In modern poultry farming, we have become experts at monitoring the environment. Birds are continuously monitored by sensors that measure ambient temperature, relative humidity, CO2, ammonia, air velocity, light intensity, and other factors. However, there is a fundamental disconnect: we measure “environmental comfort” assuming it equates to “animal comfort.”
In many cases, an anthropomorphic view of animal welfare is applied, which involves interpreting animal well-being from a human perspective, attributing emotions and experiences similar to our own. That is, one imagines how a human being would feel in the same situation as the animal, prioritizing aspects such as happiness, stress, or boredom over physical indicators. This perspective can lead to misinterpretations or inappropriate decision-making.
In contrast, the zoocentric view is the one that evaluates animal welfare from the perspective of the animal itself based in the five domains (good nutrition, good environment, good health, good behavior and mental state).
Avian bioacoustics is emerging as the discipline capable of assessing animal welfare from the bird’s own perspective. Thanks to this technology, and especially to the latest advances in the artificial intelligence interpretation of recorded chick (or chicken) sounds, we can go far beyond measuring welfare through indirect indicators, such as thermometers, and begin to directly understand it by interpreting the chick’s vocalizations. This isn’t science fiction; it’s advanced technology that we are already implementing in some of the largest chicken producers in Spain.
The paradigm shift from measuring “The Environment” to measuring “Animal-centered Signal”
Unlike environmental sensors, vocalizations are what we call an animal-based indicator. A thermometer might read 32°C in a chick’s brooder box, theoretically registering a correct measurement, but if there’s a draft at ground level (wind chill effect), the sensor won’t detect it. The chick, however, will vocalize it immediately. Another example is the handling of birds: a sensor cannot register the stress that handling can cause, but the bird will express it through changes in its vocal pattern. These acoustic signals are direct information about the animal’s internal state, something that no traditional environmental sensor can provide.
Birds are the most vocal animals in the animal kingdom, employing a wide range of sounds to communicate, defend their territory, and express their internal state. From an ethological perspective, the chick is a precocial and social species whose survival depends on constant acoustic communication: with the mother in natural environments or with the group in industrial production. Its vocalizations are not random noise, but coded signals that transmit precise information about its physiological condition and well-being.
Recently, with the advent of IoT devices, big data, and artificial intelligence, researchers have been able to record and analyze in depth the different types of bird vocalizations and their meaning. When analyzing vocalizations in intensive production systems, birds are not studied individually, but rather as a group. Thus, the analysis focuses on how the vocalizations of a flock of birds vary in response to changes in the environment or management, identifying patterns that reflect the overall state of the group.
The Importance of Correctly Interpreting the “Peep Peep Peep” of Chicks
For poultry professionals, being able to distinguish between the two basic acoustic categories allows for quick identification of the birds’ condition:
1-. Pleasure/Contact Calls:
These are low-energy vocalizations, lasting 0.2 to 0.4 seconds, with a low repetition frequency. This acoustic pattern occurs when the bird is in thermal comfort, feeding, or exploring. Acoustically, they have a narrow bandwidth and appear in spectrograms as small “droplets.”
2-. Distress Calls:
These are the birds’ alarm signals. They are characterized by high energy, short duration (<0.2 seconds), repetitive nature, and a high repetition frequency. Depending on the bird’s age, their range is between 2.5 kHz and 4.5 kHz, a higher frequency than in pleasure calls. These calls are a generalized response to negative stressors such as cold, hunger, pain, or social isolation.
The preceding images are spectrograms we recorded, showing time on the horizontal axis and frequency on the vertical axis. Black indicates lower energy, and white indicates higher energy. Both spectrograms record vocalizations from day-old chicks in shipping rooms. The upper image (pleasure calls) shows calls of pleasure, and the lower image (distress calls) shows calls of anxiety or discomfort.
Bioacoustics to collect “what birds tell us” has existed for decades; what has changed is our ability to interpret, to “read” in real time the vocalizations of poultry
The scientific literature contains numerous studies on bird vocalizations, ranging from descriptions of different vocalization patterns and disease detection to monitoring and assessing bird welfare.
Regarding bird welfare, scientific evidence has been compiled in various publications, such as the 2014 study by Curtin et al., which describes how the number of call repetitions per unit of time is an indicator of stress, suggesting a higher level of stress associated with more frequent calls. A more recent publication from 2024 by Collins et al. shows that isolated chicks vocalize with greater intensity, duration, and spectral entropy than those that can see other chicks, even if only a reflection in a mirror (studies also known as Mirror Studies).
This has direct implications for management: a chick that lags behind or is trapped far from the group not only suffers from heat stress, but also from acute social panic that triggers its metabolic rate and yolk sac consumption, vocalizing the stress it experiences.
Precision Livestock Farming (PLF) refers to the use of advanced technologies to monitor animals in real time, with the aim of improving their welfare, productivity, and sustainability. Within this approach, bioacoustics has emerged as an innovative branch that allows for the diagnosis and monitoring of avian health through the analysis of their vocalizations. This method is completely non-invasive, as it requires no physical contact or direct handling, reducing stress and avoiding disruption to the bird’s natural behavior, thus ensuring more reliable data. Furthermore, it allows for continuous monitoring without interrupting production routines. By focusing on the sounds emitted by the birds, it transforms vocalizations into objective indicators of well-being, improving both the accuracy and efficiency of the system.
Current science proposes the use of the distress call rate, the number of vocalizations, or the vocalization frequency as indicators that reflect the state of the birds.
Early detection of high values in these indicators in a batch reveals underlying welfare problems that, if not corrected in time, could lead to productivity problems such as the feed conversion ratio or an increase in mortality.
Currently, technology that allows for real-time data processing and analysis is available to the industry at an affordable cost, enabling improvements in production processes and generating alerts that allow for the correction of potential production problems. The chick’s voice acts as the most sophisticated early warning system in the hatchery (hatchers and shipping room), during chick transport, and on the farm, as it is the animal that vocally expresses its well-being or discomfort.
