoring versus acoustic monitoring states
that although radar is capable of monitoring each flying bird,…
“acoustic methods gives species information….”
An excerpt of the discussion of acoustic software follows:
“Where do we go from here with this acoustic technology? How far
off is species call-recognition software? Evans feels that automated
call recognition is possible, given sufficient development funding,
and would dramatically reduce the time and cost of data analysis. In
the Nebraska study, computer call-recognition algorithms were used to
detect probable calls and to copy them to a computer hard drive, thus
allowing remote access to call data without the intervening “quiet”
periods.
Please read the entire article at
http://www.nationalwind.org/pubs/avian98/21-Evans-Acoustics.pdf
Contact information provided for Bill Evans, Consulting
Ornithologist and Acoustical Researcher, Ithaca, NY, while a 1999
co-chair for a Cornell workshop on “Avian Mortality at Communications
Towers” is given as William R. Evans. P.O. Box 46 Mecklenburg, NY
14863. Ph. 607/272-1786.
http://216.239.53.100/search?q=cache:CoAiIaq9go8C:migratorybirds.fws.gov/issues/towers/evanintr.html+analyzing+bird+vocalizations+technology&hl=en&ie=UTF-8
An excerpt from a presentation given by Bill Evans at the 1999
Cornell Workshop, titled “Applications of Avian Night Flight Call
Monitoring for Towerkill Mitigation,”at
http://migratorybirds.fws.gov/issues/towers/evans.html, has some
interesting highlights about acoustic monitoring, even though it’s
primary focus is on helping to reduce the rate of bird kills near wind
towers.
“Besides its applications for imaging broad front species composition
and relative abundance, acoustic monitoring has proven to be a useful
tool for monitoring avian activity in close proximity to towers. As I
mentioned in my introduction, acoustic monitoring documented
collisions and many incidences of alarm calls when a microphone was
placed under a 317-foot tower in Nebraska. Also, in that study, call
notes of migrating songbirds were recorded and the acoustic record
indicates periods during some evenings when calling rates increase
concurrently with call loudness. These appeared to have been
incidences when songbirds were circling the lights on the tower.
Software has been developed to automatically log such call notes and
the technology exists today to outfit towers with acoustic sensors
that could transmit information calling information to a research
station. A researcher could simultaneously monitor hundreds of towers
in a region for calling situations that indicate a kill might be
taking place. This information could be used to alert field
researchers to which towers to check in the morning. It could also be
used to automatically monitor how many nights a year birds are
congregating in the vicinity of towers, how often during a night, and
roughly in what numbers. Such acoustic monitoring might also be used
to trigger alternative lighting schemes that would be less attractive
to migrating songbirds.”
A paper, titled “Acoustic Monitoring of Night-Migrating Birds: A
Progress Report,” by Bill Evans and Kenneth Rosenberg at
http://birds.cornell.edu/pifcapemay/evans_rosenberg.htm, goes into
more technical detail about acoustic bird call monitoring. Excerpts
follow:
“This paper discusses an emerging methodology that uses electronic
technology to monitor vocalizations of night-migrating birds. On a
good migration night in eastern North America, thousands of call notes
may be recorded from a single ground-based, audio-recording station,
and an array of recording stations across a region may serve as a
"recording net" to monitor a broad front of migration……. Night-flight
calls of 35 species of migrant landbirds have been identified by
spectrographic matching with diurnal calls recorded from
known-identity individuals; call types of another 31 species are
known, but are not yet distinguishable from other similar calls in
several species complexes. Efforts to use signal-processing technology
to automate the recording, detection, and identification of
night-flight calls are currently under way at the Cornell Lab of
Ornithology.”
“Most species of North America's migrant landbirds make their
transcontinental flights at night, and many species give short
vocalizations while they fly. By aiming microphones at the night sky,
a volume of sky-with dimensions dependent on microphone design-can be
monitored for calls (Graber and Cochran 1959). A variety of microphone
and recording station designs have been used for this purpose,
depending on the specific monitoring goals and the recording
environment (Graber and Cochran 1959, Dierschke 1989, Evans 1994). In
many regions of North America, a recording station may detect
thousands of calls during a single migration night (Graber and Cochran
1960, Evans 1994). Species known to give night-flight calls include
the warblers (Parulinae), sparrows (Emberizinae), cuckoos (Cuculidae),
rails (Rallidae), herons (Ardeidae), and Catharus thrushes. Groups not
known to give regular vocalizations in night migration are the vireos
(Vireonidae), flycatchers (Tyrannidae), and orioles (Icterinae). If a
monitoring protocol is consistently maintained, an array of microphone
stations can provide information on how the species composition and
number of vocal migrants vary across time and space. Such data have
application for monitoring avian populations and identifying their
migration routes. In addition, detection and classification of
distinctive call-types is possible with computers (Mills 1995, Taylor
1995), thus information on bird populations might be gained
automatically. In this paper, we summarize the current state of
knowledge for identifying night-flight calls to species; present
selected results from four ongoing studies that are monitoring
night-flight calls; and discuss the implications of this research for
conservation of migratory landbirds.
(The use of microphones and accompanying recording technology is
discussed in detail, similar to the other papers referenced by Evans.
A bit more detail is provided about the software):
“Calls were detected on the recordings by listening through
headphones (Evans) and by signal analysis software written in the
Bioacoustics Research Program at the Cornell Laboratory of Ornithology
(Mills 1995). This software was designed to detect short high-pitched
call notes, which range in frequency from 5-9 kHz. All sound analysis
employed the software program Canary (Charif et al. 1995).”
“A long-standing impediment to the development of night-flight call
monitoring has been call identification. The night-flight calls of
many species, such as warblers and sparrows, are like single cricket
chirps, typically between 0.05 and 0.25 seconds long. Their high
frequencies (5-9 kHz) make them especially difficult for the human ear
to distinguish.”
“Since 1985, Evans has systematically determined the type of
night-flight call given by most species in eastern North America.
Three techniques were used to acquire this information (see Evans
1994). First, structural details of night-flight calls were compared
with diurnal calls of known identity through spectrographic analysis
(Fig. 2). The diurnal calls were typically recorded from birds in
visible flight, and such calls were considered as likely to be the
same call type used during night migration. The other two methods of
call determination consisted of correlating the seasonal timing and
geographic range in which various types of night-flight calls were
recorded with known timing and migration ranges for each species.”
“During five spring migrations, this recording station recorded over
50,000 calls of migrating birds. Basic evidence for the identity of
these species' night-flight calls was compiled by spectrographically
matching migratory contact notes from observed birds during the day
with distinctive night-flight calls (Fig. 2). Identities were then
further corroborated by matching the seasonal time of occurrence of
the tentatively identified call-types with the migrational databases
compiled by Cruickshank and Taylor (Evans, in prep)”
**” The question most frequently asked regarding this emerging
technique involves species identification and problems associated with
non-calling or non-detected individuals. We believe that the issue of
species identification has been addressed partly through careful
comparisons with calling birds of known identity, and through the use
of modern spectrographic analysis. Our knowledge of call identities
and variations within species will be refined as field recordists
continue to work in new areas of North America, and as
computer-analysis techniques become more sophisticated.”**
***Please see charts in the above article which help to address your
question about how species-specific and varied bird vocalizations can
be.***
The paper, “Acoustic Surveys of Birds Using Electronic Recordings:
New Potential from an Omnidirectional Microphone System,” by Dr. Keith
Hobson. Canadian Wildlife Service at
http://flash.lakeheadu.ca/~rrempel/CVX/research_paper.pdf, examines
the use of “audio recordings for avian point counts……in particular,
the newly developed omnidirectional microphone system with exceptional
recording performance, to see if this could adequately replace a
trained observer in the field.” Since the demand for trained
individuals, who can “identify acoustically as many as 120 species”
far exceeds the supply, the need for audio technology is immediate.
One advantage of the microphone approach is the ability for “tapes
to be interpreted by a single, trained expert,” which would thus serve
as a “control for observer variability.”
Although directional microphones have been used in the past to
record bird point counts, they lacked the ability to census in all
directions, as a human observer can do. Therefore, the omnidirectional
microphone, developed by River Forks Research Corporation in Prince
Albert, Saskatchewan, proved a better alternative.
(To read technical specifics about the microphone and its
accessories, refer to the section under “Microphone” in the report.)
To read further about the advantages and disadvantages associated
with employment of the omnidirectional microphone and the ability to
recognize individual species vocalizations as compared to a human
observer, please read the entire article. (Allow some time for the PDF
file to load!)
Contact information:
Dr. Keith Hobson
Canadian Wildlife Service
115 Perimeter Rd.
Saskatoon, SK
S7N 0X4
306-975-4102
River Forks Research Corporation
2557 Mcdonald Avenue
Prince Albert, SK Canada S6V 2V8
A recent study by the Patuxent Wildlife Research Center in Maryland
is focused on identifying individual birds within specific taxa by
monitoring vocalizations. An excerpt of the study follows:
“In recent years, the technology for recording and analyzing bird
vocalizations has undergone considerable improvements. Analyses of
vocalizations that formerly required use of sophisticated equipment in
specialized laboratories can now be accomplished on personal
computers. Improved analytical techniques allow for the identification
of individual birds by their vocalizations. Although the few current
studies have been conducted with a small number of passerine species,
these techniques may be equally useful for colonial-nesting birds and
other non-passerines and hold the potential for developing innovative
approaches for monitoring populations of many bird species. We propose
to explore the use of vocalizations of individual birds in the
development of monitoring techniques for colonial waterbirds. In this
study, we will determine whether individuals of specific taxa can be
distinguished and identified by their vocalizations. The primary
emphasis will on nocturnal and crevice/burrow nesting species because
reliable monitoring methods do not presently exist for most of these
taxa. ** If this study finds that individuals can be positively
identified by their vocalizations**, a second study will be necessary
to explore using vocalizations in capture-recapture models to estimate
population size.”
You can read an abstract of the proposed study, “Exploring the use of
recorded sounds for monitoring waterbird populations,” (7/26/2002) at
http://www.pwrc.usgs.gov/research/sis2002/sispwrcpage160.html
Contact information for the individual in charge of the above project
is also listed:
Melanie J Steinkamp, USGS Patuxent Wildlife Research Center:
melanie_steinkamp@usgs.gov
Analyzing bat populations with voice technology (not birds, but still
useful!)
“Researchers here have shown that computer technology can be used to
help estimate how many bats are in an area, simply by analyzing
recorded bat calls.”
“Researchers used a computerized neural network that differentiates
between the distinct vocal patterns of individual bats. The program
helped estimate how many bats produced the calls that were recorded.
This neural network is similar to computer voice recognition programs
for humans. The findings are especially promising for habitat
managers, according to Stephen Burnett, study co-author and a graduate
student in evolution, ecology and organismal biology at Ohio State
University. "Relying on a computer to separate the recorded voices is
one way of determining the number of animals in an area without
disturbing them in their natural habitat," he said.”
Read “Researchers Use “Voice Recognition” Program to Count Bats.”
Ohio State University (11/6/1999) at
http://www.naturalworldtours.co.uk/article/november61999g.stm
Sound Anaysis Software
For a very comprehensive website on software for bioaccustics, as
well as links to computer hardware considerations, refer to
http://eebweb.arizona.edu/faculty/hopp/sound.html#anim .
“For people trying to decide on a system or software my suggestion
would be to clearly answer three main questions: First, what exactly
is my research question, and what type(s) of procedures will I need a
system to perform? Second, what hardware do I currently have, and what
might I need to change/add/upgrade? (most of the software listed below
will work with a wide variety of sound cards). Third, what am I
willing/able to pay? Having balanced those three major variables in
the equation is probably the best starting point. Having answered
those questions, you can then look for resources that address
particular needs. Or select a few that seem reasonable, and e-mail
specific questions to whomever hosts the site.”
“For those who need a opening primer of computer-sound hardware and
software I suggest you begin with the first few links listed under
General Audio Reference and Resource Sites below. These give a good
introduction to the hardware involved in sound acquisition and
replication, and introductory information for related topics.”
***Scroll down the entire page for a wealth of links and
information***
The Borror Laboratory of Bioacoustics at Ohio State University is a
good resource for recording equipment and any questions you may have.
http://blb.biosci.ohio-state.edu/ Contact information is located on
the website.
The Bioacoustics Research Program at Cornell University,
http://birds.cornell.edu/BRP/ , has great links on their website for
sound recording hardware and software programs used for research.
http://birds.cornell.edu/BRP/Popup.html
http://birds.cornell.edu/BRP/ARUTerrestrial.html
Contact:
Bioacoustics Research Program, Cornell Lab of Ornithology
159 Sapsucker Woods Rd, Ithaca, NY 14850
phone 607-254-2408; fax 607-254-2439
Tips for conducting your own research:
Since you were not specific on what your research specifically
entails, other than an interest in bird vocalization species
recognition in the field, that is a hard aspect of your question to
answer.
Therefore, all I can suggest is that you analyze the various research
projects being conducted in major universities and wildlife
organizations dealing with bird populations. For example, Cornell has
several research projects listed on their website at
http://birds.cornell.edu/BRP/ResBird.html
Another suggestion is to go through the links on the Bioacoustics
site hosted by Ohio State University at
http://blb.biosci.ohio-state.edu/bioacoustics_links.htm
You can also peruse through various ornithology-related journals for
ideas….if you need more direction. The website at
http://biology.queensu.ca/~mennilld/links.html#Bird%20Sounds has a
wealth of journal links, but access to most is forbidden without a
subscription.
Another way to get further ideas and directions for research is to
sort through the research job listings posted at “Ornithological Jobs:
Positions and Opportunities Available Online” at
http://birds.cornell.edu/OSNA/ORNJOBS.htm
Variations in bird vocalizations
Research reveals there are differences in same-species bird songs
based on location! (Now there is some interesting research!)
The article “Birds: Avian accents appear in their songs,” by Stan
Freeman. Union News (1/25/1999) at
http://www.masslive.com/news/hf/feed/daily/ae123bir.html reveals that
variations in bird songs of the same species can differ even within a
few miles of separation.
“Using computer analysis of recorded bird songs, ornithologists at
the University of Massachusetts and elsewhere are finding that most
birds, from chestnut-sided warblers to indigo buntings, have subtle or
even pronounced differences in the way they deliver their songs based
on where they live”.
“Sometimes, as they've found in Massachusetts, the songs can differ
over just a few miles.”
"One great example is the black-capped chickadee which has a
different song on Martha's Vineyard than it does on the mainland,"
said Bruce E. Byers, a UMass ornithologist who primarily studies the
songs of warblers.”
“The chickadee's song may sound like "Hey sweetie!" And in most
places in the United States where chickadees are found, the first note
of the song is higher than the second. But on the Vineyard, both
"words" are delivered using a note of the same pitch, he said.”
“It has been known for perhaps the last 50 years that the songs of
birds do have geographic variations, but computers have helped to show
just what those subtle differences are. Ornithologists can create a
"sonogram" of a bird's song that graphically shows the frequency and
duration of the notes”
"It's only been in the last decade that we could do it rapidly using
a sufficiently powerful computer. We can do it in real time so that we
can play a song and see what it looks like at the same time," Byers
said.
Read the entire article for more fascinating information!
Additional information:
A fascinating article about the correlation between bird songs and
music has some extremely interesting insights for those interested in
bird vocalizations.
“One major disadvantage of recording bird vocalizations (regardless
of whether the medium is pen and paper, computer graphics or a sound
record) is that it standardizes the samples at hand. Deviations from
the standard tend to be relegated out of sight. This may apply to
differences within the individual: day to day variation; development
of singing during a season; the way a bird may have to build up a new
repertory after moulting. On the other hand it may apply to
differences between individuals: older birds can display expertise
exceeding that of younger ones by far; some individuals have a more
variegated repertory than others; a keen ear might even detect
differences in the basic timbre (clarity vs. hoarseness); birds may
adapt their song to the characteristics of their habitat; in their
song birds may show regional dialects. Another shortcoming of
recording bird sounds is that it usually treats the items in
isolation. This is obvious in the case of notation, but even sound
records often focus on individual species. Singling out one bird at a
time, sonic field guides aim at helping enthusiasts to recognize
separate species, rather than at the appreciation of a total sound
image and the interplay going on in it.”
“Every bird sings and calls within a context. On the one hand that of
its own motivations. It may sing to define its territory acoustically,
to attract a female. Young Blackbirds perform singing exercises. There
are species that sometimes sing for no apparent reason at all, just
for the fun of it. There are various types of warning signals. On the
other hand, one doesn't hear birds in isolation. Blackbirds remain
within hearing range of each other. As a result several individuals
are often audible at the same time, but other bird species as well;
and insects, and the rustling of leaves - the whole environment
sounds.”
“What's more, listening to a number of Blackbirds one cannot but
conclude that each listens to the others, spacing its song in a way
that enables the others to fill in phrases, sometimes mimicking those
others or even other species - reminiscent of weaving patterns,
patterns of call and response. These animals adjust their song to the
circumstances.”
Read “Songs Soaring (or do birds read music?),” by Rene van Peer.
World Forum for Accoustic Ecology. (7/21/1994) at
http://interact.uoregon.edu/MediaLit/WFAE/readings/Natsound/Songs.html
For what it’s worth: (It might be worth a call to find out about their
software)
From the University of Victoria, Dept. of Linguistics at
http://web.uvic.ca/ling/research/phonetics.htm
“In addition to the auditory, articulatory and acoustic study of
human speech, research projects in the lab have studied bird, seal and
whale vocalizations. Lab software and courseware has been developed in
close cooperation with the C.A.L.L. Facility for language learning and
with Speech Technology Research Ltd.”
Your question has many aspects, and I have tried to cover all the
bases with the information you have provided. It sounds like you have
some fun and interesting work ahead of you! The information above
should be helpful, but please don’t hesitate to ask if you need
further clarification.
umiat-ga
Google Search Strategy
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