This chapter provides an in-depth study of applying wireless sensor networks (WSNs) to real-world habitat monitoring. The authors developed a set of system design requirements covering hardware, software, protective enclosures, and system architecture to meet the needs of biologists. In the summer of 2002, 43 nodes were deployed on a small island off the coast of Maine, streaming live data onto the web. The chapter discusses the challenges and experiences from a four-month deployment, analyzing environmental and node health data to evaluate system performance. The integration of WSNs with their environment provides high-density environmental data, which is useful for predicting system operation and network failures. Based on over one million data readings, the authors analyze node and network design, develop network reliability profiles, and failure models. The chapter is structured into several sections: 1. **Introduction**: Explains the potential benefits of WSNs for habitat monitoring and the need for a system that produces useful data while leveraging sensor network research for robustness and predictable operation. 2. **Habitat Monitoring**: Discusses the biological need for sensor networks and the requirements for collecting useful data for life scientists. 3. **Network Architecture**: Describes the tiered architecture for habitat monitoring applications, including sensor nodes, sensor patches, gateways, and base stations. 4. **Application Implementation**: Details the application software, sensor board design, packaging strategy, and experiment goals. 5. **System Analysis**: Evaluates the behavior of the sensor network, including network dynamics and node performance. 6. **Node Analysis**: Analyzes the performance and reliability of individual nodes, focusing on sensor readings and power management. 7. **Related Work**: Reviews previous studies on habitat monitoring using WSNs. The chapter concludes with insights and recommendations for future research and applications of WSNs in habitat monitoring.This chapter provides an in-depth study of applying wireless sensor networks (WSNs) to real-world habitat monitoring. The authors developed a set of system design requirements covering hardware, software, protective enclosures, and system architecture to meet the needs of biologists. In the summer of 2002, 43 nodes were deployed on a small island off the coast of Maine, streaming live data onto the web. The chapter discusses the challenges and experiences from a four-month deployment, analyzing environmental and node health data to evaluate system performance. The integration of WSNs with their environment provides high-density environmental data, which is useful for predicting system operation and network failures. Based on over one million data readings, the authors analyze node and network design, develop network reliability profiles, and failure models. The chapter is structured into several sections: 1. **Introduction**: Explains the potential benefits of WSNs for habitat monitoring and the need for a system that produces useful data while leveraging sensor network research for robustness and predictable operation. 2. **Habitat Monitoring**: Discusses the biological need for sensor networks and the requirements for collecting useful data for life scientists. 3. **Network Architecture**: Describes the tiered architecture for habitat monitoring applications, including sensor nodes, sensor patches, gateways, and base stations. 4. **Application Implementation**: Details the application software, sensor board design, packaging strategy, and experiment goals. 5. **System Analysis**: Evaluates the behavior of the sensor network, including network dynamics and node performance. 6. **Node Analysis**: Analyzes the performance and reliability of individual nodes, focusing on sensor readings and power management. 7. **Related Work**: Reviews previous studies on habitat monitoring using WSNs. The chapter concludes with insights and recommendations for future research and applications of WSNs in habitat monitoring.