A Bird Song Detector for improving bird identification through Deep Learning: a case study from Doñana

Passive Acoustic Monitoring with automatic recorders is essential for ecosystem conservation but generates vast unsupervised audio data, posing challenges for extracting meaningful information. Deep Learning techniques offer a promising solution. BirdNET, a widely used model for bird identification, has shown success in many study systems but is limited in some regions due to biases in its training data. A key challenge in bird species detection is that many recordings either lack target species or contain overlapping vocalizations. To overcome these problems, we developed a multi-stage pipeline for automatic bird vocalization identification in Do\~nana National Park (SW Spain), a region facing significant conservation threats. Our approach included a Bird Song Detector to isolate vocalizations and custom classifiers trained with BirdNET embeddings. We manually annotated 461 minutes of audio from three habitats across nine locations, yielding 3,749 annotations for 34 classes. Spectrograms facilitated the use of image processing techniques. Applying the Bird Song Detector before classification improved species identification, as all classification models performed better when analyzing only the segments where birds were detected. Specifically, the combination of the Bird Song Detector and fine-tuned BirdNET compared to the baseline without the Bird Song Detector. Our approach demonstrated the effectiveness of integrating a Bird Song Detector with fine-tuned classification models for bird identification at local soundscapes. These findings highlight the need to adapt general-purpose tools for specific ecological challenges, as demonstrated in Do\~nana. Automatically detecting bird species serves for tracking the health status of this threatened ecosystem, given the sensitivity of birds to environmental changes, and helps in the design of conservation measures for reducing biodiversity loss