La Nature is beginning to be measured as much by its silences as by its sounds.Where before it was enough to look, now scientists also need to listen to understand what is happening to life on the planet and comprehend the sensory experiences in natureIn the midst of a biodiversity crisis, hearing has become a key tool, and birds, a kind of sonic thermometer of the health of ecosystems.
In this context, a pioneering project has been born: a global bird sound bank designed to listen to the planet's biodiversityBehind this initiative is a large international team led from Spain that has achieved what until recently seemed like science fiction: to gather, accurately annotate and make publicly available thousands of recordings of bird songs and calls from virtually all over the world.
What is the WABAD World Bird Sound Bank?
The World Annotated Bird Acoustic Dataset (WABAD) is the full name of this enormous global sound archive. It is a rigorously annotated set of acoustic data on birds, created with a very clear objective: to facilitate the development of algorithms that automatically identify species by their songs or callsand use that information to monitor biodiversity on a large scale.
The project is coordinated by the Spanish biologists Esther Sebastián-González, from the Department of Ecology at the University of Alicante (UA), and Cristian Pérez-Granados, from the Centre de Ciència i Tecnologia Forestal de Catalunya (CTFC), in Solsona (Lleida). What began as the idea of a small group of specialists has become an international scientific network with more than one hundred researchers from 29 countries involved in data collection and recording.
This public bank collects recordings of nearly 1.200 types of birds from all five continentsIn other words, we are not dealing with a local or partial collection, but with a truly global archive that integrates soundscapes from very different environments: tropical forests, coastal wetlands, grasslands, Mediterranean mountains, agricultural areas or Asian jungles, among many others.
The underlying idea is as simple as it is powerfulIf we know which birds sing in a place and at what time, we can deduce how that ecosystem is changing over time. And if we can train artificial intelligence to automatically recognize those songs, then we can monitor large areas of the planet without needing ornithologists constantly patrolling the territory.
In short, WABAD presents itself as a critical scientific infrastructure for listening to the state of biodiversity, generate reliable data and support decision-making in conservation and environmental management at both local and global levels.
A global sound archive: figures and scope of the project
One of WABAD's greatest strengths is the magnitude and diversity of its contentIt's not just about collecting isolated audio recordings, but about building a highly detailed sonic portrait of the world's birdlife. The dataset currently includes:
- 5.047 minutes of audio files analyzed and noted.
- More than 90.000 vocalization tags of birds, each one associated with a species and a specific moment in the recording.
- 1.192 recorded bird species, which are close to the total of approximately 1.200 mentioned in the general descriptions of the project.
- 72 different habitats distributed throughout the world, ranging from temperate forests to tropical rainforests, including marshes, Mediterranean scrubland or rural landscapes.
This data comes from a wide range of countriesThe list includes territories as varied as Vietnam, Taiwan, New Caledonia, Guinea-Bissau, Guatemala, China, Cyprus, Ukraine, Costa Rica, Argentina, Burkina Faso, Dominican Republic, New Zealand, Poland, Sweden, Cameroon, Scotland, Canada, United States, Uganda, Germany, France, Greece, Mexico, Colombia, Brazil, Indonesia and, of course, Spain.
If we analyze the volume of information by continent, Europe leads the ranking to 1.722 minutes of recordingsapproximately one-third of the total. This is followed by Ibero-American countries with 939 minutes, North America with 858, Asia with 831, Africa with 408 y Oceania with 289 minutesThis distribution reflects, on the one hand, where work has been most intensive so far and, on the other hand, the regions with the greatest potential for growth in future phases of the project.
WABAD's value lies not only in the number of minutes collected, but also in the quality and accuracy of the annotationsEach vocalization is marked with the exact second the bird emits the song or call, providing an extraordinary level of detail. This second-scale notation allows for the construction of very fine training sets for artificial intelligence algorithmscapable of learning to distinguish species even when there are multiple overlapping sounds or ambient background noise, including the noise pollution.
Thanks to this combination of geographic breadth, habitat variety, and accurate annotation, WABAD ranks among the most complete and robust acoustic databases of birds developed to date, and becomes a pillar for bioacoustics and soundscape ecology.
How bird recordings are collected and annotated
To feed this global database, it's not enough to go out into the field with a handheld recorder and record a few birdsongs. The methodology is based on the use of automatic recording devices installed in the wild, which remain in the same place for weeks or even months, capturing everything that sounds around them.
These Acoustic recorders are left camouflaged in the natural environmentThese sensors are attached to trees, posts, or other discreet structures and programmed to record at specific times or continuously, depending on the sampling objective. This method yields realistic soundscapes, with birdsong mixed with the sounds of wind, insects, mammals, and distant human activity.
Once the devices have been collected, the most laborious part begins: listen, identify and note the vocalizationsTeams of experts analyze the audio recordings and mark the second at which each species sings, adding a corresponding label. In many cases, they use spectrograms (visual representations of sound) to better locate and differentiate the songs in dense recordings.
This meticulous work generates thousands of records labeled with very fine temporal precisionEach annotation not only indicates which species is vocalizing, but also at what exact moment in the recording it appears, which is fundamental for training algorithms that learn to recognize complex sound patterns.
Furthermore, The data is integrated with contextual information The recording also provides information about the habitat and location of the soundscape, allowing scientists to associate specific soundscapes with particular types of ecosystems or levels of human disturbance. This context greatly enriches the potential use of the sound bank, as it allows researchers to study how bird communities change depending on their environment.
Spain on the global sound map: Doñana, El Hondo and more
Spain plays a prominent role in this project, not only because of its scientific leadership, but also because of the variety of national ecosystems included in WABADIn the Iberian Peninsula, the following have been selected emblematic places for bird conservation, which provide a great wealth of songs and species.
Among the Spanish enclaves represented in the database are the Doñana national park, one of the most important wetlands in Europe, and the El Hondo area in Alicante, another key area for waterfowl and migratory birds. Also appearing Solsona (Lleida), with its forests and efforts to reforestation, Zarzalejo (Madrid), areas of Navarra, the region of Land of Pine Forests (Valladolid), Villena y Ontígola (Toledo), among other rural and forest landscapes.
In the case of the peninsula, the data shows that The most frequently "heard" species are the common chaffinch and the common blackbirdThese two birds are widespread and familiar to anyone who has walked through a park or forest in Spain. Their songs are repeated time and again in recordings, placing them among the top-ranked vocalizations recorded.
Alongside them, other birds stand out, such as the common nightingale, corn bunting and robinwhich also accumulate a considerable number of records. It is noteworthy that among the twenty species with the most vocalizations also appear Hawaiian birds such as the 'apanane, the 'amakihi, and the 'iwiThis reflects the truly global dimension of the project, in which European, American, Asian and Pacific species coexist in the same database.
The role of Spanish research on this sound map of the planet is especially relevantThe coordination from the University of Alicante and the CTFC, together with the participation of numerous national groups, places Spain in a benchmark position within applied bioacoustics, demonstrating that cutting-edge projects on a global scale are also being promoted from here.
From observing with binoculars to listening with algorithms
For decades, bird monitoring has almost always been based on visual and auditory censuses carried out by peopleTeams of ornithologists would travel along established routes, noting the species seen or heard, and repeat this work year after year. Although this approach has generated invaluable information, it has several limitations: it is time-consuming, requires highly specialized personnel, and is difficult to scale up to large areas or very long monitoring periods.
The arrival of the Automated bioacoustics is a game-changerInstead of relying solely on human observers, they can now be deployed sensors that continuously “listen” to the environment and send the data to computer systems. This is where WABAD fits in as a key piece: it provides the material that the algorithms need to learn to recognize birds by their sounds.
Thanks to thousands of vocalization tags, data scientists can training artificial intelligence models These models are capable of distinguishing sound patterns, identifying species in noisy recordings, and quantifying their presence over time. They not only say "a blackbird is singing here," but also allow us to measure how frequently that species appears in a specific area or how its activity varies at different times of the year.
In practice, this technological leap means that ecosystems can to be monitored much more frequently, accurately and economicallyA set of sensors distributed throughout a natural park can generate a kind of "real-time sound x-ray", indicating which species are present, which are declining, which suddenly appear or return after environmental restoration.
Furthermore, this algorithm-based approach has another important advantage: It reduces the need for constant human presence in the fieldAs Esther Sebastián-González herself explains, automatic systems prevent a person from having to spend hours and hours in the field counting birds, since the algorithm identifies the species and makes it easy to know how many different ones are detected in a specific place and time.
Birds as bioindicators: what their songs tell us
Birds have long been considered excellent bioindicators of the state of ecosystemsTheir presence, abundance, or disappearance can reflect changes in habitat structure, air quality, food availability, noise pollution, and even the effects of climate change.
Listening to their songs is, in a way, like Listen to the health of the environmentWhen a soundscape is enriched with a greater diversity of species and different types of vocalizations, it is usually a sign of a functional and relatively well-preserved ecosystem. Conversely, when the environment becomes impoverished and the recordings are reduced to a few generalist species or those highly tolerant of disturbance, something is usually wrong.
The possibility of Compare soundscapes before and after an environmental performance This is one of the most interesting applications of this sound bank. For example, after ecological restoration in a degraded wetland or a burned forest, analyzing how the diversity of bird songs changes can offer early clues about the system's recovery, long before the change is evident to the naked eye.
This approach has enormous potential for evaluating the effectiveness of environmental policies and conservation projectsPublic administrations, national park managers or those responsible for protected areas can rely on acoustic information to make more informed decisions, prioritize actions or detect problems in time.
In addition to all this, the Acoustic monitoring is a non-invasive techniqueThere is no need to capture or handle animals, their behavior is not significantly altered, and large areas can be covered with minimal impact on wildlife. At a time when biodiversity loss is accelerating, having monitoring tools that do not add further pressure to ecosystems is especially valuable.
Overall, the global bird sound bank is establishing itself as an essential tool This is valuable both to the scientific community and to those who manage the land. It allows us to study biodiversity through sound, improve automatic identification systems, and bring society closer to a powerful idea: that the planet can also be protected by listening to how it sings, how it falls silent, and how its symphony of voices changes in response to our actions.
