The mini microphone is built in the nest box camera. The audio will be transported to the application together with the audio. Click the microphone icon on the tools bar, you should hear the voice from your birdhouse. If you can hear the audio in live video but not in the recording files, please follow the below guide to enable the audio recording in the nest box camera.
Introductions
This below instruction is suitable for the IP (WiFi) birdhouse camera from Green-Backyard, Gardenature, Oertl, Green-feathers, and Handykam which are using iCSee or XMEYE mobile application. If you prefer XMEYE, please skip to the second section below. Both iCSee and XMEYE are Interchangeable.
iCSee (PRO)
1. First, go to iCSee Pro, and tap the camera to view the live video. Then tap the settings icon on the top right hand corner.
2. Next choose “Advanced Setting”.
3. Now slide the button next to Audio to right (turn green).
4. Tap “OK” on the top right screen to save. Now the audio will be recorded as well as the video.
XMEYE
1.First, go to XMEYE, and tap the camera to view the live video. Then tap the home icon on the middle of tool bar.
2.Next choose “Encode Config”.
3.Now slide the Audio tab to TURN ON audio for both main stream and sub stream. Tap “Save” on the top right corner. Now the audio will be recorded as well as the video.
Related Source
How to playback the video on birdhouse camera( iOS & Android )