There are invaluable ecological resources in Quanzhou Bay Estuary Wetland (QBEW) such as mangroves and hence it is a habitat for various waterbirds (Lin et al., 2021; Juan, et al., 2011).QBEW plays a vital role in maintaining ecological balance, since it can help maintain biodiversity, regulate runoff, improve water quality, regulate microclimate, supply food and industrial materials, and provide tourism resources. However, with the rapid economic growth, QBEW faces severe environmental problems, such as water and air pollution, overfishing, invasive alien species, and urban land encroachment. These issues seriously endanger the habitat of native waterbirds, which are sensitive to changes in the environment (Wang et al., 2022; Pöysä et al., 2021). Thus, the species and population of waterbird often regard as environmental indicators (Green and Elmberg, 2014; Beatty et al., 2014; Zhang et al., 2018; Luo et al., 2019; Fan et al., 2021). There are plenty of waterbirds wintering in QBEW every year, including 10 kinds of national first-level key protected birds such as Egretta eulophotes, Platalea minor, Pelecanus crispus, Tringa guttifer and Ciconia boyciana, and 25 kinds of national second-level key protected birds such as Cygnus columbianus, Egretta sacra, and Halcyon smyrnensis. Heron is a dominant species in QBEW area and its numbers have increased significantly following the implementation of environmental restoration policies which implemented between 2016 and 2019 (Zhang et al., 2021). Among them, the most abundant waterbird is the Egretta garzetta, accounting for 65.82% of the total. Ardea cinerea accounted for 15.46% while Ardea alba accounted for 13.91%. Besides, Alpina and Larus ridibundus have also been observed in large groups widely distributed in QBEW (Chen et al., 2017). Although lots of sparrows are observed in the peripheral farming areas and vill/ages, most of waterbirds live in mudflat mangrove areas. Many waterbirds habitats have been disturbed or destroyed due to human activities, and waterbirds diversity and population have declined, which may indicate a weakening of mangrove conservation capacity in QBEW.
Although the QBEW Nature Reserve carried out lots of measures on the ecological restoration of mangroves and waterbird habitats, and even deployed many monitoring videos. It is still difficult tell the total number of different species of waterbirds, and it is hard to get a dynamic and comprehensive picture of changes in waterbirds. As an indicator of biodiversity, waterbirds are always deserving of being surveyed for biodiversity conservation. Recording the species and their population is crucial to understanding wetland environments. Managers can use the recorded data to see the distributions of different species of waterbirds, changes in the population of each species ,and analyze the relationship between waterbirds and their habitats. Therefore, to better protect the waterbirds and wetland resources in QBEW, we need to design and implement an intelligent waterbird automatic identification system that can automatically detect, identify, and monitor waterbirds in real-time.
With the rapidly development of deep learning-based image and video recognition algorithms, AlexNet, ResNet, Unet, and FCN algorithm showed great performance on objects identifications (Krizhevsky et al., 2012; Ronneberger et al., 2015; Long et al., 2015; Villa et al., 2018). These deep learning algorithms obtain huge success in many fields such as medical image segmentation, animal identification, face identification and remote sensing image recognition. R-CNN (Region-Convolutional Neural Network, Liu et al., 2020) series, SSD (Single Shot MultiBox Detector) (Liu et al., 2016), and YOLO (You Only Look Once) series are three widely used (Girshick et al., 2015) deep learning algorithms in the real-time applications of objects identification. Fast R-CNN (Faster R-CNN, Morera et al., 2020) is a new version of R-CNN which can recognize target objects faster than R-CNN with high accuracy, but the model training process is still very time-consuming, and it needs more labeled samples (Yan et al., 2021) and computation capability (Yan et al., 2021) compared with YOLO series algorithms (Wang et al., 2022; Yang et al., 2020; Chou et al., 2022; Lei et al., 2022).The SSD series algorithms are also time consuming relative to YOLO series algorithms. YOLOv5 is the latest version of the current YOLO series algorithms, which is a developed version of YOLO4. Although the recognition accuracy of both models are similar, YOLOv5 is much less time-consuming than YOLOv4, and its model size is almost only 10% of YOLOv4. Among these algorithms, YOLOv5 has the lightest model size, and it needs less computer resource. Moreover, the detection speed of YOLOv5 is fastest, up to 140 FPS. As Table 1 listed, YOLOv5 has obvious advantages and can meet the demand of real-time detecting in QBEW. Considering the current situation of QBEW and the trade-off between recognition accuracy and speed, we choose YOLOv5, and based on this, we designed and built an intelligent system for automatic monitoring of water birds.
Table 1
The comparison of deep learning models
Model | Advantages |
Flexible | Light model size | Low training time | High accuracy | Fast detecting speed | Fewer training sets |
YOLOv5 | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ |
YOLOv4 | ✔ | | | ✔ | | ✔ |
SSD | | | | ✔ | | |
Faster R-CNN | | | | ✔ | | |